Characterization of Leaf Photosynthetic Properties for No-Tillage Rice

Rice Science, 2007, 14(4): 283-288 Copyright © 2007, China National Rice Research Institute. Published by Elsevier BV. All rights reserved

Characterization of Leaf Photosynthetic Properties for No-Tillage Rice CHEN Song1, XIA Guo-mian 2, ZHAO Wei-ming3, WU Fei-bo1, ZHANG Guo-ping1 (1Agronomy Department, Zhejiang University, Hangzhou 310029, China; 2 Agricultural Bureau of Xiaoshan, Zhejiang Province, Xiaoshan 311203, China; 3 Agricultural Bureau of Zhejiang Province, Hangzhou 310021, China)

Abstract: A study was conducted to determine the influence of no-tillage cultivation on leaf photosynthesis of rice plants under field conditions. Experiments with the treatments, no-tillage and conventional tillage were carried out at three locations (Jiaxing, Hangzhou, and Xiaoshan, Zhejiang Province, China) for two years (2005 and 2006). Grain yield was constant in Jiaxing, but slightly higher in Hangzhou and Xiaoshan under no-tillage cultivation than that under conventional cultivation. In comparison with the conventional cultivation, no-tillage cultivation showed less biomass accumulation before heading and higher capacity of matter production during grain filling. A significantly higher leaf net photosynthetic rate was observed for the plants under no-tillage than for those under conventional tillage. The fluorescence parameter (Fv/Fm) in leaf did not show any difference between the two cultivations. The effect of cultivation management on transpiration rate (Tr) and SPAD value of rice leaf was dependent on the location and year. Key words: photosynthesis; leaf; rice; no-tillage; plough; yield

Rice (Oryza sativa L.) is one of the most important food crops in the world as well as in China. Currently, the annual planting area of rice in China is approximately 3.1 × 107 ha with a production of 2 × 108 t, which accounts for 39% of the total grain production [1]. More than 90% of paddy fields in southern China belong to wetlands. Transplanting is the traditional but still dominant system of rice production [2]. This involves growing rice seedlings in a nursery bed and later transplanting them into a main field. The land preparation consists of soaking, ploughing and puddling (harrowing under saturated soil conditions) after harvesting the previous crop. The farmers are eager to have an alternative rice production system, as the land preparation and seedling transplanting in the traditional system cost energy and labor largely. The rapid decline of rice planting area in southern China in the recent two decades may explain for the importance of innovating new rice production system [3]. In addition, the preparation of paddy fields may accelerate mineralization of organic matter, reduce soil fertility, increase water consumption, and deteriorate chemical and physical properties of soil [4]. On the other hand, no-tillage or minimum tillage cultivation of crops is widely practiced in temperate agricultural areas as a Received: 4 June 2007; Accepted: 20 July 2007 Corresponding author: ZHANG Guo-ping ([email protected])

method for labor-saving and soil conservation [5]. There are enough scientific evidences proving that no-tillage has positive effects on chemical, physical and biological properties of soil, including reduced soil erosion and improved soil fertility and structure [6]. However, in the fields with reduced or no tillage, effective nutrition or fertilizers are often concentrated on the shallower surface layer of soil, and the crops tend to have shallow root system and stronger competition from weeds for space and nutrition. Much effort has been made to develop the no-tillage and direct seeding as an effective crop production system for saving labor and improving soil properties [7]. Recently the new production system is applied in the southern China. Commonly, the system is considered to be effective in reducing consumption of labor, water and nutrition, while it maintains similar even higher yield as the conventional cultivation system [8-10]. According to Chen et al [8], no-tillage cultivation of rice showed the advantage in tillering and panicle development over the conventional cultivation. Gu et al [9] proposed that higher root activity and photosynthetic rate of flag leaf during grain filling contributed to the high yield of no-tillage cultivation. Liao et al [10] compared nitrogen nutrition of the rice plants under different cultivations, and found no-tillage cultivation had the same N accumulation in

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mature plants as the conventional cultivation. However, little research has been done to study the difference in rice leaf photosynthesis between no-tillage and conventional tillage cultivations.

