Abstract:

【Objective】 To ascertain the effects of rice-based cropping system, organic manure and ground water level on soil inorganic phosphorus forms. 【Method】 A long-term stationary experiment was carried out to study this subtect based on the fractional schemes proposed by Jiang Bai-fan, et al. 【Result】 Results showed that the contents of total inorganic phosphorus of the tested plough layer soils in different treatments ranged from 398.56 to 546.10 mg?kg-1, with (471.4±40.5) mg?kg-1 on average. O-P and Fe-P were the two main forms of inorganic phosphorus in the reddish-yellow clayey paddy soi1 that was derived from quaternary red clay and the two fractions accounted for 39.20%-38.59% of total inorganic phosphorus. Among the 3 rice-based cropping systems, the contents of total inorganic phosphorus in the treatment of rice-rice-flooded fallow in winter were higher than those in the treatments of rice-rice- rapeseed and rice-rice-green manure. The total inorganic phosphorus contents in the treatment of inorganic fertilizer were higher than those in the treatments of high rate of applied of manure and normal rate of applied manure. Low ground water level can increase the inorganic phosphorus contents in the soil. The contents of Fe-P in the treatments of rice-rice-flooded fallow in winter and rice-rice-rapeseed were higher than those in the treatments of rice-rice-green manure. As time goes on, the contents of Ca2-P, Ca10-P and Fe-P decreased under the same rice-based cropping system, while the contents of Al-P, Ca8-P and O-P increased. The contents of Ca10-P, Fe-P and Al-P in the treatment of inorganic fertilizer were higher than those in the treatments of normal rate of applied manure and high rate of applied manure. As time goes on, the contents of Ca2-P, Ca10-P and Fe-P decreased under the same organic manure application, while the contents of Al-P, O-P and Ca8-P increased. The contents of Ca10-P and Fe-P in the treatment of low ground water level were higher than those in the treatment of high ground water level, while the contents of Ca2-P and O-P in the treatment of high ground water level were lower than those in the treatments of low ground water level. As time goes on, the contents of Ca2-P and Fe-P decreased under the same ground water level, while those of Al-P, O-P and Ca8-P increased 【Conclusion】Crop planting in winter can decrease inorganic P content, while green manure application in winter can decrease Fe-P content. Inorganic fertilizer application could increase total inorganic P and Ca10-Pand Fe-P and Al-P contents. Lower ground water level is beneficial to accumulation of inorganic P.

Key words: rice-based cropping system, organic manure, ground water level, inorganic phosphorus, paddy soil