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Effect of depth of fertilizer banded-placement on growth, nutrient uptake and yield of oilseed rape (Brassica napus L.)
Europ. J. Agronomy 62 (2015) 38–45
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Effect of depth of fertilizer banded-placement on growth, nutrient uptake and yield of oilseed rape (Brassica napus L.) Wei Su a,b , Bo Liu a,b , Xiaowei Liu c , Xiaokun Li a,b , Tao Ren a,b , Rihuan Cong a,b , Jianwei Lu a,b,∗ a
Department of Plant Nutrition, College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China Key Laboratory of Arable Land Conservation (Middle and Lower Reaches of Yangtze River), Ministry of Agriculture, Wuhan 430070, China c Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China b
a r t i c l e
i n f o
Article history: Received 25 February 2014 Received in revised form 25 August 2014 Accepted 9 September 2014 Keywords: Fertilizer banded-placement depth Oilseed rape Shoot growth Root growth Nutrient uptake Seed yield
a b s t r a c t A better understanding of crop growth and nutrient uptake responses to the depth of fertilizer bandedplacement in the soil is needed if growth and nutrient uptake responses are to be maximized. A two-year field study covering two rape seasons (2010–2011 and 2011–2012) was conducted to examine the effect of banded-placement of N–P–K fertilizer at various depths on growth, nutrient uptake and yield of oilseed rape (Brassica napus L.). The results showed that fertilization at 10 cm and 15 cm soil depth produced greater taproot length and dry weight than fertilization at 0 cm and 5 cm. 0 cm and 5 cm deep fertilization significantly increased the lateral root distribution at 0–5 cm soil depth, while 10 cm and 15 cm deep fertilization induced more lateral root proliferation at 5–15 cm soil depth. At 36 days after sowing (DAS), 5 cm deep fertilization produced better aboveground growth and nutrient uptake than 10 cm and 15 cm deep fertilization. However, reversed results were observed after 36 DAS. 10 cm and 15 cm deep fertilization produced more rapeseed than 0 cm and 5 cm deep fertilization, moreover, the yield difference was more significant in drought season (2010–2011) than in relatively normal season (2011–2012). In summary, these results preliminarily suggest that both 10 cm and 15 cm are relatively proper fertilizer placement depth when the practice of banding fertilizer is used in oilseed rape production. But from the viewpoint of diminishing the production cost, 10 cm deep fertilization should be recommended in actual farming. Because 15 cm deep fertilization may require higher mechanical power input, and thus resulting in higher cost of production. © 2014 Elsevier B.V. All rights reserved.
1. Introduction Optimizing the fertilization method to simultaneously achieve high nutrient use efficiency and high crop productivity is necessary in modern agriculture, because modern agricultural production not only needs to meet the increasing demand for global food production, but also needs to minimize depletion of natural resources and deterioration of environmental conditions (Cassman, 1999; Cassman et al., 2003; Tilman et al., 2002). Extensive studies have been performed to contrast the effects of different fertilizer application methods on nutrient use efficiency,
∗ Corresponding author at: Department of Plant Nutrition, College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China. Tel.: +86 27 87288589; fax: +86 27 87288589. E-mail addresses: [email protected] (W. Su), [email protected] (J. Lu). http://dx.doi.org/10.1016/j.eja.2014.09.002 1161-0301/© 2014 Elsevier B.V. All rights reserved.
crop productivity and nutrient loss. In general, banding fertilizer in soil could result in increased fertilizer use efficiency and crop yield compared with other application methods. Nash et al. (2013) found that strip-till and deep banding placement of nitrogen (N) fertilizer produced significantly greater corn yield than no-till system with broadcast N fertilizer in poorly drained claypan soils. Borges and Mallarino (2001) studied the improvement of potassium (K) application method for corn in 15 experimental sites, the results showed that the deep-band K placement increased the K uptake of corn over the broadcast K in 14 sites. Ma et al. (2013) reported that side-banded application of ammonium and phosphorus (P) could significantly improve maize growth, nutrient uptake and grain yield on a calcareous soil, which was associated with localized nutrient-induced root proliferation. In a three-year field experiment, Trapeznikov et al. (2003) observed that higher wheat yield occurred in the treatments with banded placement of granulated NPK fertilizer at 8–10 cm depth compared with homogeneous application fertilizer in the 0–18 cm soil layer; moreover, the
W. Su et al. / Europ. J. Agronomy 62 (2015) 38–45
difference was more significant in the drought season. All of these results indicated that banding fertilizer had some advantages in improving crops growth and nutrient uptake compared with broadcasting or mixing fertilizer. The emergence of comparative advantages is mainly attributed to two factors. (1) Banding fertilizer saturates the soil solution with nutrients especially slowly-mobile nutrients such as P and K in a relatively small area within the root zone, which can reduce fixation and adsorption of nutrients by soil particles, and thus increasing nutrients availability (Farmaha et al., 2013; Fernández and White, 2012; McLaughlin et al., 2011). Additionally, when fertilizer is applied in soil with deep bands, relatively greater water availability in the subsurface of soil will enhance nutrient-solution and nutrient-transport, which is also in favor of a higher nutrient availability (Li, 2008; McLaughlin et al., 2011). (2) Localized nutrient concentrations especially localized N and P concentrations resulted from banding fertilizer can stimulate root development and establishment of a virtually ideal root architecture, and thus increasing crops nutrient uptake and yield (Shen et al., 2013). Besides improving nutrient use efficiency and crop yield, banding fertilizer also could reduce the nutrient loss. Rochette et al. (2009) reported that banding urea significantly decreased the ammonia volatilization by 52% compared to urea broadcast in a notill soil. Cheng et al. (2002) found that N2 O + NO emissions from urea fertilizer were lower from band than broadcast application applied to Chinese cabbage. Kimmell et al. (2001) observed significant P placement effects on P runoff losses. As reported by them, P runoff losses were significantly lower with knife placement P compared with broadcast P. Although banding fertilizer in the root zone represents an effective fertilization practice to simultaneously achieve high nutrient use efficiency and high crop productivity, it still has the room for further improvement. As pointed in reports by Mcconnell et al. (1986) and Murphy and Zaurov (1994), the effect of banding fertilizer on crop growth, nutrient uptake and yield significantly varied with the change of fertilizer placement depth, suggesting determining the proper placement depth is an effective approach for further improving the effect of banding fertilizer. Oilseed rape is the most important oil crop in China with about 7.3 million hectares of the total sown areas and 14.0 million tons of the total rapeseed yields in 2012 (FAOSTAT, 2014). For a long time, the alternative fertilization technique for oilseed rape in China was only broadcast or broadcast and incorporation into the soil surface (0–3 cm depth) due to the shortage of both labor force and farm machines. Partially related to these imprudent fertilization methods, the nutrient use efficiency of oilseed rape was always maintained on a low level. In recent years, banding fertilizer has become an emerging fertilization technique in oilseed rape production in China with rapid development of agricultural mechanization (Ma et al., 2010; Wu et al., 2005, 2007; Zhou et al., 2011), which offered an opportunity to improve the productivity and nutrient use efficiency of oilseed rape. But as the technique which is in the early stages of adoption, the underlying strategy of banding fertilizer such as proper depth of fertilizer placement remains largely to be determined. Therefore, we conducted a two-year field experiment in main oilseed rape producing area of China. The overall goal of this study was to preliminarily determine proper fertilizer placement depth, thereby helping farmers perfect the practice of banding fertilizer. In order to achieve this goal, we examined the effect of depths of N–P–K fertilizer banded-placement on shoot growth, nutrient uptake and seed yield of oilseed rape. Besides, given that different depths of fertilizer placement could result in changes in root morphology (Murphy and Zaurov, 1994; Weligama et al., 2008), and thus determining shoot growth and nutrient uptake (Hammer et al., 2009; Singh et al., 2005; Wang et al., 2004), we also assessed root response of oilseed rape to different depths
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of N–P–K fertilizer banded-placement including taproot growth parameters and lateral root distribution. 2. Materials and methods 2.1. Experimental site Oilseed rape were grown for two seasons (2010–2011 and 2011–2012) in rotation with rice at the Experimental Farm of Huazhong Agricultural University (30◦ 28 12 N, 114◦ 21 05 E, 27 m ASL), Wuhan, China. With a subtropical monsoon climate, the experimental site’s mean annual temperature is 16.7 ◦ C and its winter mean temperature is 3.8 ◦ C. The mean annual rainfall is 1257 mm, around 70% of it is concentrated during the months of March–August. The experimental field’s soil was a yellowish brown clay loam with bulk density 1.41 g cm−1 , pH 5.72 (1: 5 soil: water suspension), organic matter 18.25 g kg−1 , total N 1.10 g kg−1 , OlsenP 18.23 mg kg−1 , exchangeable K 80.26 mg kg−1 in the topsoil layer (0–30 cm). Climate condition during the two seasons is shown in Fig. 1. In both the seasons, temperatures during the oilseed rape growing period were similar and close to the long-term mean, except for significantly lower temperature in January 2011. Total rainfall during the growing period was 210 mm in 2010–2011 and 564 mm in 2011–2012, respectively. The mean rainfall during the growing period over the last 30 years was 592 mm at the study area. The period from the 2010–2011 was therefore considered to be seriously dry. In the 2011–2012, rainfall from November 2011 to February 2012 (108 mm) was only 54% of the long-term mean (201 mm), whereas the amount from March 2012 to May 2012 (456 mm) was 17% more than long-term mean (391 mm), which indicated that there was an obviously maladjusted precipitation in this season. 2.2. Experimental design and crop management The experiment consisted of five treatments, each with three replicates in a completely randomized block design: (1) no fertilization (ck); (2) N–P–K fertilizer banded placement at soil depth of 0 cm (D0 ); (3) N–P–K fertilizer banded placement at soil depth of 5 cm (D5 ); (4) N–P–K fertilizer banded placement at soil depth of 10 cm (D10 ) and (5) N–P–K fertilizer banded placement at soil depth of 15 cm (D15 ). The plot size was 4 m × 5 m. All fertilization treatments received N 180 kg ha−1 as urea (N 46%), P 40 kg ha−1 as calcium superphosphate (P 5.2%) and K 100 kg ha−1 as potassium chloride (K 52.3%). The full rates of fertilizers were applied just before seeding. A mixture of N, P and K fertilizers was banded in terms of designed depth. Each plot consisted of 15 fertilizer bands 5 m in length and 0.20 m apart. Winter type oilseed rape (cv. Huashuang 5, supplied by the Wuhan Research Branch of the National Rapeseed Genetic Improvement Center) was seeded on 9 October 2010 and 17 October 2011, harvested on 13 May 2011 and 18 May 2012 for the season of 2010–2011 and 2011–2012, respectively. The method of hill-seeding was used in present study. Forty hills were arranged on each fertilizer band. Intrarow spacing of hills was 0.11 m with three seeds per hill. After emergence of oilseed rape completed, only one plant was left in each hill. Plant population of 0.3 million per hectare was maintained. No irrigation was adopted in the whole life of oilseed rape in both seasons. 2.3. Sampling and measurement Plant height and number of leaves of oilseed rape were determined at 36 and 76 days after sowing (DAS) during seedling stage in 2010–2011 and 2011–2012. Heights of eight randomly selected
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Fig. 1. Monthly total rainfall and monthly mean temperature during the oilseed rape season in 2010–2011, 2011–2012 and the long-term mean (1980–2009) at the experimental site.
