Study On The Mechanism Of Potassium Solubilization By A Highly Efficient Potassium Solubilizing Bacterium And Its Improvement To Soil

In recent years,due to excessive reclamation and irrational use of chemical fertilizers,soil nutrient status deteriorated and fertility decreased,which affected agricultural production to a certain extent.Soil investigation in Heilongjiang Province showed that the soil nitrogen and phosphorus content was sufficient,the potassium content was insufficient,and the potassium deficiency area of farmland continued to expand,which affected the sustainable development of agriculture and the further development of soil potential.Potassium-dissolving bacteria can decompose the insoluble mineral potassium in soil into quick-available potassium,improve soil texture and crop yield,and provide a choice for the enhancement of potassium in black soil.Based on a strain of highly efficient potassium-releasing bacteria S1,which was screened and isolated from the soil of the northeast black soil area in the previous period,this study optimized its culture conditions through single factor optimization and orthogonal experiment.Under the optimized culture conditions,liquid chromatography and amino acid detection were carried out on the products of the potassium-releasing bacteria in the process of potassium-releasing to explore its potassium-releasing mechanism.Finally,the pot experiment of alfalfa planting in saline-alkali soil was carried out by combining a variety of fertilizers with potassium solubilizing bacteria S1,and the improvement effect of potassium solubilizing bacteria S1 on soil was comprehensively evaluated.The main results are as follows:The single factor experiment showed that the optimal medium for the potassium-releasing bacteria S1 was composed of 1.0%mannitol,1.0%peptone and 0.5%K₂HPO₄.The single factor experiment and orthogonal experiment were used to optimize the fermentation conditions.The initial p H value of the medium was the most influential factor for the growth and propagation of the potassium-releasing bacteria S1.Culture time,medium loading and inoculation amount were followed by temperature,which had the least influence.The optimal culture conditions for controlling potassium releasing bacteria S1 were culture temperature 30℃,culture time 48h,initial p H value 6.5,medium loading 80m L/250m L and inoculation amount 5%.The concentration of bacterial solution in fermentation liquid was the highest,and the OD₆₀₀value of bacterial solution was 1.824.Potassium content in the solution reached 4.325mg/L.The results showed that S1 could secrete a variety of organic acids,mainly malic acid and citric acid,and the concentration of organic acids would change with the increase of the fermentation time of the strain.The content of citric acid was positively correlated with the culture time.The concentration of citric acid was higher than that of other organic acids in each period.Amino groups in the process of potassium hydrolysis were analyzed by amino acid analyzer.The results showed that the bacteria S1 could secrete a variety of amino acids during the process of potassium hydrolysis,and the content of serine was higher than other amino acids at all times.According to the analysis of the changes of organic acids and amino acids,in the fermentation medium of potassic bacteria S1,the change of soluble potassium was significantly positively correlated with organic acids on 1～2 days,but was significantly positively correlated with amino acids only on the first day,and the correlation was not obvious at other times.The analysis of the dissolution effect of the potassium-releasing bacteria on the mineral surface showed that the strain would produce bacteria-mineral complex on the surface of silicate minerals.With the increase of time,the weathering effect of minerals became more obvious.The energy spectrum analysis showed that the content ofK element was higher,and the strain S1 had stronger potassium solubility.The pot experiment of alfalfa planting was carried out by combining the laboratory potassium releasing agent S1 with other kinds of fertilizer on the market.The results showed that:Each treatment group had a certain degree of improvement effect on soil physical and chemical properties,among which the combined treatment group of sheep manure fermentation organic fertilizer and potassium releasing agent S1 had the best improvement effect on soil physical and chemical properties.Compared with blank control group,soil porosity,water content,organic matter content and available potassium increased by 12.33%,11.92%,11.41g·kg^-1and 57.56mg·kg^-1,respectively.In the single treatment group,potassium-releasing agent S1 had a significant improvement effect on soil K content,and the available K content was increased by 62.54mg·kg^-1,but the improvement effect on other physical and chemical properties was not as good as that of organic fertilizer.At the same time,the potassium solubilizer group can also improve the phenomenon of high salt and high p H value of saline-alkali soil to a certain extent,and has a good effect on the improvement of alkaline and salinized soil.The growth and development indexes of alfalfa were also significantly affected in the treatment group.Compared with the blank group,the plant height,germination rate,root length and fresh weight of alfalfa were significantly improved by 4.29cm,18%,7.04cm and0.176g,respectively.There was a certain correlation between plant growth and soil physical and chemical properties.Root length was significantly positively correlated with p H,organic matter,available K,slow available K and total P.The comprehensive analysis showed that the soil improvement effect of potassium antiseptic agent S1 was better,and the soil improvement effect was significant when the potassium antiseptic agent S1 was combined with organic fertilizer.