沼液化肥全氮配比对土壤微生物及酶活性的影响

通过田间试验,研究了N-P2O5-K2O(120-90-135 kg/hm2)施用量相同的条件下,沼液化肥不同全氮配比(沼液全氮分别占0%、15%、30%、45%和100%)对旱地红壤微生物(细菌、真菌、放线菌)数量、酶(脲酶、脱氢酶)活性和硝化强度的影响。结果表明,随沼液全氮比例的增加,土壤细菌、放线菌、真菌数量均呈倒"U"形增加,且较单施化肥处理(未施沼液)分别提高3.88%~40.78%、1.64%~31.15%、28.21%~79.49%。随着花生生育进程的推进,脲酶活性随沼液全氮比例增加而升高;脱氢酶活性先降低,开花期后升高。沼液全氮45%处理显著提高了花生结荚期和收获期土壤脲酶、脱氢酶活性和硝化强度。利用主成分分析对土壤微生物活性进行综合评价,依据主成分解释总变量和碎石图提取了2个主成分反映原变量的92.13%的信息。第1主成分主要综合了细菌、真菌、放线菌数量、微生物总量和硝化强度的信息;第2主成分主要综合了脲酶、脱氢酶活性的信息。主成分综合得分图直观地显示了等氮磷钾条件下沼液化肥全氮配比对旱地红壤微生物活性的综合影响。具体为BS30BS45BS100BS15NPKCK。因此,等氮磷钾条件下沼液全氮15%~100%处理有利于提高土壤微生物活性,特别是沼液全氮30%处理,同时其花生籽粒产量也达到了最大值(2 875 kg/hm2)。

Effect of total nitrogen ratio of biogas slurry/chemical fertilizer on microflora and enzyme activities of soil

Abstract: Biogas slurry was known to influence soil-plant ecosystem when it was applied as a fertilizer, especially in combination with chemical fertilizer. However, limited information was available regarding how this combination affected soil microflora and enzyme activities. In the present research, a two-year field experiment was conducted to evaluate the effects of the application of biogas slurry combined with chemical fertilizer on the quantity of soil edaphon, enzyme activities (urease, dehydrogenase) as well as nitrification intensity in upland red soil, Southern China under the same input of N-P2O5-K2O (120-90-135 kg/hm2). The soil was fertilized with 6 treatments, including CK (no fertilizer), NPK (chemical fertilizer only), BS100 (biogas slurry only) and other 3 combination treatments with different biogas slurry and chemical fertilizer (BS15, BS30, BS45). The nitrogen in biogas slurry under BS15, BS30 and BS45 accounted for 15%, 30% and 45% of applied total nitrogen respectively, which were respectively 18, 36 and 54 kg/hm2 and applied with biogas slurry and the remaining amounts of nitrogen were applied with chemical fertilizer. The results showed that the quantities of soil bacteria, fungi, actinomyces responded significantly to the application of biogas slurry combined with chemical fertilizer, which increased by 3.88%-40.78%, 1.64%-31.15% and 28.21%-79.49% respectively compared to NPK treatment. The quantities of soil edaphon (bacteria, fungi, actinomyces) all showed a trend of decreasing after initial increase with the percentage of nitrogen in biogas slurry accounting for applied total nitrogen amount increasing. In addition, the urease activity showed a trend of increasing, and the dehydrogenase activity showed a trend of increasing after an initial decrease, with the percentage of nitrogen in biogas slurry accounting for applied total nitrogen amount increasing in the 4 growth stages. Therein, BS45 treatment significantly increased the activities of soil urease and dehydrogenase as well as nitrification intensity at the stages of bearing pod and harvesting. Besides, the principal component analysis (PCA) was used to evaluate the soil biological activity. The obtained results showed that 2 principal components, which reflected 92.13% of the original information, were extracted from the initial indices. Within the primary principal component (PC1), the quantities of bacteria, fungi, actinomyces and the total microorganism as well as nitrification intensity were the main impact factors. Meanwhile, the activities of urease and dehydrogenase were the main impact factors in the secondary principal component (PC2). Based on synthesis scores calculated from the 2 principal component scores, the effects of the application of biogas slurry combined with chemical fertilizer on soil biological activities displayed an order as follows: BS30 > BS45 > BS100 > BS15 > NPK > CK. The results suggest that proper application of biogas slurry combined with chemical fertilizer (BS30) can increase the microbial quantity and enzyme activities in upland red soil. Moreover, the peanut yield also reached the highest (2875 kg/hm2) under the treatment BS30.