Effects of Long-Term Application of Sulfur-Containing and Chloride-Containing Chemical Fertilizers on Rice Yield and Its Components

Agricultural Sciences in China

May 2011

2011, 10(5): 747-753

Effects of Long-Term Application of Sulfur-Containing and Chloride-Containing Chemical Fertilizers on Rice Yield and Its Components 1 SHEN Pu, LI Dong-chu, GAO Ju-sheng, XU Ming-gang, WANG Bo-ren and HOU Xiao-juan Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences/Key Laboratory of Crop Nutrition and Fertilization, Ministry of Agricultur, Beijing 100081, P.R.China

Abstract Impacts of 33-yr of application of S-containing and Cl-containing chemical fertilizers on rice (Oryza sativa L.) yield and its components were investigated in a red paddy field experiment, south China. The treatments included: 1) adding 302 kg SO42--S ha-1 yr-1 with application of (NH4)2SO4, K2SO4, and calcium superphosphate (SO42-); 2) adding 56 kg SO42--S and 176 kg Cl ha-1 yr-1 with application of urea, calcium superphosphate, and KCl (Cl-+SO42-); 3) adding 516 kg Cl ha-1 yr-1 with application of NH4Cl, KCl, and KH2PO4 (Cl-). Under each treatment, the applied N, P, and K nutrients were controlled at conventional rates of 150 kg N ha-1 yr-1, 75 kg P2O5 ha-1 yr-1, 225 kg K2O ha-1 yr-1, respectively. Under the S-containing fertilizer application, soil SO42--S content showed a first increasing then decreasing trend with years, and was significantly negatively correlated with annual rice yield. Average annual yield significantly declined in an order of Cl-, Cl - +SO42-, and SO42-. Under the Cl- treatment, soil SO42--S content was maintained at about 26.5 mg kg-1, not showing deficiency. From 1990 to 2000, rice yield declined rapidly under the SO 42- treatment, and was significantly lower than that under the Cltreatment. After then, there was no significant difference in yield among the treatments. Our results demonstrated that long-term application of S-containing fertilizer could result in excessive accumulation of SO42--S in the red paddy soils of south China, therefore producing a certain threat to rice growth. The Cl-containing fertilizer could be relatively safe. Key words: rice (Oryza sativa L.), long-term fertilization, sulfur-containing fertilizer, chloride-containing fertilizer, yield, component

INTRODUCTION Sulfur (S) and chloride (Cl) are nutrition elements required for crop growth, which in soil are taken up by crops in available forms such as soluble SO42- and Cl-. They can produce significant effects on growth and development of crops such as rice (Islam and Ponnamperuma 1982; Vong et al. 2004). Due to frequent introduction of S and Cl into soil as subsidiary nutrients with chemical fertilizer application, researchers usually ignored studies on effects of S and Cl on

crops ago (Liu et al. 1989; Li et al. 1991; Gao et al. 2002). In recent two decades, S-containing and Clcontaining fertilizer studies have received increasing attention. The S fertilizer application, for instance, was suggested to promote rice growth, enhance rice yield, and improve rice quality (Liu et al. 1990; Deng et al. 1994; Fan and Ye 1994), and to improve soil environment and increase soil nutrient (e.g., nitrogen, phosphorus) contents (Jiang et al. 1995; Yang et al. 2005). However, Zou et al. (2006) reported that SO42-S was accumulated obviously in the soil and the crop after continuous application of the S fertilizer, and such

This paper is translated from its Chinese version in Scientia Agricultura Sinica. Correspondence XU Ming-gang, Professor, Tel: +86-10-82105636, E-mail: [email protected]; GAO Ju-sheng, Tel: +86-746-3841016, E-mail: [email protected]

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accumulation increased the soil acidity, decreased oxidation-reduction potential, and in turn deteriorated soil physicochemical properties inhibited nutrient uptake by the crop, and adversely affected the crop yield. Cl was seldom found to be significantly accumulated in rice ecosystems, and Cl introduced into soil with conventional fertilization did not cause Cl toxicity to the crop grown on non-saline soil (Su et al. 1997; Huang et al. 1997; Mao et al. 2000; Li et al. 2002). However, previous studies were concentrated on short-term responses of soil and crops to S-containing and Cl-containing fertilizers. Rice demands for S and Cl are relatively small, and thus short-term experiments may be difficult to allow detectable or expected results. Panicle number per plant (PN), grain number per panicle (GNP) and 1 000-grain weight (1 000 GW) are common and important components of rice yield, which interact to affect rice yield. Different fertilizers generally have different influences on the rice yield components (Yuan et al. 2005; Gao and Zhou 2007). The objective of this study was to investigate accumulation characteristics of soil SO42--S and Cl- and dynamic changes in rice yield and its components under 33-yr application of S-containing and Cl-containing fertilizers, and to further examine effects of the fertilizers on rice in a red paddy field experiment, south China. The results will provide scientific basis for safe and sustainable use of S-containing and Clcontaining fertilizers in the red paddy soil region, South China.

