稻秆对硫铵氮去向和水稻生长的影响

盆栽试验以混合肥料的碳氮比值为指标基施等量硫铵(15N)和不等量稻秆,在同一盆内连续植稻三季,研究稻秆对15N硫铵氮素的去向和水稻生产的影响,以及被固定氮的残效。结果表明,稻秆显著地抑制硫铵的肥效及延缓水稻生长和发育的作用仅发生于植稻的第一季,并和混合肥料的碳氮比有关。对二、三季水稻氮的贡献很小,但高碳氮比处理能回收较多的硫铵氮素并取得较大的水稻反应。植稻三季后,硫铵混合和不混合稻秆处理的水稻生物产量间及稻穗中硫铵氮素的总和间(不含最高稻秆用量处理),均没有显著差异。 硫铵氮素的固定作用在第一季作物表现十分明显。残留土壤中的硫铵氮素颇为稳定,在连续植稻过程中不易释放出来被水稻吸收,尤其是在第三季。硫铵氮素的损失主要发生于植稻的第一和笫二季,稻秆对其固定具有防止硫铵氮素损失的作用。

EFFECT OF RICE STRAW ON (NH4)2SO4-N BALANCE AND RICE PRODUCTION IN PADDY SOIL

Rice straw and ¹⁵N labeled (NH₄)₂SO₄, respectively supplied in four C/N ratios, were basal dressed to grow three consecutive seasons rice crops in pots to investigate the influence of straw materials, not only in the current first season, but also in the second and third seasons on the fate of applied (NH₄)₂SO₄-N and rice production, as well as the residual effects of three sampling stages just after each harvest. As expected, the straw materials might significantly delay the (NH₄)₂SO₄-N uptake by rice and then retard the growth and development of rice crops. These effects were solely observed in the current 1st season and related to the quantity of added straw. In the further 2nd and 3rd seasons, more (NH₄)₂SO₄-N recovery and greater rice responses were obtained in the higher straw supply treatment though both responses were extremely poor. After plantation of 3 seasons rices, no significant difference of the sum total dry weight or the sum recovery of applied N in panicles (except that in the highest straw supply treatment) in 3 seasons between the straw and strawless treatments was presented. The immobilization of (NH₄)₂SO₄-N was apparent in the 1st season and related not only to the soil, but also to the added straw. The applied N residual in soil was rather stable and hardly decomposed to release available N for the further season rice crops, especially those at the time after harvesting 2nd season rice, though the basal dressed (NH)₂SO₄-N losses would last two seasons in the rice pot experiment.