土壤有机质含量对红壤性稻田残留氮在团聚体内分布的影响

Effects of soil organic matter content on the distribution of residual nitrogen in aggregates in a red paddy soil

化肥氮的残留及其分布对后季作物氮素供给和氮素损失均有重要影响。通过在田间试验中设置^(15)N标记微区,在相同施氮量(150 kg/hm^(2))条件下,明确低有机质、中有机质和高有机质红壤性稻田化肥氮的残留量及其在不同粒径土壤团聚体中的分布。结果表明:与低有机质土壤相比,中有机质和高有机质土壤大团聚体(0.25~2 mm)的比例较高,而粘粉粒(<0.053 mm)的比例较低。不同粒径团聚体的全氮含量均随土壤有机质含量的提高而显著升高。在相同氮肥投入下,化肥氮在中有机质和高有机质土壤中的残留量较低有机质土壤显著增加,增幅分别为60.08%和93.93%。与低有机质土壤相比,高有机质土壤中的残留氮在大团聚体、微团聚体(0.053~0.25 mm)和粘粉粒中的含量分别显著增加了76.58%、108.32%和110.85%。土壤残留氮主要分布在大团聚体中(42.87%~46.81%)。随土壤有机质含量的升高,残留氮在大团聚中的比例有所下降,而在粘粉粒中的比例有所升高,但均未达显著水平。因此,培肥地力不仅能够提高土壤大团聚体的比例,促进土壤团粒结构的形成,还有利于土壤对残留氮的固持,从而降低红壤性稻田的氮素损失。

The amount and distribution of residual mineral nitrogen plays a critical role in nitrogen supply for subsequent crops as well as nitrogen losses.A field experiment was carried out with the ^(15)N-labelling technique to explore the effect of soil organic matter content on the residue of mineral fertilizer nitrogen in soil aggregates in a red paddy soil under the same nitrogen rate(150 kg/hm^(2)).The results showed that compared with that in the low-organic matter soil,the proportion of macroaggregates(0.25~2 mm)was higher in medium-and high-organic matter soils,while the proportion of silt and clay(<0.053 mm)was lower.The concentration of total nitrogen increased with increasing soil organic matter content in all aggregate sizes.Compared with the low-organic matter soil,the contents of total residual nitrogen in medium-and high-organic matter soils were significantly increased by 60.08%and 93.93%under the same nitrogen input,respectively.Compared with that in the low-organic matter soil,the content of residual nitrogen in the high-organic matter soil increased by 76.58%,108.32%,and 110.85%in macroaggregates,microaggregates(0.053~0.25 mm),and silt and clay,respectively.Residual nitrogen was mainly located in macroaggregates(42.87%~46.81%).With the increasing of soil organic matter content,the proportion of residual nitrogen tended to decrease in soil macroaggregates,but tended to increase in silt and clay,albeit with no significant differences.Thus,improving soil fertility can not only increase the proportion of macroaggregates and enhance soil aggregation,but also contribute to the retention of residual mineral nitrogen and thus reduce nitrogen losses in the paddy soil.