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Study on the Optimum N Rates Under Spring Cabbage-Maize-Winter Cabbage Rotation System
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Agricultural Sciences in China
2007, 6(11): 1322-1329
ScienceDirect
November 2007
Study on the Optimum N Rates Under Spring Cabbage-Maize-Winter Cabbage Rotation System HE Chum-long, GUO Xi-sheng, WANG Weng-junand WU Ji The Soil and Fertilizer Institute, Anhui Academy of Agricultural Sciences, Hefei 230031, P.R.China
Abstract In this paper, field trials in two soils with different N,, were conducted to study the effects of mineral N content (N,,) in soil on the maximum yield N rate (MYNR), N recovery of cabbage under spring cabbage-maize-winter cabbage rotation system, and the correlation of N fertilization with cabbage yield and quality, and to provide the theoretical basis for N recommendation for high-yield, quality, and safety production of vegetables. The effects of six N rates of 0, 90, 180, 270, 360, and 450 kg ha-1 on the yield, N recovery of spring cabbage, maize, and winter cabbage, water-soluble sugar, Vc, and nitrate content of vegetables were observed. The results showed that soil N,, had a remarkable influence on the MYNR in the first spring cabbage season. The MYNR for spring cabbage lessened in the soil with high N,,. Soil N,, could be helpful to N recommendation only for the seasonal growing crop because its effects on the following crop yield was less with the active transformation of soil Nmn. The farmer's practice was 1.8-3.2 times higher than the MYNR of cabbage resulted in the nitrate enrichment of groundwater. Both N application rate and N,, in the soil profile affected N recovery, whereas, the relay intercropping maize in the cabbage field increased the N recovery at a higher N application rate. Lower N rate (less than 90 kg ha-1) improved the yield and quality of cabbage at the same time; higher N rates increased cabbage yield, but decreased the quality; extremely high N rates of application deceased both yield and quality of cabbage. It was concluded that the soil N,, had close correlations with MYNR and N recovery of the seasonal growing cabbage. Although the residual effects of the N fertilizer were obvious in Shajiang black meadow soil, cabbage-maize rotation increased the N recovery in treatments with higher N rates. Considering the effects of N rates on cabbage yield and quality, it is necessary to reduce the N rate and lower the yield target for obtaining a better quality of vegetable produce.
Key words: cabbage, rotation system, N rate, Shajiang black meadow soil
INTRODUCTION Due to the large requirements for water and fertilizer and the obvious effects of N on vegetable growth, the overuse of N fertilizer in pursuit of benefit resulted in the degradation of vegetable quality, eco-environment deterioration, and reduction in economic efficiency. It is important to study the optimum N application rate in
vegetable cropping system for the quality and highyielding vegetable production, quality of human living improvement, and ecological environment protection. The popular overuse of fertilizer in vegetable production in China, especially the N fertilizer,has led to the nitrate content in produces exceeding the safety standard and increasing environmental hazards to groundwater (Shen 1990; Chen and Zhang 1996; Zhang et al. 2002). Because the transformations of N in farmland eco-
This paper is translated from its Chinese version in Scientia Agricultura Sinica. HE Chuan-long, Professor, Tel: +86-551-2160243.E-mail: hc160128 @ yahoo.ccm.cn
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Studv on the ODtimum N Rates Under SDring Cabbage-Maize-Winter Cabbage Rotation Svstem
system are complicated, and many mechanisms have not been fully understood up to now, only semiquantified N recommendations are adopted in actual production (Zhu 1981; Zhang et al. 1988). Recently, there have been some studies on Nm,oas a fertilizer recommendation index for seeking the fully quantified N fertilization technique. The N recommendations for wheat and vegetables in the northern China dryland, depending on soil Nm to some extent, have solved the previous N overuse problems caused by irrational fertilization based on the experiences (Ziegler et al. 1996; Liao et al. 2001). Many researches on N application under different crop rotation systems are concentrated on the grain crops. For example, the results of Marrow plot experiment, Illinois University, show that the N losses in a plot with continuous growth of maize are hugest, whereas are lowest in a plot of maize-oat-clover rotation. Tian et al. (2007) has recently reported that crop rotation can improve the N nutrition in soils with low N content. Taking a 0-20 cm layer as the effective zone of plant nutrient absorption to evaluate soil N balance in winter wheat-summer maize rotation, Wang et al. (2006) has found that the soil residual Nmnhas significant effects on crop yield and N fertilizer responses. Residual soil N of a previous cropping season could remarkably promote the growth and reduce the seasonal N recovery of the later crops. Large N rate or overuse of N could even decrease the yield. Some reports on vegetable and deep-root grain crop rotation mainly focused on the role of vegetable and grain crop rotation in the amelioration of secondary salinization and nitrate accumulation to protect land (Zhang et al. 1995; Wang 1998; Du et al. 2005; Meng et al. 2006). Generally, proper N application could significantly increase the content of soluble solids and N containing substances (amino acid and protein), organic acid, and carotene in vegetable produces, whereas, overuse of N decreased the content of N-free nutrition compounds, such as, Vc, total sugar, and soluble sugar (Ren et al. 2004). The studies on the N rate of Chinese cabbage indicated that, within the
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optimum economic N rate of 310 kg ha-', the nitrate content in the produce and the apparent N losses in the soil-plant system increased linearly with the N rate increasing, which suggested that the yield response of Chinese cabbage to N fertilization could not harmonize with the quality improvement and environment impacts (Li et al. 2003). Although there have been many researches concentrated on the effects of N fertilizer on the yield, quality, and fertilizer recovery, soil Nmin-basedN recommendation for seasonal growing vegetables and grain crops, as well as vegetable-deep root grain crop rotation on soil salt and nitrate, few has been reported on the effects of different N rate in soils with different Nminunder spring cabbage-maize-winter cabbage rotation system. The present field trials are designed to study the effects of N application on the yield, quality, and N recovery of the soils with different Nmin,to demonstrate the effects of soil N,,, on MYNR, N recovery of different crops under spring cabbage-maizewinter cabbage rotation system, and the correlation of N rates with qualities of cabbage produce, so as to provide N application technique for good quality, highyield, and safe production.
MATERIALS AND METHODS Experiment soil and site Field trials were conducted in 2005 and 2006, at the Madian Experimental Station, Anhui Academy of Agricultural Sciences, Mengcheng County, Anhui Province, China. The test soil type was Shajiang black meadow soil. The basic properties of the test soils are shown in Table 1.
The design of treatments The same six N rates were designed for spring cabbage and winter cabbage: (1) CK, 0 kg ha-'; (2) 90 kg ha-';
Table 1 The agrochemicalproperties of the experimental soils Trial 1 2
Organic matter (g kg-I) 13.2 14.6
Total N (g kg-1) 0.98 1.18
Readily available P (mg kg-1) 41.3 41.8
Readily available K (mg kg-1) 131.9 165.9
NO,--N (mgkg 1) 23.9 40.7
NH,+-N (mg kg I ) 7.4 23.9
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(3) 180 kg ha-'; (4) 270 kg ha-'; (5) 360 kg ha-'; and (6) 450 kg ha-'. Each treatment received P20, 90 kg ha-' and K,O 225 kg ha-'. For maize, 90 kg N ha-' was applied to all treatments except the CK. The plot area of trial 1 was 30 m2 with four replications. The varieties were Zhonggan 11 (spring cabbage), Tunyu 1 (maize), and Huannan Xinfeng (winter cabbage). The plot area of trial 2 was 40 m2 with three replications. The varieties of crops were 8132 (spring cabbage), Zhengdan 958 (maize), and Shanghai Xinfeng (winter cabbage). Sixty percent of N as basal dressing was applied on the furrows of the ridges, and 40% of N as top dressing in the point application for spring cabbage. For maize, N was applied at the initial tasseling stage. For winter cabbage, 50% of N was applied as basal dressing, and the remaining N as top dressing in two splits at the initial and middle stages of heading by point application, respectively. All P and K fertilizers were applied as basal dressing. The fertilizer sources were urea (N, 46%), single superphosphate (P,O,, 12%), and potassium chloride (K20, 60%). The soils of the plough layer were collected before experiment for analysis of soil organic matter, total nitrogen, readily available P, and K. Soils from 0-20, 20-40, and 40-60 cm were collected for analysis of N,. (NO,--N and NHl-N). The fresh produce samples of spring cabbage and winter cabbage before harvest were collected for analysis of Vc, soluble sugar, and nitrate. The dry plant samples of cabbage and maize were collected for testing of N.
