Study On The Decomposition Of Returned Rice Straw In Greenhouse In Weinter

Decomposition of returned straw in the field has significant effects on soil heat,soil nutrition,and soil microbial.At the same time,change of soil environment will contribute to the decomposition.Rice straw is an abundant renewable resource,consisting one third of total quantity of straw.However,it is very difficult for rice straw to decay because of its great ratio of C/N and low temperature condition,which is not suitable for microorganisms to work.So,currently,it is hard for returned rice straw to produce positive effect on soil quality in a short period.It is urgent to find a rational way to solve this problem.In this paper,bio-reactor method was applied and rice straw was returned into ditch in greenhouse,and then its decomposition and effect on soil temperature,soil nutrition and soil microbial were studied.The obtained results are listed below:1.Effects of returned rice straw on soil temperature in greenhouse varied in different space and time scaleThe soil temperature after the rice straw returned was detected by setting temperature sensors in different layers,and then this data was analyzed in different space scale and time scale.The results showed that it had great effects on soil temperature on the layer 5 cm,10 cm and 15 cm.Specifically,the difference of soil temperature between layers was reduced after rice straw was returned into soil.The daily or weekly soil temperature average value changed insignificantly,while the daily minimum temperature was raised,and temperature difference was reduced significantly.These advantages would produce a stable environment for crops and reduce low temperature disadvantages.2.The effect of returned rice straw on soil temperature could be enhanced when rice straw was returned in different waysCompared to returning mere rice straw,rice straw supplied with cow manure or biological agents,covering on surface and adding more rice straw all could produce bigger effect on soil temperature in greenhouse in winter,among which rice straw supplied with biological agents increased daily soil minimum temperature most and reduced temperature difference most.It was also found there was significant positive correlation between daily soil minimum temperature and the residual ash content,and negative correlation between daily soil temperature difference and the residual ash content of returned rice straw.The result indicated that the decomposition of returned rice straw was the main inner reason which made soil temperature change in greenhouse in winter.3.The content of soil available nutrients could be raised after rice straw was returned in greenhouse in winterResults of nutrients determining analysis indicated that although there was no significant effects on C,total N,total P and total K content,available nutrients in soil were significantly added after rice straw was returned by 90 days.The regression analysis showed there were significant positive correlations between both available N and K content and the residual ash content,which indicated that the decomposition would contribute to accumulation of these nutrients.4.Returned rice straw could have different effects on the bacterial community and fungi community in soilNumbers of bacteria were significantly increased after different treatments,among which the number of bacteria under treatment T4(by biological agents)increased greatest.Types and diversity of bacterial were also promoted.Different from mere returning rice straw,returning rice straw and biological agents significantly reduced the amount of fungi,which indicated that this treatment maybe has produced some products that could inhibit some fungi,which could contribute to inhibition to soil-borne diseases.5.Returned rice straw decayed much in soil in greenhouse in winter,and treatment ways had significant effect on decomposed products of returned rice strawColor,odor and pH of returned rice straw all changed much,and the weight loss ratio of returned rice straw was over 55%after 90 days.Rice straw supplied with cow manure,biological agents and more rice straw all raised the residual ash content of decomposed rice straw.Further study showed that there was no negative effect on germination of tomato and cucumber seeds any more after 90 days.Moreover,the decomposed products could effectively inhibit cucumber Fusarium’s growth;the smallest inhibition ratio was 65.41%,and the largest reached 73.46%.These results indicated that returning rice straw and biological agents could effectively contribute to promoting decomposition,adding nutrients,eliminating toxicity of decomposed rice straw and inhibiting cucumber Fusarium’s growth.Results from this study can provide guide for the utilization of rice straw,and improvement of soil quality(temperature,nutrients content,microbial and et al),and inhibition on some soil-borne pathogenic fungi in greenhouse in winter.