| We studied the potential of chemical fertilizer reduction combined with green manure rape returning to field on nitrogen accumulation,transport and soil microecology of maize.This study aims to provide a scientific and practical basis for efficient maize production when green manure replaces chemical fertilizer in irrigated oasis.The field experiment was undertaken in split-plot design.There were two main treatments:(i)winter fallow-maize(WF)(control),(ii)Green Manure(GM)-maize(GM:Brassica napus L.).The sub-treatments included five rates of chemical nitrogen(N)applied at maize total growth periods:0(N0),189(N189),216(N216),243(N243),270(N270)kg·hm-2.The N of 270 kg·hm-2 is a conventional practice for local farmers,while the N of 243 kg·hm-2,216 kg·hm-2 and 189 kg·hm-2 are 10%,20%and 30%reduction of N270.The main conclusions are as follows:Returning green manure rape to the field significantly increased the activities of catalase,sucrase,urease and alkaline phosphatase at the jointing,tasseling,grain-filling and mature periods of maize by 7.13%?13.22%,24.23%?38.69%,7.13%?13.22%,6.27%?8.05%and 17.07%?48.96%,respectively.Specially,the effect of green manure returning to field reached a significant level on soil alkaline phosphatase activity,which of GM without nitrogen fertilizer was not significantly higher than WF-N270 treatment for whole growth periods of maize,while the alkaline phosphatase activity of GM-N243treatment increased significantly by 20.02%?59.37%.The green manure returning at the full flowering period significantly increased the contents of soil organic matter,total nitrogen,alkali-hydrolyzed nitrogen,total phosphorus,available phosphorus and available potassium of each growth period of maize,but had no significant effect on the total soil potassium content.Nitrogen and available phosphorus increased significantly,and the increases were 4.04%?9.57%,9.45%?21.61%and 7.38%?8.38%,respectively.With green manure returning and the application of chemical fertilizer being reduced by 10%,the content of soil organic matter,total nitrogen,alkali-hydrolyzed nitrogen and available phosphorus increased by 10.19%?18.54%,7.02%?11.64%,15.83%?47.40,and 6.81%?10.24%,compared with the conventional nitrogen application in winter idle fields.The effect of green manure rape on the soil fungal community was significant,and the effect of green manure on the fungal community structure was even more significant.Green manure increased the relative abundance of beneficial microorganisms at the fungal phylum and genus levels,the relative abundances of Zygomycota and Basidiomycota at the phylum level were significantly increased by 48.75%and 67.12%;the relative abundance of Mortierella at the genus level increased was 47.37%,and the RDA analysis showed that the change of soil enzyme activity was the main factor affecting the change of fungal community structure.After the green manure returning to field,the maize yield was significantly increased by 8.97%compared with the winter fallow treatment,of which the average increase in the number of grains per ear was 5.44%.The impact of green manure on100-grain weight did not reach a significant level in 2020,while the increase in 2021was 6.09%.The maize yield of GM-N243 treatment was reaching the peak at 13481.77kg·hm-2,which was 9.80%higher than WF-N270 treatment.From the linear plus platform model,it can be seen that when the nitrogen application rate of green manure was 238 kg·hm-2,the maximum yield was 14312.20 kg·hm-2,which reduced nitrogen application by 11.19%with the yield increase for 4.82%compared with WF treatment.The green manure significantly increased the nitrogen accumulation at the tasseling and mature periods of maize plants,and the nitrogen transport from the maize stem and the contribution rate of the transport to the grain increased significantly by 14.33%and9.34%compared with WF treatment,however the nitrogen transport of the maize leaves was not highly affected by green manure returning.The nitrogen fertilizer agronomic efficiency and nitrogen fertilizer utilization rate of GM-N243 treatment significantly increased by 24.18%and 29.36%,respectively,compared with WF-N270 treatment. |
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