Effect of total nitrogen ratio of biogas slurry/chemical fertilizer on microflora and enzyme activities of soil
Zheng Xuebo;Fan Jianbo;He Yuanqiu;Cui Jian;Xu Lei;Zhu Zhenqiu;Zhou Jing;Institute of Soil Science, Chinese Academy of Sciences;University of Chinese Academy of Sciences;National Engineering Research and Technology Center for Red Soil Improvement, Red Soil Ecological Experiment Station, Chinese Academy of Sciences;Institute of Biology Resource, Jiangxi Academy of Sciences;
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.