长期施肥对黑垆土无机磷形态的影响研究

对黄土高原旱地黑垆土进行25年长期定位肥料试验,对土壤无机P形态、数量和对作物的有效性进行了研究。结果表明,石灰性土壤无机P的组成以Ca10-P占绝对优势,约占无机P总量的57.7%,其次是闭蓄态P(O-P),占17.9%,而Al-P、Fe-P、Ca8-P分别占5.9%、5.7%、10.1%,最少的为Ca2-P,只有2.8%。所有施肥处理中,各形态无机P均以土粪 NP含量最高;Ca2-P、Ca8-P、Al-P以N处理最低,而Fe-P、O-P、Ca10-P以CK处理最低;长期施肥对无机P各组分相对含量也有影响,耗P处理主要是Ca2-P、Ca8-P、Al-P的降低,而施P处理是Ca10-P的降解和Ca2-P的积累。与1990年比较,CK处理均有下降;N处理除O-P、Ca10-P有增加外,其他各组分含量均下降;而NP、秸杆. NP、土粪、土粪. NP处理均呈增加趋势。不同处理对土壤有效P和缓效态P均有不同程度的影响,而与无效态P关系不大。同时做了各形态无机P与作物产量的相关性分析,在各级无机P与产量的相关性中,Ca2-P、Ca8-P、Al-P都达到了极显著水平,其中以Ca8-P与产量的相关性最高,而Fe-P、O-P、Ca10-P也都达到了显著水平。

EFFECTS OF LONG-TERM FERTILIZATION ON FORMS OF INORGANIC PHOSPHORUS IN CALCIC KASTANOZEMS

Variation of forms, contents, and bioavailability of soil inorganic phosphorus in upland Calcic Kastanozems of the Loess Plateau under long-term fertilization were studied. The results showed that the fraction of Ca₁₀-P occupied the largest percentage, or 57.7 % of the total inorganic phosphorus in the soil. O-P came the next, accounting for about 17.9 %, and then was followed by Al-P, Fe-P, Ca₈-P and Ca₂-P, which accounted for 5.9 %, 5.7 % and 10.1 %, respectively. In the fertilization treatments, Treatment M+NP was the highest in inorganic phosphorus, whatever the forms; Treatment N the lowest in Ca₂-P, Ca₈-P and Al-P, and Treatment CK the lowest in Fe-P, O-P and Ca₁₀-P. Long-term fertilization also affected relative contents of inorganic phosphorus of different forms. The phosphorus consuming treatments (N & CK) resulted in decrease of mainly Ca₂-P, Ca₈-P and Ca₁₀-P, whereas the treatment of phosphorus application did mainly in degradation of Ca₁₀-P and accumulation of Ca₂-P. Compared with the findings in 1990, phosphorus of all fractions decreased in CK. In Treatments N, phosphorus of all fractions, except O-P and Ca₁₀-P, declined, but in Treatments NP, S+NP, M and M+NP, all fractions showed increasing trends. Different treatments had different effects on available P and potential phosphorus, which, however, had nothing to do with unavailable P. The correlation analyses of different forms of inorganic P with crop yield were conducted. The correlations of Ca₂-P, Ca₈-P and Al-P with crop yield reached a high level of significance. Among the three, Ca₈-P was the best correlated with yield, and Fe-P, O-P and Ca₁₀-P were also significantly correlated with yield.