Effects of Topdressing with Nitrogen on Photosynthesis and Grain-Filling Characteristics of Spring Maize after Anthesis
To further investigate yield potential and N utilization of maize in the rain-fed agricultural area of Northeast China,a field experiment was conducted using spring cultivar Fumin985 as the experimental material.Five nitrogen fertilization treatments were implemented using drip fertigation:N-fertilizer applied 100％at sowing(CK),40％at sowing,and 60％at V6(T1),40％at sowing,20％at V6,and 40％at VT(T2),40％at sowing,15％at V6,30％at VT,and 5％at R2(T3),40％at sowing,10％V6,30％at VT,and 20％at R2(T4).And the SPAD value of ear leaf,net photosynthetic rate of ear leaf,phosphoenolpyruvate carboxylase activity of ear leaf,grain bulk densi-ty and yield were studied.The grain-filling processes of maize were analyzed by Logistic model to analyze the grout-ing parameters.The results indicated that grain yield(13 901 kg/ha)of T4 was significantly higher than that of the other treatments.Compared to CK,the net photosynthetic rate of ear leaf,phosphoenolpyruvate carboxylase activity of ear leaf,active grain-filling period,maximum filling rate time,and the grain bulk density of T4 increased by 42.8％,20.6％,13.7 d,2.4 d,and 1.2％,respectively.Applying 40％of nitrogen fertilizer at sowing,10％at V6,30％at VT and 20％at R2(T4)can obtain more photosynthate,extend grain filling period,and increase 100-kernel weight of maize and grain yield in the rain-fed agricultural area of Northeast China.
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