Analytical methods 2, 6-Dichlorophenol indophenol titration was used for analysis of Vc content of fresh produce samples of cabbage; HC1 hydration-Cureduction was used for direct titration for soluble sugar; phenol-disulfonicacid method
was used for nitrate content. Water and 2 mol L 1KCl solution were used for extraction of soil NO,--N and NH,+-N, respectively. Phenol-disulfonic acid method was used for measuring NO,--N and indigo phenol blue spectrophotmetry for measuring NH,+-N. The plant samples were digested with H,S04-H,02 and used Kjeldahl's method for N content. The routine methods were used for analysis of soil organic matter, total N, readily available P and K (Agrochemistry Specialized Committee of Society of Chinese Soil Science 1983).
RESULTS The yield responses of springfwintercabbageand maize to N fertilizer The yield responses of spring cabbage to N fertilizer The average N application rates for each of the spring and winter cabbages by local vegetable growers were 555 kg ha-', which led to a large accumulation of mineral nitrogen in the soil. Soil Nm, (NO,--N and NH,+-N) in 0-60 cm-soil layer at trials 1 and 2 were 142.2 and 244.0 kg ha-', respectively, based on the soil analysis before experiment. Our experiment results showed that different soil N- had considerable influence on the MYNR of the spring cabbage. Table 2 indicates that the spring cabbage yields of the two trials were the highest at NlS0, with 25.0 and 19.2% increments over control for trials 1 and 2, respectively. The yield of spring cabbage decreased, whereas, the N rates further increased. The nitrogen rate for reaching maximum yield (25 094.3 kg ha-') of trial 1 was 236.2 kg ha-', by the fertilizer response equation, y = 20 3 16+ 40.4627~- 0.085662 (R2= 0.9171). The maximum economic nitrogen rate was 165.8 kg hx' (the fertilizer N price: 3.91 RMB yuan kg-', price of spring cabbage: 0.32
Table 2 The effect of different N rates on crop yields in the rotation system (kg ha-') N rate (kg ha-I)
0 90 180 270 360 450
Trial 1 Spring cabbage 20333 c 22917 b 23313 b 25 375 a 22875 b 21 688 bc
Trial 2
Maize
Winter cabbage
Spring cabbage
Maize
Winter cabbage
5796 c 6229 bc 6 500 ab 6798 a 6446 ab 6283 abc
45 750 d 73250 c 78417 b 85 125 a 87 958 a 80 167 b
28 188 d 32458 b 33 596 a 29458 c 28313 d 24533 e
6635 d 6825 cd 7 015 bc 7394 a 7258 a 7 177 ab
55 792 d 84833 c 87 667 bc 90083 ab 92 500 a 86 167 bc
"be small letters mean significance at 5% level. The same as below.
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Study on the Optimum N Rates Under Spring Cabbage-Maize-Winter Cabbage Rotation System
RMB yuan kg-'). The fertilizer response equation of trial 2 wasy=28974+37.929x - 0.10892 (RZ=0.8702). The maximum yield of 32 276.6 kg ha-' could be achieved at the rate of 174.2 kg N ha-'. The maximum economic N rate was 118.1 kg ha-'. It indicated that the MYNR and economic N rates for spring cabbage varied with soils containing different Nmin. The MYNR for spring cabbage at trial 1 was 35.6% higher than that at trial 2 because of relatively low soil N,, at trial 1. For trial 1, N application rate of farmer's practice was 2.4 times higher than MYNR, 3.4 times higher than the economic yield N rate; was 3.2 times and 4.7 times higher for trial 2, respectively. Obviously, the nitrogen fertilizer was seriously overused by vegetable growers. The response of different N rate treatments on following maize yield With N split application of 90 kg ha-' at the tasseling stage, the yield of followingmaize at the treatment N,,, was the highest. The maximum yields of trials 1 and 2 were 6 798 and 7 393.8 kg ha-', 17.3 and 14.9% of the increase over the control, respec5ely. The extremely high N rate was not only unfavorable to the yield of spring cabbage, but also reduced f J o w i n g maize yield. The maize yield decreased at the treatment of 360 kg N ha-' in spring cabbage season. The N rate (555 kg ha-') of farmer's practice in spring cabbage season had a negative impact on following maize. If MYNR was taken (trial 1: 236.2 kg ha-', trial 2: 174.2 kg ha-') as the N application rate in the spring cabbage, split application of 90 kg N ha-' could not obtain the maximum yield. Further studies on N application of maize were needed for exploring the yield potential of maize. The response of different N rates on winter cabbage yield The yields of winter cabbage at treatment N,,, were the highest in both trials (Table 2). The yield of winter cabbage at trials 1 and 2 were 92.3 and 65.8% of increases compared with the control, respectively. The reason for higher yield increases in winter cabbage than in spring cabbage might be that they had no N fertilizer applied for three seasons, and the soil N supply exhausted gradually by seasons in control. The N fertilizer response equation of winter cabbage at trial 1 was y=48 129+255.08x-O.4096x2(R2=0.9601). The maximum yield (87843 kg ha-') could be obtained at the N rate of 3 11.4 kg ha-'. The conventional N rate was 1.9
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times as high as that of MYNR. The N fertilizerresponse regression equation at trial 2 was y = 59 549 +233.41~0 . 3 9 3 6 ~(R2=0.9048). ~ The maximum yield (94 151 kg ha-') could be obtained at the N rate of 296.5 kg ha-'. The conventional N rate was 1.8 times as MYNR. The MYNR of winter cabbage was higher than that of spring cabbage. This might be because of the higher yield and N requirements of winter cabbage. The MYNR of winter cabbage at trial 1 was only 5% higher than that at trial 2, which implied that the influence of different soil Ndn at the beginning of the experiment on the winter cabbage yield reduced.
The effect of nitrogenon the quality of cabbage Lower N rate increased the soluble sugar and Vc content of cabbage, whereas, higher rate of N decreased the content of soluble sugar and Vc (Table 3). The highest soluble sugar contents of spring cabbage at trials 1 and 2 were obtained at the treatments of N,, and NI8,, with 20.5 and 16.7% of increase over the control. The highest Vc contents were obtained at treatment N,,, with 16.5 (trial 1) and 4.5% (trial 2) of increase over the control, respectively. The highest soluble sugar contents of winter cabbage at the two trials were at the treatments of N,,, with 11.5% (trial 1) and 8.8% (trial 2) of increase over the control. The highest Vc content of winter cabbage was obtained at the treatments of N,, and N,,, at trials 1 and 2, with increase of 13.0 and 9.4% over the control. The N rates for better quality parameters of vegetable produces were much lower than those of MYNR. Compared to the control, NO,--N content of spring cabbage with the N rates of 90, 180, 270, 360, and 450 kg ha-' increased by 26.5, 50.9, 75.2, 149.3, and 138.3% at trial 1, and 44.7, 45.8, 67.3, 178.2, and 185.0% at trial 2. NO,--N in winter cabbage increased by 32.9, 44.6, 53.4, 77.6, and 68.2% at trial 1, and 21.0, 24.6,25.5, 39.3, and 46.3% at trial 2. The NO; -N content of cabbage increased with the N rates. The effects of N rates on the NO;-N content of spring cabbage were more obvious than those of the winter cabbage. The NO,--N content of winter cabbage increased relatively slowly and gently with the N rates, whereas, NO,--N content of spring cabbage increased slowly at N rate less than 270 kg ha-', and sharply at
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the rate exceeding 360 kg N ha-'.
