土壤肥力与秸秆还田

作物秸秆内含有丰富的氮、磷、钾、钙、镁等多种营养元素和有机质。据测定,湿玉米秸秆中含氮量为0.61％,含磷量为O.27%,含钾量为2.28％,有机质含量为15％左右,1250公斤玉米桔秆相当于4000公斤土杂肥的有机质含量。作物秸秆切碎还田可改善土壤团粒结构和理化性能,增加土壤的有机质含量,降低土壤容重,增加土壤孔隙度,使土壤疏松,通气性提高,贮水量增加。

Dissolution and Fractionatoon of Calcium-Bound and Iron-and Aluminum-Bound Humus in Soils

This paper deals with the development of a sequential extraction method to separate the Ca-bound and Fe-and Al-bound humus from soils.First,comparative analyses were carried out on dissolution of synthetic organo-mineral complexes by different extractants,i.e.0.1M Na4P2O7,0.1M NaOH+0.1M Na4P2O7 mixture,0.1M NaOH,0.5M (NaPO3)6 and 0.5M neutral Na2SO4.Among the five extractants,0.1M NaOH+0.1M Na4P2O7 mixture was the most efficient in extracting humus from various complexes.0.5M Na2SO4 had a better specificity to Ca than 0.5M (NaPO3)6,by only extracting Ca-bound humus without destorying Fe-and Al-bound organo-mineral complexes.Then sequential extractions first with 0.5M Na2SO4 and then with 0.1M NaOH+0.1M Na4P2O7 mixture were applied to a series of soil samples with different degrees of base saturation.The cations were dominated by Ca in the 0.5M Na2SO4 extract and by Al in the 0.1M NaOH+0.1M Na4P2O7 mixture.The sequential extraction method can efficiently separate or isolate Ca-bound and Fe-and Al-bound humus from each other.