plants per plot were measured from the soil level to the ligule of the uppermost fully expanded leaf and the average height was calculated. Using same plants, number of full expanded leaves was counted and the average number of leaves was calculated. Plants were sampled at the growth stages of seedling (36 DAS, 76 DAS in both seasons), flowering (163 DAS in 2010–2011, 160 DAS in 2011–2012) and maturity (216 DAS in 2010–2011, 214 DAS in 2011–2012). Eight representative plants per plot at each sampling time were cut at the ground level to determine shoot dry matter and nutrient uptake. The aboveground tissues were dried in an oven for 30 min at 105 ◦ C to deactivate enzymes, and then dried at 70 ◦ C for three days until a constant weight was reached. Plant materials were combined, ground to pass a 1-mm mesh screen, and then digested by H2 SO4 and H2 O2 (Bao, 2000). The total N and P concentrations of digests were determined using an automated continuous flow analyzer (Seal, Norderstedt, Germany). The total K concentration of plant digests was determined using a flame photometer (FP640). Nutrient uptake was calculated as the product of dry matter accumulation by nutrient concentration. Whole roots were sampled at growth stages of seedling (76 DAS in 2010–2011 and 2011–2012) and flowering (163 DAS in 2010–2011, 160 DAS in 2011–2012) using a monolith method (Böhm, 1979). Three representative whole roots were harvested per plot at each sampling time. Lateral roots were removed from taproot using a scissors. The length and diameter of taproot were measured using a ruler and a caliper, respectively, and the average length and diameter of taproot were calculated. After morphology investigation, taproots in each plot were dried in an oven for three days at 70 ◦ C, and then taproot dry weights were measured. An auger sampling method was used to assess lateral root distribution (Böhm, 1979). Soil cores (5-cm diameter) at depths of 0–5 cm, 5–10 cm and 10–15 cm were taken at growth stages of seedling (76 DAS in 2010–2011 and 2011–2012) and flowering (163 DAS in 2010–2011, 160 DAS in 2011–2012) within the fertilizer band in the middle of two plants to evaluate the effect of depth of fertilizer placement on lateral root distribution of oilseed rape. Three cores were taken at each depth in each plot. Roots in soil cores were washed out with tap water and then rinsed three times with deionized water. Root dry weight was measured after oven drying at 70 ◦ C for three days, and root mass density was calculated. At maturity stage, a total of 10 m2 of mature rapeseed were collected and threshed in each plot, from which the yield was determined.
2.4. Statistics analysis Data were subjected to one-way ANOVA, and significant differences in means between the treatments were compared by the Fisher’s protected least significant difference (LSD) procedure at P < 0.05 with the SPSS 17.0 software program (SPSS Inc, 2008). Figures were prepared using the Origin 8.0 software program. 3. Results 3.1. Taproot growth of oilseed rape Fertilization at different soil depths had significant influences on taproot growth of oilseed rape (Table 1). Taproot length of oilseed rape was higher in the D10 and D15 treatments than in the D0 and D5 treatments at 76 DAS and flowering stage in both seasons. However, significant difference was only found at 76 DAS. There was no significant change in the top diameter of taproot of oilseed rape in response to depth of fertilizer placement at 76 DAS and flowering stage in both seasons. However, the top-5 cm diameter of taproot was significantly bigger in the D10 and D15 treatments than in the D0 and D5 treatments at 76 DAS and flowering stage in both seasons. Similar to the top-5 cm diameter of taproot, the top-10 cm diameter of taproot in the D10 and D15 treatments also showed a significant increase compared with D0 and D5 treatments at flowering stage in both seasons. Taproot dry weight of oilseed rape was significantly higher in the D10 and D15 treatments than in the D0 and D5 treatments. The taproot dry weight increased by 50–75%, 20–40% at 76 DAS, 26–37%, 31–33% at flowering stage in D10 and D15 treatments compared with D0 treatment in 2010–2011 and 2011–2012, respectively. 3.2. Lateral root distribution of oilseed rape The lateral root distribution was expressed as lateral root mass density in different soil layers (Fig. 2). Fertilization at 5 cm soil depth (D5 ) caused significantly higher lateral root mass at 0–5 cm soil layer compared with fertilization at 10 cm (D10 ) and 15 cm (D15 ) soil depth at 76 DAS and flowering stage in both seasons. Similar but less marked effect was observed when fertilizer was applied at 0 cm soil depth (D0 ). For the 5–10 cm soil layer, the highest lateral root mass density occurred in the D10 treatment at 76 DAS and flowering stage in both season. Lateral root mass density in the D15 treatment was relative higher than that in the D5 treatment at 76 DAS and flowering stage in both seasons, but significant difference
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Table 1 Taproot growth parameters of oilseed rape at different growth stages as affected by depth of fertilizer placement in 2010–2011 and 2011–2012. Treatment
Seedling (76 DAS)
Flowering
Taproot length (cm)
Top
Top-5 cm
2010–2011 D0 D5 D10 D15
10.6c 11.5c 12.9b 14.9a
12.4a 12.8a 13.7a 13.7a
2011–2012 D0 D5 D10 D15
11.0b 10.9b 12.9a 13.3a
10.5a 11.3a 10.4a 11.0a
Taproot dry weight (g plant−1 )
Taproot length (cm)
4.7c 5.3b 5.9ab 6.2a
1.6b 1.9b 2.4a 2.8a
6.0bc 5.6c 6.7ab 7.2a
2.0b 2.2b 2.8a 2.6a
Taproot diameter (mm)
Taproot diameter (mm)
Taproot dry weight (g plant−1 )
Top
Top-5 cm
Top-10 cm
18.2a 18.3a 20.1a 19.1a
16.3a 16.9a 16.8a 16.8a
10.3c 10.9c 14.2a 13.0b
5.1b 6.0b 8.1a 9.2a
3.5c 3.6c 4.8a 4.4b
18.5a 18.3a 20.4a 21.2a
15.0a 16.0a 15.7a 15.7a
10.6c 11.3bc 12.4ab 13.1a
5.9b 6.7b 7.9a 8.2a
3.6b 3.8b 4.7a 4.8a
Within a column for each season, values followed by different letters are significantly different according to LSD (0.05).
was only observed at flowering stage. Between the treatments, the lowest lateral root mass density at 5–10 cm soil layer occurred in the D0 treatment at 76 DAS and flowering stage in both seasons, but except at 76 DAS in 2011–2012, no significant differences were observed between the D0 and D5 treatments. For the 10–15 cm soil layer, the lateral root mass density was significant higher in the D15 treatment than in the D0 , D5 and D10 treatments except at 76 DAS in 2011–2012 when no significant difference was observed between the treatments. There were no significant differences in lateral root mass density between the D0 , D5 and D10 treatments at 76 DAS and flowering stage in both seasons.
3.3. Shoot growth of oilseed rape Fertilization at different soil depths had significant influences on shoot growth and dry matter accumulation of oilseed rape. Plant height and number of leaves per plant were higher in the D5 treatment than in the D0 , D10 and D15 treatments at 36 DAS in both seasons (Table 2). However, at 76 DAS, higher plant height and number of leaves per plant were observed in the D10 and D15 treatments rather than in the D5 treatment. Shoot dry matter responses to depth of fertilizer placement changed with time (Table 2). At 36 DAS, shoot dry matter of oilseed
Fig. 2. Distribution of lateral root mass density of oilseed rape at different growth stages as affected by depth of fertilizer placement in 2010–2011 and 2011–2012. Bars represent the standard error (n = 3). Within a growth stage for each season, bars with different letters are significantly different according to LSD (0.05).
