水稻不同移栽密度的氮肥效应及氮素去向

NITROGEN UTILIZATION EFFICIENCY AND FATE OF FERTILIZER UNDER DIFFERENT TRANSPLANTING DENSITY

利用15N示踪技术,研究不同移栽密度对水稻产量、氮肥吸收利用及氮素去向的差异。结果表明,随移栽密度增大,水稻产量显著增加,穗粒数、结实率和千粒重降低,子粒与秸秆氮素含量、肥料利用率及其残留量增加,而氮素损失降低。水稻所吸收的氮素约2/3来源于土壤氮,1/3来源于当季肥料氮。不同移栽密度处理间,肥料利用率为16.69%~26.69%,氮肥残留率为17.12%~21.08%,有52.23%~66.19%的肥料损失。无论哪种密度下,肥料主要残留在0~20cm土层中。种植密度为40cm×40cm时,0~20cm土层氮素残留量为28.54kg/hm2,占施肥量的12.97%,高于50cm×50cm和30cm×30cm处理而在40~60cm土层的氮素残留量为7.34kg/hm2,比50cm×50cm和30cm×30cm处理同层残留量降低了57.90%~59.29%。

Field experiments were conducted to study rice yield,N uptake and fertilizer fate by using urea labeled with ^15N under transplanting density of 30cm×30cm,40cm×40cm and 50cm×50cm.The results showed that higher transplanting density significantly increased rice yield.Grain-panicle,seed setting rate and 1000-grain weight decreased with the transplanting density increasing. ^15N-content in grain and straw of rice,nitrogen use efficiency and ^15N-fertilizer residue were all high at high density,but ^15N-fertilizer loss was low. Almost 1/3 of the total N uptake by rice supplied by fertilizer,and 2/3 N came from soil. Nitrogen use efficiency were 16.69%～26.69%, 15N-fertilizer residue ratio were 17.12%～21.08%,and 15N-fertilizer loss were 52.23%～66.19% among three treatments.15N-fertilizer residue mainly distributed in 0～20cm top soil.The amounts of fertilizer residue in 0～20cm top soil under transplanting density of 40cm×40cm was almost 28.54kg/hm^2,taking 12.97% of the total applied fertilizer,which was higher than that of 50cm×50cm and 30cm×30cm.Under the density of 40cm×40cm,the amounts of fertilizer residue in 40～60cm soil profile was 7.34kg/hm^2,and it was 57.90%～59.29% less than that of 50cm×50cm and 30cm×30cm.