Optimization Of Influencing Conditions Of Rice Straw Decomposition And Its Effects On Soil Nutrients And Vegetable Growth

Crop straw is one of the main wastes in agricultural production.It is also a widely used renewable biomass resource because it is rich in organic matter,nitrogen,phosphorus and other nutrients.However,due to its huge output,difficult disposal,and improper handling will cause serious problems such as environmental pollution.Therefore,an efficient,safe and environmentally friendly treatment method is needed to maximize the utilization of crop straw resources.As one of the most effective means of disposing crop straw,straw decomposed and returning to the field has drawed much attention in recent years.In this thesis,the crop straw and chemical fertilizer bio-aerobic co-composting technology are used,and rice straw is taken as the research object,and the rice straw decomposing is combined with chemical nitrogen and phosphate fertilizer.And to optimize the straw decomposition initial conditions,the amount of decomposition agent,moisture content and initial carbon-nitrogen ratio?C/N?and carbon-phosphorus ratio?C/P?are adjusted.Moreover,the theoretical basis and technical support to rice straw decomposing were also provided.At the same time,the effects of rice straw decomposing on soil nutrient and vegetable growth were studied by field experiment.Mainly get the following research results:?1?Different amounts of decomposition agent A(Factor A:A₀,A_0.5,A_1.0;%,mass percentage),moisture content(Factor B:B₅₀,B₆₀,B₇₀;%,mass percentage),and initial C/N ratio(Factor C:C₂₀,C₂₂,C₂₅)are the initial conditions of rice straw decomposing.During rice straw decomposing,orthogonal experiment is carried out to study the changes of the pH,C/N ratio,decomposing rate?DR?,dissolved organic carbon?DOC?,decomposing UV-visible spectral parameters,NH₄⁺-N,seed germination index?GI?,and other indicators.And the best initial conditions for rice straw decomposing were screened.The results showed that:1)At the end of the decomposition?42 d?,most of the treatments pH values are in compliance with the composting decomposed standard?8.00⁹.00?.And GI values are consistent with low toxicity??50%?or fully maturity??80%?.The C/N ratio with A₀B₇₀C₂₅,A_0.5B₇₀C₂₂,and A_1.0B₆₀C₂₅5 treatments?13.1,14.4,and 16.4,respectively?is basically in line with the optimal C/N ratio of the decomposed product?15.0?;while the A₀B₅₀C₂₀ treatment has pH,GI,and DR values?7.05,34.9%,and 30.7%?is significantly lower than other treatments,and its C/N ratio?25.7?is significantly higher.2)The optimal decomposing conditions under different influences of the amount of decomposition agent,moisture content,and initial C/N ratio are:decomposition agent A dosage 0.5%,moisture content 70%,and initial C/N ratio 25.?2?During the decomposition of rice straw,the changed pH,C/N ratio,C/P ratio,DR,DOC,UV-Vis spectral parameters,NH₄⁺-N,NO₃^--N,GI,and other indicators were studied.To further screen the best initial C/P ratio,the rice stalk decomposition experiment with different initial C/P ratios was adjusted.The results showed that:1)The GI value of the unregulated initial C/P ratio did not meet the requirement for less toxicity to plant seeds?GI?50.0%was less toxic to plant seeds?,while others adjusted the initial C/P ratio,the GI value is in compliance with the requirements,and the initial C/P ratio is not significantly affected by the pH and other indicators.2)The optimal decomposition conditions under the influence of different initial C/P ratios are:initial C/P ratio of 120.?3?To study the dynamic changes of pH,soil nitrogen form transformation,soil available phosphorus,and phosphorus form fractionation during soil culture,the soil culture experiment of adding rice straw decomposed products was carried out.The results showed that different rice straw decomposed products could increase the total amount of ammonia nitrogen and nitrate nitrogen in soil by 47.4%⁶9.2%.Comparing with the result of the initial C/P ratio on rice straw rot,the initial C/P ratio was 120,and the decomposed products is added to the soil,which is more conducive to the improvement of soil nutrients.?4?To study the effects of rice straw decomposed product on soil nutrients and vegetable growth,it was used as the base fertilizer to carry out field experiments.The results showed that:1)Adding rice straw decomposed product as base fertilizer,when the application rate is8000 kg·hm^-2,it can increase soil organic matter content by 9.12%²4.4%,increase the yield of cabbage by 5.31%,and reduce the nitrate content of cabbage by 10.1%,but the yield of lettuce is reduced by 16.2%.2)When the application rate is 2000 kg·hm^-2,although the yield of cabbage is reduced by 8.69%,the nitrate content of cabbage can be reduced by 31.2%,and the yield of lettuce is increased by 13.1%.