| Extension of intensive cultivation mode of dwarf rootstock apple make mechanization operation in orchard be possible.With the development of agricultural modernization and the advocacy of green agriculture,straw mulching has become a new trend.Although the grass cover in orchard is beneficial to the stability of the soil stratification,the growth of the grass also needs water and fertilizer,which is not suitable for orchard in arid area.Straw mulching has the effect of improving the soil properties.However,straw mulch is prone to fire,and the wind protection and rain erosion effect are poor.This study put forward a kind of straw mechanized layered overlay process.A comparative study was made on four models of straw layer mulching,grass and soil mixed mulching,grass mulching,and tillage.The technological parameters of mechanized layered coverage of straw were optimized,which provides a theoretical basis for mechanized layered mulching of orchard straw.The main conclusions are as follows:(1)Compared with grass soil mixed cover,grass mulching,and clear tillage,the straw layered overlay did better in improving soil moisture,insulation,soil nutrient and weed suppression.In dry season,the soil moisture content of soil underground 0~10cm was 3%~5% higher than that of other modes;in the cold seasons,the soil temperature was 0.8℃ higher than that of other models.The variation of soil temperature was minimum,less than 1.5 ℃;The contents of soil organic,alkali hydrolyzable nitrogen,available phosphorus and available potassium increased by 3.33g/kg,25.68mg/kg,3.46mg/kg and 189.15mg/kg,respectively,much higher than that of tillage and grass mulching models.The inhibitory effect on weeds was also very significant.In autumn and spring,52.7% and 65.9% were decreased compared with the tillage control model.(2)Compared with the grass soil mixed cover,grass mulching and clear tillage,straw mulching could obviously increase fruit yield and fruit quality.In this model,the apple production reached 605.9kg/667m2 for two-years old apple trees.Compared with the grass mulching and clear tillage,yields were increased by 23.4% and 60.8%.(3)Orthogonal experiments were conducted with straw covering thickness,thickness of soil layer and length of straw as the factors.The effects of straw mulching on soil temperature,soil moisture content,soil fertility and weed number were analyzed.Finally,the optimum parameters of the mechanized layered coverage of straw were determined.It shows that the thickness of straw mulch was 15 cm,the thickness of overlaying soil was less than 3cm,and the length of straw was 6cm.(4)Straw decomposition was studied under the condition of straw mulching.The results showed that the weight loss rate and thickness change rate of straw were fast in early stage and were slow in later stage.In the first two months,the decomposition rate was the fastest.The observation and analysis of the microstructure of straw showed that during the decomposition of straw,the change of decaying pore was slow in early stage and fast in later stage,which might be related to the decomposition rate of cellulose,hemicellulose,and lignin.(5)The mulching period of the mechanized layered coverage of orchard straw was 180 d,the straw mulching amount was 1200kg/667m2,and the soil mulching amount was 11.4m3/667m2This study provides a theoretical basis for straw mechanical layering. |
