不同固体微生物菌剂对砒砂岩土壤性质和紫花苜蓿生长的影响

为研制改良砒砂岩土壤、强化植物生长的微生物菌剂,该研究以嗜盐芽孢杆菌Bacillus halotolerans P75、苜蓿中华根瘤菌Sinorhizobium meliloti D10、巨大芽孢杆菌Bacillus megaterium H3和枯草芽孢杆菌Bacillus subtilis HB01为原料,利用生物基材吸附混合,制备4种单一固体微生物菌剂和多种复合固体微生物菌剂。通过分析pH值、有机质含量、有效氮磷钾含量、酶活性和细菌数量等指标来研究添加微生物菌剂对砒砂岩土壤性质和紫花苜蓿幼苗生长的影响。结果表明,与不添加微生物菌剂的对照组相比,微生物菌剂能够使砒砂岩土壤pH值降到中性附近,促使土壤有机质、碱解氮、速效磷、速效钾含量显著增加,提高了土壤蔗糖酶和脲酶活性,增加了土壤细菌数量,同时促进了紫花苜蓿幼苗生长,其中以含菌株P75、D10和H3以及含菌株P75、D10、H3和HB01的复合菌剂的效果最佳。该试验研究可以为微生物菌剂在砒砂岩区土壤改良和植被恢复方面的应用提供试验基础和参考。

Effects of different solid microbial agents on soil properties of Pisha sandstone and the growth of alfalfa

Pisha sandstone mainly distributes in the interprovincial border areas of Shanxi, Shaanxi and Inner Mongolia in the Yellow River Basin of China. These distribution areas are difficult to carry out effective treatment due to serious soil erosion and deteriorative ecological environment. Therefore, the main challenge is to improve the soil matrix of Pisha sandstone suitable for plant growth, which can be applied to soil ecological restoration and vegetation restoration in Pisha sandstone areas. In this study, the plant growth-promoting bacteria Bacillus halotolerans P75, Sinorhizobium meliloti D10, Bacillus megaterium H3 and Bacillus subtilis HB01 were used as raw materials to meet the challenge. After the strains were activated and centrifuged, the bacterial cell pellets were re-suspended in sterile water to obtain the four bacterial suspension of P75, D10, H3 and HB01. Then, the bacterial suspension was thoroughly mixed with organic/inorganic substrates at a volume-mass ratio of 1:1, and dried at 37 ℃ to prepare four kinds of single solid bacterial agents. Afterwards, 11 kinds of composite solid bacterial agents were obtained by mixing the four kinds of single solid bacterial agents uniformly according to different combinations of equal mass. The greenhouse pot experiment was carried out from March to April, 2019. 17 test groups in total were set in each pot with 300 g Pisha sandstone, where 15 test groups were the soil matrix of Pisha sandstone containing 15 different microbial agents at a mass ratio of 5% respectively, and two groups were the Pisha sandstone with the same amount of biological substrate and the Pisha sandstone without treatment. Each pot of soil matrix was watered regularly, and the soil indexes for the soil matrix of Pisha sandstone in each test group were tested after one month. A 20-day seedling experiment was performed on the planted alfalfa under the condition of the original potted soil matrix. The improvement effects of different solid microbial agents on the properties of Pisha sandstone were evaluated by the soil pH, organic matter content, available nitrogen content, available phosphorus content, available potassium content, enzyme activities and the number of bacteria, as well the seedling growth. The results showed that the addition of organic/inorganic substrates can improve the soil quality of Pisha sandstone, and promote the growth of plant seedlings, compared with the untreated control group. Compared with the effect of organic/inorganic substrates on improving Pisha sandstone soil, the addition of microbial agents can significantly increase the content of organic matters by 18.4%-30.0%, the content of alkali-hydrolyzed nitrogen by 19.7%-30.4%, the content of available phosphorus by 12.4%-47.8%, the content of available potassium by 25.3%-82.9%, the invertase activity by 13.2%-58.0%, the urease activity by 13.0%-37.7%, and the total number of soil bacteria reached more than 107 CFU/g. Compared with the effect of soil matrix containing biological substrate on Alfalfa seedling promoting, the soil matrix containing microbial agents can further increase the seedling height by 18.0%-39.2%, the root length by 37.4%-70.5%, the shoot fresh weight by 56.3%-94.1%, the root fresh weight by 106.5%-234.6%, the shoot dry weight by 32.8%-90.5%, and the root dry weight by 108.8%-301.2%. The optimum results were found in the compound agent A3 containing strains P75, D10 and H3, and A4 containing strains P75, D10, H3 and HB01. According to the soil indexes of each test group and the growth of Alfalfa seedlings, the optimal combination of P75+D10+H3 and P75+D10+H3+HB01 were finally determined for the improvement of the Pisha sandstone soil.