| In recent years,due to the rapid development of industry and agriculture in the Chaohu Lake Basin,the application of chemical fertilizers and pesticides in the farmland has aggravated the nitrogen,phosphorus and other nutrients into the lake and accumulated continuously,resulting in a large number of cyanobacteria breeding in Chaohu Lake,and the eutrophication of the lake has become increasingly serious.Cyanobacteria is rich in nutrients such as nitrogen and phosphorus.Composting and utilization of cyanobacteria can not only solve the problem of cyanobacteria pollution,but also produce organic fertilizer to turn waste into treasure.However,due to the high cost of organic fertilizer,it is necessary to increase the added value of agricultural products in order to increase farmers’ income and improve economic benefits.Selenium is essential to the basic functions of life and is an essential trace element related to human health.Therefore,it is very important to develop organic selenium enriched fertilizer to produce selenium enriched agricultural products,and it has broad application prospects.This study conducted laboratory and outdoor aerobic composting experiments by adding exogenous selenium to explore the effects of different inorganic selenium treatments and different organic selenium concentrations on the composting process of selenium enriched cyanobacteria.At the same time,potted and field experiments were carried out to study the effects of decomposed selenium enriched cyanobacteria organic fertilizer on soil improvement,crop growth quality,selenium content,yield and economic benefits.The main research conclusions are as follows:1.Three treatment groups of selenium-enriched Bacillus subtilis,sodium selenite,and blank control were set up to study the effects of different selenium treatments on aerobic composting of cyanobacteria.The results indicated that the maximum temperature of the treatment with selenium enriched Bacillus subtilis was higher than that of the other two groups,and the temperature reached above 50℃ for 11 days,while the temperature of blank control and sodium selenite treatment exceeded 50℃ for 8 days and 10 days.At the end of composting,the compost products of the three treatments have met the organic fertilizer standard,the p H was maintained at 5.5～8.5,and the seed germination index was not less than85%.Compared with the other two groups,the organic matter content of the treatment with selenium enriched Bacillus subtilis increased by 8.72%～9.13%,the total nutrient content increased by 4.70%～5.60%,and the total selenium content increased by 0.21～1.92 times.2.Four treatment groups of 0% selenium yeast,0.5% selenium yeast,1% selenium yeast and 1.5% selenium yeast were set up to study the effects of different organic selenium concentrations on aerobic composting of cyanobacteria.The results showed that the the overall temperature of each treatment with the addition of selenium enriched yeast was higher than the treatment without addition.On the 46 th day of composting,the p H values of 0%selenium yeast,0.5% selenium yeast,1% selenium yeast,and 1.5% selenium yeast were 7.36,7.42,7.24,and 7.11 respectively,which met the p H requirements of compost products.The organic matter of the four treatment groups decreased by 19.97%～22.07%,the total nitrogen decreased by 1.77%～3.8%,and the total nutrient increased by 1.18～1.31 percentage points,and the compost products have met the organic fertilizer standard.Compared with the treatment without adding selenium yeast,the total selenium content of the three treatment groups with selenium yeast increased by 0.81～3.88 times.The results showed that the more selenium yeast added,the total selenium content in the pile will increase accordingly.Adding1% or 1.5% selenium yeast will have a higher effective selenium content in the compost product,and the composting effect will be relatively better.3.The pot experiment of pakchoi was carried out with decomposed organic selenium enriched fertilizer.The plant height,root length and fresh weight of pakchoi treated with selenium enriched Bacillus subtilis and sodium selenite were significantly higher than those treated with blank control(p<0.05).Compared with that of the control group,the total selenium content of pakchoi treated with selenium enriched Bacillus subtilis and sodium selenite increased by 127.73% and 112.53%,and the organic selenium content also increased by 135.45% and 102.73% respectively.At the same time,the application of selenium enriched organic fertilizer reduced the accumulation of lead and cadmium in the pakchoi.The results showed that the inoculation of selenium enriched Bacillus subtilis could improve the utilization rate of selenium,effectively increase the selenium content and the proportion of organic selenium in the pakchoi,and make the produced selenium enriched agricultural products safer.4.Applying decomposed selenium enriched organic fertilizer for field planting could increase soil organic matter and nutrient content.Compared with organic fertilizer and conventional fertilization methods,the total selenium content of the selenium enriched organic fertilizer treatment increased by 316.84%～392.69%,and the organic selenium content increased by 354.32%～462.25%,indicating that the selenium enriched organic fertilizer could significantly increase the total selenium and organic selenium content of watermelon pulp(p<0.05).The soluble sugar content of the selenium enriched organic fertilizer treatment increased by 0.42～0.69 percentage points,the sugar-acid ratio increased by 8.66%～14.39%,and the vitamin C content increased by 5.15%～10.38%.In conclusion,the application of selenium enriched organic fertilizer could effectively improve the quality of crops,and improved yield and economic benefits. |
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