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淡灰钙土和灌淤土均属石灰性土壤,是宁夏引黄灌区主要的耕种土壤。一般富钾缺磷缺氮,开垦初期,磷肥与氮肥配合使用,肥效很高。过去认为石灰性土壤的可溶性磷酸根很不稳定,易被 Ca~(++)固定成难溶性磷酸盐,从而降低肥效,因此很重视磷肥的施用,磷酸施量一般相当氮素用量的60～80％(表1)。但随着耕种年代的延续,不断向土壤施入磷素后,磷肥的肥效逐渐变得不够明显,淡灰钙土上这种现象尤为突出。本文试对这两类土壤磷素的动态变化规律,及合理施磷、提高肥料经济效益问题作一探讨。一、渠口农场历年氮、磷施量与产量变化分析
Light gray soil and irrigated silt belong to calcareous soil, which is the main cultivated soil in irrigated area of Yellow River in Ningxia. Generally rich in phosphorus and nitrogen deficiency, early reclamation, phosphate fertilizer and nitrogen fertilizer with high efficiency. In the past, it was considered that the soluble phosphate in calcareous soil was unstable and could be easily immobilized as insoluble phosphate by Ca ~ (++) 80% (Table 1). However, with the continuation of the cultivation years, the continuous application of phosphorus to the soil, the fertilizer efficiency becomes less obvious, the phenomenon of light gray soil is particularly prominent. This paper attempts to test the dynamic changes of these two types of soil phosphorus, phosphorus, and improve the economic efficiency of fertilizer to make a discussion. First, the drainage farm calendar years nitrogen and phosphorus application and yield changes