MATERIALS AND METHODS Study site and experimental design This study was conducted at a long-term fertilizer experimental site (26°45´36´´N, 111°52´12´´E), established in the Red Soil Experimental Station of Chinese Academy of Agricultural Sciences, south China in 1975. The region belongs to a subtropical monsoon climate with average annual temperature of 17.8°C, active accumulated temperature (>10°C) of 5 648°C, frost-free season of 293 d, and mean annual rainfall of 1 150-1 350 mm. The tested soil was classified as a paddy soil developed from the Quaternary red earth, with initial properties of pH (H2O) 6.85, organic matter 22.3 g kg-1,

SHEN Pu et al.

total N 1.29 g kg-1, total P 0.28 g kg-1, total K 7.30 g kg-1, alkali-hydrolyzable N 183.9 mg kg-1, available P 18.2 mg kg -1, exchangeable K 124.2 mg kg-1 at 0-20 cm depth. Since 1975, the experimental field has been continuously cultivated with a rice-rice (Oryza sativa L.) double cropping under conventional mouldboard ploughing. In each year, the early rice was transplanted (20 cm×20 cm spacing) at the end of April, and harvested at the end of July, and the late rice was transplanted (20 cm×25 cm spacing) at the end of July, and harvested on 10-25 October. The used rice variety was the local conventional one, and was changed once every 3-5 yr. There were three treatments including SO 42-, Cl +SO42-, and Cl- treatments. Under the SO42- treatment, 302 kg SO42--S ha-1 yr-1 were added with application of c o m b i n e d ( N H 4) 2S O 4, K 2S O 4, a n d c a l c i u m superphosphate. Under the Cl-+SO42- treatment, 56 kg SO42--S and 176 kg Cl ha-1 yr-1 were added with application of combined urea, calcium superphosphate, and KCl. Under the Cl- treatment, 516 kg Cl ha-1 yr-1 were added with application of combined NH4Cl, KCl, and KH2PO4. Under each treatment, the applied N, P, and K amounts were controlled at conventional rates of 150 kg N ha-1 yr-1, 75 kg P2O5 ha-1 yr-1, 225 kg K2O ha-1 yr-1, respectively. N contents in urea, NH4Cl, and (NH4)2SO4 were 46.0, 25.0, and 20.0%, respectively. P2O 5 contents in calcium superphosphate and KH2PO4 were 12.0 and 52.2%, respectively; K2O contents in KH2PO4, KCl, and K2SO4 were 34.6, 60.0, and 50.0%, respectively. All the fertilizers were applied as basic fertilizers. The SO42- and Cl- treatments were replicated four times, and the Cl-+SO42- treatment was replicated two times. The size of each plot was 25 m2 (10 m×2.5 m).

Sampling and analysis In each year, rice growth status was investigated in regular rice growth stages; rice yield, PN, GNP, and 1 000 GW were measured after harvest for each rice; soil samples were taken from each plot at depth of 020 cm after the late rice harvest. Soil SO42--S, extracted with Ca(H2PO4)2-CH3COOH, was determined by using BaSO4 spectrophotometry method. Soil Cl- was extracted with distilled water, and was measured by AgNO3 titration method. Data collected from 1982 to

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Effects of Long-Term Application of Sulfur-Containing and Chloride-Containing Chemical Fertilizers on Rice Yield

2008 were used in this study. Statistical analysis was performed in DPS. All data obtained were subjected to the one-way analysis of variance (ANOVA) with a LSD test. Difference at P<0.05 was considered statistically significant. Regression analysis was used to quantify relationships between the measured variables with years and between rice yields with soil SO42--S and Cl- contents.

