铵对土壤钾素释放、固定影响的研究

INFLUENCE OF AMMONIUM ON RELEASE AND FIXATION OF POTASSIUM IN SOIL

铵对钾素固定释放影响的研究表明,铵在提高土壤原有钾素的有效性方面作用不大,相反,它可使钾更紧闭在矿物层间复三角孔穴中,从而使酸溶性钾减少。铵的吸附固定可减少施入土壤的钾肥的固定,从而提高钾肥的肥效,伹也易造成肥料钾的流失。在铵、钾施用次序上,先施铵后施钾时肥料钾固定最少;先施钾后施铵时肥料钾固定最多;铵、钾同时施用时固定率居中。

Influence of ammonium on release and fixation of potassium in soils was studied with eight soils derived from basalt, loess sediment etc. The increasing in availability of potassium in the soils was little by adding various amounts of ammonium under condition of submergence or alternate wetting and drying, but after wetting NH_4^+ can prevent new fixation of K released from soil through airdried, thus keeping availability of potassium in the soil. For soils with mica and illite as dominent clay minerals, K extracted with 1 mol/L boiling HNO_3 from soil added with NH_4^+ is 33 75 μg K/g less than that from soil without adding NH_4^+.It indicates that NH_4^+ can efficiently make potassium be occluded in the ditrigonal hole of 2:1 minerals, and the potassium will release difficultly.Fertilizer K fixed in soils without leaching with NH_4^+ and Ca^(++) is 3.3-37.4%.After Ca^(++) leaching, it has no more change compared with soils without leaching,except very few soils. The capacity of K fixation is greatly decreased in soils with NH_4^+ leaching, only about 4% of fertilizer K is fixed. NH_4^+ fixed in soils may dicreese the fixation of K from fertilizer and increase K fertilizer efficiency, but often could cause leaching loss of K. Effects of NH_4^+ and Ca^(++) on K fixation in soils depend on the compsition of clay minerals in soil.The sequence of applying NH_4^+ and K^+ significantly influences the fixation of fertilizer K in soil. After 7 days of applying NH_4^+ followed by applying K, the fixation percentage of added K is the least, being 4.7-17.8%, and it is the highest, being 14.9-30.5%, when K^+ was added 7 days before applying NH_4^+. When K^+ and NH_4^+ are added simultaneously, it is intermediate, being 4.7-24.1%.