合成磷源在石灰性潮土中的形态转化及氮肥形态对其的影响

利用盆栽试验研究了几种人工合成磷源在轻粘质潮土根际和本体土壤中的形态转化及配施不同形态氮肥对其形态转化的影响,结果表明,作物耗竭引起根际所有形态无机磷不同程度的下降.施入土壤的DCP(CaHPO4*2H2O)、OCP(Ca8(PO4)6)、Al-P(AlPO4*nH2O)等大部分转化为其它形态无机磷,而Fe-P(FePO4*nH2O)和FA(Ca10(PO4)6F2)大部分以自身形态存在,尤其是FA很少向其它形态转化,根际条件促进了它们向其它无机磷形态的转化.Al-P和FA等的形态转化明显受氮肥形态的影响,Al-P配施NO-3-N下,绝大部分转化为磷灰石,NH+4-N配施下促进了FA向其它形态的转化,在所有的磷源处理中,根际和本体磷酸铁都有显著地增加,NH+4-N和CO(NH2)2处理下存在磷酸铁的根际累积;其次是磷酸二钙和磷酸铝也有明显地增加,二者存在根际的亏缺.不同磷源的形态转化规律与其有效性大小相一致.

EFFECT OF DIFFERENT NITROGEN FERTILIZERS ON TRANSFORMATION OF SYNTHESIZED PHOSPHATES IN CALCAREOUS CHAO SOILS

Pot trials were conducted to study the effects of NH₄⁺-N, CO(NH₂)₂ and NO₃^--N on the transformation of several synthesized phosphates in light clay calcareous Chao soil. The results indicated that treatment with maize and no added P decreased to different degree the content of all inorganic P species in rhizosphere. DCP, OCP, Al-P applied mostly transformed into other inorganic phosphates other than dicalcium phosphate, octacalcium phosphate, aluminum phosphate respectively. However, Fe-P, especially FA applied, mainly existed in their corresponding forms in soil and the condition in rhizosphere is favorable for their transformation into other inorganic phosphates. The transformation of Al-P and FA applied in soil were significantly affected by forms of nitrogen fertilizer. Al-P coupled with NO₃^--N predominantly transformed into apatite. FA coupled with NH₄⁺-N was more favorable for its transformation into other inorganic phosphates except apatite than coupled with other two N forms. The content of ferric phosphate in rhizosphere and bulk soil significantly increased in all treatments and accumulated in rhizosphere when coupled with NH₄⁺-N and CO (NH₂)₂. Besides dicalcium phosphate and aluminum phosphate content also increased markedly and both of them were lower in rhizosphere than those in bulk soil. Their transformations in soil, especially in rhizosphere, were consistent with their availability.