Soil Respiration As Influenced By Soybean,Maize And Sorghum Growth

In order to ascertain the effects of soil respiration under crop growth,we conducted a pot experiment planted Soybean(Glycine max),Maize(Zea mays)and Sorghum(sorghum bicolor).The soil respiration rate during crop growing season were sampled by static closed chamber method and analyzed by gas chromatography.Based on the study on variation of soil respiration under different crops,we obtain the characteristics and laws of soil respiration in different crops growth.The main research results are as follows:1.There was a significantly different in soil respiration rates between crop growth soil and corresponding comparison bare soil.They had obvious seasonal variation in soil respiration rate under growing of Soybean,Maize and Sorghum.There have weakly difference between crop growth soil and corresponding comparison bare soil within about 30d after crop sowing,but since then began to appear significantly different in two kinds of treatments soil.Generally speaking,the soil respiration rate increase with the growth process under crop growth in the early growth stage,in growth medium reach to peak,and then decreased with the prolonged growth,the soil respiration rate reduced to no significant difference between crop gro wth soil and comparison bare soil in the end.However,during the whole experiment,the bare soil respiration rate maintained at a low level,data volatility is very weak.Through correlation analysis indicated,there were significant correlations of quadratic function between Soybean,Maize and Sorghum soil respiration rates and growing days of crops.While the seasonal change of soil respiration rates in bare soils were not significant and their correlations days after sowing were weak.2.The total amount of soil respiration under crop growth was significantly higher than bare soils,crop growth soil respiration was 1.9 to 4.9 times as high as that in bare soil.There has a largest difference in the total amount of soil respiration between Soybean,growth soil and corresponding comparison bare soil,followed by Maize,the least difference emerged in Sorghum soil.3.In whole growth period,the total amount of soil respiration under crop growth was medium-term stage of growth>early stages of growth>later stages of growth.Under the same conditions,Soybean,Maize and Sorghum’s soil respiration during medium-term stage accounted 76.6%,60.3%and 59.5%of the total soil respiration.4.Rhizosphere respiration also has a significant seasonal variation,and the change tendency is consistent with the corresponding control bare soil respiration.There were significant correlations of quadratic function between Soybean,Maize and Sorghum rhizosphere respiration rates and growing days of crops,in whole growth period,rhizosphere respiration ratio were medium-term stage of growth>early stages of growth>later stages of growth.In different growth periods,Soybean,Maize and Sorghum’s rhizosphere respiration to soil respiration contribution rates were 22.4%～86.5%,24.2%～72.3%and 20.8%～65.3%,among them,rhizosphere respiration in medium-term stage of crop growth was the greatest contribution to soil respiration.5.Soybean soil respiration and rhizosphere respiration improved by increase amount of fertilizer,the total of soil respiration and rhizosphere respiration,average soil respiration rate and variation width in high level fertilizer application Soybean soil was higher in low level fertilizer application Soybean soil.But fertilizer application had no significant effect on bare soil respiration.6.Soil respiration varies along with changes in the type of crops.Under the same conditions,in whole growth period,Soybean,Maize and Sorghum soil respiration rate variation range were 15.2～992.6,9.1～411.1 and 14.4～288.4 mg Cm-2h-1.Whether it is the average soil respiration rate,or the total amount of soil respiration and variation width,they were both Soybean>Maize>Sorghum,Rhizosphere respiration,average rhizosphere respiration rate and variation width were also Soybean>Maize>Sorghum.7.There has a significant correlation index between Soybean,Maize and Sorghum soil respiration and air temperature.Temperature coefficient of sensitivity(Q10)was Soybean>Maize>Sorghum.However,the correlation between bare soil respiration and soil temperature was not significant.8.There has a significant positive correlation between crop biomass and soil respiration.This explains that the more crops synthesis,the more energy consumed by root system absorbing nutrients and water to supply crop growth.9.In summary,carbon dioxide emissions in conditions of crop growth primary controlled by crop growth.Rhizosphere respiration was a major contributor to the soil respiration under growth of crops.Crop type,fertilizer application and temperature were the main factors which influenced soil respiration under the crop growth.