The effects of N rate on N recovery of plant in rotation system The results of Table 4 indicate that the N recovery decreases with the N rates at both trials. The N recovery in the treatment of N,, was 2.4-3.3 times as high as that in treatment of N,,,. The soil Nminalso had an influence on the N recovery. The average N recoveries for the first, second, and third crops at trial 1 were 71.4, 15.7, and 10.8% higher than those at trial 2. The N recoveries of plants were lower in the soils with higher Nmin.The effect of soil Nminon N recovery was the most obvious in the first crop of spring cabbage, and reduced gradually in the second and third crops. The obvious influence of soil Nminon the N recovery of seasonal growing crops and lessening in the following crops was due to the rapid transformation of soils N,io
and the losses in many pathways, which were similar to the influence of soil Nminon the MYNR of spring cabbage and winter cabbage. The much higher N recoveries of maize with treatment of higher N rates than that of spring cabbage revealed that the spring cabbage intercropping with maize was an effective growing model for increasing N recovery. To shallow root crops, such as cabbage, it was difficult to utilize the huge amount of N that leached downward to the soil layer, below 30 cm, which possibly caused the pollution of groundwater if not be fully used. Intercropping with maize whose roots extend 2 m deep (Zhang G L and Zhang S 1998) increased N recovery and reduced the hazards of groundwater pollution by using the residual N from the cabbage season.
DISCUSSION Many researches show that the loss and residues of N
Table 3 The effects of different N rates on the quality of cabbage Trial 1
N rate (kg ha-1)
Trial 2
vc (mg kg-9
NO, -N (mg kg-9
87 e llOd 131 c 152 b 215 a 207 a 133 d 177 c 193 b 205 b 237 a 224 a
Spring cabbage
0 90 180 270 360 450
17.1 c 20.6 a 19.1 b 19.4 ab 19.3 ab 19.0 b
383.0 b 446.0 a 363.0 c 311.0 e 382.0 bc 340.0 d
Winter cabbage
0 90 180 270 360 450
53.7 c 59.9 a 59.7 a 56.1 b 52.1 c 51.7 c
702.0 b 793.0 a 724.0 b 673.0 c 655.0 c 657.0 c
Sugar (g kg-1) 26.4 c 28.8 b 30.8 a 27.0 c 27.2 bc 16.0 d 53.3 bc 58.0 a 54.5 b 53.5 bc 53.6 b 50.9 c
Vc (mg kg-I)
NO,--N (mg kg-1)
375.0 a 392.0 a 329.0 c 348.0 b 297.0 d 305.0 d 862.0 c 873.0 b 943.0 a 824.0 d 681.0 e 631.0 f
79 d 115c 116 c 133 b 220 a 226 a 146 d 177 c 182 c 183 bc 204 ab 214 a
Table 4 The effects of different N rates on N recovery under cabbage-maize rotation system Maize
Spring cabbage N rate (kg ba-l) Trial 1
Trial 2
0 90 180 270 360 450 0 90 180 270 360 450
N accumulation (kg ha-1) 81 e 114d 146 c 158 b 172 a 152 bc 108 e I32 d 142 c 150 b 161 a 144 bc
N recovery
6) 37.2 a 36.5 a 28.5 b 25.3 c 15.8 d 26.2 a 19.2 b 15.7 c 14.6 c 7.9 d
N accumulation (kg ba-1) 61 c 85 b 87 b 94 a 99 a 94 a 61 e 83 d 94 c 116 b 124 a 116 b
Winter cabbage N recovery (46) 31.4 ab 31.8 a 29.2 bc 27.6 c 18.4 d 25.4 a 24.8 a 26.8 a 25.8 a 16.8 b
N accumulation (kg ba-1) 70 e 111 d 131 c 191 a 203 a 165 b 91 e 146 d 158 c 195 a 200 a 177 b
N recovery (%)
36.6 a 34 b 36.8 a 32.5 c 20.2 d 37.6 a 29.9 bc 32 b 27.8 c 18 d
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Study on the Optimum N Rates Under Spring Cabbage-Maize-Winter Cabbage Rotation System
in soil are low when N is applied at a lower rate. At an irrationallyhigher N application rate, the residual N and N losses are large. The prevention of N overuse is essential to the issues of N management in the current high-yielding situation (Ju et al. 2002). There exists the popular N overuse in vegetable production. Yuan et al. (2000) reported that the NO,--N accumulation was up to 1000 kg ha-' at 200-400 cm layers in a soil growing vegetables. The large accumulation of mineral nitrogen in the soils in our experiments is because of growing vegetables for many years and higher N application, which has led to only 19.2-25.0% of yield increase, and decrease of crop yield in response to N fertilization. The groundwater NO,--N contents are 11.6-93.1 mg L-' with an average of 45.6 mg L-' according to this survey, 94.4% of which exceed the national standards of China (20 mg L-' NO,--N). The N recommendation has an importance in lowering N uses for cabbage production. The rotation of vegetables with grain crop can ameliorate many stresses in vegetable growing soil. Comparisons of soil salt and NO,--N contents in two cropping models of the single vegetable cropping and vegetable-grain crop rotation in a vegetable growing area indicate that the vegetable-maize rotation reduces the salt content and electric conduction (EC) in 0-20 cm layer by 43 and 36%, respectively, and NO,--N by 32% in 0-60 cm soil over a single vegetable system. Vegetable and maize rotation has remarkably decreased the accumulation of salt and nitrate in the soil of the greenhouse (Meng et al. 2006). There have been reported that the soil EC has declined from 2.5 to 1.O ms cm-I after cultivation for 55 d in summer (Wang 1998),and the soil salt content has effectively decreased by one season of maize cropping in summer (Zhang et al. 1995; Du et al. 2005). The experiments here suggest that because the deep-rooted maize can take up the mineral nitrogen leached to deeper soil layer, the rotation of cabbage-maize considerablyincreases the N recovery of plants with higher N fertilizer, and reduces the N pollution to groundwater. Because the N uptake of the plant is closely correlated with the original soil nitrate (Ye and Li 2002), the N application should take the N supply of soil into account. Using soil N- is a newly developed technique for N fertilizer recommendation (Zhang et al. 2002). N recommendation by European KNS-system
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(Kulturbegleitendes Nmn Sollwerte) is based on soil inorganic nitrogen (Nmn= NH,+-N+ NO,--N) detection, in consideration of plant N uptakes at different growth stages, the lowest limitation of Nmnat different growth periods, and corresponding root length of the plant. The reasearchers from the China Agricultural University have successfully adopted the N recommendation by using N,,,,,,for wheat and vegetables in the dryland of northern China (Chen 1997; Liao et al. 2001). These experiments indicate that the soil Nmnis closely correlated with the MYNR of cabbage. The N application rates for obtaining maximum yield and economic yield at trial 1 are higher than those at trial 2 because of relatively low soil Nmn. However, the soil Nmnhas obvious influence only on the N rate of the seasonal growing crop. Deep studies on the correlation of soil Nmnwith the cabbage yield and N application rate at different layers can make the possibility to quantify N fertilizer recommendation for spring cabbage-maize-wintercabbage, which become essential to N fertilizer saving, yield increase, and ecological environment protection. In China, the rapid growth of N application has led to little increment in soil total nitrogen in the farmland because of serious losses of N. Generally, the N recovery decreases, while the N losses and soil residual N increase with the raise of N application rate (Zhu 2000). In research on the fates of N in winter wheatsummer maize rotation, Ju et al. (2003) found that 20.9-48.4% of fertilizer nitrogen remained at 0-100 cm soil layer after one season of crop, which could be used by the following crops. These results reveal that the N applied in the spring cabbage season has obvious residual effects on maize. A higher N rate in a previous crop not only reduces the spring cabbage yield, but the maize yield too. The obvious residual effects of N in Shajiang black meadow soil might contribute to a higher content of clay dominated with 2: 1 Montmorillonite, the ammonium fixation and high CEC (cation exchange capacity) (Zhang 1988; Wang et al.2001). The quality of vegetable produce becomes increasingly important. However, the target of yield and quality cannot be coordinated at the same time. After summarizing the relation of the N application with vegetable yield and quality parameters, Haedter (1997) has pointed out that as far as the yield and nitrate
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content of vegetables are concerned, it is difficult to harmonize them. There have been some arguments that the N fertilizer has no significant negative influences on Vc content, even if one increases the Vc content in many vegetable species at the optimum N rate. Only higher N rate can result in the reduction of Vc content (Sorensen 1993; Chen et al. 2003). For most of the vegetables, increasing N rate reduces the Vc content in the produce, because the N content of the cabbage head is negatively correlated with Vc and sugar content (Guo et al. 2004). The results of these researches indicate that proper N application (N rate less than 90 kg ha-') increases the yield and quality at the same time, and a further increase in N rate increases the cabbage yield, although decreases the quality. An extremely high N rate decreases both yield and quality of cabbage. Therefore, the reduction of N application rate can obtain a better quality at the expense of lowering the yield.
