紫云英还田量对烟田土壤微生物及酶的影响

为在翻耕条件下合理施用紫云英,保障农业的可持续性发展,定位试验研究了15000kg·hm-2、22500kg·hm-2、30000kg·hm-2紫云英还田和22500kg·hm-2紫云英还田减施化肥(施肥时扣除紫云英中氮、磷、钾)及紫云英不还田5个处理对烟田土壤微生物数量、微生物活度、酶的影响。结果表明:烟草生育期内,不同处理好气性细菌数量呈前期均迅速上升、中期均稍有上升,但后期各有升降的趋势;烟草生长早期,紫云英还田减施化肥能增加好气性细菌数量。放线菌数量烟草生育前期略有下降,中期有所回升,后期又缓慢下降;烟草生长早期,紫云英还田能增加放线菌数量;整个烟草生育期,紫云英还田减施化肥可减少放线菌数量。真菌呈现烟草生育前中期迅速上升,后期缓慢下降的趋势;相对较少的紫云英还田量对土壤真菌数量增长的刺激作用较为明显。微生物活度呈烟草生育前期下降、中期趋于平稳、后期迅速升高达到最高点的趋势;烟草成熟期,紫云英还田的微生物活度明显高于不还田处理,增加紫云英还田量,微生物活度增加,但紫云英还田减施化肥会降低微生物活度。土壤纤维素酶活性以烟草旺长期为界点,表现出前期增加、后期下降的特点;烟草生长后期,紫云英还田土壤的纤维素酶活性高于对照土壤。土壤脲酶活性呈先快速下降,再缓慢上升,最后再快速上升趋势。土壤蛋白酶活性呈烟草生育前期下降,后期缓慢上升的特点;土壤蛋白酶活性与紫云英施用量呈正相关。过氧化氢酶活性在烟草各生育期的变化不大。土壤生物学评价发现,22500kg·hm-2紫云英翻耕还田栽培烟草较佳。

Effect of incorporation of Astragalus sinicus on microbe and enzyme dynamics in tobacco cultivated soils

The organic fertilizer A. sinicus has a strong nitrogen fixing ability. The effect of returning A. sinicus to tobacco culti-vated soils on microbial population, activity and enzyme activity was investigated with the aim of enhancing sustainable agro-devel-opment. The treatments were set at 15 000 kg·hm^-2, 22 500 kg·hm^-2, 30 000kg·hm^-2 A. sinicus, as well as NPK-reduced 22 500kg·hm^-2 A. sinicus, in which NPK amount in A. sinicus was reduced from fertilizer, with non A. sinicus treatment as the control. The results show that aerobic bacteria population rapidly increases in the early growth stage of tobacco, followed by a sluggish increase in the middle stages, with the various population trend in the late growth stages under different treatments. During the early tobacco growth stage, soil aerobic bacteria population is increased under NPK-reduced 22 500 kg·hm^-2 A. sinicus treatment compared to the CK. Actinomycete population slowly decreases in the early growth stage, minimally increases in the middle stage and then decreases in the late stage of growth under different treatments. Actinomycete population in soils with A. sinicus is higher than in the CK at the early growth stage, and is lower under NPK-reduced 22 500 kg·hm^-2 A. sinicus treatment during the whole growth stage. Fungi population increases rapidly in the early and middle growth stages, and decreases afterwards. A little A. sinicus stimulates fungus growth. Soil microbial activity decreases in the early stages, stabilizes in the middle stages, and gradually increases, reaching its peak in the late growth stages. Microbial activity is significantly higher in soil with A. sinicus than in CK soil in tobacco mature stage. It increases with increasing A. sinicus amount, but decreases in soils with NPK-reduced 22 500 kg·hm^-2 A. sinicus. Cellulase activity increases before blossom stage and decreases afterwards. Cellulase activity in soils with A. sinicus is higher than in soils without A. sinicus in later growth stage. Initially, urease activity sharply declines, then increases slightly, but again sharply increases during the late stage. Protease activity decreases in the early stage, and increases slightly in the late stage of growth. Protease activity increases with increasing A. sinicus in the soil. Alterations in soil catalase activity are not severe in the entire tobacco growth season. Based on the analysis and evaluation of the quantity and activity of soil microbes, the optimal application rate of A. sinicus is 22 500 kg·hm^-2.