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Table 2 Shoot growth parameters of oilseed rape at different growth stages as affected by fertilization and depth of fertilizer placement in 2010–2011 and 2011–2012. Treatment
Seedling 36 DAS
2010–2011 ck D0 D5 D10 D15 2011–2012 ck D0 D5 D10 D15
Flowering
Maturity
76 DAS
Plant height (cm)
Number of leaves per plant
Shoot dry matter (kg ha−1 )
Plant height (cm)
Number of leaves per plant
Shoot dry matter (kg ha−1 )
Shoot dry matter (kg ha−1 )
Shoot dry matter (kg ha−1 )
6.8c 12.9b 15.5a 15.0a 13.6b
5.4c 6.2b 6.8a 6.4ab 6.0b
126d 686b 850a 695b 458c
12.8c 24.2b 25.0b 32.8a 32.5a
6.4c 8.3b 8.7ab 9.2a 9.5a
423d 2375c 3550b 4443a 4148a
2533d 6160c 8514b 10630a 10118a
4600d 9883c 12870b 15870a 15489a
9.7c 14.9a 15.9a 12.6b 11.6b
5.1c 6.0ab 6.4a 5.9ab 5.6b
156d 361b 479a 329b 247c
11.0c 18.6b 20.2b 25.5a 26.4a
6.3c 7.6b 8.2ab 8.3ab 8.7a
575c 2287b 2839a 3067a 3113a
1821d 6246c 7164b 8505a 8124a
4975d 10069c 11461b 12821a 12991a
Within a column for each season, values followed by different letters are significantly different according to LSD (0.05).
rape was significantly higher in the D5 treatment than in the D0 , D10 and D15 treatments in both seasons. Between the D0 , D10 and D15 treatments, shoot dry matter in the D0 treatment paralleled that in the D10 treatment, while shoot dry matter in the D15 treatment was significantly lagged behind that in the D0 and D10 treatments at 36 DAS in both seasons. However, at 76 DAS, flowering and maturity stages, shoot dry matter was significantly higher in the D10 and D15 treatments than in the D0 and D5 treatments. The shoot dry matter increased by 75–87%, 34–36% at 76 DAS, 64–73%, 30–36% at flowering stage and 57–61%, 27–29% at maturity stage in the D10 and D15 treatments compared with D0 treatment in 2010–2011 and 2011–2012, respectively. 3.4. Shoot N, P and K concentration and N, P and K uptake of oilseed rape The concentration of N, P and K nutrients in the shoot of oilseed rape was presented in Table 3. The differences in N
concentration between the fertilization treatments were small throughout the whole life of oilseed rape in both seasons, except at 76 DAS in 2011–2012 when the N concentration was substantially lower in the D0 and D5 treatments than in the D10 and D15 treatments. At 36 and 76 DAS, shoot P concentration in the D10 and D15 treatments was significantly higher than that in the D0 and D5 treatments in both seasons. However, at flowering and maturity stages, no significant differences in P concentration were observed between the fertilization treatments. At 36 DAS, significant higher shoot K concentration occurred in the D0 and D5 treatments between the fertilization treatments in both seasons, which were the observations opposite to N and P concentration. After 36 DAS, there were no significant differences in shoot K concentration between the fertilization treatments. Shoot nutrient uptake of oilseed rape in response to depth of fertilizer placement varied depending on the growth stage (Table 4). The highest N, P and K uptake occurred in the D5 treatment at 36 DAS in both seasons. No significant differences in N, P and K uptake
Table 3 Shoot N, P and K concentration of oilseed rape (mg kg−1 ) at different growth stages as affected by fertilization and depth of fertilizer placement in 2010–2011 and 2011–2012. Growth stage N Seedling (36 DAS) Seedling (76 DAS) Flowering Maturity Seed Straw P Seedling (36 DAS) Seedling (76 DAS) Flowering Maturity Seed Straw K Seedling (36 DAS) Seedling (76 DAS) Flowering Maturity Seed Straw
2011–2012
2010–2011 ck
D0
D5
D10
D15
ck
D0
D5
D10
D15
40.3b 29.7b 16.4b
47.5a 33.3a 19.5a
46.7a 32.1a 19.6a
49.0a 32.9a 19.8a
49.4a 33.0a 20.8a
42.8b 25.8c 22.8b
50.3a 35.3b 26.3a
50.5a 37.4b 26.0a
53.3a 43.8a 26.8a
54.0a 43.2a 25.8a
30.3b 3.9b
36.1a 4.6a
36.3a 4.4a
36.1a 4.4a
36.3a 4.8a
31.9b 4.6c
37.1a 6.8b
36.9a 6.8b
40.5a 8.6a
38.3a 8.0ab
2.2c 1.7c 2.5b
3.5b 2.5b 3.1a
3.9b 2.5b 3.1a
4.5a 2.9a 3.2a
4.8a 3.0a 3.2a
3.0c 2.5c 3.6b
3.5bc 2.6c 4.4a
4.2ab 3.6b 4.6a
4.6a 4.5a 4.3a
4.9a 4.3ab 4.4a
5.5a 0.5a
5.8a 0.6a
6.0a 0.6a
5.9a 0.6a
6.1a 0.6a
7.0b 0.8b
7.8a 1.1a
7.8a 1.2a
7.8a 1.1a
7.6a 1.0a
31.3c 24.4b 19.3b
38.1a 28.4a 24.2a
36.3ab 28.6a 25.0a
34.9b 28.1a 24.4a
34.6b 28.7a 23.9a
34.2c 25.1b 21.1b
45.1ab 36.1a 29.9a
47.1a 35.1a 30.1a
42.7ab 37.1a 31.4a
41.0b 38.0a 32.3a
5.4b 17.7b
6.9a 21.2a
6.6a 21.1a
7.0a 20.8a
7.4a 21.1a
6.4b 22.4b
7.0a 27.0a
6.7ab 27.1a
7.0a 27.4a
6.8ab 27.2a
Within a line for each season, values followed by different letters are significantly different according to LSD (0.05).
W. Su et al. / Europ. J. Agronomy 62 (2015) 38–45
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Table 4 Shoot N, P and K uptake of oilseed rape (kg ha−1 ) at different growth stages as affected by fertilization and depth of fertilizer placement in 2010–2011 and 2011–2012. Treatment
Flowering
Seedling 36 DAS
Maturity
76 DAS
N uptake
P uptake
K uptake
N uptake
P uptake
K uptake
N uptake
P uptake
K uptake
N uptake
P uptake
K uptake
2010–2011 ck D0 D5 D10 D15
5.1d 32.6b 39.3a 34.0b 22.6c
0.3d 2.4c 3.3a 3.1b 2.3c
4.0d 26.4b 30.4a 24.2b 15.9c
12.7d 78.8c 114.0b 146.3a 136.4a
0.7d 6.0c 9.0b 12.8a 12.3a
10.2d 66.6c 101.4b 125.0a 117.9a
41.5d 120.5c 166.9b 210.5a 210.3a
6.2d 19.1c 26.2b 33.9a 32.1a
48.7d 150.7c 213.7b 259.5a 241.3ab
40.1d 124.5c 155.8b 193.5a 189.4a
6.6d 18.7c 24.2b 29.1a 29.2a
71.7d 173.2c 227.1b 276.7a 276.7a
2011–2012 ck D0 D5 D10 D15
6.6d 18.1b 24.2a 17.5b 13.3c
0.5c 1.3b 2.0a 1.5b 1.2b
5.3d 16.5b 22.7a 14.0b 10.1c
14.8d 80.8c 106.2b 134.7a 134.0a
1.4d 6.0c 10.3b 13.8a 13.2ab
14.5d 82.6c 98.4b 113.9a 117.8a
41.2d 164.6c 187.1bc 227.5a 209.8ab
6.5c 27.5b 32.7ab 36.6a 35.4a
38.5d 187.1c 216.0b 267.1a 262.9a
61.6c 151.5b 169.0b 219.2a 206.4a
12.5c 29.7b 33.8ab 36.6a 35.5a
80.4d 198.5c 228.2b 257.8a 267.9a
Within a column for each season, values followed by different letters are significantly different according to LSD (0.05).
Fig. 3. Seed yield of oilseed rape as affected by fertilization and depth of placement in 2010–2011 and 2011–2012. Bars represent the standard error (n = 3). Within a season, bars with different letters are significantly different according to LSD (0.05).
was observed between the D0 and D10 treatments, however, significant lag in N, P and K uptake was occurred in the D15 treatment compared with the D0 and D10 treatments at 36 DAS in both seasons. At 76 DAS, flowering and maturity stages, the lowest N, P and K uptake occurred in the D0 treatment between the fertilization treatments, while higher N, P and K uptake occurred in the D10 and D15 treatments rather than in the D5 treatment, indicating that fertilization at 10 cm or 15 cm soil depths helped to improve the shoot nutrient uptake of oilseed rape after early growth stage.
3.5. Seed yield of oilseed rape Seed yield of oilseed rape had a significant response to depth of fertilizer placement (Fig. 3). The highest rapeseed yield occurred in the D10 treatment in both seasons. Rapeseed yield in the D15 treatment was relatively lower than that in the D10 treatment, however, no significant difference was observed between the two treatments in both seasons. Between the four fertilization treatments, the lowest rapeseed yield occurred in the D0 treatment in both seasons. The rapeseed yield increased by 55% and 24% in the D10 treatment compared with D0 treatment in 2010–2011 and 2011–2012, respectively.
