| The Loess Plateau is a typical rain-fed agricultural planting area in China.Based on the problems of poor soil organic matter,relatively excessive fertilizer application,soil nutrient loss easily caused by concentrated rainfall in summer,and surplus of one harvest but insufficient of two with water and heat resources,field experiments were carried out in the Loess Plateau wheat region of southern Shanxi province where systematically studied the water and fertilizer effects of winter wheat rotation with different green manures,the yield effects of subsequent winter wheat crops and the effects of tilled green manure on soil fungal diversity,to clarify the nutrient supply potential of green manure and soil nutrient regulation,and combined with the water-consuming characteristics of green manure,we screened out the suitable local dry plateau winter wheat filling green manure crops for efficient production,aiming to provide a theoretical basis for the construction of a reasonable summer green manurewinter wheat model in the dry Loess Plateau wheat area.The main results obtained are as follows:(1)Under the condition of reduced chemical fertilizer application,the "summer green mature-winter wheat" planting mode can improve the winter wheat yield and water and fertilizer utilization efficiency.From 2019 to 2020,the average yield of winter wheat was still increased by 3% compared with fallow treatment after replacing 18%-42% nitrogen fertilizer with green fertilizer in summer off period,and the yield of winter wheat under soybean,small black bean and mung bean treatments was increased by 5%-10% compared with fallow treatment;Planting green fertilizer in the summer off period could improve the water production efficiency of winter wheat,and soybean,small black bean and mung bean treatments increased by 21.5--33.9% compared with farmer treatments(P<0.05).Planting green fertilizer in summer fallow time could improve partial nitrogen productivity,agronomic efficiency of nitrogen fertilizer,recovery rate of nitrogen fertilizer in season and partial phosphorus productivity of winter wheat,and mung bean treatment was the highest,which increased by 68.5%,111.9%,110.4% and 25.5% compared with farmer treatment,respectively(P<0.05).Replacing fertilizer with soybean,mung bean,crotalum and sweet clover increased the nitrate nitrogen storage in 200 cm soil after winter wheat harvest.The net income of farmers was increased by 21.2%(P<0.05),18.5%(P<0.05)and 6.0%(P<0.05)by planting mung bean,small black bean and soybean at the same time.(2)Compared with fallow treatment,planting green manure increased soil water consumption in summer free period.In 2020,the average water fallow efficiency of soybean,small black bean and mung bean treatment was 38.7%,which was 10% lower than that of farmer treatment(P<0.05);Soil water storage in 200 cm of soybean,small black bean and mung bean treatments was 373 mm on average,which was 8.4% lower than that in farmer treatments(P<0.05).The dry matter returning amount of soybean,small black bean and mung bean were 3868,3999,2766 kg·hm-2,respectively,and the unit water consumption biomass of soybean and small black bean was the highest,with an average of 19.1 kg·hm-2·mm-1.The total nutrient return(N+P2O5+K2O)of soybean,small black bean and mung bean were 281,288 and 242 kg·hm-2,respectively.The nitrogen uptake and accumulation of green manure in the summer off period decreased the nitrogen storage in 200 cm soil before winter wheat sowing and alleviated the nitrogen leaching.The average nitrogen storage in 200 cm soil under the treatment of small black bean,soybean and mung bean was 13.2% lower than that under the treatment of farmers(P<0.05).(3)The planting of overturning green manure did not change the richness of soil fungal community in the summer fallow time,but the planting of overturning small black bean increased the number and evenness of soil fungal physiological groups,and the planting of overturning soybean significantly decreased the evenness of soil fungus.The soil fungal community of wheat field in the dry tablelands of south Shanxi province was mainly composed of ascomycetes basidiomycetes and host fungi.The relative abundance of Ascomycetes(Cofaecitomycetes)in the soil was increased by planting overpressed soybean,but the relative abundance of Basidiomycetes(Symbomycetes)in the soil was significantly decreased by planting overpressed soybean and mung bean.In conclusion,in the winter wheat planting area of the dry highland of South Shanxi on the Loess Plateau,the planting of overturning green manure in the fallow time would increase the soil water consumption,and reduce the accumulation of nitrate nitrogen and the range of leaching in the soil.The wheat yield could be increased by 3% after the substitution of 18--42% nitrogen.At the same time,the planting of overturning green manure could improve the fertilizer use efficiency and soil fungal diversity index of winter wheat.Combined with the comprehensive performance of green manure water,fertilizer effect and influence on microbial diversity,small black bean is more suitable to be planted in wheat area of dry highland in south of Shanxi Province than other green manure of legumes. |
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