MATERIALS AND METHODS Experimental site and soil property Field experiments were conducted at the experiment farm of Zhejiang University, Huajiachi campus, Hangzhou, Zhejiang Province (30°27′N, 120°11′E) and the experimental station of Nanhu, Jiaxing, Zhejiang Province (30°43′ N, 120°46′ E) in 2005 and the Agricultural Research Institute of Xiaoshan, Zhejiang Province (30°27′N, 120°11′E) and the experimental station of Nanhu, Jiaxing, Zhejiang Province in 2006. The data of basic soil fertility of the three experiment locations are shown in Table 1. The plot area was 33 m2 and there were three replications for each treatment. The rice variety used was Jialeyou 2 (151A× DH32), a japonica hybrid rice bred by the Jiaxing Academy of Agricultural Sciences, Zhejiang. Two cultivation methods were used, namely tillage and no-tillage. Land preparation for tillage cultivation was conducted as that commonly used locally: ploughing after harvesting of previous crop, and then soaking and puddling. Plots for no-tillage cultivation were firstly treated with herbicide (butachlor) 7 days prior to seeding. The plots were soaked for 2 days with water before seeding and leveled with a shovel. In both tillage and no-tillage plots, seeds were immersed in water for 2 days then broadcasted at a rate of 15 kg/ha. N fertilizer was supplied in the form of urea at a rate of 195 kg/ha N, with 30% being applied before seeding, 30% and 40% top-dressed at the tillering and booting stages, respectively. Potassium fertilizer was applied before seeding in the form of potash chloride at a rate of 300 kg/ha. During rice growth, weeds, insects and diseases were chemically controlled as required.

Measurements of photosynthesis, fluorescence and SPAD value of rice leaf The sampling and measurements were carried out at the mid-tillering, booting and heading stages. Net photosynthetic rate, stomatal conductance and transpiration rate were measured with a LI-6400 portable photosynthesis system (LI-COR, Lincoln, NE) on the uppermost fully expanded leaves. Five leaves were measured for each plot. Meanwhile, chlorophyll fluorescence was measured using a portable pulse-modulated fluorometer (Mini-PAM, H. Walz) and chlorophyll content, expressed as SPAD value, was determined using a SPAD meter (SPAD-502, 1989 Minolta Co., Ltd). At least 20 leaves were measured for each plot. Statistical analysis All data were subjected to ANOVA using the statistical software SAS8.0 for Windows and comparisons between the treatments with P < 0.05 were considered significantly different.

RESULTS Grain yield and its components No-tillage cultivation had significantly higher grain yield than conventional cultivation in both Hangzhou and Xiaoshan, however, there was no significant difference between the two cultivation systems in Jiaxing (Table 2). The effects of the cultivation methods on yield components varied with years, locations and were also depended on the yield components. However, no significant difference in 1000-grain weight between no-tillage and conventional tillage was found. For number of panicles per plant, there was no significant difference between the two cultivation methods in Jiaxing for both years. For number of grains per panicle and filled grain rate, no-tillage was significantly lower and higher than

Table 1. The basic soil fertility in the three experiment locations. Organic carbon (g/kg)

Available P (mg/kg)

Available K (mg/kg)

Total N (g/kg)

pH

Hangzhou

35.20

50.69

66.70

3.26

6.59

Xiaoshan

23.52

20.88

44.28

1.47

7.06

Jiaxing

33.91

36.48

126.20

2.30

6.06

Experiment location

CHEN Song, et al. Characterization of Leaf Photosynthetic Properties for No-Tillage Rice

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Table 2. Grain yield and its components under the two cultivation methods. Year 2005

2006

1000-grain weight (mg)

