水稻土肥际微域铵对钾形态转化与迁移的影响

通过室内土柱培养试验，研究了水稻土肥际微域铵对钾形态转化与迁移的影响。结果表明，钾自肥际向非肥际的扩散距离随钾肥用量增加而增加，施同等铵态氮条件下，施钾量增加2.4倍，导致肥际钾含量最高区域水溶态钾含量提高了2.1倍，交换态钾和非交换态钾则分别提高了1.7和 0.3倍，而钾的迁移距离提高了16.4%（12 mm），说明肥际钾的固定能力有限，钾肥量增加导致更多的钾以有效性较高的形态存在。同等钾量条件下，施用铵态氮肥显著提高了水稻土肥际钾含量最高区域水溶态钾含量，使钾的迁移距离较未施铵时增加了23.2%（16 mm）；铵钾共施还显著提高了肥际到普通土壤过渡区域中交换态钾含量，降低了所有土样中的非交换态钾含量。铵钾共施显著抑制了肥际微域中肥料钾向非交换态的转化，这种抑制作用随距肥际距离的增加而减弱。利用不同回归方程拟合由肥际到非肥际钾的分布曲线，无论是水溶态钾还是交换态钾，反S型曲线 y = a / 1 + b exp (c×x)] 可以很好地拟合由肥际到非肥际K+ 的分布。

Transformation and movement of potassium in ferti-sphere of paddy soil as affected by co-application of ammonium

A soil column incubation experiment was conducted in this study to investigate the effect of NH4+ on transformation and movement of K+ in ferti-sphere of paddy soil. The results showed that movement of K+ increased with K dose. In presence of same amount of NH4+, as K dose increased by 2.4 times, the water-extractable K (WE-K), Exchangeable K (E-K) and non-exchangeable K (NE-K) in the nearest part of ferti-sphere significantly increased by 2.1, 1.7 and 0.3 times, respectively. While the K diffusion distance increased by 16.4% (12 mm) as K dose increased. The results indicated that fixation of K in ferti-sphere is somewhat limited; more portion of K remained in labile form as K dose increased. Co-application of NH4+ and K significantly increased both WE-K in the nearest part of ferti-sphere and the K diffusion distance as compared with K solely applied treatment. Co-application of NH4+ significantly increased E-K in the transition area from ferti-sphere to bulk soil and reduced NE-K in all the soil samples that NH4+ possibly reached. Co-application of NH4+ significantly restrained transformation of added K into NE-K in ferti-sphere, and the effect declined as the distance from ferti-sphere increased. Different models were compared to describe the change of K concentration from ferti-sphere to bulk soil, for both WE-K and E-K, the anti-S-shape curve y = a / 1 + b exp (c × x)] can be well fitted.