不同形态氮素对种植大豆土壤中微生物数量及酶活性的影响

采用框栽试验方法,研究6种不同形态氮素生物固氮(N0)、硝态氮(N1)、铵态氮(N2)、氨基酸态氮(N3)、蛋白态氮(N4)和酰胺态氮(N5)]对种植大豆土壤中微生物数量及土壤酶活性动态变化的影响。结果表明:各大豆生育期内真菌、细菌、放线菌数量和土壤脲酶、蔗糖酶活性对不同形态氮素的反应不同;三大菌群在组成上以细菌数量占绝对优势,数量上均在花期时达到峰值,即均随着大豆生育期的推进呈单峰曲线变化;花期不同形态氮处理下的土壤微生物总数量有差异,具体表现为N5N3N2N1N4N0。土壤多样性指数的变化趋势随着生育期的推进呈缓慢下降趋势,与土壤微生物数量的变化趋势不一致,因此,评价土壤生物多样性指数应将两者结合起来。土壤脲酶和蔗糖酶活性随着生育期的推进亦为单峰曲线变化趋势,但脲酶与蔗糖酶活性的变化趋势不同,其高峰期出现在鼓粒期。

Effects of different nitrogen forms on microbial quantity and enzymes activities in soybean field

In this paper, pot experiments were conducted to study the effects of different N forms, including biological nitrogen fixation(N0), NO₃^--N(N1), NH₄⁺-N(N2), amino acid-N(N3), protein-N(N4) and amide-N(N5) on microbial quantity and enzyme activities in soil at the growth stages of soybean. All N fertilizers were applied as base fertilizers with the same amount. The results show that bacteria are the predominant ones among microorganisms. The maximum population of bacteria, actinomyces and fungi are observed at the flowering stage, and the change of microorganism is a single-peaked curve at the whole growth stages. As the growing phases of soybean, the total amounts of microorganisms and biodiversity indices were different among treatments supplied with different forms of nitrogen. Moreover, the amounts of the microorganisms change with different forms of nitrogen treatments at the flowering stage with an order: N5 > N3 > N2 > N1 > N4 > N0. In addition, the change of the biodiversity indices shows a slowly decreased trend. Therefore, the two important factors should be combined to evaluate quality of the soil. The activities of urease and invertase were single-peaked curves with the growing phases as well, however, the maximum urease activity appears at the podding stage while that of the invertase activity at the flowering stage.