CONCLUSION The N fertilization of the farmer's practice was 1.8-2.3 times greater than the MYNR of cabbage, which led to the groundwater nitrate content exceeding the standard in the vegetable production area. Soil Nminhad an influence on the MYNR and N recovery of growing cabbage, but little effect on the following crop, and could be taken as the basis for N recommendation of cabbage. The cabbage-maize rotation increased the N recovery of plants, with higher N treatment in Shajiang black meadow soil that had obvious N residual effects. Lower N rate (less than 90 kg ha-') could increase yield and quality simultaneously; increasing the N rate could increase the yield, but decrease the quality; and extremely high N rate decreased both the yield and quality of cabbage. Therefore, the reduction of N rate and yield could assure better quality of vegetable produce in vegetable production.
Acknowledgements This research was sponsored by Key Technologies R&D Program of Anhui Province during the 10th FiveYear Plan Period, China (040030342). The authors thank Zhu Laihong and Wang Hongbing, graduated in 2006 from Anhui Agricultural University, China, for
conducting the plant analysis.
References Agrochemistry Specialized Committee of Society of Chinese Soil Science. 1983.AnalyticalManuaIsof SoilAgro-Chemistry. Science Press, Beijing. (in Chinese) Chen J S, Tang S H, Zhang F B, Xu P Z, Zhang Z X. 2003. Effects of N and S fertilizer combination on yield and quality of floweringChinesecabbage. Chinese Journal of Soil Science, 34, 36-39. (in Chinese) Chen X P. 1997. Introduction to the fertilizer recommendation project by soil and plant analysis. Soils and Fertilizers, 151, 46-47. (in Chinese) Chen X P, Zhang F S. 1996. The problems and countermeasures of vegetable fertilization in Beijing. Journal of China Agricultural University, 1,63-66. (in Chinese) Du L F, Liu W K, Liu J L. 2005. Salt status of greenhouse soil and their influencing factors in Hebei Province. Soils and Fertilizers, 197, 17-21. (in Chinese) Guo X S, Zhu H B, Wang W J, Ye S Y, Wu J, Wu L S. 2004. Effects of different rates of nitrogen and potash on yield and quality of cabbage.Plant Nutrition and Fertilizer Science, 10, 161-166. (in Chinese) Haerdter R. 1997. Plant nutrition and fertilizationfor high-yielding and quality of vegetables. In: Xie J C, Chen J X, eds, Soil Fertility of Vegetable Garden and Rational Fertilization of Vegetables. Hohai University Press, Nanjing. pp. 1-11. (in Chinese) Ju X T, Liu X J, Zou G Y, Wang Z H, Zhang F S. 2002. Evaluation of nitrogen loss way in winter wheat and summer maize rotation system. Scientia Agn'cultura Sinica, 35, 1493- 1499. (in Chinese) Ju X T, Pan J R, Liu X J, Zhang F S. 2003. Study on the fate of nitrogen fertilizer in winter wheathummer maize rotation system in Beijing suburban. Plant Nutrition and Fertilizer Science, 9,264-270. (in Chinese) Li J L, Chen X P, Li X L, Zhang F S. 2003. Effect of N fertilization on yields, nitrate content and N apparent losses of Chinese cabbage. Acta Pedologica Sinica, 40,261-266. (in Chinese) Liao X Y, Zhang Y Z, Liu X J, Chen X P, Zhang F S. 2001. The current status and prospects of research in nitrogen behavior in soils. Southwest China Journal of Agricultural Sciences, 14, 94-98. (in Chinese) Meng Y L, Liu Z Y, Li J. 2006. Effects of vegetable-grainrotation on salt and nihic nitrogen contents in greenhouse soil. Journal of Henan Agricultural Sciences, 382, 81-87. (in Chinese) Ren H Z, Yuan L P, Me G Q, Zhang F M. 2004. Progress on the influence of nitrogen nutrition to vegetables quality. Journal of Huazhong Agricultural University, 35, 194-197. (in
02007, CAAS. All rights reserved.Published by ElsevierLM.
Study on the Optimum N Rates Under Spring Cabbage-Maize-WinterCabbage Rotation System Chinese) Shen H. 1990. Characteristics of element accumulation and transformationon vegetable farm soil of the suburbs of Beijing. Acta Pedologica Sinica, 27, 104-112. (in Chinese) Serensen J N. 1993. Use of the Nmin method for optimization of vegetable nitrogen nutrition.Acta Horticulturae,339,79-192. Tian X P, Xue J F, Han X R. 2007. Effects of long-term crop rotation and continuous cropping on nitrogen in albic soil. Journal of Soil and Water Conservation, 21, 185-187. (in Chinese) Wang X J. 1998. Analysis on secondary soil salinization in solar greenhouse. Northern Horticulture, 120, 12-13. (in Chinese) Wang X N, Wang Z H, Li S X. 2006. Soil nitrogen balance in winter wheat and summer maize rotation system on dry land of Loess Plateau. Plant Nutrition and Fertilizer Science, 12, 759-764. (in Chinese) Wang Z M, Zhu P L, Huang D M, Liu H Q, Jiang L R. 2001. Transformation of straw ”N in the submerged soil. Jiangsu Journal of Agricultural Sciences, 17, 236-240. (in Chinese) Ye Y L, Li S X. 2002. The influence of initial nitrate-nitrogen leaching on soil nitrate content and wheat nitrogen uptake. Agricultural Research in the Arid Areas, 20, 26-29. (in Chinese) Yuan X M, Tong Y A, Yang X Y,Li X L, Zhang F S. 2000. Effect of organic manure. on soil nitrate nitrogen accumulation. Soil and Environmental Sciences, 9, 197- 200. (in Chinese) Zhang C L, Zhang Y D, Zhong Q S. 1995. The effects of different
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crops in rotation to reduce secondary salinization and continuous cropping obstacles in protected vegetable cultivation. Chinese Journal of Soil Science, 26,257-259. (in Chinese) Zhang G L, Zhang S. 1998. Development of research on nitrogen leaching in cropland. Soils, 30,291-297. (in Chinese) Zhang H Y, Chen Q, Tang L L, Li H F, Li X L, Liebig H P.2002. Comparison of conventional and recommended water and nitrogen practices on spinach growth and water and nitrogen usage. Plant Nutrition and Fertilizer Science, 8, 48-53. (in Chinese) Zhang J M. 1988. Shaijing black meadow soil productive potential and comprehensive amelioration. In: Zhang J M, ed, Study on Comprehesive Amelioration of Shaijing Black Meadow Soil. Anhui Science and Technology Press, Hefei. pp. 2-11. (in Chinese) Zhang S L, Zhu Z L, Xu Y H, Chen R Y, Li A R. 1988. Studies on the optimal rate of application of nitrogen fertilizer for rice and wheat in Taihu Lake. Soils, 20, 5-9. (in Chinese) Zhu Z L. 1981. General aspects of the study on soil and fertilizer nitrogen in Australia. Soils, 13, 199-201. (in Chinese) Zhu Z L. 2000. Loss of fertilizer N from plants-soil system and the strategies and techniques for its reduction. Soil and Environmental Sciences, 9, 1-6. (in Chinese) Ziegler J, Strohmeier K, Brand T. 1996. Nitrogen supply of vegetables based on the “KNS-system”. Acta Horticulturae, 428,223-233. (Edited by ZHANG Juan)
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Agricultural Sciences in China
2007, 6(11): 1322-1329
ScienceDirect
November 2007
Study on the Optimum N Rates Under Spring Cabbage-Maize-Winter Cabbage Rotation System HE Chum-long, GUO Xi-sheng, WANG Weng-junand WU Ji The Soil and Fertilizer Institute, Anhui Academy of Agricultural Sciences, Hefei 230031, P.R.China
Abstract In this paper, field trials in two soils with different N,, were conducted to study the effects of mineral N content (N,,) in soil on the maximum yield N rate (MYNR), N recovery of cabbage under spring cabbage-maize-winter cabbage rotation system, and the correlation of N fertilization with cabbage yield and quality, and to provide the theoretical basis for N recommendation for high-yield, quality, and safety production of vegetables. The effects of six N rates of 0, 90, 180, 270, 360, and 450 kg ha-1 on the yield, N recovery of spring cabbage, maize, and winter cabbage, water-soluble sugar, Vc, and nitrate content of vegetables were observed. The results showed that soil N,, had a remarkable influence on the MYNR in the first spring cabbage season. The MYNR for spring cabbage lessened in the soil with high N,,. Soil N,, could be helpful to N recommendation only for the seasonal growing crop because its effects on the following crop yield was less with the active transformation of soil Nmn. The farmer's practice was 1.8-3.2 times higher than the MYNR of cabbage resulted in the nitrate enrichment of groundwater. Both N application rate and N,, in the soil profile affected N recovery, whereas, the relay intercropping maize in the cabbage field increased the N recovery at a higher N application rate. Lower N rate (less than 90 kg ha-1) improved the yield and quality of cabbage at the same time; higher N rates increased cabbage yield, but decreased the quality; extremely high N rates of application deceased both yield and quality of cabbage. It was concluded that the soil N,, had close correlations with MYNR and N recovery of the seasonal growing cabbage. Although the residual effects of the N fertilizer were obvious in Shajiang black meadow soil, cabbage-maize rotation increased the N recovery in treatments with higher N rates. Considering the effects of N rates on cabbage yield and quality, it is necessary to reduce the N rate and lower the yield target for obtaining a better quality of vegetable produce.
