小麦秸秆还田后不同水稻品种对简化穗肥施用的响应及其成因

Response Difference and Its Cause Reasons for Simplified Panicle Fertilization in Different Rice Varieties After Wheat Straw Return

【目的】探讨小麦秸秆还田条件下不同水稻品种产量、颖花分化和退化、土壤微生物活性及碱解氮对简化穗肥施用响应的差异及其原因。【方法】以迟熟中粳南粳9108和中籼扬稻6号两个品种为试材,研究秸秆还田方式(全量还田和不还田)和简化穗肥处理(0﹕0,不施穗肥;2﹕0,全施促花肥;1﹕1,促花肥和保花肥各施一半;0﹕2,全施保花肥)互作条件下产量、颖花分化和退化等的差异及其相互关系。从秸秆腐解和养分释放、土壤微生物量和酶活性变化、土壤碱解氮含量等角度分析水稻颖花分化和退化的机制。【结果】(1)秸秆还田后,南粳9108和扬稻6号的产量分别平均增加4.2%和3.2%。穗肥处理中,两品种分别以2﹕0和1﹕1处理的产量最高;而秸秆不还田处理下,两品种产量均以1﹕1处理最高。在施氮量180—360 kg N·hm-2范围内穗肥处理的产量趋势一致;(2)秸秆还田后0—30 d为快速腐解期,秸秆中的碳和氮迅速释放,30d时土壤中的细菌、真菌和放线菌的数量平均增加179.2%,脲酶、酸性磷酸酶和蔗糖酶的活性平均增加88.8%;40—60d秸秆腐解和碳氮释放速率变缓,微生物数量和酶活性迅速降低;60—90 d秸秆腐解和碳氮释放基本停滞,微生物数量和酶活性缓慢下降。秸秆还田后10—40 d,土壤碱解氮含量平均降低4.8%,50—90 d平均增加5.2%;(3)秸秆还田后,土壤碱解氮的增加使供试水稻的颖花分化数平均增加1.4%,颖花退化数平均降低12.3%,颖花现存数平均增加4.4%,每穗粒数(每穗颖花现存数)的增加是水稻增产的主要原因。南粳9108和扬稻6号2﹕0处理下颖花退化率秸秆还田较不还田处理分别降低23.5%和7.6%。南粳9108在2﹕0处理下的颖花分化数和退化数较1﹕1处理分别增加8.9和5.7朵/穗,扬稻6号分别增加6.8和11.6朵/穗。由于颖花分化数的增幅大于颖花退化数的增幅,故南粳9108的颖花现存数以2﹕0处理最多,而扬稻6号则以1﹕1处理最多。【结论】秸秆还田提高了水稻产量,全施促花肥南粳9108产量最高,扬稻6号则是促保均施处理的最高。产量提高的原因主要通过显著降低颖花退化率和退化数,增加每穗粒数实现的。南粳9108颖花退化率下降的幅度大于扬稻6号,是两个品种颖花现存数对不同穗肥处理响应差异的主要原因。

【Objective】The aim of this study was to explore and analyze the differences in yield,panicle differentiation and degeneration,soil microbial activity,and response of soil alkali-hydrolysable nitrogen to simplified panicle fertilization among different rice varieties under the condition of wheat straw return(SR).【Method】As test materials,two cultivars were selected,including late maturing medium japonica rice Nanjing 9108(NJ 9108)and indica rice Yangdao 6(YD6).Rice yield,spikelet differentiation,and degeneration were evaluated under the interactive conditions of SR and simplified panicle fertilization(0﹕0,no panicle fertilization;2﹕0,full application of spikelet-promoting fertilizer;1﹕1,equal application of spikelet-promoting and protecting fertilizers;0﹕2,full application of spikelet-protection fertilizer).The nutritional basis of rice spikelet differentiation and degeneration was analyzed in terms of nutrient release from straw decomposition,alterations in soil microbial communities and enzyme activity,and soil alkaline nitrogen content.【Result】(1)After SR,the average yield of NJ 9108 and YD 6 increased by 4.2%and 3.2%,respectively.Under panicle fertilization treatments,the highest yield for NJ9108 and YD6 was achieved under the 2﹕0 and 1﹕1 treatment,respectively.After no wheat straw return treatment(NR),the yield of both varieties was highest under the 1﹕1 treatment.The yield trend of panicle fertilization treatments was consistent within the range of 180-360 kg N·hm-2.(2)After SR,the initial 0-30 days were a period of rapid decomposition,with the rapid release of carbon and nitrogen from the straw.At 30 days,the average number of bacteria,fungi,and actinomycetes in the soil increased by 179.2%,and the average activity of urease,acid phosphatase,and sucrase increased by 88.8%.During the period of 40 to 60 days,the straw's decomposition and carbon-nitrogen release rates diminished,and the number of microorganisms and enzyme activities decreased significantly.Decomposition and carbon-nitrogen release of straw essentially stalled between 60 and 90 days,while the number of microorganisms and enzyme activities decreased gradually.From 10 to 40 days after SR,the soil's alkali-hydrolysable nitrogen content decreased by an average of 4.8%,while it increased by an average of 5.2%between 50 and 90 days.(3)After SR,the increase in soil alkali-hydrolysable nitrogen caused an increase of 1.4%in the average number of spikelets differentiation,a decrease of 12.3%in the average number of spikelets degeneration,but an increase of 4.4%in the average number of surviving spikelets.Rice harvest increased primarily due to an increase in the number of spikelets per panicle(the number of surviving spikelets per panicle).After SR,the 2﹕0 treatment reduced the rate of spikelet degeneration in NJ9108 and YD6 relative to NR by 23.5%and 7.6%,respectively.The number of spikelet differentiation and degeneration of NJ9108 increased by 8.9 and 5.7 spikelets per panicle under the 2﹕0 treatment relative to the 1﹕1 treatment,whereas Yangdao 6 increased by 6.8 and 11.6 spikelets per panicle,respectively.As the increase in the number of spikelets differentiation was greater than the increase in the number of spikelets degeneration,NJ9108 had the highest number of surviving spikelets under the 2﹕0 treatment,while YD6 had the highest number under the 1﹕1 treatment.【Conclusion】Wheat straw return increased rice yield,with NJ 9108 achieving the highest yield under the full application of spikelet-promoting fertilizer and Yangdao 6 achieving the highest yield under the equal application of spikelet-promoting and protecting fertilizers.Those factors that contributed to the increase in yield were mainly due to a significant reduction in the rate and number of spikelets degeneration and an increase in the number of spikelets per panicle.The decrease in the rate of spikelets degeneration for NJ 9108 was greater than that for YD6,which was the main reason for the difference in their response to different panicle fertilization treatments in terms of the number of surviving spikelets.