4. Discussion 4.1. Root responses of oilseed rape Plant root plasticity in development and architecture in response to localized nutrient supply is well demonstrated in different plant species (Drew, 1975; Hodge, 2004, 2006, 2009; Weligama et al., 2008). The plastic responses of roots mostly depend on enhanced lateral root density and elongation in nutrient-rich patches especially in P-rich or N-rich patches (Drew, 1975). In present study, important differences in the lateral root characteristics of the different fertilizer placement depth treatments were also found. Surface placement of fertilizer (0 cm and 5 cm) significantly induced proliferation of lateral roots at 0–5 cm soil layer. Higher lateral root proliferation in the subsoil was in favor of nutrient and water uptake by plant in the deeper soil layers (Caldwell and Richards, 1989; Hammer et al., 2009; Singh et al., 2005; Wang et al., 2004), which could make a important contribution to oilseed rape growth especially when nutrient has been exhausted at later growth stage or water stress has occurred. Not only was lateral root distribution of oilseed rape was affected by fertilizer placement depth, the taproot morphology and growth of oilseed rape was also significantly affected by it. In this study, diameter of the taproot at 5 cm and 10 cm from top were
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significantly higher in the subsurface fertilization treatments (10 cm and 15 cm) than in the surface fertilization treatments (0 cm and 5 cm) both at 76 DAS and flowering stage, at the same time, subsurface fertilization also induced increase of taproot length compared with surface fertilization. Thus, significant increase in dry weight of taproot was observed when fertilizer was applied at subsurface of soil. Taproot is an important sink organ for oilseed rape. More sufficient taproot reserves during winter could ensure oilseed rape start growing more quickly in spring (Mendham et al., 1981; Rathke et al., 2006). 4.2. Shoot growth, nutrient uptake and seed yield of oilseed rape The results of initial dry matter accumulation of oilseed rape (36 DAS) showed that 5 cm deep fertilization produced better aboveground growth than localized fertilization at the 10 cm and 15 cm soil depth. It was probably attributed to earlier root nutrients capture with 5 cm deep fertilization than with 10 cm and 15 cm deep fertilization. Compared with earlier root N and P capture, earlier root K capture probably made greater contribution for improved shoot growth with 5 cm deep fertilization. This statement was based on the observation, i.e. between N, P and K nutrients, only shoot K concentration was significantly higher in the treatment of 5 cm deep fertilization than in the treatments of 10 cm and 15 cm deep fertilization at 36 DAS, which indicated that significant plant K response occurred in the treatment of 5 cm deep fertilization. The occurrence of significant K response rather than N and P response at initial growth stage of oilseed rape was probably due to relatively low soil K status (soil exchangeable K 80.26 mg kg−1 ). After 36 DAS, shoot growth of oilseed rape receiving deep subsurface fertilization improved with time. Significant higher shoot dry matter accumulation was observed in the treatments of 10 cm and 15 cm deep fertilization at flowering and maturity stages. The improved shoot growth response to subsurface fertilization coincided with the development of a deeper and more extensive root system, which could exploit fertility and water localized at lower depth. With higher shoot dry matter, subsurface-fertilization plants still had comparable or higher shoot N, P and K concentrations after initial growth stage which also indicated better N, P and K nutrition of plant in the subsurface fertilization treatments. Similar to the condition of dry matter accumulation, nutrient accumulation in the shoot of subsurface-fertilization plants also significantly exceeded that in surface-fertilization plants after initial growth stage. Considering comparable nutrient input between the fertilization treatments, higher nutrient accumulation in plants implied higher nutrient use efficiency and lower nutrient loss risk. The seed yield results showed that subsurface fertilization produced more rapeseed than surface fertilization in both seasons. However, yield difference between the subsurface fertilization and the surface fertilization was much smaller in 2011–2012 than in 2010–2011. A comparison of precipitation during the oilseed rape growing period in this study showed a large difference between the two seasons. Specifically, precipitation during the growing period was 210 mm in 2010–2011, which was only 37.2% of the precipitation in 2011–2012, suggesting that serious drought occurred in 2010–2011. More significant yield difference between the subsurface fertilization and the surface fertilization in dry season indicated that subsurface fertilization probably increased the drought resistance of oilseed rape. In China, oilseed rape is mainly cultivated in an area of 6.0 million hectares along the Yangtze River basin (National Bureau of Statistics of China, 2012), where seasonal drought especially autumn and winter drought is prevailing. According to statistics, currently, the mean frequency of autumn drought and winter drought has exceeded 30% and 28% in this region, respectively (Huang et al., 2013; Sui et al., 2012). Seasonal drought exerts some adverse influences on germination, growth
and physiological metabolism of oilseed rape, and thus affecting the rapeseed yield and quality (Champolivier and Merrien, 1996; Jensen et al., 1996; Zhang et al., 2011). It has been a crucial limitation for oilseed rape production in this region. According to the presented findings, subsurface fertilization may be a useful management strategy to improve or stabilize yield of oilseed rape when the seasonal drought occurs. 4.3. Determination of relatively proper fertilizer placement depth Based on the results of nutrient uptake and seed yield in present study, both 10 cm and 15 cm are relatively proper fertilizer placement depth when the practice of banding fertilizer is used in oilseed rape production. But considering the factor that 15 cm deep fertilization may require higher mechanical power input, and thus resulting in higher cost of production, 10 cm deep fertilization should be recommended in actual farming. Acknowledgments The study was supported by Specialized Research Fund for the Doctoral Program of Higher Education (20120146120021), the Earmarked Fund for China Agriculture Research System (CARS13), the Fundamental Research Funds for the Central Universities (2013PY113), the Key Project of National Science & Technology Support Plan (2010BAD01B05), and the Program for Changjiang Scholars and Innovative Research Team in University of China (IRT1247). References Bao, S.D., 2000. Soil Agricultural-Chemical Analysis. China Agricultural Press, Beijing, China, pp. 264–267 (in Chinese). Böhm, W., 1979. Methods of Studying Root Systems. Springer, New York. Borges, R., Mallarino, A.P., 2001. Deep banding phosphorus and potassium fertilizers for corn managed with ridge tillage. Soil Sci. Soc. Am. J. 65, 376–384. Caldwell, M.M., Richards, J.H., 1989. Hydraulic lift: water efflux from upper roots improves effectiveness of water uptake by deep roots. Oecologia 79, 1–5. Cassman, K.G., 1999. Ecological intensification of cereal production systems: yield potential, soil quality, and precision agriculture. Proc. Natl. Acad. Sci. USA 96, 5952–5959. Cassman, K.G., Dobermann, A., Walters, D.T., Yang, H., 2003. Meeting cereal demand while protecting natural resources and improving environmental quality. Annu. Rev. Environ. Resour. 28, 315–358. Champolivier, L., Merrien, A., 1996. Effects of water stress applied at different growth stages to Brassica napus L. var. oleifera on yield, yield components and seed quality. Eur. J. Agron. 5, 153–160. Cheng, W., Nakajima, Y., Sudo, S., Akiyama, H., Tsuruta, H., 2002. N2 O and NO emissions from a field of Chinese cabbage as influenced by band application of urea or controlled-release urea fertilizers. Nutr. Cycl. Agroecosyst. 63, 231–238. Drew, M.C., 1975. Comparison of the effects of a localized supply of phosphate, nitrate, ammonium and potassium on the growth of the seminal root system, and the shoot, in barley. New Phytol. 75, 479–490. Farmaha, B.S., Fernández, F.G., Nafziger, E.D., 2013. Distribution of soybean roots, soil water, phosphorus and potassium concentrations with broadcast and subsurface-band fertilization. Soil Sci. Soc. Am. J. 76, 1079–1089. FAOSTAT, 2014. FAO Statistics Division. Available from: http://faostat3.fao.org/faostat-gateway/go/to/download/Q/*/E. Fernández, F.G., White, C., 2012. No-till and strip-till corn production with broadcast and subsurface-band phosphorus and potassium. Agron. J. 104, 996–1005. Hammer, G.L., Dong, Z., McLean, G., Doherty, A., Messina, C., Schusler, J., Zinselmeier, C., Paszkiewicz, S., Cooper, M., 2009. Can changes in canopy and/or root system architecture explain historical maize yield trends in the US corn belt? Crop Sci. 49, 299–312. Hodge, A., 2004. The plastic plant: root responses to heterogeneous supplies of nutrients. New Phytol. 162, 9–34. Hodge, A., 2006. Plastic plants and patchy soils. J. Exp. Bot. 57, 401–411. Hodge, A., 2009. Root decisions. Plant Cell Environ. 32, 628–640. Huang, W.H., Sui, Y., Yang, X.G., Dai, S.W., Li, M.S., 2013. Characteristics and adaptation of seasonal drought in southern China under the background of climate change. III. Spatiotemporal characteristics of seasonal drought in southern China based on the percentage of precipitation anomalies. Chin. J. Appl. Ecol. 24, 397–406 (in Chinese with English abstract). Jensen, C.R., Mogensen, V.O., Mortensen, G., Fieldsend, J.K., Milford, G.F.J., Andersen, M.N., Thage, J.H., 1996. Seed glucosinolate, oil and protein contents of
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Shen, J.B., Li, C.J., Mi, G.H., Li, L., Yuan, L.X., Jiang, R.F., Zhang, F.S., 2013. Maximizing root/rhizosphere efficiency to improve crop productivity and nutrient use efficiency in intensive agriculture of China. J. Exp. Bot. 64, 1181–1192. Singh, D.K., Sale, P.W.G., Routley, R.R., 2005. Increasing phosphorus supply in subsurface soil in northern Australia: rationale for deep placement and the effects with various crops. Plant Soil 269, 35–44. SPSS Inc., 2008. SPSS Statistics Base 17.0 User’s Guide. SPSS Inc., Chicago, USA, pp. 314–319. Sui, Y., Huang, W.H., Yang, X.G., Li, M.S., 2012. Characteristics and adaption of seasonal drought in southern China under the back ground of global climate change. II. Spatiotemporal characteristics of drought for wintering grain and oil crops based on crop water deficit index. Chin. J. Appl. Ecol. 23, 2467–2476 (in Chinese with English abstract). Tilman, D., Cassman, K.G., Matson, P.A., Naylor, R., Polasky, S., 2002. Agricultural sustainability and intensive production practices. Nature 418, 671–677. Trapeznikov, V.K., Ivanov, I.I., Kudoyarova, G.R., 2003. Effect of heterogeneous distribution of nutrients on root growth, ABA content and drought resistance of wheat plants. Plant Soil 252, 207–214. Wang, Y., Mi, G.H., Chen, F.J., Zhang, J.H., Zhang, F.S., 2004. Response of root morphology to nitrate supply and its contribution to nitrogen accumulation in maize. J. Plant Nutr. 27, 2189–2202. Weligama, C., Tang, C., Sale, P.W.G., Conyers, M.K., Liu, D.L., 2008. Localized nitrate application together with phosphorus enhances root proliferation of wheat and maximizes rhizosphere alkalization in acid subsoil. Plant Soil 312, 101–115. Wu, M.L., Guan, C.Y., Tang, C.Z., Chen, S.Y., Luo, H.F., Wang, G.H., Xie, F.P., Li, X., Yang, W.M., 2007. Experimental research on 2BYF-6 type no-tillage rape combine seeder in paddy stubble field. Trans. Chin. Soc. Agric. Eng. 23, 172–175 (in Chinese with English abstract). Wu, M.L., Guan, C.Y., Tang, C.Z., Xie, F.P., Yang, W.M., Zhao, J.H., 2005. 2BF-6 type no-tillage combine seeder for rape in stubbly field. Trans. Chin. Soc. Agric. Eng. 21, 103–106 (in Chinese with English abstract). Zhang, J., Cui, Y., Sun, Y., Yan, M., Hu, L.Y., 2011. Effect of different degree of drought stress on germination and seedling growth of rapeseed (Brassica napus L.). Agric. Res. Arid Areas 29, 164–167 (in Chinese with English abstract). Zhou, K.Y., Lou, Q.Q., Hong, X.L., Qiu, Z.J., Ying, X.F., 2011. Technical specification and practice of rape whole process mechanized production in Zhejiang Province. J. Zhejiang Univ. (Agric. Life Sci.) 37, 295–299 (in Chinese with English abstract).