Key words: cabbage, rotation system, N rate, Shajiang black meadow soil
INTRODUCTION Due to the large requirements for water and fertilizer and the obvious effects of N on vegetable growth, the overuse of N fertilizer in pursuit of benefit resulted in the degradation of vegetable quality, eco-environment deterioration, and reduction in economic efficiency. It is important to study the optimum N application rate in
vegetable cropping system for the quality and highyielding vegetable production, quality of human living improvement, and ecological environment protection. The popular overuse of fertilizer in vegetable production in China, especially the N fertilizer,has led to the nitrate content in produces exceeding the safety standard and increasing environmental hazards to groundwater (Shen 1990; Chen and Zhang 1996; Zhang et al. 2002). Because the transformations of N in farmland eco-
This paper is translated from its Chinese version in Scientia Agricultura Sinica. HE Chuan-long, Professor, Tel: +86-551-2160243.E-mail: hc160128 @ yahoo.ccm.cn
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Studv on the ODtimum N Rates Under SDring Cabbage-Maize-Winter Cabbage Rotation Svstem
system are complicated, and many mechanisms have not been fully understood up to now, only semiquantified N recommendations are adopted in actual production (Zhu 1981; Zhang et al. 1988). Recently, there have been some studies on Nm,oas a fertilizer recommendation index for seeking the fully quantified N fertilization technique. The N recommendations for wheat and vegetables in the northern China dryland, depending on soil Nm to some extent, have solved the previous N overuse problems caused by irrational fertilization based on the experiences (Ziegler et al. 1996; Liao et al. 2001). Many researches on N application under different crop rotation systems are concentrated on the grain crops. For example, the results of Marrow plot experiment, Illinois University, show that the N losses in a plot with continuous growth of maize are hugest, whereas are lowest in a plot of maize-oat-clover rotation. Tian et al. (2007) has recently reported that crop rotation can improve the N nutrition in soils with low N content. Taking a 0-20 cm layer as the effective zone of plant nutrient absorption to evaluate soil N balance in winter wheat-summer maize rotation, Wang et al. (2006) has found that the soil residual Nmnhas significant effects on crop yield and N fertilizer responses. Residual soil N of a previous cropping season could remarkably promote the growth and reduce the seasonal N recovery of the later crops. Large N rate or overuse of N could even decrease the yield. Some reports on vegetable and deep-root grain crop rotation mainly focused on the role of vegetable and grain crop rotation in the amelioration of secondary salinization and nitrate accumulation to protect land (Zhang et al. 1995; Wang 1998; Du et al. 2005; Meng et al. 2006). Generally, proper N application could significantly increase the content of soluble solids and N containing substances (amino acid and protein), organic acid, and carotene in vegetable produces, whereas, overuse of N decreased the content of N-free nutrition compounds, such as, Vc, total sugar, and soluble sugar (Ren et al. 2004). The studies on the N rate of Chinese cabbage indicated that, within the
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optimum economic N rate of 310 kg ha-', the nitrate content in the produce and the apparent N losses in the soil-plant system increased linearly with the N rate increasing, which suggested that the yield response of Chinese cabbage to N fertilization could not harmonize with the quality improvement and environment impacts (Li et al. 2003). Although there have been many researches concentrated on the effects of N fertilizer on the yield, quality, and fertilizer recovery, soil Nmin-basedN recommendation for seasonal growing vegetables and grain crops, as well as vegetable-deep root grain crop rotation on soil salt and nitrate, few has been reported on the effects of different N rate in soils with different Nminunder spring cabbage-maize-winter cabbage rotation system. The present field trials are designed to study the effects of N application on the yield, quality, and N recovery of the soils with different Nmin,to demonstrate the effects of soil N,,, on MYNR, N recovery of different crops under spring cabbage-maizewinter cabbage rotation system, and the correlation of N rates with qualities of cabbage produce, so as to provide N application technique for good quality, highyield, and safe production.
MATERIALS AND METHODS Experiment soil and site Field trials were conducted in 2005 and 2006, at the Madian Experimental Station, Anhui Academy of Agricultural Sciences, Mengcheng County, Anhui Province, China. The test soil type was Shajiang black meadow soil. The basic properties of the test soils are shown in Table 1.
The design of treatments The same six N rates were designed for spring cabbage and winter cabbage: (1) CK, 0 kg ha-'; (2) 90 kg ha-';
Table 1 The agrochemicalproperties of the experimental soils Trial 1 2
Organic matter (g kg-I) 13.2 14.6
Total N (g kg-1) 0.98 1.18
Readily available P (mg kg-1) 41.3 41.8
Readily available K (mg kg-1) 131.9 165.9
NO,--N (mgkg 1) 23.9 40.7
NH,+-N (mg kg I ) 7.4 23.9
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(3) 180 kg ha-'; (4) 270 kg ha-'; (5) 360 kg ha-'; and (6) 450 kg ha-'. Each treatment received P20, 90 kg ha-' and K,O 225 kg ha-'. For maize, 90 kg N ha-' was applied to all treatments except the CK. The plot area of trial 1 was 30 m2 with four replications. The varieties were Zhonggan 11 (spring cabbage), Tunyu 1 (maize), and Huannan Xinfeng (winter cabbage). The plot area of trial 2 was 40 m2 with three replications. The varieties of crops were 8132 (spring cabbage), Zhengdan 958 (maize), and Shanghai Xinfeng (winter cabbage). Sixty percent of N as basal dressing was applied on the furrows of the ridges, and 40% of N as top dressing in the point application for spring cabbage. For maize, N was applied at the initial tasseling stage. For winter cabbage, 50% of N was applied as basal dressing, and the remaining N as top dressing in two splits at the initial and middle stages of heading by point application, respectively. All P and K fertilizers were applied as basal dressing. The fertilizer sources were urea (N, 46%), single superphosphate (P,O,, 12%), and potassium chloride (K20, 60%). The soils of the plough layer were collected before experiment for analysis of soil organic matter, total nitrogen, readily available P, and K. Soils from 0-20, 20-40, and 40-60 cm were collected for analysis of N,. (NO,--N and NHl-N). The fresh produce samples of spring cabbage and winter cabbage before harvest were collected for analysis of Vc, soluble sugar, and nitrate. The dry plant samples of cabbage and maize were collected for testing of N.