Treatment

No. of panicles per plant

No. of grains per panicle

Filled grain rate

Hangzhou

No tillage Conventional

11.65 b 13.21 a

186.15 b 204.88 a

0.84 a 0.77 b

27.30 a 27.20 a

10.92 a 9.53 b

Jiaxing

No tillage Conventional

10.04 a 10.82 a

174.83 b 177.53 a

0.80 a 0.78 b

25.47 a 25.70 a

9.07 a 8.95 a

Xiaoshan

No tillage Conventional

9.55 a 8.61 b

214.22 b 228.41 a

0.85 a 0.83 b

27.93 a 28.06 a

9.19 a 8.24 b

Jiaxing

No tillage Conventional

11.97 a 12.21 a

164.37 b 168.42 a

0.88 a 0.86 b

28.80 a 29.10 a

9.19 a 9.18 a

Site

Yield (t/ha)

Values followed by different letters within a column in a site are significantly different at the P=0.05 level according to the Turkey’s test.

conventional tillage, respectively, irrespective of year and location. It may be seen that the higher grain yield in no-tillage relative to that in conventional tillage is mainly due to greater rate of filled grains. Total biomass The effect of the cultivation methods on biomass accumulation during growth is shown in Fig. 1. On the whole, before heading conventional tillage had larger biomass than no-tillage, and at maturity the opposite was true, but for Jiaxing in 2005 the two cultivations had almost the same total biomass at maturity. Hence, in

Fig. 1. The plant biomass at different stages.

comparison with the conventional cultivation, no-tillage cultivation had less biomass accumulation before heading and higher capacity of matter production during grain filling. The correlation analysis showed that there was no significant correlation between photosynthetic rate and total biomass, indicating that total biomass accumulation is mostly dependent on the whole photosynthetic potential of the plant, rather than photosynthesis of a single leaf. Photosynthetic rate and Fv/Fm In general, little difference in photosynthetic rate

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Fig. 2. Photosynthetic rates at different stages.

(Pn) was found between the two tillage cultivations (Fig. 2). However the differences varied with growth stages and experimental locations. At the mid-tillering stage, no-tillage had higher Pn than conventional tillage in the two years and two locations, except for Xiaoshan in 2006. At the booting stage, the differences between the two cultivations varied with years, with no-tillage being higher than conventional tillage in 2005, and no difference in 2006. At the heading stage the differences between the two cultivations became smaller in comparison with those at the previous growth stage. Obviously, the dynamic change of net photosynthesis during the growth stage

was dependent on the variety and environment. The genotype showed the maximum photosynthetic rate was around mid-tillering, and then tended to decline slowly. While in 2005, remarkable decline after flowering might be attributed to bad weather (much raining). For Fv/Fm, no significant differences were detected between the two cultivations in all measurements, except for Jiaxing in 2005, where no-tillage was smaller than conventional tillage at the booting stage (Table 3). Transpiration rate and SPAD value The effect of cultivation methods on transpiration

Table 3. Effect of cultivation method on fluorescence, transpiration rate and SPAD value. Year

Site

Mid-tillering Booting 2005 Hangzhou

Jiaxing

2006 Xiaoshan

Jiaxing

Transpiration rate (mmol/m2·s)

Fv/Fm

Treatment

Heading

Mid-tillering

Booting

SPAD value Booting

Heading

No tillage Conventional

0.79 a 0.78 a

0.82 a 0.83 a

0.79 a 0.78 a

11.28 a 11.96 a

6.48 a 5.92 b

Heading Mid-tillering 4.54 b 5.04 a

41.87 a 39.40 b

44.23 a 44.43 a

47.43 b 48.76 a

No tillage Conventional

0.82 a 0.82 a

0.79 b 0.81 a

0.82 a 0.82 a

9.07 a 7.16 b

9.05 a 8.24 b

7.68 b 10.27 a

40.07 a 38.10 b

45.90 a 46.86 a

44.83 b 46.76 a

No tillage Conventional

0.80 a 0.80 a

0.80 a 0.79 a

0.80 a 0.80 a

6.78 a 6.89 a

6.17 b 6.95 a

2.94 b 3.80 a

40.07 a 38.80 a

43.83 a 45.00 a

47.13 b 48.60 a

No tillage Conventional

0.79 a 0.79 a

0.83 a 0.82 a

0.79 a 0.79 a

6.30 a 6.16 b

5.72 b 6.42 a

4.88 a 5.09 a

39.80 a 40.47 a

39.96 b 42.23 a

40.13 a 38.93 a

Means followed by different letters within a column in a site are significantly different at the P≤0.05 level according to the Turkey’s test.

