| Rhizobia based microbial compound fertilizer has great potential contributing to the growth of Soybean of Sichuan province. The main purposes of this experiment was first to screen out those rhizobium strains which can efficiently work with main cultivated soybean species in Sichuan and make Rhizobia fertilizer with them replacing those Chemical nitrogen fertilizer in order to increase the production of soybean also to reduce environmental pollution. The tested strains are those 170 isolated soybean rhizobia from preliminary work. And the experiment was using Nandou 12 to do tieback test (micro nitrogen hydroponics) which can help soybean growth and check the matching ability with Gongxuan No.1, Chuandou No.14 and Shehong local varieties. In the meantime, i survey and evaluate physiological and biochemical parameters of the strains such as acid and alkali resistance stress resistance, phosphobacteria, secretion of growth hormone and so on. At last screen out the best rhizobia strains for high effective compound microbial fertilizer.(1) Activated 180 strains of rhizobia and devided them into two groups. The hydroponic screening experiments of the first group(81 strains) results that:Among 81 strains,73 of them had nodulated. Average nodules number of each strain was 0.7～ 48/plant. The average dry weight of the plant of each strain was in the range of 0.43～ 0.96g. Of all plants 46 (56.8%) of them had higher dry weight than CK(Reference plant),13(14.5%) of them showed significant differences from CK. Combining various indicators resulted from the first hydroponic experiment,13 relatively efficient strains had been screened out.The hydroponic screening experiments of the second group(89 strains) results that:All of them had nodulated. Average nodules number of each strain was 11.7-58.3/plant. The average dry weight of the plant of each strain was in the range of 0.38-1.18g. Of all plants 71 (79.8%) of them had higher dry weight than CK,9(11.1%) of them showed significant differences from CK. According to the result,9 relatively efficient strains had been screened out. Combining the above result 22 rhizobia stains has been selected: SS23,S20,S40,SS39,SS37,S12,SS58,SS50,S35,S43,SS18,S119,slz1-3,SS41,SS22,S12 6,S114,S85,SS16,S82,S3,S1.(2) Use all 22 screened strains to do hydroponic experiments on three different soybean species (Gongxuan No.1,local varieties, ChuandouNo.14). Experiment on Gongxuan No.1 results that:average nodules number was 1-36/plant of each strain.The average dry weight of S35,S3,SS58 and S82 were relatively higher than CK(0.6/plant).Experiment on local varieties demonstrates that:average nodules number was 4-44/plant of each strain.There were 14 of them surpass CK on dry weight. And S114,S34,S82,SS16 and S119 are significant better than CK. And experiment on Chuandou No.14 revealed that all 22 strains nodulated except SS39. The average nodules number was 3-49/plant.The dry weight was in the range of 0.42 and 1.29g, and we had 5 of them higher than CK. They are:S82,S35,SS39,SS22,S119.(3)Doing the research on resilience-promoting properties of screened strains. Acid tolerance test showed that these strains reacted stronger in the alkali resistance than the acid resistance. S119 and S114 can grow in strong acid medium containing.90.1% of them can grow in ph5.0 condition.95.5% can grow in ph6.0.Only 13 of them can grow in phl2,Rest of the rhizobia can all grow in a ph5-l 1 condition indicated certain tolerance for acid and alkali. Measurement of salt tolerance showed that there were 12 of them (54.4%) are highly salt tolerated can grow in 4% NaCl condition, all of them can’t be raised in 5% NaCl condition. In heat resistance test, strains had a better resistance capability in low temperature. SS16, S35, S12, S114 showed strong resistance to heat since the strains still showed vitality at 40℃. After the 60℃ heat shock treatment for half an hour, strains S43 and S3 cultured at 28℃ lost vitality.In trace element sensitivity test, strains showed low sensitivity of acid and ammonium molybdate, and high sensitivity of ferrous sulfate. Strains show strong vitality in Ammonium molybdate medium (all of them can grow under 0.8% Ammonium molybdate medium),(72.7%)16 of them can grow in 1% Ammonium molybdate medium.All of them can grow in 0.02%～0.08% Boric acid condition.21(95.5%) of them show strong vitality in 0.1% Boric acid condition except SS39. Under 0.1% ferrous sulfate condition 17 (77.3%) of them can grow. Only 2 (0.91%) can survive in 0.30% ferrous sulfate condition, and grow badly, all of them can survive under 0.60% and 1% ferrous sulfate condition.In resolving Phosphorus and Potassium experiment combining the results of AI-P, Ca-Pand Fe-P, we get a conclusion that SS37,SS50 showed significant ability on solubilizing inorganic phosphorus, and S35,S12 and S119 were very capable of solubilizing organic phosphorus. The strains which had nice potassium solubilizing ability were S1,SS22,SS37 and S82. And at last in IAA secretion experiment,16(72.7%)of them can secret IAA.strain SS50, S1, S35 and S114 secreted the largest growth hormone for more than 100ppm/strain. 5(22,7%)of them secreted 50-100 ppm/stain,2(9.1%) secreted 30-50ppm/strain, 4(18.2%)secreted 10-30ppm. And 6 of them can’t secret IAA.Based on the conclusion of all the experiments above, i had screened out 22 efficient rhizobium strains which works greatly with soybean Nandou No.12. And among these strains,S20,S3,S35,S82,SS58 match nicely with Gongxuan No.1.S114,S35,S82,S119 and SS16 match nicely with Shehong local varieties, and S119,SS22,S35,S39,S82 match nicely with Chuandou No.14.Thus, S82,S35 and S119 exhibited the best matching capabilities. S82 and S35 showed high matching ability, and their growth PH range is 4-12. S35 has strong Salt tolerance (4%NaC1) compared S82 can only grow in 0.5%NaCl medium. Also S35 can grow in high temperature(40℃), but S82 can’t, identified to be qualified to be the main material of microbial inoculum of field experiments.And it shows strong ability in acid and alkali stress resistance, phosphobacteria(very capable of solubilizing organic phosphorus), secretion of growth hormone(above 100ppm) tests, and compare to that S82 have less ability in phosphobacteria(can’t solubilize organic phosphorus) and secretion of growth hormone(10-30ppm) tests. |
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