| In the semi-arid area,the soil formation process is weak,and the mother sand is strong,and the drought is low,making the available phosphorus content of the soil is particularly low,only about 3 mg·kg-1,which is one of the important factors limiting crop growth.The presence of large amounts of calcium carbonate in calcareous soils makes it very easy for the phosphorus to be immobilized by specific adsorption and lose its effectiveness.The use of microbiological methods to promote the release of available P from the more abundant P in calcareous soil is of great significance for improving the supply of P in calcareous soil and increasing the yield of crops.This paper aims at the transformation of phosphorus in calcareous soil,through independent screening of native phosphorus-solubilizing bacteria in Ningxia and conducting field cultivation experiments.The main results are as follows:1.The rhizosphere soils of Ningxia com,alfalfa and other crops were collected.Phosphate-solubilizing bacteria were isolated and screened by using Mongina inorganic phosphorus medium with tricalcium phosphate as single phosphorus source.According to the size of hydrolysis circle(D/d?1.95),20 strains of phosphate-solubilizing bacteria were screened.After liquid fermentation test,a strain A-8 with good ability of dissolving inorganic phosphorus was obtained,and the total amount of phosphorus was 187.92 mg·L-1,where the soluble phosphorus content is 115.51 mg·L-1.Through morphological observation,physiological and biochemical tests and molecular identification of 16S rDNA,the results showed that strain A,8 was Enterobacter cloacae.2.The liquid culture test was used to determine the effect of different culture conditions on the phosphate-reducing effect of strain A-8.The results showed that the optimal conditions for the phosphate-resolving of strain A-8 in inorganic phosphorus medium was:sucrose 1%(carbon source).Ammonium sulfate 0.5%(nitrogen source),carbon to nitrogen ratio 20:1,initial pH 7.0,ambient temperature 30?.3.Field trials showed that applying different concentrations of phosphate-solubilizing bacteria could improve the status of soil phosphorus supply,and plant height,stem diameter,and dry matter accumulation of rapeseed were significantly increased compared to unfertilized bacteria.When the concentration of phosphate-solubilizing bacteria was 1×108 CFU·mL-1,the available phosphorus content in the soil during the whole growth period was significantly increased,and the range of increase was from 13%to 38%.At the same time,the total phosphorus content in the soil was significantly reduced with a smaller decrease.Can reach 4%?6%;for the growth of feed rapeseed,with the extension of the crop growth time,the concentration of phosphorus bactericide can effectively increase the plant height,dry matter accumulation.When the concentration of phosphate-solubilizing bacteria was 1 x 1012 CFU·mL-1 applied to the soil,the effect of phosphorus conversion on the soil was normal.However,with regard to the growth trend and nutrient accumulation of the oilseed rape,the concentration of the bacteria significantly increased the crop stem diameter.,Significantly increased nitrogen,phosphorus and potassium nutrients accumulation in the above-ground parts of crops,respectively,compared with CK increased by 65%,72%and 69%,compared with other bacteria concentration treatment.4.There were significant differences in available phosphorus content in different soils with different N rates and phosphate solubilizers.The amount of nitrogen applied was 120 kg·hm-2,which was significantly different compared to other fertilizer treatments,and was significantly different from that of CK.In comparison,the available phosphorus increased by 16%to 40%during the whole crop growth period,with a significant increase.At the same time,the total phosphorus content in the soil decreased,and compared with CK,the reduction ranged from 15%to 25%.As for the growth status of feed rapeseed,with the extension of the crop growth time,the growth of feed rape,the absorption of nitrogen,phosphorus and potassium,and the fresh grass yield were different.The application of 120 kg·hm-2 N fertilizer had a good effect on the plant height,and it was significantly increased by 35%?50%compared with CK.When the crop was transformed from the vegetative growth stage to the reproductive growth stage,The treatment significantly increased the stem and dry matter accumulation of crops;and for the above-ground nitrogen,phosphorus,and potassium accumulations at the harvest time,the application of 120 kg·hm-2 nitrogen increased by 71%and 73%compared with CK,respectively.,65%,and other nitrogen treatments have significant differences. |
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