CHEN Song, et al. Characterization of Leaf Photosynthetic Properties for No-Tillage Rice

rate was dependent on the locations and years before heading stage (Table 3). At the mid-tillering stage, the transpiration rate was higher under no-tillage than under conventional tillage in Jiaxing, but in Hangzhou and Xiaoshan there was no significant difference between the two cultivation methods. At the booting stage, the effect of cultivation methods varied with years, i.e. in 2005, no-tillage had significantly higher transpiration rate than conventional tillage, while in 2006 the opposite was true. At the heading stage, no-tillage was significantly lower than conventional tillage in the two years and two locations, except for Jiaxing in 2006, where showed no significant difference between the two treatments. The differences in SPAD values between the two treatments varied with years and locations (Table 3). At the mid-tillering stage, no-tillage had higher SPAD values than conventional tillage in 2005, while in 2006, the difference was not found. At the booting stage, the difference was only found in Jiaxing in 2006. At the heading stage, there was significant difference between the two treatments, with conventional tillage being larger than no-tillage, but not in Jiaxing in 2006.

DISCUSSION A huge number of studies have been done on the influence of tillage on crop growth and yield. However, available reports provided the contrast results. Su et al [11] found a positive yield response to no-tillage in wheat and corn when the experiments were conducted in sub-humid area of the Loess Plateau. In contrast, Kato et al [12] reported that no-tillage led to reduced rice yield in comparison with the conventional planting system in southern Asia. In general, the influence of tillage method on rice yield varied with years and locations, depending on fallow management and environmental conditions. In our experiment, on the whole, no-tillage had slightly higher grain yield than conventional tillage. The yield may be limited by sink and source or both of them. Total grain number, as calculated by the product of grain number per panicle and number of panicles per unit area, is used as an index of sink size [13]. In the current study, the plants under no-tillage had larger source than those under conventional tillage. Thus, it may be concluded that rice yield increase under no-tillage is mainly due to increased source.

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The effect of no-tillage cultivation on rice growth and yield has been largely reported. Huang et al [14] found that no-tillage rice had greater leaf area index before flowering and biomass accumulation during grain filling stage. Feng et al [15] studied the effects of no-tillage under different nitrogen levels, and noted that no-tillage cultivation had greater biomass accumulation under higher nitrogen level compared to conventional cultivation. However, no report is available on the difference in photosynthetic properties of rice between the two cultivation systems. Little is known about the difference in photosynthetic rate between different tillage systems. In this study, a significantly higher photosynthetic rate was found in the plants under no-tillage in comparison with that under conventional tillage. However, the difference between the two tillage cultivations became smaller at late stage. Jiang et al [16] discovered no difference in photosynthetic rate between no-tillage and conventional tillage treatment at the heading stage. A close relationship between photosynthetic rate and leaf nitrogen content was reported for both greenhouse- and field-grown rice plants [17-18]. Leaf chlorophyll content or SPAD value has been used in various crops as an indirect indicator of plant nitrogen status [19]. In this study, no-tillage increased the SPAD value at the heading stage compared with conventional tillage. Fluorescence is a very useful tool in the study of photosynthetic apparatus to stress [20]. Our study did not find significant difference between the two tillage systems in fluorescence yield during the whole growth stage. It might be deduced that the plants under no-tillage have the similar environmental conditions as those under conventional cultivation did.

ACKNOWLEDGEMENTS This work was financially supported by the Department of Science and Technology of Zhejiang Province (Grant No. 2005C12024). The authors thank the Agricultural Research Institute of Xiaoshan and Agricultural Bureau of Jiaxing, Zhejiang Province for their kind help.

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