Contents lists available at ScienceDirect
European Journal of Agronomy journal homepage: www.elsevier.com/locate/eja
Effect of depth of fertilizer banded-placement on growth, nutrient uptake and yield of oilseed rape (Brassica napus L.) Wei Su a,b , Bo Liu a,b , Xiaowei Liu c , Xiaokun Li a,b , Tao Ren a,b , Rihuan Cong a,b , Jianwei Lu a,b,∗ a
Department of Plant Nutrition, College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China Key Laboratory of Arable Land Conservation (Middle and Lower Reaches of Yangtze River), Ministry of Agriculture, Wuhan 430070, China c Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China b
a r t i c l e
i n f o
Article history: Received 25 February 2014 Received in revised form 25 August 2014 Accepted 9 September 2014 Keywords: Fertilizer banded-placement depth Oilseed rape Shoot growth Root growth Nutrient uptake Seed yield
a b s t r a c t A better understanding of crop growth and nutrient uptake responses to the depth of fertilizer bandedplacement in the soil is needed if growth and nutrient uptake responses are to be maximized. A two-year field study covering two rape seasons (2010–2011 and 2011–2012) was conducted to examine the effect of banded-placement of N–P–K fertilizer at various depths on growth, nutrient uptake and yield of oilseed rape (Brassica napus L.). The results showed that fertilization at 10 cm and 15 cm soil depth produced greater taproot length and dry weight than fertilization at 0 cm and 5 cm. 0 cm and 5 cm deep fertilization significantly increased the lateral root distribution at 0–5 cm soil depth, while 10 cm and 15 cm deep fertilization induced more lateral root proliferation at 5–15 cm soil depth. At 36 days after sowing (DAS), 5 cm deep fertilization produced better aboveground growth and nutrient uptake than 10 cm and 15 cm deep fertilization. However, reversed results were observed after 36 DAS. 10 cm and 15 cm deep fertilization produced more rapeseed than 0 cm and 5 cm deep fertilization, moreover, the yield difference was more significant in drought season (2010–2011) than in relatively normal season (2011–2012). In summary, these results preliminarily suggest that both 10 cm and 15 cm are relatively proper fertilizer placement depth when the practice of banding fertilizer is used in oilseed rape production. But from the viewpoint of diminishing the production cost, 10 cm deep fertilization should be recommended in actual farming. Because 15 cm deep fertilization may require higher mechanical power input, and thus resulting in higher cost of production. © 2014 Elsevier B.V. All rights reserved.
1. Introduction Optimizing the fertilization method to simultaneously achieve high nutrient use efficiency and high crop productivity is necessary in modern agriculture, because modern agricultural production not only needs to meet the increasing demand for global food production, but also needs to minimize depletion of natural resources and deterioration of environmental conditions (Cassman, 1999; Cassman et al., 2003; Tilman et al., 2002). Extensive studies have been performed to contrast the effects of different fertilizer application methods on nutrient use efficiency,
∗ Corresponding author at: Department of Plant Nutrition, College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China. Tel.: +86 27 87288589; fax: +86 27 87288589. E-mail addresses: [email protected] (W. Su), [email protected] (J. Lu). http://dx.doi.org/10.1016/j.eja.2014.09.002 1161-0301/© 2014 Elsevier B.V. All rights reserved.
crop productivity and nutrient loss. In general, banding fertilizer in soil could result in increased fertilizer use efficiency and crop yield compared with other application methods. Nash et al. (2013) found that strip-till and deep banding placement of nitrogen (N) fertilizer produced significantly greater corn yield than no-till system with broadcast N fertilizer in poorly drained claypan soils. Borges and Mallarino (2001) studied the improvement of potassium (K) application method for corn in 15 experimental sites, the results showed that the deep-band K placement increased the K uptake of corn over the broadcast K in 14 sites. Ma et al. (2013) reported that side-banded application of ammonium and phosphorus (P) could significantly improve maize growth, nutrient uptake and grain yield on a calcareous soil, which was associated with localized nutrient-induced root proliferation. In a three-year field experiment, Trapeznikov et al. (2003) observed that higher wheat yield occurred in the treatments with banded placement of granulated NPK fertilizer at 8–10 cm depth compared with homogeneous application fertilizer in the 0–18 cm soil layer; moreover, the
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difference was more significant in the drought season. All of these results indicated that banding fertilizer had some advantages in improving crops growth and nutrient uptake compared with broadcasting or mixing fertilizer. The emergence of comparative advantages is mainly attributed to two factors. (1) Banding fertilizer saturates the soil solution with nutrients especially slowly-mobile nutrients such as P and K in a relatively small area within the root zone, which can reduce fixation and adsorption of nutrients by soil particles, and thus increasing nutrients availability (Farmaha et al., 2013; Fernández and White, 2012; McLaughlin et al., 2011). Additionally, when fertilizer is applied in soil with deep bands, relatively greater water availability in the subsurface of soil will enhance nutrient-solution and nutrient-transport, which is also in favor of a higher nutrient availability (Li, 2008; McLaughlin et al., 2011). (2) Localized nutrient concentrations especially localized N and P concentrations resulted from banding fertilizer can stimulate root development and establishment of a virtually ideal root architecture, and thus increasing crops nutrient uptake and yield (Shen et al., 2013). Besides improving nutrient use efficiency and crop yield, banding fertilizer also could reduce the nutrient loss. Rochette et al. (2009) reported that banding urea significantly decreased the ammonia volatilization by 52% compared to urea broadcast in a notill soil. Cheng et al. (2002) found that N2 O + NO emissions from urea fertilizer were lower from band than broadcast application applied to Chinese cabbage. Kimmell et al. (2001) observed significant P placement effects on P runoff losses. As reported by them, P runoff losses were significantly lower with knife placement P compared with broadcast P. Although banding fertilizer in the root zone represents an effective fertilization practice to simultaneously achieve high nutrient use efficiency and high crop productivity, it still has the room for further improvement. As pointed in reports by Mcconnell et al. (1986) and Murphy and Zaurov (1994), the effect of banding fertilizer on crop growth, nutrient uptake and yield significantly varied with the change of fertilizer placement depth, suggesting determining the proper placement depth is an effective approach for further improving the effect of banding fertilizer. Oilseed rape is the most important oil crop in China with about 7.3 million hectares of the total sown areas and 14.0 million tons of the total rapeseed yields in 2012 (FAOSTAT, 2014). For a long time, the alternative fertilization technique for oilseed rape in China was only broadcast or broadcast and incorporation into the soil surface (0–3 cm depth) due to the shortage of both labor force and farm machines. Partially related to these imprudent fertilization methods, the nutrient use efficiency of oilseed rape was always maintained on a low level. In recent years, banding fertilizer has become an emerging fertilization technique in oilseed rape production in China with rapid development of agricultural mechanization (Ma et al., 2010; Wu et al., 2005, 2007; Zhou et al., 2011), which offered an opportunity to improve the productivity and nutrient use efficiency of oilseed rape. But as the technique which is in the early stages of adoption, the underlying strategy of banding fertilizer such as proper depth of fertilizer placement remains largely to be determined. Therefore, we conducted a two-year field experiment in main oilseed rape producing area of China. The overall goal of this study was to preliminarily determine proper fertilizer placement depth, thereby helping farmers perfect the practice of banding fertilizer. In order to achieve this goal, we examined the effect of depths of N–P–K fertilizer banded-placement on shoot growth, nutrient uptake and seed yield of oilseed rape. Besides, given that different depths of fertilizer placement could result in changes in root morphology (Murphy and Zaurov, 1994; Weligama et al., 2008), and thus determining shoot growth and nutrient uptake (Hammer et al., 2009; Singh et al., 2005; Wang et al., 2004), we also assessed root response of oilseed rape to different depths
