氮肥减量配施有机肥对豫中地区冬小麦-夏玉米轮作生产力和土壤性质的影响

Effects of reduced chemical nitrogen input combined with organic fertilizer ap-plication on the productivity of winter wheat and summer maize rotation and soil properties in central Henan Province

为了探索豫中地区冬小麦-夏玉米轮作的减氮潜力,构建适宜的作物养分管理体系,通过连续3年的田间定位试验,研究了化学氮肥减量配施有机肥对冬小麦-夏玉米轮作系统生产力和土壤性质的影响。田间试验设置10个处理,包括完全不施肥(CK)、农户常规施氮量(100%CNF)、农户常规施氮量递减20%(80%CNF、60%CNF和40%CNF)、单施有机肥(OF)、农户常规施氮量配施有机肥(100%CNF+OF)及氮肥减量配施有机肥(80%CNF+OF、60%CNF+OF和40%CNF+OF)。分析各处理间小麦、玉米籽粒产量和地上部生物量以及土壤理化性质、酶活性和细菌群落的差异。结果表明,不配施有机肥条件下,小麦和玉米籽粒产量和地上部生物量均以80%CNF处理最高。与100%CNF相比,80%CNF处理小麦籽粒产量和地上部生物量分别增加9.67%~10.55%和30.53%~35.76%,玉米籽粒产量和地上部生物量分别增加28.06%~51.42%和29.62%~41.27%。有机肥施用进一步扩大氮肥减量空间,60%CNF+OF和40%CNF+OF处理小麦产量较80%CNF处理无差异,60%CNF+OF处理玉米产量较80%CNF处理无差异。减氮及其配施有机肥并不影响土壤有机质、易氧化有机碳和全氮含量以及pH,但大幅降低硝态氮含量,对铵态氮、速效磷和速效钾含量的影响因处理不同而异。与100%CNF相比,减氮配施有机肥增加土壤脲酶和芳基硫酸酯酶活性,但降低了β-葡萄糖苷酶活性,对蔗糖酶、碱性磷酸酶和脱氢酶活性无显著影响。减氮配施有机肥处理能够改善土壤细菌群落α多样性,60%CNF+OF和40%CNF+OF处理辛普森指数和均匀度指数较100%CNF均显著增加。减氮配施有机肥也显著影响土壤细菌群落β多样性,且氮肥减量相较有机肥施用效果更为突出。在门水平,变形菌门、放线菌门和酸杆菌门是细菌群落优势成员,减氮配施有机肥较100%CNF处理显著降低放线菌门平均相对丰度为10.92%~14.39%;在属水平,减氮配施有机肥处理显著增加unclassified Gp6和Sphingomonas平均相对丰度,但降低了Nocardioides、Kribbella、Lechevalieria、Promicromonospora、Massilia、Glycomyces和Dongia平均相对丰度。冗余分析表明,速效钾和硝态氮含量是影响细菌群落结构最重要的2个土壤理化因子。共发生网络分析也证实,化学氮肥减施增强了细菌群落成员的互作强度,提高了细菌互作网络的复杂性和连通性。本试验条件下,小麦和玉米季农户常规施氮量分别减少60%和40%并各配施3000 kg∙hm^(−2)有机肥能够维持相对较高的轮作生产力,这不仅能够实现最大减氮潜力,同时还能改善土壤微生物多样性和群落结构。

To explore the potential of nitrogen(N)reduction in winter wheat and summer maize rotation system located at central Henan Province and pursue the best crop nutrient management strategy,the effects of reduced chemical N fertilization(RCN)combined with organic fertilizer application(OFA)on rotation system productivity and soil properties were assessed through a field experiment over three years.Ten treatments were employed in the present study:without fertilization(CK),farmers’chemical N application rate(100%CNF),gradually reducing the chemical N application rate by 20%(80%CNF,60%CNF,and 40%CNF),applying organic fertilizer alone(OF),and combined application of RCN and OFA(100%CNF+OF,80%CNF+OF,60%CNF+OF,and 40%CNF+OF).The differences in grain yields and aboveground biomass of wheat and maize,soil physicochemical properties,enzymes activities,and bacterial communities among treatments were analyzed.In the absence of OFA,the highest grain yield and aboveground biomass for wheat and maize were achieved with 80%CNF.Compared with 100%CNF,grain yield and aboveground biomass of wheat in 80%CNF significantly increased by 9.67%−10.55%and 30.53%−35.76%,respectively,and those of maize in 80%CNF significantly increased by 28.06%−51.42%and 29.62%−41.27%,respectively,suggesting that farmers’conventional fertilization constituted excessive N supply.Furthermore,reducing 20%of farmers’chemical N fertilization significantly increased rotation system productivity.The OFA could further release the space for N reduction,which was confirmed by the lack of statistical difference in wheat grain yield among 60%CNF+OF,40%CNF+OF,and 80%CNF;and in maize grain yield between 60%CNF+OF and 80%CNF.The RCN alone or in combination with OFA did not alter the contents of soil organic matter,easily oxidized organic carbon,and total nitrogen,or pH,but substantially reduced the NO3−-N content.The effects of RCN and OFA on the contents of NH4+-N,available phosphorus,and available potassium varied among treatments.Compared to 100%CNF,RCN combined with OFA significantly increased the activities of urease and arylsulfatase and reduced the activity ofβ-glucosidase but did not affect the activities of sucrase,alkaline phosphatase,and dehydrogenase.The combination of RCN with OFA improved theαdiversity of the bacterial community.This was indicated by the Simpson and evenness indices in 60%CNF+OF and 40%CNF+OF being significantly higher than those of 100%CNF.The RCN combined with OFA also significantly changed theβdiversity of the bacterial community,which was more dependent on RCN rather than OFA.At the phylum level,Proteobacteria,Actinobacteria,and Acidobacteria dominated the bacterial community.The combinations of RCN and OFA significantly reduced the average relative abundance of Actinobacteria by 10.92%–14.39%.At the genus level,RCN combined with OFA significantly increased the average relative abundances of unclassified GP6 and Sphingomonas,whereas reduced the average relative abundances of Nocardioides,Kribbella,Lechevalieria,Promicromonospora,Massilia,Glycomyces,and Dongia.Redundancy analysis demonstrated that available potassium and NO3−-N contents were the two most important soil environmental variables driving the bacterial community structure.In addition,co-occurrence network analysis also indicated that RCN strengthened the interactions of species in the bacterial community and yielded highly complex and connected associations among bacterial taxa.In the current study,reducing 60%and 40%of farmers’chemical N fertilization in wheat and maize production,respectively,and in combination with 3000 kg∙hm^(−2) of OFA in each season could maintain relatively high rotation productivity.This fertilization regime not only maximized the potential of N reduction in the rotation system but also improved soil microbial diversity and community structure.Notably,the optimal fertilization regime obtained here must be re-verified across crop varieties,organic fertilizers,and fields.Moreover,the long-term effects of RCN and OFA on yield and soil properties in winter wheat and summer maize rotation systems in central Henan Province need to be further assessed.