Effects Of Seedingrate And Nitrogen Application On Grain Yield And Nitrogen Useefficiency In Wheat Under Rotarytillage With Rice Straw

Straw incorporation is an important ways of utilization of straw,and affects nutrient balance of soil and crop yield and nitrogen utilization effmciency.To explore the effects of seedingrate and nitrogen fertilizer management on grain yield and nitrogen use efficiency of wheat under rotary tillage with rice straw,which will provide theoretical basis for high yield and high efficiency cultivation.Field experiments were conducted in Xuzhou and Rugao during 2013-2015 to explore the effect of seeding rate,nitrogen rate and ratio of basal to topdressing on grain yield,nitrogen utilization efficiency and soil nitrogen apparent surplus amount underrotary tillage with rice straw.The major results as follows:1.Underrotary tillage with rice straw,seedingrate,nitrogen rate and ratio of basal to topdressing have significant impacts on growth and yield of wheat.Increasing seeding rateand the ratio of basal fertilizercould significantly improve the spike numbers,leaf area index and photosynthetic rate of the flag leaf at anthesis,thus dry matter accumulation from anthesis to maturity and grain yield had improved under low nitrogen rate 150 kg/hm~2 and appropriate nitrogen rate 225 kg/hm~2.While under excessive nitrogen rate 270 kg/hm~2,increasing seeding rateandtopdressing rate leaded to reduced the percentage of effective tillers,post-booting leaf area index,photosynthetic rate of the flag leaf at anthesis and post-anthesis dry matter accumulation that would bring the grain yield decreased.The ratio of basal fertilizer and topdressing at jointing and booting stages 6:3:1 was the optimal,which could simultaneously improve grain yield.2.Underrotary tillage with rice straw,increasing seeding rate,nitrogen rate and basal ratio of nitrogen could significantly increase the nitrogen accumulation during different growth stages before anthesis.The nitrogen accumulation at anthesis-maturity stage increased with increasing topdressing at booting ratio.With the decreasing of nitrogen rate and topdressing ratio,the translocation rates and contribution rates increased significantly,seeding rate had no significant influence on the translocation rates and contribution rates.Increasing seeding rate or decreasing nitrogen rate could significantly improve of nitrogen uptake efficiency and nitrogen agronomy efficiency.The ratio of basal fertilizer and topdressing at jointing and booting stages 6:3:1 could simultaneously improve nitrogen uptake efficiency and nitrogen agronomy efficiency.3.Decreasing seeding rate or increasing nitrogen rate could significantly raise the 0-40cm soil layer NO3--N and NH4+-N content.Before the anthesis,the inorganic nitrogen content executes along with the base and topdressing at jointing fertilizer inputs increases obviously increases,but the inorganic nitrogen content executes along with the topdressing at booting fertilizer inputs increases obviously increases at anthesis and maturity.Apparent nitrogen surplus and deficit were different at different growth stages among treatments.During the whole growth season,with the increasing of nitrogen rate and topdressing ratio,the apparent nitrogen surplusincreased significantly but increasing seeding rate could reduce the apparent nitrogen surplus.Increasing seeding rate with reduced nitrogen rate properly and increased the ratio of basal fertilizer underrotary tillage with rice straw decreased NO3--N leaching,maintained the balance in soil-wheat system.In conclusion,under this test condition,it had advantage to improve wheat growth,reduce loss ofinorganic nitrogen content,increase nitrogen uptake andutilization,and then enhance yield and nitrogen utilization efficiency whenseeding rate were increased to 180 kg/hm~2,nitrogen rate was225 kg/hm~2 and the ratio of basal fertilizer and topdressing at jointing and booting stages was 6:3:1 in Xuzhou,and seeding rate were increased to 135 kg/hm,nitrogen rate was225 kg/hm~2 and the ratio of basal fertilizer and topdressing at jointing and booting stages was 6:3:1 in Rugao.In conclusion,increasing seeding rate with reduced nitrogen rate properly and increased the ratio of basal fertilizer underrotary tillage with rice straw could improve grain yield and nitrogen use efficiency.