Analytical methods 2, 6-Dichlorophenol indophenol titration was used for analysis of Vc content of fresh produce samples of cabbage; HC1 hydration-Cureduction was used for direct titration for soluble sugar; phenol-disulfonicacid method
was used for nitrate content. Water and 2 mol L 1KCl solution were used for extraction of soil NO,--N and NH,+-N, respectively. Phenol-disulfonic acid method was used for measuring NO,--N and indigo phenol blue spectrophotmetry for measuring NH,+-N. The plant samples were digested with H,S04-H,02 and used Kjeldahl's method for N content. The routine methods were used for analysis of soil organic matter, total N, readily available P and K (Agrochemistry Specialized Committee of Society of Chinese Soil Science 1983).
RESULTS The yield responses of springfwintercabbageand maize to N fertilizer The yield responses of spring cabbage to N fertilizer The average N application rates for each of the spring and winter cabbages by local vegetable growers were 555 kg ha-', which led to a large accumulation of mineral nitrogen in the soil. Soil Nm, (NO,--N and NH,+-N) in 0-60 cm-soil layer at trials 1 and 2 were 142.2 and 244.0 kg ha-', respectively, based on the soil analysis before experiment. Our experiment results showed that different soil N- had considerable influence on the MYNR of the spring cabbage. Table 2 indicates that the spring cabbage yields of the two trials were the highest at NlS0, with 25.0 and 19.2% increments over control for trials 1 and 2, respectively. The yield of spring cabbage decreased, whereas, the N rates further increased. The nitrogen rate for reaching maximum yield (25 094.3 kg ha-') of trial 1 was 236.2 kg ha-', by the fertilizer response equation, y = 20 3 16+ 40.4627~- 0.085662 (R2= 0.9171). The maximum economic nitrogen rate was 165.8 kg hx' (the fertilizer N price: 3.91 RMB yuan kg-', price of spring cabbage: 0.32
Table 2 The effect of different N rates on crop yields in the rotation system (kg ha-') N rate (kg ha-I)
0 90 180 270 360 450
Trial 1 Spring cabbage 20333 c 22917 b 23313 b 25 375 a 22875 b 21 688 bc
Trial 2
Maize
Winter cabbage
Spring cabbage
Maize
Winter cabbage
5796 c 6229 bc 6 500 ab 6798 a 6446 ab 6283 abc
45 750 d 73250 c 78417 b 85 125 a 87 958 a 80 167 b
28 188 d 32458 b 33 596 a 29458 c 28313 d 24533 e
6635 d 6825 cd 7 015 bc 7394 a 7258 a 7 177 ab
55 792 d 84833 c 87 667 bc 90083 ab 92 500 a 86 167 bc
"be small letters mean significance at 5% level. The same as below.
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Study on the Optimum N Rates Under Spring Cabbage-Maize-Winter Cabbage Rotation System
RMB yuan kg-'). The fertilizer response equation of trial 2 wasy=28974+37.929x - 0.10892 (RZ=0.8702). The maximum yield of 32 276.6 kg ha-' could be achieved at the rate of 174.2 kg N ha-'. The maximum economic N rate was 118.1 kg ha-'. It indicated that the MYNR and economic N rates for spring cabbage varied with soils containing different Nmin. The MYNR for spring cabbage at trial 1 was 35.6% higher than that at trial 2 because of relatively low soil N,, at trial 1. For trial 1, N application rate of farmer's practice was 2.4 times higher than MYNR, 3.4 times higher than the economic yield N rate; was 3.2 times and 4.7 times higher for trial 2, respectively. Obviously, the nitrogen fertilizer was seriously overused by vegetable growers. The response of different N rate treatments on following maize yield With N split application of 90 kg ha-' at the tasseling stage, the yield of followingmaize at the treatment N,,, was the highest. The maximum yields of trials 1 and 2 were 6 798 and 7 393.8 kg ha-', 17.3 and 14.9% of the increase over the control, respec5ely. The extremely high N rate was not only unfavorable to the yield of spring cabbage, but also reduced f J o w i n g maize yield. The maize yield decreased at the treatment of 360 kg N ha-' in spring cabbage season. The N rate (555 kg ha-') of farmer's practice in spring cabbage season had a negative impact on following maize. If MYNR was taken (trial 1: 236.2 kg ha-', trial 2: 174.2 kg ha-') as the N application rate in the spring cabbage, split application of 90 kg N ha-' could not obtain the maximum yield. Further studies on N application of maize were needed for exploring the yield potential of maize. The response of different N rates on winter cabbage yield The yields of winter cabbage at treatment N,,, were the highest in both trials (Table 2). The yield of winter cabbage at trials 1 and 2 were 92.3 and 65.8% of increases compared with the control, respectively. The reason for higher yield increases in winter cabbage than in spring cabbage might be that they had no N fertilizer applied for three seasons, and the soil N supply exhausted gradually by seasons in control. The N fertilizer response equation of winter cabbage at trial 1 was y=48 129+255.08x-O.4096x2(R2=0.9601). The maximum yield (87843 kg ha-') could be obtained at the N rate of 3 11.4 kg ha-'. The conventional N rate was 1.9
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times as high as that of MYNR. The N fertilizerresponse regression equation at trial 2 was y = 59 549 +233.41~0 . 3 9 3 6 ~(R2=0.9048). ~ The maximum yield (94 151 kg ha-') could be obtained at the N rate of 296.5 kg ha-'. The conventional N rate was 1.8 times as MYNR. The MYNR of winter cabbage was higher than that of spring cabbage. This might be because of the higher yield and N requirements of winter cabbage. The MYNR of winter cabbage at trial 1 was only 5% higher than that at trial 2, which implied that the influence of different soil Ndn at the beginning of the experiment on the winter cabbage yield reduced.
The effect of nitrogenon the quality of cabbage Lower N rate increased the soluble sugar and Vc content of cabbage, whereas, higher rate of N decreased the content of soluble sugar and Vc (Table 3). The highest soluble sugar contents of spring cabbage at trials 1 and 2 were obtained at the treatments of N,, and NI8,, with 20.5 and 16.7% of increase over the control. The highest Vc contents were obtained at treatment N,,, with 16.5 (trial 1) and 4.5% (trial 2) of increase over the control, respectively. The highest soluble sugar contents of winter cabbage at the two trials were at the treatments of N,,, with 11.5% (trial 1) and 8.8% (trial 2) of increase over the control. The highest Vc content of winter cabbage was obtained at the treatments of N,, and N,,, at trials 1 and 2, with increase of 13.0 and 9.4% over the control. The N rates for better quality parameters of vegetable produces were much lower than those of MYNR. Compared to the control, NO,--N content of spring cabbage with the N rates of 90, 180, 270, 360, and 450 kg ha-' increased by 26.5, 50.9, 75.2, 149.3, and 138.3% at trial 1, and 44.7, 45.8, 67.3, 178.2, and 185.0% at trial 2. NO,--N in winter cabbage increased by 32.9, 44.6, 53.4, 77.6, and 68.2% at trial 1, and 21.0, 24.6,25.5, 39.3, and 46.3% at trial 2. The NO; -N content of cabbage increased with the N rates. The effects of N rates on the NO;-N content of spring cabbage were more obvious than those of the winter cabbage. The NO,--N content of winter cabbage increased relatively slowly and gently with the N rates, whereas, NO,--N content of spring cabbage increased slowly at N rate less than 270 kg ha-', and sharply at
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the rate exceeding 360 kg N ha-'.
