The Effect Of Rice Straw Mulch On The Soil Traits And Rice Yield

Rice and wheat straw,as a cheap organic fertilizer source of high quality,is rich in organic matter.The application of straw can improve soil structure as well as the composition of soil microbial community.Moreover,it contains nutrients such as nitrogen,phosphorus and potassium necessary for crop growth,thus can improve soil nutrition status,promote crop growth,and improve crop yield.Traditionally it has been a dominant practice to increase soil fertility with straw returning.It is also one the most important ways to utilize straw and eliminate the environmental problems caused by misuse of straw.This paper studied the effects of chemical fertilizer application accompanied with various patterns of straw returning on soil physical and chemical properties,soil microbial community and rice yield in the paddy-rice rotation practice.The objective was to provide scientific and technical references for improving soil structure and fertility and resource utilization rate,in order to realize a sustainable,productive,efficient and safe crop production.The total straw was mechanically crushed,mixed into soil by rotary tillage.Four treatments,including no straw returning(CK),wheat straw returning in rice field(W),rice straw returning in wheat field(R),and both wheat and rice straw returned to either rice or wheat field(RW),were conducted in this experiment.Soil physiochemical properties such as soil pH,EC,organic matter,total nitrogen,alkali-hydrolyzable nitrogen,available phosphorus and potassium,soil microbial community structure,as well as rice yield and its components were determined.The main results are as follows:1.As compared with CK,i.e.without straw returning,soil pH at tillering and mature stages decreased in all treatments with straw returning,while soil exchangeable cations(EC)increased at the tillering stage and decreased at mature stage.Straw returning treatment increased soil organic matter,total nitrogen,alkali-hydrolyzable nitrogen,available phosphorus and available potassium,especially at the tillering stage of rice when the significantly increase was observed.There was no significant difference between treatments with different straw returning patterns.During the whole rice growth period,the content of alkali-hydrolyzable nitrogen increased first and then decreased after heading stage,while the content of soil available phosphorus decreased and then increased and kept stable after heading stage,while available potassium decreased till jointing stage and then remained constant.Overall,straw returning in both seasons(RW)improved soil fertility significantly more efficient than the other treatments,which were showed little difference from CK.2.The determination of soil properties showed that after rice harvesting,stratified sampling,the contents of soil organic matter,total nitrogen,ammonium nitrogen,nitrate nitrogen and available potassium decreased along soil depth,while soil available phosphorus content followed the sequence of 20-30cm>10-20cm>0-10cm>30-40cm.The reason could be that soil available phosphorus at the depth of 20-30cm had not been taken up by crops and thus accumulated,as a result of straw returning.Straw returning influenced soil fertility in the surface layer but not in the deep layer.In both 0-10 cm and 10-20 cm soil layers,soil organic matter,total nitrogen,available phosphorus and available potassium of the treatment RW,were the highest and significantly higher than those in CK.There was no difference between both season(RW)and one season(R or W)straw returning.In the 20-30 cm and 30-40 cm soil layers,the organic matter and total nitrogen content of RW were lower than those of CK.The contents of soil inorganic nitrogen(ammonium nitrogen and nitrate nitrogen)varied in different soil layers with no cleart pattern.3.Analyses of soil collected from late maturing stage of rice indicated that,the soil bacterial community structure was not significantly different at the phylum level.Proteobacteria was the predominant microorganisms in the paddy soil,followed by Acidobacteria,Chloroflexi,Planctomycetes and Gemmatimonadetes.The relatively abundance of the above phyla accounted for 85%of the total soil bacteria in all treatments.At the genus level,the relative abundance of dominant genus Geobacter in the treatment of R,W and RW all increased,while the abundance of purple non-sulfur bacteria(Rhodoplanes)decreased,as compared with CK.The composition of microbial community(OTU)in each treatment varied greatly,indicating that different straw returning patterns could induce the development of the specific microorganisms in paddy soils.4.In this study,compared with CK,straw returning could increase the rice yield,with the increase rate of 4.76%-11.61%.With regards to the rice yield component factors,the number of ears,number of grain per ear,seeds per ear,and 1000-seed weight were higher in the treatment of RW than the rest.The yield in the treatment with straw returning for only one season(R and W)increased to a certain extent compared with CK but no significant difference was detected.In summary,straw returning could increase soil fertility and crop yield,with the significant effects observed in the treatment of returning both wheat and rice straw in two seasons(RW),but not in one season(R or W).It is suggested that both wheat and rice straw be returned to the fields in rice-wheat rotation agricultural practices,in order to effectively increase soil fertility and achieve sustainable,high-yield and high-efficiency crop production.