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of N–P–K fertilizer banded-placement including taproot growth parameters and lateral root distribution. 2. Materials and methods 2.1. Experimental site Oilseed rape were grown for two seasons (2010–2011 and 2011–2012) in rotation with rice at the Experimental Farm of Huazhong Agricultural University (30◦ 28 12 N, 114◦ 21 05 E, 27 m ASL), Wuhan, China. With a subtropical monsoon climate, the experimental site’s mean annual temperature is 16.7 ◦ C and its winter mean temperature is 3.8 ◦ C. The mean annual rainfall is 1257 mm, around 70% of it is concentrated during the months of March–August. The experimental field’s soil was a yellowish brown clay loam with bulk density 1.41 g cm−1 , pH 5.72 (1: 5 soil: water suspension), organic matter 18.25 g kg−1 , total N 1.10 g kg−1 , OlsenP 18.23 mg kg−1 , exchangeable K 80.26 mg kg−1 in the topsoil layer (0–30 cm). Climate condition during the two seasons is shown in Fig. 1. In both the seasons, temperatures during the oilseed rape growing period were similar and close to the long-term mean, except for significantly lower temperature in January 2011. Total rainfall during the growing period was 210 mm in 2010–2011 and 564 mm in 2011–2012, respectively. The mean rainfall during the growing period over the last 30 years was 592 mm at the study area. The period from the 2010–2011 was therefore considered to be seriously dry. In the 2011–2012, rainfall from November 2011 to February 2012 (108 mm) was only 54% of the long-term mean (201 mm), whereas the amount from March 2012 to May 2012 (456 mm) was 17% more than long-term mean (391 mm), which indicated that there was an obviously maladjusted precipitation in this season. 2.2. Experimental design and crop management The experiment consisted of five treatments, each with three replicates in a completely randomized block design: (1) no fertilization (ck); (2) N–P–K fertilizer banded placement at soil depth of 0 cm (D0 ); (3) N–P–K fertilizer banded placement at soil depth of 5 cm (D5 ); (4) N–P–K fertilizer banded placement at soil depth of 10 cm (D10 ) and (5) N–P–K fertilizer banded placement at soil depth of 15 cm (D15 ). The plot size was 4 m × 5 m. All fertilization treatments received N 180 kg ha−1 as urea (N 46%), P 40 kg ha−1 as calcium superphosphate (P 5.2%) and K 100 kg ha−1 as potassium chloride (K 52.3%). The full rates of fertilizers were applied just before seeding. A mixture of N, P and K fertilizers was banded in terms of designed depth. Each plot consisted of 15 fertilizer bands 5 m in length and 0.20 m apart. Winter type oilseed rape (cv. Huashuang 5, supplied by the Wuhan Research Branch of the National Rapeseed Genetic Improvement Center) was seeded on 9 October 2010 and 17 October 2011, harvested on 13 May 2011 and 18 May 2012 for the season of 2010–2011 and 2011–2012, respectively. The method of hill-seeding was used in present study. Forty hills were arranged on each fertilizer band. Intrarow spacing of hills was 0.11 m with three seeds per hill. After emergence of oilseed rape completed, only one plant was left in each hill. Plant population of 0.3 million per hectare was maintained. No irrigation was adopted in the whole life of oilseed rape in both seasons. 2.3. Sampling and measurement Plant height and number of leaves of oilseed rape were determined at 36 and 76 days after sowing (DAS) during seedling stage in 2010–2011 and 2011–2012. Heights of eight randomly selected
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Fig. 1. Monthly total rainfall and monthly mean temperature during the oilseed rape season in 2010–2011, 2011–2012 and the long-term mean (1980–2009) at the experimental site.
plants per plot were measured from the soil level to the ligule of the uppermost fully expanded leaf and the average height was calculated. Using same plants, number of full expanded leaves was counted and the average number of leaves was calculated. Plants were sampled at the growth stages of seedling (36 DAS, 76 DAS in both seasons), flowering (163 DAS in 2010–2011, 160 DAS in 2011–2012) and maturity (216 DAS in 2010–2011, 214 DAS in 2011–2012). Eight representative plants per plot at each sampling time were cut at the ground level to determine shoot dry matter and nutrient uptake. The aboveground tissues were dried in an oven for 30 min at 105 ◦ C to deactivate enzymes, and then dried at 70 ◦ C for three days until a constant weight was reached. Plant materials were combined, ground to pass a 1-mm mesh screen, and then digested by H2 SO4 and H2 O2 (Bao, 2000). The total N and P concentrations of digests were determined using an automated continuous flow analyzer (Seal, Norderstedt, Germany). The total K concentration of plant digests was determined using a flame photometer (FP640). Nutrient uptake was calculated as the product of dry matter accumulation by nutrient concentration. Whole roots were sampled at growth stages of seedling (76 DAS in 2010–2011 and 2011–2012) and flowering (163 DAS in 2010–2011, 160 DAS in 2011–2012) using a monolith method (Böhm, 1979). Three representative whole roots were harvested per plot at each sampling time. Lateral roots were removed from taproot using a scissors. The length and diameter of taproot were measured using a ruler and a caliper, respectively, and the average length and diameter of taproot were calculated. After morphology investigation, taproots in each plot were dried in an oven for three days at 70 ◦ C, and then taproot dry weights were measured. An auger sampling method was used to assess lateral root distribution (Böhm, 1979). Soil cores (5-cm diameter) at depths of 0–5 cm, 5–10 cm and 10–15 cm were taken at growth stages of seedling (76 DAS in 2010–2011 and 2011–2012) and flowering (163 DAS in 2010–2011, 160 DAS in 2011–2012) within the fertilizer band in the middle of two plants to evaluate the effect of depth of fertilizer placement on lateral root distribution of oilseed rape. Three cores were taken at each depth in each plot. Roots in soil cores were washed out with tap water and then rinsed three times with deionized water. Root dry weight was measured after oven drying at 70 ◦ C for three days, and root mass density was calculated. At maturity stage, a total of 10 m2 of mature rapeseed were collected and threshed in each plot, from which the yield was determined.
2.4. Statistics analysis Data were subjected to one-way ANOVA, and significant differences in means between the treatments were compared by the Fisher’s protected least significant difference (LSD) procedure at P < 0.05 with the SPSS 17.0 software program (SPSS Inc, 2008). Figures were prepared using the Origin 8.0 software program. 3. Results 3.1. Taproot growth of oilseed rape Fertilization at different soil depths had significant influences on taproot growth of oilseed rape (Table 1). Taproot length of oilseed rape was higher in the D10 and D15 treatments than in the D0 and D5 treatments at 76 DAS and flowering stage in both seasons. However, significant difference was only found at 76 DAS. There was no significant change in the top diameter of taproot of oilseed rape in response to depth of fertilizer placement at 76 DAS and flowering stage in both seasons. However, the top-5 cm diameter of taproot was significantly bigger in the D10 and D15 treatments than in the D0 and D5 treatments at 76 DAS and flowering stage in both seasons. Similar to the top-5 cm diameter of taproot, the top-10 cm diameter of taproot in the D10 and D15 treatments also showed a significant increase compared with D0 and D5 treatments at flowering stage in both seasons. Taproot dry weight of oilseed rape was significantly higher in the D10 and D15 treatments than in the D0 and D5 treatments. The taproot dry weight increased by 50–75%, 20–40% at 76 DAS, 26–37%, 31–33% at flowering stage in D10 and D15 treatments compared with D0 treatment in 2010–2011 and 2011–2012, respectively. 3.2. Lateral root distribution of oilseed rape The lateral root distribution was expressed as lateral root mass density in different soil layers (Fig. 2). Fertilization at 5 cm soil depth (D5 ) caused significantly higher lateral root mass at 0–5 cm soil layer compared with fertilization at 10 cm (D10 ) and 15 cm (D15 ) soil depth at 76 DAS and flowering stage in both seasons. Similar but less marked effect was observed when fertilizer was applied at 0 cm soil depth (D0 ). For the 5–10 cm soil layer, the highest lateral root mass density occurred in the D10 treatment at 76 DAS and flowering stage in both season. Lateral root mass density in the D15 treatment was relative higher than that in the D5 treatment at 76 DAS and flowering stage in both seasons, but significant difference
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Table 1 Taproot growth parameters of oilseed rape at different growth stages as affected by depth of fertilizer placement in 2010–2011 and 2011–2012. Treatment
Seedling (76 DAS)
Flowering
Taproot length (cm)
Top
Top-5 cm
2010–2011 D0 D5 D10 D15
10.6c 11.5c 12.9b 14.9a
12.4a 12.8a 13.7a 13.7a
2011–2012 D0 D5 D10 D15
11.0b 10.9b 12.9a 13.3a
10.5a 11.3a 10.4a 11.0a
Taproot dry weight (g plant−1 )
Taproot length (cm)
4.7c 5.3b 5.9ab 6.2a
1.6b 1.9b 2.4a 2.8a
6.0bc 5.6c 6.7ab 7.2a
2.0b 2.2b 2.8a 2.6a
Taproot diameter (mm)
Taproot diameter (mm)
Taproot dry weight (g plant−1 )
Top
Top-5 cm
Top-10 cm
18.2a 18.3a 20.1a 19.1a
16.3a 16.9a 16.8a 16.8a
10.3c 10.9c 14.2a 13.0b
5.1b 6.0b 8.1a 9.2a
3.5c 3.6c 4.8a 4.4b
18.5a 18.3a 20.4a 21.2a
15.0a 16.0a 15.7a 15.7a
10.6c 11.3bc 12.4ab 13.1a
5.9b 6.7b 7.9a 8.2a
3.6b 3.8b 4.7a 4.8a
Within a column for each season, values followed by different letters are significantly different according to LSD (0.05).
was only observed at flowering stage. Between the treatments, the lowest lateral root mass density at 5–10 cm soil layer occurred in the D0 treatment at 76 DAS and flowering stage in both seasons, but except at 76 DAS in 2011–2012, no significant differences were observed between the D0 and D5 treatments. For the 10–15 cm soil layer, the lateral root mass density was significant higher in the D15 treatment than in the D0 , D5 and D10 treatments except at 76 DAS in 2011–2012 when no significant difference was observed between the treatments. There were no significant differences in lateral root mass density between the D0 , D5 and D10 treatments at 76 DAS and flowering stage in both seasons.