RESLUTS Effects of S-containing and Cl-containing fertilizer on rice yield Generally, the rice yield in each treatment decreased

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from 1982 to 2008 (Fig. 1). Under the Cl-, Cl-+SO42-, and SO42- treatments, the average annual yields were 5 738.9, 5 657.5 and 5 633.8 kg ha-1 for early rice, and 4 831.9, 4 603.8, and 4 557.0 kg ha -1 for late rice, respectively. During 1982 to 1990, the rice yield showed neither significant decline with years nor significant difference among the treatments (Table 1). Then, from 1990 to 1999, the rice yields slowly decreased. During this period, the mean yield of early rice under the Cltreatment was significantly higher than that under the SO42- treatment, and the mean yield of late rice under the treatments of Cl- and Cl-+SO42- was significantly higher than that under the SO42- treatment (Table 1). Then, from 2000 to 2008, the rice yield tended to increase, and showed no significant difference among the treatments (Table 1).

Fig. 1 Changes in yields of early rice (left) and late rice (right) (1982-2008). as below.

, significant correlation at P<0.01, respectively. The same

**

Table 1 Average annual yields of early and late rice under different treatments during different periods (kg ha-1) Rice type

Treatment

Early rice

Cl Cl-+SO42SO 42Cl Cl-+SO42SO 42-

Late rice

Year 1982-1990 6 355.4 a 6 287.6 a 6 305.4 a 5 296.4 a 5 027.5 a 5 230.1 a

1991-1999 5 050.3 a 4 971.4 ab 4 572.3 b 4 649.8 a 4 482.2 a 3 915.7 b

2000-2008 5 811.0 a 5 713.6 a 6 023.7 a 4 580.9 a 4 335.3 a 4 528.7 a

Average 5 738.9 a 5 657.5 a 5 633.8 a 4 831.9 a 4 603.8 a 4 557.0 a

Values denoted by different letters within the same column are significantly different (P<0.05).

Accumulation characteristics of SO42--S and Clin soil Under the SO42- treatment, soil SO42--S content showed a first increasing then decreasing trend from 1982 to 1999, with the maximum value of 158 mg kg-1 (Fig. 2). Similar trend was also found under the Cl-+SO42- treat-

ment (Fig. 2). Under the Cl - treatment, soil SO42--S content showed no significant change with years, which was almost maintained at about 26.5 mg kg-1 over the critical value (10-15 mg kg-1) (Fig. 2). The average content of SO42--S in soil significantly declined in an order of SO42- (97.6 mg kg-1), Cl-+SO42- (44.2 mg kg-1), and Cl - (26.3 mg kg -1 ) (Fig. 2). After 33-yr of

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fertilization, compared with the initial value (31.8 mg kg-1), soil Cl- content in the SO42- treatment increased by 22.0%; soil Cl- content in the Cl -+SO42- treatment almost maintained at about 30.0 mg kg-1; soil Cl- content in the Cl- treatment decreased by 45.7% (Fig. 2). Regression analysis was used to quantify the relation-

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ship between rice yield and soil SO42--S and Cl- contents (Fig. 3). Mean annual rice grain yield was found to be significantly and negatively correlated with soil SO42--S content (R2=0.1279, P<0.01). There was no significant correlation between rice yield and soil Clcontent.

Fig. 2 Changes of contents of SO42--S (left) and Cl- (right) in soils.

Fig. 3 Correlations between contents of SO42--S and Cl- in paddy soil and total yield of early and late rice.

Effects of S-containing and Cl-containing fertilizer on rice yield components Dynamic in rice yield components under different treatments are shown in Fig. 4. Under all the three treatments, PN showed a significant increase with years (late rice: R2=0.1995, P<0.01); GNP also presented a significant increase with years (early rice: R2=0.3147, P<0.01; late rice: R2=0.1279, P<0.05); while 1 000 GW decreased significantly with years (early rice: R2=0.2548, P<0.01; late rice: R2=0.1269, P<0.01). GNP of the early and late rice was significantly higher (5.1 and 5.7%, respectively) under the SO42- treatment than the Cl- treatment. There were no significant differences in

PN or 1 000 GM among the treatments.

DISCUSSION SO42- and Cl- are prone to be leached because soil colloid mainly takes negative charges. Thus, SO42- and Clintroduced into soil with fertilization are generally considered to be seldom accumulated. But, our results showed that long-term application of the S-containing and Cl-containing fertilizers resulted in a certain accumulation of SO42- and Cl- in soil, and the accumulation effects increased with increasing amounts of the applied fertilizers. Fan and Hao (2002) and Zou et al.

