不同收获期的籽粒苋绿肥还田对土壤养分的影响

为研究不同时期收获的籽粒苋还田后对土壤养分的影响,采用室内恒温培养模拟籽粒苋还田,测定了生长45,55和65 d收获的籽粒苋还田后土壤可溶性碳(DOC),无机氮(Nmin),速效钾,缓效钾含量的变化趋势.研究结果表明,不同时期收获的籽粒苋还田后0~14 d,土壤DOC,Nmin,速效钾,土壤缓效钾含量均显著增加,籽粒苋氮表观释放率达到19.5%以上,而钾表观释放率在63.4%以上;还田14~56 d,土壤Nmin,速效钾,缓效钾含量均为生长45 d收获的处理>55 d收获的处理>65 d收获的处理>对照,但此阶段各处理土壤DOC,组成土壤Nmin的铵态氮(除45 d收获的还田处理)与对照之间没有显著差异;还田56 d后,添加籽粒苋的土壤Nmin是对照的3.4倍,速效钾是对照的3.1倍,缓效钾是对照的1.1倍.此外,培养期间生长45 d收获的籽粒苋氮,钾表观释放率低于生长55和65 d收获的籽粒苋.由此表明,籽粒苋还田14 d后对土壤有效养分就有明显改善效果,籽粒苋生长45 d收获还田效果较好.

Green manure returning effect of Amaranthus hypochondriacus harvested at differ-ent times on soil fertility

In order to study the returning effect of Amaranthus hypochondriacus on soil fertility,an incubation experiment was carried out to simulate the returning of A.hypochondriacus as green manure to the field.The dynamic change in concentrations of DOC (soil dissolved organic carbon),Nmin (mineral nitrogen),available potassium and slowly released potassium was measured in the soil with plants harvested on 45,55 and 65 d af-ter growth.During the first 14 d of incubation,the concentrations of soil DOC,Nmin,available potassium and slowly released potassium increased significantly compared to the control.Apparent nitrogen release rate in A.hypochondriacus was more than 19.5%,and for potassium,it was above 63.4%.During 14-56 d of incu-bation,soil Nmin,available potassium,slowly released potassium concentrations showed the order as sample harvested on 45 d after growth>55 d>65 d>Control,but there were no differences in soil NH4 +-N and DOC concentration between the treatments and control (for NH4 +-N,sample harvested on 45 d as an exception). After 56 d of incubation,Nmin concentration in the soil was 3.4 times of that under Control,available potassi-um concentration was at least 3.1 times and slowly released potassium concentration was at least 1.1 times un-der all treatments with A.hypochondriacus .In addition,the treatments using A.hypochondriacus harvested on 45 d resulted in lower apparent release rates of nitrogen and potassium than the other two treatments using A.hypochondriacus during the incubation.Conclusively,returning A.hypochondriacus to soils obviously im-proved soil available nutrients,and the plants harvested on 45 d showed better effect on soil fertility.