3.3. Shoot growth of oilseed rape Fertilization at different soil depths had significant influences on shoot growth and dry matter accumulation of oilseed rape. Plant height and number of leaves per plant were higher in the D5 treatment than in the D0 , D10 and D15 treatments at 36 DAS in both seasons (Table 2). However, at 76 DAS, higher plant height and number of leaves per plant were observed in the D10 and D15 treatments rather than in the D5 treatment. Shoot dry matter responses to depth of fertilizer placement changed with time (Table 2). At 36 DAS, shoot dry matter of oilseed
Fig. 2. Distribution of lateral root mass density of oilseed rape at different growth stages as affected by depth of fertilizer placement in 2010–2011 and 2011–2012. Bars represent the standard error (n = 3). Within a growth stage for each season, bars with different letters are significantly different according to LSD (0.05).
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W. Su et al. / Europ. J. Agronomy 62 (2015) 38–45
Table 2 Shoot growth parameters of oilseed rape at different growth stages as affected by fertilization and depth of fertilizer placement in 2010–2011 and 2011–2012. Treatment
Seedling 36 DAS
2010–2011 ck D0 D5 D10 D15 2011–2012 ck D0 D5 D10 D15
Flowering
Maturity
76 DAS
Plant height (cm)
Number of leaves per plant
Shoot dry matter (kg ha−1 )
Plant height (cm)
Number of leaves per plant
Shoot dry matter (kg ha−1 )
Shoot dry matter (kg ha−1 )
Shoot dry matter (kg ha−1 )
6.8c 12.9b 15.5a 15.0a 13.6b
5.4c 6.2b 6.8a 6.4ab 6.0b
126d 686b 850a 695b 458c
12.8c 24.2b 25.0b 32.8a 32.5a
6.4c 8.3b 8.7ab 9.2a 9.5a
423d 2375c 3550b 4443a 4148a
2533d 6160c 8514b 10630a 10118a
4600d 9883c 12870b 15870a 15489a
9.7c 14.9a 15.9a 12.6b 11.6b
5.1c 6.0ab 6.4a 5.9ab 5.6b
156d 361b 479a 329b 247c
11.0c 18.6b 20.2b 25.5a 26.4a
6.3c 7.6b 8.2ab 8.3ab 8.7a
575c 2287b 2839a 3067a 3113a
1821d 6246c 7164b 8505a 8124a
4975d 10069c 11461b 12821a 12991a
Within a column for each season, values followed by different letters are significantly different according to LSD (0.05).
rape was significantly higher in the D5 treatment than in the D0 , D10 and D15 treatments in both seasons. Between the D0 , D10 and D15 treatments, shoot dry matter in the D0 treatment paralleled that in the D10 treatment, while shoot dry matter in the D15 treatment was significantly lagged behind that in the D0 and D10 treatments at 36 DAS in both seasons. However, at 76 DAS, flowering and maturity stages, shoot dry matter was significantly higher in the D10 and D15 treatments than in the D0 and D5 treatments. The shoot dry matter increased by 75–87%, 34–36% at 76 DAS, 64–73%, 30–36% at flowering stage and 57–61%, 27–29% at maturity stage in the D10 and D15 treatments compared with D0 treatment in 2010–2011 and 2011–2012, respectively. 3.4. Shoot N, P and K concentration and N, P and K uptake of oilseed rape The concentration of N, P and K nutrients in the shoot of oilseed rape was presented in Table 3. The differences in N
concentration between the fertilization treatments were small throughout the whole life of oilseed rape in both seasons, except at 76 DAS in 2011–2012 when the N concentration was substantially lower in the D0 and D5 treatments than in the D10 and D15 treatments. At 36 and 76 DAS, shoot P concentration in the D10 and D15 treatments was significantly higher than that in the D0 and D5 treatments in both seasons. However, at flowering and maturity stages, no significant differences in P concentration were observed between the fertilization treatments. At 36 DAS, significant higher shoot K concentration occurred in the D0 and D5 treatments between the fertilization treatments in both seasons, which were the observations opposite to N and P concentration. After 36 DAS, there were no significant differences in shoot K concentration between the fertilization treatments. Shoot nutrient uptake of oilseed rape in response to depth of fertilizer placement varied depending on the growth stage (Table 4). The highest N, P and K uptake occurred in the D5 treatment at 36 DAS in both seasons. No significant differences in N, P and K uptake
Table 3 Shoot N, P and K concentration of oilseed rape (mg kg−1 ) at different growth stages as affected by fertilization and depth of fertilizer placement in 2010–2011 and 2011–2012. Growth stage N Seedling (36 DAS) Seedling (76 DAS) Flowering Maturity Seed Straw P Seedling (36 DAS) Seedling (76 DAS) Flowering Maturity Seed Straw K Seedling (36 DAS) Seedling (76 DAS) Flowering Maturity Seed Straw
2011–2012
2010–2011 ck
D0
D5
D10
D15
ck
D0
D5
D10
D15
40.3b 29.7b 16.4b
47.5a 33.3a 19.5a
46.7a 32.1a 19.6a
49.0a 32.9a 19.8a
49.4a 33.0a 20.8a
42.8b 25.8c 22.8b
50.3a 35.3b 26.3a
50.5a 37.4b 26.0a
53.3a 43.8a 26.8a
54.0a 43.2a 25.8a
30.3b 3.9b
36.1a 4.6a
36.3a 4.4a
36.1a 4.4a
36.3a 4.8a
31.9b 4.6c
37.1a 6.8b
36.9a 6.8b
40.5a 8.6a
38.3a 8.0ab
2.2c 1.7c 2.5b
3.5b 2.5b 3.1a
3.9b 2.5b 3.1a
4.5a 2.9a 3.2a
4.8a 3.0a 3.2a
3.0c 2.5c 3.6b
3.5bc 2.6c 4.4a
4.2ab 3.6b 4.6a
4.6a 4.5a 4.3a
4.9a 4.3ab 4.4a
5.5a 0.5a
5.8a 0.6a
6.0a 0.6a
5.9a 0.6a
6.1a 0.6a
7.0b 0.8b
7.8a 1.1a
7.8a 1.2a
7.8a 1.1a
7.6a 1.0a
31.3c 24.4b 19.3b
38.1a 28.4a 24.2a
36.3ab 28.6a 25.0a
34.9b 28.1a 24.4a
34.6b 28.7a 23.9a
34.2c 25.1b 21.1b
45.1ab 36.1a 29.9a
47.1a 35.1a 30.1a
42.7ab 37.1a 31.4a
41.0b 38.0a 32.3a
5.4b 17.7b
6.9a 21.2a
6.6a 21.1a
7.0a 20.8a
7.4a 21.1a
6.4b 22.4b
7.0a 27.0a
6.7ab 27.1a
7.0a 27.4a
6.8ab 27.2a
Within a line for each season, values followed by different letters are significantly different according to LSD (0.05).
W. Su et al. / Europ. J. Agronomy 62 (2015) 38–45
43
Table 4 Shoot N, P and K uptake of oilseed rape (kg ha−1 ) at different growth stages as affected by fertilization and depth of fertilizer placement in 2010–2011 and 2011–2012. Treatment
Flowering
Seedling 36 DAS
Maturity
76 DAS
N uptake
P uptake
K uptake
N uptake
P uptake
K uptake
N uptake
P uptake
K uptake
N uptake
P uptake
K uptake
2010–2011 ck D0 D5 D10 D15
5.1d 32.6b 39.3a 34.0b 22.6c
0.3d 2.4c 3.3a 3.1b 2.3c
4.0d 26.4b 30.4a 24.2b 15.9c
12.7d 78.8c 114.0b 146.3a 136.4a
0.7d 6.0c 9.0b 12.8a 12.3a
10.2d 66.6c 101.4b 125.0a 117.9a
41.5d 120.5c 166.9b 210.5a 210.3a
6.2d 19.1c 26.2b 33.9a 32.1a
48.7d 150.7c 213.7b 259.5a 241.3ab
40.1d 124.5c 155.8b 193.5a 189.4a
6.6d 18.7c 24.2b 29.1a 29.2a
71.7d 173.2c 227.1b 276.7a 276.7a
2011–2012 ck D0 D5 D10 D15
6.6d 18.1b 24.2a 17.5b 13.3c
0.5c 1.3b 2.0a 1.5b 1.2b
5.3d 16.5b 22.7a 14.0b 10.1c
14.8d 80.8c 106.2b 134.7a 134.0a
1.4d 6.0c 10.3b 13.8a 13.2ab
14.5d 82.6c 98.4b 113.9a 117.8a
41.2d 164.6c 187.1bc 227.5a 209.8ab
6.5c 27.5b 32.7ab 36.6a 35.4a
38.5d 187.1c 216.0b 267.1a 262.9a
61.6c 151.5b 169.0b 219.2a 206.4a
12.5c 29.7b 33.8ab 36.6a 35.5a
80.4d 198.5c 228.2b 257.8a 267.9a
Within a column for each season, values followed by different letters are significantly different according to LSD (0.05).
Fig. 3. Seed yield of oilseed rape as affected by fertilization and depth of placement in 2010–2011 and 2011–2012. Bars represent the standard error (n = 3). Within a season, bars with different letters are significantly different according to LSD (0.05).
was observed between the D0 and D10 treatments, however, significant lag in N, P and K uptake was occurred in the D15 treatment compared with the D0 and D10 treatments at 36 DAS in both seasons. At 76 DAS, flowering and maturity stages, the lowest N, P and K uptake occurred in the D0 treatment between the fertilization treatments, while higher N, P and K uptake occurred in the D10 and D15 treatments rather than in the D5 treatment, indicating that fertilization at 10 cm or 15 cm soil depths helped to improve the shoot nutrient uptake of oilseed rape after early growth stage.
