| The yield,quality and economic benefits of cotton has affected seriously by the long-term continuous cropping in Xinjiang.The application of biochar and organic fertilizer can effectively alleviate the obstacle of crop continuous cropping.Besides,the effects of biochar and organic fertilizer on soil and its crops are strongly associated with soil types and crop types.And,Gray desert soil and Aeolian sandy soil are the important and major soil types of cotton fields in Xinjiang.Therefore,the study on the reduction effect of cotton straw biochar and organic fertilizer on continuous cropping cotton field,and the response of different soil types to cotton straw biochar and organic fertilizer,which can provide scientific and reasonable theoretical basis for the reduction of continuous cropping obstacles in Xinjiang cotton field.In this study,a field buried pipe method was used in the teaching experimental site of Shihezi University in 2018,and Xinluzao No.45 was planted in the experiment.Orthogonal experiments of adding biochar and applying organic fertilizer were carried out on two types of soils(Gray desert soil and Aeolian sandy soil).The field soil was amended with biochar at 3 rate of 0%(B0),1%(B1),3%(B3)of the soil dry weight,and with organic fertilizer at 3 rate of 0%(M0),3%(M3),6%(M6).The effects of biochar and organic fertilizer amended on soil nutrients,root physiological activity,root growth,biomass accumulation and seed-cotton yield in key growth stages of cotton(budding and flocculation stages)were studied.The response differences of Gray desert soil and Aeolian sandy soil to the reduction measures of continuous cropping obstacle were analyzed.The main results were as follows: 1.The application of biochar or organic fertilizer significantly inhanced the contents of organic matter(OM),total nitrogen(TN),available phosphorus(AP)and available potassium(AK)in Gray desert soil and Aeolian sandy soil.In addition,the application of organic fertilizer alone significantly increased the total phosphorus content of Gray desert soil,but significantly reduced the total potassium content of Aeolian sandy soil.It is noteworthy that the effects of biochar or organic fertilizer amended on soil pH and nutrients of Aeolian sandy soil are stronger than those of Gray desert soil.The combination of biochar and organic fertilizer significantly affected the pH of Aeolian sandy soil,but didn't significant in Gray desert soil.The contents of organic matter,total nitrogen,available phosphorus and available potassium in the two types of soils were significantly higher than those in the control or single application.In addition,there were differences in total phosphorus and total potassium between the two soil types under the combined application of the two fertilizers.2.The application of biochar or organic fertilizer improved the physiological activity of cotton root system,including the activity of cotton root system,glutamine synthetase activity(GS)and nirate reductase activity(NR).And alleviate the root senescence damage,significantly maintain the nutrient uptake and utilization ability of cotton in Grey desert soil at the later growth stage.Specially,the improvement degree of Aeolian desert soil is greater than that of Grey desert soil.Combination of biochar and organic fertilizer was superior to single application of organic fertilizer or biochar in improving root activity and enzymes with nutrient uptake and utilization of cotton.However,there were differences in the best combination of two soil types.3.Adding biochar can improve the root architecture of cotton in two soil types of cotton fields,and provide a strong resource guarantee for cotton growth by establishing a huge root system with stronger absorption and transportation functions.In addition,the effects of applying organic fertilizer on the root characteristics of two soil types of cotton were different.Under the application of organic fertilizer,cotton root system in Grey desert soil has larger root structure and more efficient absorption function.The physical function of cotton roots in Aeolian sandy soil can be improved by increasing the thickness of cotton roots.The combination of biochar and organic fertilizer significantly increased the cotton root system index,and biochar played a leading role in the combination.The combination of biochar and organic fertilizer made up for the deficiency of organic fertilizer and improved the effect.The cotton root system in Aeolian sandy soil is more sensitive to the changes of soil environment caused by the combination of the two fertilizers than that in Grey desert soil,and has a significant effect on the growth of cotton root system.4.Grey desert soil with biochar application can improve yield due to the strict control in distribution of underground and aboveground biomass during the whole growth period,and optimizing rootshoot ratio.Biochar inhibits the root and aboveground biomass of cotton at early growth stage in Aeolian sandy soil,resulting in no significant increase in cotton yield at late growth stage.The application of organic fertilizer increased the root and aboveground biomass of cotton in the early growth stage of two soil types,but reduced the aboveground redundancy in the late growth stage,and effectively increased the yield of seed-cotton.Suitable root-shoot ratio is the key to increase cotton seed cotton yield.Combination of biochar and organic fertilizer could significantly increase cotton yield in Aeolian sandy soil,but had no significant effect on cotton yield in Grey desert soil.In conclusion,comprehensive analysis of soil nutrient changes,physiological characteristics of cotton root growth and cotton yield,continuous cropping reduction measures should be taken in different soil types.The experiment showed that the highest of seed-cotton yield in Grey desert soil at 6% organic fertilizer combined with 1% biochar application,and in Aeolian sandy soil at combined with 6% organic fertilizer and 3% biochar. |
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