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Fig. 4 Trends in rice yield components under the three treatments (1982-2008). *, significant correlation at P<0.05.

(2004a) also reported similar results. SO42- and Cl-, as anions, can compete with other anionic nutrients such as HPO42- and NO3- for uptake by crops. Therefore, increasing soil SO42- and Cl- contents can generally influence soil nutrient balance and nutrient uptake by rice to a certain degree. There is an evidence that adding SO42- into soil increases leaching loss of NO3-, and that Cl- enhances use efficiency of nitrogen through inhibiting production of NO 3- in soil (Chen et al. 1993b). Additionally, SO42- and Cl- are acid-causing ions, and thus their accumulation in soil can often decrease soil pH value, and in turn can affect rice growth and development (Chen et al. 1993b; Gao et al. 2002). Moreover, under the oxygen-poor environment in the rice system, accumulation of SO42- in soil usually contributes to produce reductive matters such as H2S, and thus causes black root disease of rice and adverse effects on rice growth and development (Zou et al. 2004b). In our study, at the early stage of the experiment (1975-1999), soil SO42--S content in the SO42- treatment showed an increasing trend with years in general. Then, after 2000, the SO42--S content significantly decreased with years. This indicated SO42- adsorbed on the surface soil might be saturated in 2000. Then SO42- might be accumulated in the deep soil due to irrigation and rainfall leaching (Liao and Qu 2004). In recent years, SO2 emission has gradually decreased with more and more attention

paid by Chinese government to environmental protection. Subsequently, S input into soil with dry and wet deposition has also declined (Cheng et al. 2004; Yang et al. 1999). Additionally, the gradual increase in rice yield in the SO42- and Cl-+SO42- treatments after 2000 suggests the possible increase in S output by rice absorption with years. These may be other reasons why soil SO 42--S content in the SO 42- treatment decreased significantly after 2000. At the early stage (1982-1990) of the experiment, the average annual yields of the early and late rice across the three treatments were more than 6 200 and 5 300 kg ha-1, respectively. Then, during 1990 to 2000, the rice yields in the SO42- and Cl- treatments both decreased significantly with years. This is attributed to the accumulation of SO42- and Cl- in soil which may decrease soil nutrient availability, inhibit uptake of P, Fe, Mo, B, Mg, and Cl by rice, deteriorate soil environment, and in turn decrease rice yield (Chen et al. 1993a; Zou et al. 2004b, 2006). At this stage, the rice yield under the SO42- treatment was significantly lower than that under the Cl- treatment. This elucidates that the adverse effects due to soil SO42- accumulation may be more serious than Cl-. To 2000, the adverse effects probably reached the maximum, and soil acidity possibly stopped increasing. Additionally, after then, nutrients introduced to soil with irrigation, rainfall and residue decomposi-

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tion likely improved soil environment and promoted rice growth. These may be responsible for that the rice yield in each treatment tended to increase after 2000. Dry-wet deposition and irrigation possibly continuously brought a certain amount of S into the soil, so soil SO42--S content in the Cl- treatment without S input maintained at about 26.5 mg kg-1 across years, and the rice did not show any symptom of S deficiency. There were certain differences in climate condition and rice variety among years, which could have influenced the rice yield and its components (Wu et al. 1993; Lin et al. 2007). Therefore, further studies on these aspects will be needed in our future work.

CONCLUSION Our results showed that long-term application of the Scontaining fertilizer resulted in excessive accumulation of SO42--S in soil. This in turn caused deterioration of soil environment, and produced negative effects on rice growth. Such adverse effects disappeared fast when the SO42--S content was declined. After 15-yr of fertilization (in 1990), the rice yields under the S-containing fertilizer treatment were significantly lower than the Cl-containing fertilizer treatment without S. After 2000, the yield in each treatment slowly increased with years, and there were no significant differences in rice yields among the treatments. Under the Cl-containing fertilizer treatment without S, soil SO42--S content maintained at about 26.5 mg kg-1, over the deficiency threshold value. From a sustainable agriculture view, Cl-containing fertilizer could be a relatively better fertilizer type in the red paddy soil region, southern China.

Acknowledgements This research was financially supported by the Central Public-Interest Scientific Institution Basal Research Fund, China (2008-4) and the National Key Technologies R&D Program of China (2006BAD05B09, 2006BAD02A14). We thank to Dr. Li Hui and Dr. Lou Yilai, Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, for their help in English polish.

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