The effects of N rate on N recovery of plant in rotation system The results of Table 4 indicate that the N recovery decreases with the N rates at both trials. The N recovery in the treatment of N,, was 2.4-3.3 times as high as that in treatment of N,,,. The soil Nminalso had an influence on the N recovery. The average N recoveries for the first, second, and third crops at trial 1 were 71.4, 15.7, and 10.8% higher than those at trial 2. The N recoveries of plants were lower in the soils with higher Nmin.The effect of soil Nminon N recovery was the most obvious in the first crop of spring cabbage, and reduced gradually in the second and third crops. The obvious influence of soil Nminon the N recovery of seasonal growing crops and lessening in the following crops was due to the rapid transformation of soils N,io
and the losses in many pathways, which were similar to the influence of soil Nminon the MYNR of spring cabbage and winter cabbage. The much higher N recoveries of maize with treatment of higher N rates than that of spring cabbage revealed that the spring cabbage intercropping with maize was an effective growing model for increasing N recovery. To shallow root crops, such as cabbage, it was difficult to utilize the huge amount of N that leached downward to the soil layer, below 30 cm, which possibly caused the pollution of groundwater if not be fully used. Intercropping with maize whose roots extend 2 m deep (Zhang G L and Zhang S 1998) increased N recovery and reduced the hazards of groundwater pollution by using the residual N from the cabbage season.
DISCUSSION Many researches show that the loss and residues of N
Table 3 The effects of different N rates on the quality of cabbage Trial 1
N rate (kg ha-1)
Trial 2
vc (mg kg-9
NO, -N (mg kg-9
87 e llOd 131 c 152 b 215 a 207 a 133 d 177 c 193 b 205 b 237 a 224 a
Spring cabbage
0 90 180 270 360 450
17.1 c 20.6 a 19.1 b 19.4 ab 19.3 ab 19.0 b
383.0 b 446.0 a 363.0 c 311.0 e 382.0 bc 340.0 d
Winter cabbage
0 90 180 270 360 450
53.7 c 59.9 a 59.7 a 56.1 b 52.1 c 51.7 c
702.0 b 793.0 a 724.0 b 673.0 c 655.0 c 657.0 c
Sugar (g kg-1) 26.4 c 28.8 b 30.8 a 27.0 c 27.2 bc 16.0 d 53.3 bc 58.0 a 54.5 b 53.5 bc 53.6 b 50.9 c
Vc (mg kg-I)
NO,--N (mg kg-1)
375.0 a 392.0 a 329.0 c 348.0 b 297.0 d 305.0 d 862.0 c 873.0 b 943.0 a 824.0 d 681.0 e 631.0 f
79 d 115c 116 c 133 b 220 a 226 a 146 d 177 c 182 c 183 bc 204 ab 214 a
Table 4 The effects of different N rates on N recovery under cabbage-maize rotation system Maize
Spring cabbage N rate (kg ba-l) Trial 1
Trial 2
0 90 180 270 360 450 0 90 180 270 360 450
N accumulation (kg ha-1) 81 e 114d 146 c 158 b 172 a 152 bc 108 e I32 d 142 c 150 b 161 a 144 bc
N recovery
6) 37.2 a 36.5 a 28.5 b 25.3 c 15.8 d 26.2 a 19.2 b 15.7 c 14.6 c 7.9 d
N accumulation (kg ba-1) 61 c 85 b 87 b 94 a 99 a 94 a 61 e 83 d 94 c 116 b 124 a 116 b
Winter cabbage N recovery (46) 31.4 ab 31.8 a 29.2 bc 27.6 c 18.4 d 25.4 a 24.8 a 26.8 a 25.8 a 16.8 b
N accumulation (kg ba-1) 70 e 111 d 131 c 191 a 203 a 165 b 91 e 146 d 158 c 195 a 200 a 177 b
N recovery (%)
36.6 a 34 b 36.8 a 32.5 c 20.2 d 37.6 a 29.9 bc 32 b 27.8 c 18 d
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Study on the Optimum N Rates Under Spring Cabbage-Maize-Winter Cabbage Rotation System
in soil are low when N is applied at a lower rate. At an irrationallyhigher N application rate, the residual N and N losses are large. The prevention of N overuse is essential to the issues of N management in the current high-yielding situation (Ju et al. 2002). There exists the popular N overuse in vegetable production. Yuan et al. (2000) reported that the NO,--N accumulation was up to 1000 kg ha-' at 200-400 cm layers in a soil growing vegetables. The large accumulation of mineral nitrogen in the soils in our experiments is because of growing vegetables for many years and higher N application, which has led to only 19.2-25.0% of yield increase, and decrease of crop yield in response to N fertilization. The groundwater NO,--N contents are 11.6-93.1 mg L-' with an average of 45.6 mg L-' according to this survey, 94.4% of which exceed the national standards of China (20 mg L-' NO,--N). The N recommendation has an importance in lowering N uses for cabbage production. The rotation of vegetables with grain crop can ameliorate many stresses in vegetable growing soil. Comparisons of soil salt and NO,--N contents in two cropping models of the single vegetable cropping and vegetable-grain crop rotation in a vegetable growing area indicate that the vegetable-maize rotation reduces the salt content and electric conduction (EC) in 0-20 cm layer by 43 and 36%, respectively, and NO,--N by 32% in 0-60 cm soil over a single vegetable system. Vegetable and maize rotation has remarkably decreased the accumulation of salt and nitrate in the soil of the greenhouse (Meng et al. 2006). There have been reported that the soil EC has declined from 2.5 to 1.O ms cm-I after cultivation for 55 d in summer (Wang 1998),and the soil salt content has effectively decreased by one season of maize cropping in summer (Zhang et al. 1995; Du et al. 2005). The experiments here suggest that because the deep-rooted maize can take up the mineral nitrogen leached to deeper soil layer, the rotation of cabbage-maize considerablyincreases the N recovery of plants with higher N fertilizer, and reduces the N pollution to groundwater. Because the N uptake of the plant is closely correlated with the original soil nitrate (Ye and Li 2002), the N application should take the N supply of soil into account. Using soil N- is a newly developed technique for N fertilizer recommendation (Zhang et al. 2002). N recommendation by European KNS-system
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(Kulturbegleitendes Nmn Sollwerte) is based on soil inorganic nitrogen (Nmn= NH,+-N+ NO,--N) detection, in consideration of plant N uptakes at different growth stages, the lowest limitation of Nmnat different growth periods, and corresponding root length of the plant. The reasearchers from the China Agricultural University have successfully adopted the N recommendation by using N,,,,,,for wheat and vegetables in the dryland of northern China (Chen 1997; Liao et al. 2001). These experiments indicate that the soil Nmnis closely correlated with the MYNR of cabbage. The N application rates for obtaining maximum yield and economic yield at trial 1 are higher than those at trial 2 because of relatively low soil Nmn. However, the soil Nmnhas obvious influence only on the N rate of the seasonal growing crop. Deep studies on the correlation of soil Nmnwith the cabbage yield and N application rate at different layers can make the possibility to quantify N fertilizer recommendation for spring cabbage-maize-wintercabbage, which become essential to N fertilizer saving, yield increase, and ecological environment protection. In China, the rapid growth of N application has led to little increment in soil total nitrogen in the farmland because of serious losses of N. Generally, the N recovery decreases, while the N losses and soil residual N increase with the raise of N application rate (Zhu 2000). In research on the fates of N in winter wheatsummer maize rotation, Ju et al. (2003) found that 20.9-48.4% of fertilizer nitrogen remained at 0-100 cm soil layer after one season of crop, which could be used by the following crops. These results reveal that the N applied in the spring cabbage season has obvious residual effects on maize. A higher N rate in a previous crop not only reduces the spring cabbage yield, but the maize yield too. The obvious residual effects of N in Shajiang black meadow soil might contribute to a higher content of clay dominated with 2: 1 Montmorillonite, the ammonium fixation and high CEC (cation exchange capacity) (Zhang 1988; Wang et al.2001). The quality of vegetable produce becomes increasingly important. However, the target of yield and quality cannot be coordinated at the same time. After summarizing the relation of the N application with vegetable yield and quality parameters, Haedter (1997) has pointed out that as far as the yield and nitrate
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content of vegetables are concerned, it is difficult to harmonize them. There have been some arguments that the N fertilizer has no significant negative influences on Vc content, even if one increases the Vc content in many vegetable species at the optimum N rate. Only higher N rate can result in the reduction of Vc content (Sorensen 1993; Chen et al. 2003). For most of the vegetables, increasing N rate reduces the Vc content in the produce, because the N content of the cabbage head is negatively correlated with Vc and sugar content (Guo et al. 2004). The results of these researches indicate that proper N application (N rate less than 90 kg ha-') increases the yield and quality at the same time, and a further increase in N rate increases the cabbage yield, although decreases the quality. An extremely high N rate decreases both yield and quality of cabbage. Therefore, the reduction of N application rate can obtain a better quality at the expense of lowering the yield.
