Mechnisms That Controlling Crop Yield Response To Straw Biochar Amendment

At present,soil degradation and crop straw management are two importantant issues that affecting China's agricultural production.It has become a new strategy to enhance soil fertility by converting agricultural organic wastes such as crop straw to biochar and then applying it to soils.Coverting straw to biochar via pyrolyzing provides a new and effective way for crop straw management.When applying biochar to soils,it can increase soil organic carbon storage,mitigate climate change,and improve soil rapidly.In addition,biochar amendment can also increase crop productivity.However,the response of crop productivity to biochar application depends on many factors including climate type,soil type,crop type,biochar application rate,and biochar production process.It remains unclear why and underwhat condition that biochar increase crop productivity.Therefore,the objective of this study was to investigate the mechanism that controlling crop yield response to straw biochar amendment via three independent experiments.Firstly,a pot experiment was conducted to insolate the nutrient addition and soil structure improvement effect following biochar amendment.Secondly,a pot experiment was conducted to investigate the response to rice root mophorlogy and rhizospheric soil properties to biochar amendment.Finaly,a fieldexperiment was conducted to access the effect of biochar amendment on the yield of maize and potato.The results of this study are as follows:1)There was five treatments in this pot experiment including the control(CK),raw biochar addition(BC),biochar extracts with hot water(BW),hot water washed biochar(BB)and biochar ash(BA).Result showed that the different biochar components had no significant effect on the Chinese cabbage yield and root biomass.The addition of biochar extracts and washed biochar increased the mass ratio of root to above ground biomass.Adding biochar and different components significantly reduced the nitrate content in the cabbage,but had no significant effect on the content of soluble protein and soluble sugar in the above ground part of the cabbage.The effect of different biochar composition on the VC content of pakchoi depends on soil fertility level.In addition,there was a positive correlation between the differences in yield of Chinese cabbage in different fertility soils and the availability of nutrients such as soil nitrogen,phosphorus,and potassium,while the nitrate content in Chinese cabbage had a significant negative correlation with potassium content,which may be a main reason for the reduction of nitrate content of Chinese cabbage.2)The second pot expermeint on root morphology and rhizospheric soil properties showed that biochar application significantly increased the rice production yield by 62%to 63%in the low fertility soil.But there was no significant difference between the two dosages;on high fertility soils,biochar addition at 1%significantly increased rice yield with a yield increase of 143%,but 2%treatment had no significant effect on yield.The influence of biomass charcoal on rice straw and root biomass and root morphology was correlated with soil fertility and growth period.In high fertility soils,biochar application at 2%significantly increased root and straw biomass during tillering stage.In the mature stage,biochar addition at 1%increased straw biomass;in low fertility soil,biochar application significantly improved rice yield during tillering stage.Root and straw biomass,but at the jointing and heading stage,biochar addition at 2%significantly reduced root and straw biomass.At maturity,biochar addition at 1%significantly increased straw biomass.The effect of biomass charcoal on the root morphology of rice was as follows:No significant effect was observed at the tillering stage,and the total root length,total surface area and total root tip number were significantly inhibited at the jointing stage at the heading stage,but at the ripening stage,biochar addition at 1%was observed.No significant increase in carbon application.In addition,the root system parameters of low-fertility soils showed an inhibitory effect compared with the jointing and heading stages,which may be related to the lack of nutrient supply in the later period.While biochar increases rice yield and biomass,nutrient dilution results in a decrease in nitrogen and phosphorus concentrations,but potassium concentration increases significantly.The application of charcoal inhibited root activity in the tillering stage of rice,and the 1%biochar treatment during the heading stage significantly increased the root activity of the soil with high fertility.In addition,the application of biochar coordinates the distribution of rhizosphere nutrients in the rhizosphere,but also increases the rhizosphere soil enzyme activity and microbial population.Biochar has little effect on rice soil pH,but significantly increases SOC,total nitrogen,available phosphorus,and available potassium in rhizosphere and non-rhizosphere soils,but there is a certain correlation between various nutrient distributions and growth periods.The content of rhizosphere soil in early stage of total nitrogen was high,and it was basically the same in the later period.The contents of content of rapid phosphorus in the early stage were high in the rhizosphere and higher in the non-rhizosphere in the later period;while the content of available potassium was high in the non-rhizosphere soil in the early stage and later in the rhizosphere.Biochar also significantly increased the activity of urease,sucrase,catalase,acid phosphatase,and neutral phosphatase in the rhizosphere soil.At the same time,biochar and nitrogen in the rhizosphere and non-rhizosphere also increased significantly.The most significant increase.3)The effect of biochar application on corn and potato yield is closely related to the application amount and application period.Compared with no carbon application,in the first year after application(2015),low biochar application(20 t/ha)significantly increased com and potato yields,when the biochar application increased to 40 t/hm2.At the same time,the corn production also increased significantly,while the effect of increasing potato production disappeared.In the second year of biochar application(2016),although the yield increase effect of maize and potato disappeared,the trend of increase in production was consistent with the first year,and the trend of corn biomass and yield remained consistent.The increase in potato production is mainly due to the increase in economic yield(>5 cm in potato yield).The effect of biomass charcoal application on potato quality is related to the number of years.Compared with no carbon application,the reducing sugar content and dry matter and starch content were significantly reduced in the first year(2015)and the second year(2016)aftercharcoal application.The effect of biomass charcoal on corn roots is also related to the amount and age of application.Biochar application of biochar significantly(p<0.05)increased total root length,total area,mean diameter,total root volume and number of root tips in the first year(2015)after applying biochar.In the second year,all parameters did not increase significantly.This has a high correlation with the yield results.In addition,corn and potato experiments significantly increased soil SOC and available potassium content after application of biomass charcoal,while maize test pH and available phosphorus did not increase significantly.Potato experiment significantly increased available phosphorus content,but also significant.Increase soil C/N ratio and electrical conductivity,which is basically the same after two years of carbon application.The influence of soil pH and total nitrogen content in potato trials was related to the years of application of biomass charcoal.Compared with the control,the soil pH increased significantly in the first year after the application of biochar,but there was no significant change in the second year;while the total nitrogen content did not change significantly after the first year after the application of biochar,and it increased significantly in the second year.In summary,in this experiment,biomass charcoal significantly promoted the yield of maize,potato and rice.However,the increase of crop yield is not necessarily related to the increase of soil porosity and fertility by biomass charcoal.There is a positive correlation between the effect of biomass charcoal on crop yield and the effect on crop root morphology.Regarding the biochar component,the carbon skeleton in the biochar and the biomass nutrients themselves have no significant effect on the quality of pakchoi.Biochar affects root growth by coordinating rhizosphere soil nutrients,enzymes,and microorganisms,and the root growth is directly related to crop growth and ultimately yield.