3.5. Seed yield of oilseed rape Seed yield of oilseed rape had a significant response to depth of fertilizer placement (Fig. 3). The highest rapeseed yield occurred in the D10 treatment in both seasons. Rapeseed yield in the D15 treatment was relatively lower than that in the D10 treatment, however, no significant difference was observed between the two treatments in both seasons. Between the four fertilization treatments, the lowest rapeseed yield occurred in the D0 treatment in both seasons. The rapeseed yield increased by 55% and 24% in the D10 treatment compared with D0 treatment in 2010–2011 and 2011–2012, respectively.
4. Discussion 4.1. Root responses of oilseed rape Plant root plasticity in development and architecture in response to localized nutrient supply is well demonstrated in different plant species (Drew, 1975; Hodge, 2004, 2006, 2009; Weligama et al., 2008). The plastic responses of roots mostly depend on enhanced lateral root density and elongation in nutrient-rich patches especially in P-rich or N-rich patches (Drew, 1975). In present study, important differences in the lateral root characteristics of the different fertilizer placement depth treatments were also found. Surface placement of fertilizer (0 cm and 5 cm) significantly induced proliferation of lateral roots at 0–5 cm soil layer. Higher lateral root proliferation in the subsoil was in favor of nutrient and water uptake by plant in the deeper soil layers (Caldwell and Richards, 1989; Hammer et al., 2009; Singh et al., 2005; Wang et al., 2004), which could make a important contribution to oilseed rape growth especially when nutrient has been exhausted at later growth stage or water stress has occurred. Not only was lateral root distribution of oilseed rape was affected by fertilizer placement depth, the taproot morphology and growth of oilseed rape was also significantly affected by it. In this study, diameter of the taproot at 5 cm and 10 cm from top were
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significantly higher in the subsurface fertilization treatments (10 cm and 15 cm) than in the surface fertilization treatments (0 cm and 5 cm) both at 76 DAS and flowering stage, at the same time, subsurface fertilization also induced increase of taproot length compared with surface fertilization. Thus, significant increase in dry weight of taproot was observed when fertilizer was applied at subsurface of soil. Taproot is an important sink organ for oilseed rape. More sufficient taproot reserves during winter could ensure oilseed rape start growing more quickly in spring (Mendham et al., 1981; Rathke et al., 2006). 4.2. Shoot growth, nutrient uptake and seed yield of oilseed rape The results of initial dry matter accumulation of oilseed rape (36 DAS) showed that 5 cm deep fertilization produced better aboveground growth than localized fertilization at the 10 cm and 15 cm soil depth. It was probably attributed to earlier root nutrients capture with 5 cm deep fertilization than with 10 cm and 15 cm deep fertilization. Compared with earlier root N and P capture, earlier root K capture probably made greater contribution for improved shoot growth with 5 cm deep fertilization. This statement was based on the observation, i.e. between N, P and K nutrients, only shoot K concentration was significantly higher in the treatment of 5 cm deep fertilization than in the treatments of 10 cm and 15 cm deep fertilization at 36 DAS, which indicated that significant plant K response occurred in the treatment of 5 cm deep fertilization. The occurrence of significant K response rather than N and P response at initial growth stage of oilseed rape was probably due to relatively low soil K status (soil exchangeable K 80.26 mg kg−1 ). After 36 DAS, shoot growth of oilseed rape receiving deep subsurface fertilization improved with time. Significant higher shoot dry matter accumulation was observed in the treatments of 10 cm and 15 cm deep fertilization at flowering and maturity stages. The improved shoot growth response to subsurface fertilization coincided with the development of a deeper and more extensive root system, which could exploit fertility and water localized at lower depth. With higher shoot dry matter, subsurface-fertilization plants still had comparable or higher shoot N, P and K concentrations after initial growth stage which also indicated better N, P and K nutrition of plant in the subsurface fertilization treatments. Similar to the condition of dry matter accumulation, nutrient accumulation in the shoot of subsurface-fertilization plants also significantly exceeded that in surface-fertilization plants after initial growth stage. Considering comparable nutrient input between the fertilization treatments, higher nutrient accumulation in plants implied higher nutrient use efficiency and lower nutrient loss risk. The seed yield results showed that subsurface fertilization produced more rapeseed than surface fertilization in both seasons. However, yield difference between the subsurface fertilization and the surface fertilization was much smaller in 2011–2012 than in 2010–2011. A comparison of precipitation during the oilseed rape growing period in this study showed a large difference between the two seasons. Specifically, precipitation during the growing period was 210 mm in 2010–2011, which was only 37.2% of the precipitation in 2011–2012, suggesting that serious drought occurred in 2010–2011. More significant yield difference between the subsurface fertilization and the surface fertilization in dry season indicated that subsurface fertilization probably increased the drought resistance of oilseed rape. In China, oilseed rape is mainly cultivated in an area of 6.0 million hectares along the Yangtze River basin (National Bureau of Statistics of China, 2012), where seasonal drought especially autumn and winter drought is prevailing. According to statistics, currently, the mean frequency of autumn drought and winter drought has exceeded 30% and 28% in this region, respectively (Huang et al., 2013; Sui et al., 2012). Seasonal drought exerts some adverse influences on germination, growth
and physiological metabolism of oilseed rape, and thus affecting the rapeseed yield and quality (Champolivier and Merrien, 1996; Jensen et al., 1996; Zhang et al., 2011). It has been a crucial limitation for oilseed rape production in this region. According to the presented findings, subsurface fertilization may be a useful management strategy to improve or stabilize yield of oilseed rape when the seasonal drought occurs. 4.3. Determination of relatively proper fertilizer placement depth Based on the results of nutrient uptake and seed yield in present study, both 10 cm and 15 cm are relatively proper fertilizer placement depth when the practice of banding fertilizer is used in oilseed rape production. But considering the factor that 15 cm deep fertilization may require higher mechanical power input, and thus resulting in higher cost of production, 10 cm deep fertilization should be recommended in actual farming. Acknowledgments The study was supported by Specialized Research Fund for the Doctoral Program of Higher Education (20120146120021), the Earmarked Fund for China Agriculture Research System (CARS13), the Fundamental Research Funds for the Central Universities (2013PY113), the Key Project of National Science & Technology Support Plan (2010BAD01B05), and the Program for Changjiang Scholars and Innovative Research Team in University of China (IRT1247). References Bao, S.D., 2000. Soil Agricultural-Chemical Analysis. China Agricultural Press, Beijing, China, pp. 264–267 (in Chinese). Böhm, W., 1979. Methods of Studying Root Systems. Springer, New York. Borges, R., Mallarino, A.P., 2001. Deep banding phosphorus and potassium fertilizers for corn managed with ridge tillage. Soil Sci. Soc. Am. J. 65, 376–384. Caldwell, M.M., Richards, J.H., 1989. Hydraulic lift: water efflux from upper roots improves effectiveness of water uptake by deep roots. Oecologia 79, 1–5. Cassman, K.G., 1999. Ecological intensification of cereal production systems: yield potential, soil quality, and precision agriculture. Proc. Natl. Acad. Sci. USA 96, 5952–5959. Cassman, K.G., Dobermann, A., Walters, D.T., Yang, H., 2003. Meeting cereal demand while protecting natural resources and improving environmental quality. Annu. Rev. Environ. Resour. 28, 315–358. Champolivier, L., Merrien, A., 1996. Effects of water stress applied at different growth stages to Brassica napus L. var. oleifera on yield, yield components and seed quality. Eur. J. Agron. 5, 153–160. Cheng, W., Nakajima, Y., Sudo, S., Akiyama, H., Tsuruta, H., 2002. N2 O and NO emissions from a field of Chinese cabbage as influenced by band application of urea or controlled-release urea fertilizers. Nutr. Cycl. Agroecosyst. 63, 231–238. Drew, M.C., 1975. Comparison of the effects of a localized supply of phosphate, nitrate, ammonium and potassium on the growth of the seminal root system, and the shoot, in barley. New Phytol. 75, 479–490. Farmaha, B.S., Fernández, F.G., Nafziger, E.D., 2013. Distribution of soybean roots, soil water, phosphorus and potassium concentrations with broadcast and subsurface-band fertilization. Soil Sci. Soc. Am. J. 76, 1079–1089. FAOSTAT, 2014. FAO Statistics Division. Available from: http://faostat3.fao.org/faostat-gateway/go/to/download/Q/*/E. Fernández, F.G., White, C., 2012. No-till and strip-till corn production with broadcast and subsurface-band phosphorus and potassium. Agron. J. 104, 996–1005. Hammer, G.L., Dong, Z., McLean, G., Doherty, A., Messina, C., Schusler, J., Zinselmeier, C., Paszkiewicz, S., Cooper, M., 2009. Can changes in canopy and/or root system architecture explain historical maize yield trends in the US corn belt? Crop Sci. 49, 299–312. Hodge, A., 2004. The plastic plant: root responses to heterogeneous supplies of nutrients. New Phytol. 162, 9–34. Hodge, A., 2006. Plastic plants and patchy soils. J. Exp. Bot. 57, 401–411. Hodge, A., 2009. Root decisions. Plant Cell Environ. 32, 628–640. Huang, W.H., Sui, Y., Yang, X.G., Dai, S.W., Li, M.S., 2013. Characteristics and adaptation of seasonal drought in southern China under the background of climate change. III. Spatiotemporal characteristics of seasonal drought in southern China based on the percentage of precipitation anomalies. Chin. J. Appl. Ecol. 24, 397–406 (in Chinese with English abstract). Jensen, C.R., Mogensen, V.O., Mortensen, G., Fieldsend, J.K., Milford, G.F.J., Andersen, M.N., Thage, J.H., 1996. Seed glucosinolate, oil and protein contents of
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