CONCLUSION The N fertilization of the farmer's practice was 1.8-2.3 times greater than the MYNR of cabbage, which led to the groundwater nitrate content exceeding the standard in the vegetable production area. Soil Nminhad an influence on the MYNR and N recovery of growing cabbage, but little effect on the following crop, and could be taken as the basis for N recommendation of cabbage. The cabbage-maize rotation increased the N recovery of plants, with higher N treatment in Shajiang black meadow soil that had obvious N residual effects. Lower N rate (less than 90 kg ha-') could increase yield and quality simultaneously; increasing the N rate could increase the yield, but decrease the quality; and extremely high N rate decreased both the yield and quality of cabbage. Therefore, the reduction of N rate and yield could assure better quality of vegetable produce in vegetable production.
Acknowledgements This research was sponsored by Key Technologies R&D Program of Anhui Province during the 10th FiveYear Plan Period, China (040030342). The authors thank Zhu Laihong and Wang Hongbing, graduated in 2006 from Anhui Agricultural University, China, for
conducting the plant analysis.
References Agrochemistry Specialized Committee of Society of Chinese Soil Science. 1983.AnalyticalManuaIsof SoilAgro-Chemistry. Science Press, Beijing. (in Chinese) Chen J S, Tang S H, Zhang F B, Xu P Z, Zhang Z X. 2003. Effects of N and S fertilizer combination on yield and quality of floweringChinesecabbage. Chinese Journal of Soil Science, 34, 36-39. (in Chinese) Chen X P. 1997. Introduction to the fertilizer recommendation project by soil and plant analysis. Soils and Fertilizers, 151, 46-47. (in Chinese) Chen X P, Zhang F S. 1996. The problems and countermeasures of vegetable fertilization in Beijing. Journal of China Agricultural University, 1,63-66. (in Chinese) Du L F, Liu W K, Liu J L. 2005. Salt status of greenhouse soil and their influencing factors in Hebei Province. Soils and Fertilizers, 197, 17-21. (in Chinese) Guo X S, Zhu H B, Wang W J, Ye S Y, Wu J, Wu L S. 2004. Effects of different rates of nitrogen and potash on yield and quality of cabbage.Plant Nutrition and Fertilizer Science, 10, 161-166. (in Chinese) Haerdter R. 1997. Plant nutrition and fertilizationfor high-yielding and quality of vegetables. In: Xie J C, Chen J X, eds, Soil Fertility of Vegetable Garden and Rational Fertilization of Vegetables. Hohai University Press, Nanjing. pp. 1-11. (in Chinese) Ju X T, Liu X J, Zou G Y, Wang Z H, Zhang F S. 2002. Evaluation of nitrogen loss way in winter wheat and summer maize rotation system. Scientia Agn'cultura Sinica, 35, 1493- 1499. (in Chinese) Ju X T, Pan J R, Liu X J, Zhang F S. 2003. Study on the fate of nitrogen fertilizer in winter wheathummer maize rotation system in Beijing suburban. Plant Nutrition and Fertilizer Science, 9,264-270. (in Chinese) Li J L, Chen X P, Li X L, Zhang F S. 2003. Effect of N fertilization on yields, nitrate content and N apparent losses of Chinese cabbage. Acta Pedologica Sinica, 40,261-266. (in Chinese) Liao X Y, Zhang Y Z, Liu X J, Chen X P, Zhang F S. 2001. The current status and prospects of research in nitrogen behavior in soils. Southwest China Journal of Agricultural Sciences, 14, 94-98. (in Chinese) Meng Y L, Liu Z Y, Li J. 2006. Effects of vegetable-grainrotation on salt and nihic nitrogen contents in greenhouse soil. Journal of Henan Agricultural Sciences, 382, 81-87. (in Chinese) Ren H Z, Yuan L P, Me G Q, Zhang F M. 2004. Progress on the influence of nitrogen nutrition to vegetables quality. Journal of Huazhong Agricultural University, 35, 194-197. (in
02007, CAAS. All rights reserved.Published by ElsevierLM.
Study on the Optimum N Rates Under Spring Cabbage-Maize-WinterCabbage Rotation System Chinese) Shen H. 1990. Characteristics of element accumulation and transformationon vegetable farm soil of the suburbs of Beijing. Acta Pedologica Sinica, 27, 104-112. (in Chinese) Serensen J N. 1993. Use of the Nmin method for optimization of vegetable nitrogen nutrition.Acta Horticulturae,339,79-192. Tian X P, Xue J F, Han X R. 2007. Effects of long-term crop rotation and continuous cropping on nitrogen in albic soil. Journal of Soil and Water Conservation, 21, 185-187. (in Chinese) Wang X J. 1998. Analysis on secondary soil salinization in solar greenhouse. Northern Horticulture, 120, 12-13. (in Chinese) Wang X N, Wang Z H, Li S X. 2006. Soil nitrogen balance in winter wheat and summer maize rotation system on dry land of Loess Plateau. Plant Nutrition and Fertilizer Science, 12, 759-764. (in Chinese) Wang Z M, Zhu P L, Huang D M, Liu H Q, Jiang L R. 2001. Transformation of straw ”N in the submerged soil. Jiangsu Journal of Agricultural Sciences, 17, 236-240. (in Chinese) Ye Y L, Li S X. 2002. The influence of initial nitrate-nitrogen leaching on soil nitrate content and wheat nitrogen uptake. Agricultural Research in the Arid Areas, 20, 26-29. (in Chinese) Yuan X M, Tong Y A, Yang X Y,Li X L, Zhang F S. 2000. Effect of organic manure. on soil nitrate nitrogen accumulation. Soil and Environmental Sciences, 9, 197- 200. (in Chinese) Zhang C L, Zhang Y D, Zhong Q S. 1995. The effects of different
1329
crops in rotation to reduce secondary salinization and continuous cropping obstacles in protected vegetable cultivation. Chinese Journal of Soil Science, 26,257-259. (in Chinese) Zhang G L, Zhang S. 1998. Development of research on nitrogen leaching in cropland. Soils, 30,291-297. (in Chinese) Zhang H Y, Chen Q, Tang L L, Li H F, Li X L, Liebig H P.2002. Comparison of conventional and recommended water and nitrogen practices on spinach growth and water and nitrogen usage. Plant Nutrition and Fertilizer Science, 8, 48-53. (in Chinese) Zhang J M. 1988. Shaijing black meadow soil productive potential and comprehensive amelioration. In: Zhang J M, ed, Study on Comprehesive Amelioration of Shaijing Black Meadow Soil. Anhui Science and Technology Press, Hefei. pp. 2-11. (in Chinese) Zhang S L, Zhu Z L, Xu Y H, Chen R Y, Li A R. 1988. Studies on the optimal rate of application of nitrogen fertilizer for rice and wheat in Taihu Lake. Soils, 20, 5-9. (in Chinese) Zhu Z L. 1981. General aspects of the study on soil and fertilizer nitrogen in Australia. Soils, 13, 199-201. (in Chinese) Zhu Z L. 2000. Loss of fertilizer N from plants-soil system and the strategies and techniques for its reduction. Soil and Environmental Sciences, 9, 1-6. (in Chinese) Ziegler J, Strohmeier K, Brand T. 1996. Nitrogen supply of vegetables based on the “KNS-system”. Acta Horticulturae, 428,223-233. (Edited by ZHANG Juan)
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