Effects Of Bio - Carbon And Straw Returned To Soil On Soil Physical And Chemical Shape And Yield Of Saline - Alkali Soil

This study focused on two of the most severe problems during rice production, straw resourcewaste and poor structure and productivity of saline-alkaline soil. In this study, we carried out thepot experiments and compared the influence of biochar returning and straw returning on thephysical and chemical characteristics of saline-alkaline soil, as well as rice growth and yield.Results in the present study provide a theoretical basis and technical support for the reclamationof soda saline-alkaline soil and the high and stable yield cultivation techniques of rice. The mainresults were listed as following:1. The most suitable amount for biochar and straw application were16500kg/hm2and7500kg/hm2, which permitted the best growth of rice plants during the whole growth period. Asfor the same returning amount, the tiller earring rates of biochar returning were higher than thatof straw returning. Furthermore, at both the full heading and grain filling stages, the maximumeffective leaf area appeared with16500kg/hm2biochar returning, which were6.14%and15.36%higher than that of control, respectively. Meanwhile, significant or extremely significant positivecorrelation was found between photosynthetic characteristics and yield under both conditions(r=0.8783*, r=9587**). In addition, the highest output rates of stem and sheath were found with16500kg/hm2biochar returning, respectively29.07%and40.89%, or7500kg/hm2strawreturning respectively20.28%and33.13%. As expected, changes in the conversion rates of stemand sheath are similar to the output rates under both conditions, with relatively higher rates ofbiochar returning than straw returning. Finally, we also found that under both conditions, thesugar-spikelet ratios were positively correlated to rice yields, especially for biochar returning(r=0.8783*).2. We carried out this experiment twice in2013and2014. By comparing the results from thetwo years, we found that the soil pH values of2014were8.08%~12.66%lower than that of2013,and the lowest pH values were observed with16500kg/hm2biochar returning (1.38%lower thancontrol) and16500kg/hm2straw returning (4.02%lower). Similar phenomenon was alsoobserved for the bulk density. In details, the soil bulk density of2014was7.04%~20.88%lowerthan that of2013; however, the decrease degree for straw returning was more obvious than thatfor biochar returning. This result indicated that straw returning displayed better in improving thesoil permeability than biochar returning. Moreover, the total salt contents were increased underboth conditions, however, the increased degree for biochar returning was less than that for strawreturning. When applying the same returning amount, C/N for biochar returning wassignificantly higher than that for straw returning. Furthermore, under both conditions, the potassium content gradually increased along with the increase of returning amount, suggestingthat the soil nutrient was improved by applying the straw and biochar.3. Application of16500kg/hm2biochar helped to increase the primary branch number, and atthe same returning amount, the branch number of biochar application was slightly greater thanthat of straw returning. In line with the changes in branch numer, the grain number and grainweight were also significantly increased after application of biochar and straw. Furthermore, wefound that the yield of16500kg/hm2biochar returning reached5581.13kg/hm2, increased by23.90%, and the highest yield of7500kg/hm2straw returning was4621.93kg/hm2, increased by2.61%. Notably, the yield of biochar returning was relatively higher than that of straw returningwith the same amount, increased by10.20%~35.34%.4. The agronomic efficiency, partial factor productivity and economic coefficient peaked whenusing16500kg/hm2biochar or12000kg/hm2straw. Due to the high cost, biochar returning didnot show economic benefits within short time, however, biochar returning will exhibit betterecological benefits by promoting the straw resource utilization, environment improvement, soilfertility maintenance and agriculture sustainable development.