| Straw returning is one of the sustainable utilization ways of agricultural resources and can effectively alleviate the environmental pollution caused by incineration.However,the decomposition efficiency of straw under natural conditions is low after the straw is returned to the field,which brings negative effects on soil structure and crop growth.Applying straw decomposition agent can improve the decomposition efficiency of straw and reduce the influence of low decomposition efficiency of crop straw on crop growth and development.Therefore,in this study,a combination of laboratory simulation and in situ field experiment was adopted to determine the decomposition and nutrient release laws of wheat straw under different dosage of rot agents.On this basis,the effects of enhanced decomposition of wheat straw on soil nutrients,soil enzyme activities and soybean yield and quality were investigated in the in-situ field environment.The above research and results are helpful to achieve efficient decomposition of straw and improve soil quality.The main results are as follows:（1）The effects of enhanced decomposition of wheat straw at different concentrations on the decomposition of wheat straw were investigated by laboratory simulation experiments.The results showed that the decomposition rate of wheat straw could be increased significantly in a short time.At 30-90 d,the maximum decomposition rate of wheat straw under JF2 treatment(10 mg·kg-1 and 30 kg·hm-2 in the field)reached 66.92%.At 120 days of decomposition treatment,the decomposition rate of straw increased by 15.24%,17.24%and 22.98%when treated with(5,7.5 and 10 mg·kg-1),compared with JG treatment(0 mg·kg-1).The surface microstructure of wheat straw was observed by scanning electron microscopy.It was found that with the increase of decomposition time,the surface microstructure of wheat straw under JF(5 mg·kg-1)and JF2(10 mg·kg-1)treatment was more damaged than that under JG treatment.At the 120th day,compared with the JF2 and JG treatments,the surface structure of wheat straw was enlarged,the skin was broken,and the overall structure of wheat straw was destroyed,and there was no significant difference between the JF and JF2 treatments.Considering that there was no significant difference in straw decomposition degree within 120 days after treatment with different dosage of maturation agent,the dosage of 5 mg·kg-1 was preliminarily selected from the perspective of cost control to carry out follow-up study.（2）The effects of wheat straw enhancement on soil nutrients and soil enzyme activities were investigated.The soil nutrient content and soil enzyme activity showed an increasing trend with the increase of decomposition time and dosage of wheat straw.After 120 days of decomposition,wheat straw enhanced decomposition significantly increased the contents of soil organic matter,total nitrogen,total phosphorus,total potassium,alkali-hydrolyzed nitrogen,available phosphorus and available potassium.The increment of 5,7.5 and 10 mg·kg-1 compared with JG treatment was 2.07-8.27%,4.08-9.24%,8.17-10.54%,3.36-8.79%,7.17-10.13%,5.43-9.71%and 4.43-10.09%,respectively.In terms of soil enzyme activities,enhanced rot decomposition of simulated straw culture in laboratory significantly increased the activities of soil urease,phosphatase,sucrose and cellulase.The increases of 5,7.5 and 10mg·kg-1 compared with JG treatment were 11.84-20.77%,11.49-27.81%,3.09-25.48%and5.18-14.59%,respectively.Based on the above rules of decomposition and nutrient release data,5 mg·kg-1（converted to 15 kg·hm-2 in the field）was preliminarily determined as the dosage of bactericide for subsequent field verification.（3）With the help of in situ field experiment,the effects of returning wheat straw to the field to enhance humolytic activity on soil nutrients and soil enzymes were further investigated by adding humolytic agent under the zonal compound planting mode.Under the influence of15 kg·hm-2,soil nutrient content showed an increasing trend with the increase of decomposition time of wheat straw in soil.During the soybean harvest,SR（straw returned to field without application of rancid agent）treatment and SF（straw returned to field with application of 15 Compared with NSR（straw not returned to the field）treatment,the contents of total nitrogen,total phosphorus,total potassium,alkali-hydrolyzed nitrogen,available phosphorus and available potassium increased by 3.80%and 8.15%,8.11%and 11.02%,4.12%and 8.26%,6.20%and 9.40%,6.76%and 9.10%and 6.2,respectively Compared with SR treatment,the contents of total nitrogen,total phosphorus,total potassium,alkali-hydrolyzed nitrogen,available phosphorus and available potassium in SF treatment were increased by4.19%,7.50%,3.75%,5.84%,3.96%and 5.84%,all of which reached the significant difference level（P<0.05）;Soil organic matter,soluble organic carbon（DOC）,microbial biomass carbon（MBC）,easily oxidized organic carbon（EOC）,soil macroaggregate content（≥2）in SR and SF treatments mm）content increased by 7.22%and 11.62%,10.22%and 20.79%,14.22%and24.79%,7.83%and 11.37%,9.02%and 12.83%,respectively,compared with NSR treatment.Compared with SF treatment,the contents of soil organic matter,DOC,MBC,EOC and soil macroaggregates（≥2 mm）were increased by 3.44%,17.45%,11.36%,7.29%and 4.76%,respectively,reaching a significant difference level（P<0.05）;In terms of soil enzyme activity,SF treatment and SR treatment of soil urease,Compared with NSR treatment,the activities of phosphatase,sucrase,cellulase andβ-glucosidase increased by 28.57%and 42.86%,17.08%and 28.48%,17.08%and 23.46%,14.00%and 26.48%,7.42%and 12.36%,respectively.Compared with SR treatment,the activities of urease,phosphatase,sucrase,cellulase andβ-glucosidase in soil under SF treatment were increased by 13.31%,11.94%,23.12%,5.45%and4.60%,respectively,reaching a significant difference level（P<0.05）.In conclusion,soil nutrient content and soil enzyme activities were significantly increased under the zonal compound cropping mode,and the application of rander further increased soil nutrient and soil enzyme activities.（4）Regulation of yield and quality of soybean by straw enhanced decomposition under in situ field test.Compared with NSR,SR and SF treatments increased soybean yield and 100grain weight by 0.99%and 6.42%,2.10%and 10.67%,respectively.Compared with SR treatment,SF treatment increased soybean yield and 100 grain weight by 1.12%and 6.42%,respectively.In terms of soybean grain nutrients,the contents of nitrogen,phosphorus,potassium and protein in SF and SR treatments increased 3.08%and 1.68%,9.87%and 7.48%,8.45%and 4.22%,6.00%and 9.84%compared with NSR treatments.Compared with SR treatment,the contents of total nitrogen,total phosphorus,total potassium and protein in SF were increased by 1.48%,1.03%,4.05%and 3.64%.The above results indicated that the application of straw maturation agent could further enhance the positive regulation effect of the previous wheat straw returning on soybean yield and grain nutrient content under the strip compound cropping mode. |
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