珠江三角洲平原土壤磷剖面分布及形态特征研究

Studies on P Distribution and Fractions in Soil Profile of Cultivated Land in Pearl River Delta Plain

以珠江三角洲平原由三角洲沉积物、河流沉积物和滨海沉积物发育形成的水耕人为土(水稻土)为对象,研究了水田、果园、菜地3种利用方式下不同发生层土壤全磷(TP)、有机磷(Po)、有效磷(AP)、无机磷(Pi)组分的含量和剖面分布特征,并利用液相31P核磁共振(NMR)技术测定了耕层土壤中磷形态分布。结果表明,珠江三角洲平原农田土壤全磷、有机磷、有效磷和各形态无机磷含量随土层深度增加呈减小的趋势,耕层土壤中全磷、有效磷、Al-P和Fe-P明显富集;菜地和果园耕层土壤中全磷、有效磷、Al-P、Fe-P、Ca-P和O-P含量均高于水田。土壤磷素以无机磷形态为主,无机磷、有机磷占全磷比例平均值分别为71.3%和28.7%。土壤无机磷组分以O-P和Fe-P为主,Al-P最低。Al-P、Fe-P、Ca-P、O-P与全磷呈极显著或显著正相关,有效磷与Al-P、Fe-P、O-P、全磷呈极显著正相关;Fe-P和Al-P是土壤有效磷的主要贡献者。31P-NMR结果表明,耕层土壤磷形态均以正磷酸盐为主;土地利用方式影响土壤磷组分,菜地耕层土壤中磷形态包括正磷酸盐、磷酸单酯和焦磷酸盐,水田和果园包括正磷酸盐、磷酸单酯、磷酸二酯和焦磷酸盐;水田土壤中正磷酸盐所占比例最低,磷酸单酯和磷酸二酯所占比例最高;成土母质对水田耕层土壤各形态磷所占比例影响很小。

The contents and profile distribution of total P(TP), organic P(Po), available P(AP) and inorganic P(Pi)fractions were studied in Stagnic Anthrosols(Paddy soils) derived from delta, fluvial and marine deposits under different land uses including paddy field, orchard and vegetable field in Pearl River Delta Plain.And solution31P-NMR was applied for determining the distributions of P fractionsin plough layer soils. The results indicated that the contents of soil TP, Po, AP and Pifractions decreased with the increase of soil depth. Soil TP, AP, Al-P and Fe-P enriched markedly in plough layer. Soil TP, AP, Al-P and Fe-P in plough layer of vegetable field and orchard were higher than those in paddy field. Piwas the dominant form in soil, and the percentage of Piand Poto TP was 71.3% and 28.7%,respectively. O-P and Fe-P were the dominant forms of Pi, and Al-P content was the least. There existed significantly positive correlation between Al-P, Fe-P, Ca-P, O-P and TP. And AP was significantly positively correlated with Al-P, Fe-P, O-P and TP. Fe-P and Al-P were the main contributors to soil AP. Soil P compounds identified by31P-NMR spectroscopy showed that orthophosphate was the dominant form of soil P in plough layer. Soil P fractions were affected by land use types, such as orthophosphate, orthophosphate monoesters and pyrophosphate in plough layer of vegetable field, and orthophosphate, orthophosphate monoesters, orthophosphate diesters and pyrophosphate in paddy fields and orchards. The percentage of orthophosphate in soil TP was the lowest, whereas orthophosphate monoesters,orthophosphate diesters were the highest in paddy field. Parent materials had no obvious influence on the percentage of P fractions in paddy field.