| In view of the current situation of excessive and unreasonable nitrogen application in the Huang-Huai Plain,impacts of different nitrogen application patterns and soil tillage practice on growth,yield and inorganic nitrogen content in soil under the condition of reducing nitrogen application rate in wheat,were explored providing a basis for stable yield and improve nitrogen use efficiency.Using wheat cultivar " Aikang 58" as the testing material,a 2-year field experiment was conducted with split-split-plot design[two levels of nitrogen application(240 kg·hm-2,180 kg·hm-2),two levels of soil tillage practice(rotary tillage,deep tillage)and three levels of nitrogen application patterns(broadcast application,topdressing every two rows,topdressing every three rows)] to determine root growth,root vigor,culm and tiller development,photosynthetic characteristics of leaves,content of inorganic nitrogen in 0~40 cm soil layer,grain yield,nitrogen use efficiency of winter wheat.The main results are as follows:(1)The results showed that nodal roots per plant,root vigor,culm and tiller development,leaf SPAD value,leaf area index(LAI)and dry matter accumulation in different vegetative organs reduced with the decreasing in nitrogen application rate.Compared with those in rotary tillage,there were much more nodal roots per wheat plant in middle and late growth period in deep tillage,the same as the culm and tiller development,higher root vigor,larger leaf area index,and increase in dry matter accumulation in different vegetative organs.Under a certain N rate,nodal roots per plant,root vigor,culm and tiller development,leaf SPAD value,LAI,dry matter accumulation in different vegetative organs were the highest in topdressing every two rows,the lowest in topdressing every three rows,and in between in broadcast application.(2)Reducing nitrogen fertilization decreased grain yield,increased nitrogen partial factor productivity,nitrogen uptake efficiency and nitrogen utilization efficiency.Compared with those in rotary tillage,there were higher grain yield,nitrogen partial factor productivity and nitrogen uptake efficiency,but lower nitrogen utilization efficiency in deep tillage.Under a certain N rate,grain yield,nitrogen partial factor productivity and nitrogen uptake efficiency were the highest in topdressing every two rows.(3)Content of total nitrogen in 0~20 cm and 20~40 cm soil layers decreased gradually with the development.It was relatively stable in different soil layers and decrease with the depth of soil layer.Content of total nitrogen in the treatment of reduced N application of each growing stage was lower than conventional N application.Content of total nitrogen 0~20 cm soil layer of rotary tillage was significantly higher than that of deep tillage,but 20~40 cm soil layer was significantly lower than that of deep tillage.From heading to maturity,total nitrogen in 0~20 cm and 20~40 cm soil layers of topdressing every two rows was significantly lower than those in broadcast application and topdressing every three rows.(4)Content of nitrate nitrogen and ammonium nitrogen in 0~20 cm and 20~40 cm soil layers decreased gradually with the development,there was little difference between different soil layers in the late development stage.It decrease with the deepening of soil layer,ammonium nitrogen content in 20~40 cm soil layer was relatively stable.Content of nitrate and ammonium nitrogen in the treatment of reduced nitrogen application of each growing stage was lower than conventional nitrogen application.Content of nitrate nitrogen and ammonium nitrogen 0~20 cm and 20~40 cm soil layers under rotary tillage treatment were significantly higher than those in deep tillage,but content of ammonium nitrogen in 20~40 cm soil layer was significantly lower than that in deep tillage.From heading to maturity,content of nitrate and ammonium nitrogen in 0~20 cm and 20~40 cm soil layers of topdressing every two rows were lower than those in both broadcast application and topdressing every three rows.Considering wheat root & tiller development,photosynthetic characteristics,dry matter accumulation,grain yield,nitrogen use efficiency and soil nutrient status,reducing N application from 240 to 180 kg·hm-2 under deep tillage and topdressing every two rows is optimal practice.It could be beneficial to growth and development of roots and tillers,promote absorption of nitrogen in the soil layer of 0~40 cm,maintain high grain yield and significantly improve the utilization rate of nitrogen,reduce the waste of resources and efficiency protect the agricultural environment. |
