种植大豆对土壤氮素盈亏影响的估算

应用15N示踪方法,研究了种植大豆对土壤氮素盈亏的影响,并对土壤氮素盈亏进行了估算。结果表明:大豆成熟期70.4%~88.6%的氮素转移到籽粒中,大豆氮素收获率很高,导致土壤氮素亏损;秸秆还田时土壤氮素亏损量平均为39.2kg/hm2,秸秆不还田时土壤氮素亏损量平均为49.2kg/hm2;大豆根瘤固氮率与土壤氮素盈亏量呈直线相关,根瘤固氮率越高,土壤氮素亏损量越少;秸秆还田条件下,根瘤固氮率71.5%是土壤氮素盈亏平衡点,秸秆不还田时根瘤固氮率要达到80.9%才能保障土壤氮素盈亏平衡。

ESTIMATING EFFECT OF PLANTING SOYBEAN ON PROFIT AND LOSS OF SOIL NITROGEN

~(15)N isotope tracing technique was used to estimate the effect of planting soybean on the profit and loss of soil nitrogen. Results showed that the nitrogen harvest rate of soybean was quite high and 70.4% ～ 88.6% of total nitrogen was transported to seeds, which led to the loss of soil nitrogen; and the average loss of soil nitrogen were 39.2kg/hm~2 for straw returning and 49.2kg/hm~2 for no straw returning treatments, respectively. A significant linear correlation was found between nitrogen fixation rate and the profit/loss of soil nitrogen. The loss of soil nitrogen was less with higher nitrogen fixation rate, which would reach the breakeven point of the profit and loss of soil nitrogen when nitrogen fixation rate was 71.5% for straw returning treatment, and 80.9% for no straw returning treatment.