| Crop straw is rich in nutrients such as C,N,P and K.Reasonable straw returning can fully improve the soil ecological environment,supplement various essential nutrients for the soil,and improve soil fertility,which is conducive to the growth of crops.Maize and soybean are important food crops in the Loess Plateau.The return and utilization of maize and soybean straw organic resources are crucial for soil fertility and sustainable development of regional agriculture.Therefore,in this study,on the basis of long-term different cover and fertilization field positioning,using nylon mesh bag field landfill method,analysis of corn straw and soybean straw in different cover,fertilization,field depth of decomposition characteristics,nutrient release and soil fertility dynamic effect.It provides a theoretical basis for rational utilization of straw resources and scientific management of farmland nutrients.The main research results are as follows:(1)Plastic film mulching and nitrogen application were conducive to straw decomposition and nutrient release,reducing the time required for complete straw decomposition.The longest time required for complete straw decomposition in NMN0 treatment was 570 d,and the shortest time required for complete straw decomposition in FMNU treatment was 324 d.Different nutrient release performance for potassium fastest,up to 98.11%,followed by phosphorus,77.81%,nitrogen,68.09%,carbon slowest,up to64.72%.(2)Under different straw mulching and nitrogen application conditions,the conti nuous release of straw nutrients is conducive to improving soil nutrient content and s oil properties.The increase of soil nutrients under mulching straw returning treatment was greater than that under no mulching straw returning treatment;under conventiona l nitrogen application and slow-release fertilizer straw returning,the cumulative amou nts of soil organic carbon,nitrate nitrogen,ammonium nitrogen,available phosphorus and available potassium were significantly increased.The correlation analysis results s howed that soil organic carbon,nitrate nitrogen,ammonium nitrogen,available phosp horus and available potassium had great effects on soil enzyme activity.(3)The ffect of different depth returning on the decomposition rate of corn straw was obvious in a short time.The decomposition rate of 10 cm depth returning was greater than that of 20 cm depth returning in the early stage of corn straw returning,and the difference decreased with time.The regression results showed that the time required for the complete decomposition of maize straw at the depth of 10 cm and 20 cm was 324 d and 401 d,respectively.The time required for treatment without coating was 431 d and 492 d,respectively.The soil organic carbon,nitrate nitrogen and ammonium nitrogen increased more in the 10 cm depth of straw returning,and the enzyme activities related to the transformation of soil carbon,nitrogen and phosphorus were higher,which was conducive to the decomposition of straw,and the complete decomposition time of straw was short.(4)Straw characteristics affect the decomposition characteristics and nutrient relea se of straw.Under different fertilization methods,the decomposition rate of three typ es of straw showed the trend of soybean straw > corn straw > soybean straw + corn straw,and the enzyme activities related to carbon,nitrogen and phosphorus also sho wed the trend of soybean straw > corn straw > corn straw + soybean straw.Straw d ecomposition rate was significantly correlated with soil organic carbon,nitrate nitroge n,ammonium nitrogen,available phosphorus,available potassium,soil moisture,soil t emperature and soil enzyme activity.The above results showed that the reasonable combination of plastic film mulchi ng and organic fertilizer was one of the key technical measures to promote straw de composition and straw nutrient release,and was conducive to the improvement of soi l nutrient content.From the perspective of rapid decomposition of straw,it is suggest ed that maize straw or soybean straw should be returned to the shallow plough layer soil alone in the actual agricultural production in the arid region of the Loess Plate au.The study comprehensively explored the efficient ways to regulate straw decompo sition and soil fertility quality from multiple perspectives,which can provide practical reference for optimizing straw returning technology according to soil fertility and far mland management measures in agricultural practice of loess dryland,improving soil nutrient status,promoting crop resource utilization and soil quality improvement,and promoting scientific straw returning in the region. |
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