氮磷钾肥料在土壤中转化过程的交互作用 Ⅱ.硫酸铵在水稻土中的转化

INTERACTION OF NPK FERTILIZERS DURING THEIR TRANSFORMATION IN SOILS Ⅱ. TRANSFORMATION OF AMMONIUM SULFATE IN THE PADDY SOIL

通过室内培养实验,研究了Ca(H2PO4)2和KCl对(NH4)2SO4在土壤中转化的影响。结果表明,Ca(H2PO4)2对(NH4)2SO4转化的影响较小。Ca(H2PO4)2对未施氮土壤中硝化作用的正效应,以及对施氮培养前期土壤中硝化作用的负效应可能与土壤pH的变化有关。施用KCl显著影响供试水稻土中(NH4)2SO4的转化,主要表现为:(1)施钾导致培养初期土壤中水溶性铵的增加与交换态铵的减少,与铵钾的代换作用有关,培养后期这两种形态铵的共同增加则与钾抑制硝化作用有关。(2)施钾既显著地抑制了氯化钠提取过程中土壤铵的释放,也抑制了培养过程中土壤固定态铵的释放。施钾对风干土样水溶性铵的影响与鲜样中不同,也与施钾抑制土壤风干过程中铵的释放有关。(3)钾铵同时施用,施钾促进了铵的固定。(4)施钾显著抑制了硝化作用,本文实验条件下,其直接作用机制可能并不是钾抑制了土壤中固定态铵的释放。单施钾肥会显著降低未施氮土壤中无机氮的有效性。由以上结果推测,氮钾肥配施将不仅有利于减少硝态氮的淋洗和反硝化脱氮作用,而且可增强土壤中铵的缓冲能力。这也表明土壤中钾对铵态氮肥转化的影响,可能是生产实践中氮钾肥配合施用可提高氮肥利用率的原因之一。

Effects of calcium biphosphate (MAP) and potassium chloride (KCl) on transformation of ammonium sulfate (AS) in the paddy soil were investigated through laboratory incubation. The results show that MAP can only affect transformation of AS to a limited extent. The increase in nitrification in the soil without ammonium applied and decrease in nitrification in the soil with application of MAP might be associated with change in soil pH. The application of KCl significantly affected transformation of AS in the paddy soil,mainly in the following aspects: (1) The increase in water soluble ammonium (WSA) and decrease in exchangeable ammonium (EA) as a result of the addition of KCl at the initial stage of incubation were attributed to replacement of K^(+) and NH^+_(4) in the soil,but the increase of both WSA and EA at a later stage was related to the inhibitive effect of K on nitrification. (2) The presence of potassium significantly suppressed release of fixed ammonium during incubation or extraction of the soil with NaCl. The different effects of K on WSA in the fresh soil and air-dried soil were also attributed to K inhibiting ammonium release during air-drying course. (3) When potassium and ammonium were applied together into the soil,potassium increased ammonium fixation in the soil. (4) Nitrification of ammonium in the paddy soil was significantly suppressed by KCl,which might not result directly from K inhibiting release of ammonium under the controlled condition. Application of potassium alone might decrease availability of inorganic nitrogen in the paddy soil without N application. Thus it can be inferred that combined application of potassium and ammonium will not only reduce leaching and denitrification of nitrite,but also increase buffer capacity of soil ammonium. The results indicate that the interactions between NH^+_(4) and K^(+) in the soil may be one of the reasons why combined application of potassium with nitrogen fertilizers could increase efficiency of nitrogen fertilizer in production.