秸秆还田配施不同比例化肥对晚稻产量及土壤养分的影响

Abstract

Straw is rich in organic carbon,nitrogen( N),phosphorus( P),potassium( K),silicon( Si) and other nutrients that can improve physical,chemical and biological properties,increase crop yield,and lower fertilizer costs.Straw is mainly composed of cellulose,hemicellulose and lignin,and the C /N ratio is generally about 60—80; straw is therefore not easily decomposed by microorganisms in soil. Straw also needs to absorb a certain amount of N,for which it competes with crops,affecting seedling growth. Returning straw that contains a certain proportion of fertilizer N and P can mediate the soil C /N ratio,accelerate straw decomposition,and relieve the competition for inorganic nitrogen from microorganisms during the decomposition process. To explore the decomposition patterns of straw,we designed an experiment in Jiangxi to examine changes in dry matter production,soil properties,and biological processes in response toreturning straw. The amount of crushed straw used( 3000 kg /hm2) was determined by an examination of the effects of different amounts of returning straw on early rice. We researched the effects of returning straw containing different ratios of fertilizer on rice yield,dry matter accumulation and distribution,and soil fertility. We used a single application of straw as a control. Other treatments were SN1( 3000 kg/hm2 of crushed straw + 150 kg /hm2N),SN2( 3000 kg/hm2 of crushed straw+ 225 kg /hm2N),SP1( 3000 kg/hm2 of crushed straw + 75 kg /hm2P2O5),SP2( 3000 kg/hm2 of crushed straw + 112. 5kg / hm2P2O5),SNP1( 3000 kg/hm2 of crushed straw + 150 kg /hm2 N + 75 kg /hm2P2O5),SNP2( 3000 kg/hm2 of crushed straw + 225 kg /hm2 N + 112. 5 kg /hm2P2O5),SNPK1( 3000 kg/hm2 of crushed straw + 150 kg /hm2 N + 75 kg /hm2P2O5+ 37. 5 kg /hm2K2O),SNPK2( 3000 kg/hm2 of crushed straw + 225 kg /hm2 N + 112. 5 kg /hm2P2O5+ 56. 3 kg /hm2K2O). The results demonstrate the following:( 1) Compared with the control,the returning straw with low levels of N,P,and K significantly increase the grains per spike,1000-grain weight,seed-setting rate,filled degree of grain and overall crop yield at rates of 9. 32%,4. 28%,13. 70%,2. 74% and 26. 38%,respectively.( 2) The differences in dry matter accumulation between different growth periods are significant. Dry matter accumulation is greatest in the tilling to heading period and the filling to maturity period in all treatment groups.. The following proportion of total dry matter accumulation occurred in those two periods combined: 78. 61%,79. 22%,81. 97%,77. 95%,77. 27%,78. 13%,78. 20%,79.08%,and 78. 47% in the control group,SN1,SN2,SP1,SP2,SNP1,SNP2,SNPK1 and SNPK2,respectively. The heading to filling period is a stage of rapid accumulation of material,but because of its short duration,dry matter accumulation and the ratio of accumulation to the total amount of dry matter was lower than in the other growth periods.With growth,the ratio of stem-sheath length to total plant length continuously decreased from a range of 66. 68% —77. 00%in the booting stage to a range of 25. 97% —34. 79% in the maturity period. In addition,in the SNPK1 treatment,the ratio of leaf length to the total plant length reduced from a range of 23. 00% —33. 32% in the booting stage to a range of 7.41% —21. 03% in the maturity period. The dry weight ratio of the stem-sheath to the whole plant in the booting stage,heading stage,and at maturity was significantly higher in the treatment groups than in the control group,and was highest in the SNPK1 treatment. The dry weight ratio of the leaf to the whole plant is opposite; the ratio is highest in the control group.( 3) Compared with the control group,in the treatment groups,the pH increased by 1. 97% —4. 33%,organic carbon content increased by 3. 76% —25. 05%,total nitrogen content increased by 14. 75% —45. 90%,alkaline hydrolysis nitrogen content increased by 3. 49% —39. 90%,total phosphorus content increased by 10. 00% —55. 00%,available phosphorus content increased by 10. 45% —50. 88%,total potassium content increased by 18. 27% —100%,and available potassium content increased by 9. 39% —79. 72%; the C /N ratio decreased by 6. 02% —23. 59%. These results demonstrate that returning straw that contains fertilizer improves rice yield and dry matter accumulation rates; this translates to a higher potential yield of rice crops,and an increase in the level of soil nutrients. The combined effect of returning rice straw to fields with low levels of N,P,and K is significant. This study will provide a theoretical basis for the use of straw to increase soil fertility in southern regions of China,where rice farming is abundant.