| Drought and poor soil quality are the key factors limiting the sustainable and healthy production of mountain orchards in loess hilly region of Northern Shaanxi.In this paper,the effect of planting green manure between rows of fruit trees on soil moisture and fertility was discussed through planting green manure and returning green manure to the field experiment,in order to screen out suitable green manure planting mode and management measures for mountainous orchards in hilly region of northern shaanxi and provide reference for soil management in arid mountainous orchards.On the basis of a plastic film mulched ridge system(with furrows for rainfall harvesting)between plants,taking interrow clear tillage as the control,the effects of two green manure interrow planting modes(Mixed rape and melilotus,RM;Rape-soybean rotation,RS)on soil moisture and fertility were studied.The nylon net bags method was used to study the decomposition and nitrogen,phosphorus and potassium release of three kinds of melilotus,rape and soybean under different ways of returning field by two ways of open air(B)and buried soil(F).The research results are as follows:(1)The results that interrow planting of green manure has a competition and regulating effect on 0-60 cm soil water content.In the dry season,planting green manure reduced the soil water content,the size of which was clear tillage>rape-soybean rotation>mixed rape and melilotus,and with the extension of drought time,the gap increased.In the late rainy season,planting green manure increases the soil water content,which is mixed rape and melilotus>rape-soybean rotation>clear tillage.(2)During the whole apple growing season(from April to October),the total soil evapotranspiration was clear tillage>Rape-soybean rotation>Mixed rape and melilotus.In the dry season(from April to June),evapotranspiration of soil under each treatment was small,the size of which was mixed rape and melilotus>rape-soybean rotation>clear tillage,but the difference between treatments was not significant(p > 0.05).In rainy season(from July to October),the evapotranspiration amount of soil was clear tillage>Rape-soybean rotation>mixed rape and melilotus,and there was a significant difference between three treatments in August(p < 0.05).According to the analysis of soil profile water content,planting green manure did not promote the desiccation of soil profile.(3)The initial N,P and K contents of melilotus and soybean were significantly higher than those of rape,and the nutrients of melilotus were more balanced.In 2017 and 2018,the fresh weight and the amount of nutrients returned to soil of mixed rape and melilotus were higher than rape-soybean rotation.Compared with 2017,the fresh weight of green manureand the amount of nutrients returned to the field of mixed rape and melilotus in 2018 were significantly improved.(4)The decomposition and nutrient release of the three green manures were fast in early stage and slow in late stage.After the green manure was returned to the field,the cumulative decomposition rate was all presented as soybean > melilotus > rape,the carbon release rate was similar to that of dry matter decomposition,but the cumulative release rate of nitrogen,phosphorus and potassium nutrients was different due to the different types of green manures;The nutrient cumulative release rates of the three green manures were presented as K>P>N?C;Under different ways of returning field,the cumulative decomposition rate and nutrient release rate of three green manures with plough were higher than that of mulching.(5)Mixed rape and melilotus and rape-soybean rotation both improved soil fertility.Compared with the two green manure planting models,mixed rape and melilotus had better effect in improving the content of soil organic matter,total nitrogen,nitrate nitrogen,ammonium nitrogen and available potassium,while rape-soybean rotation had better effect in improving the content of available phosphorus.And the contents of all nutrients were significantly increased in the 0-20 cm soil layer(p < 0.05).Based on the comprehensive analysis of water consumption of the water consumption of planting green manure,returning green manure and fertilizer cultivation effect,the green manure planting model suitable for the application of arid and barren mountain orchards was ridging and mulching between plants to collect rain and conserve moisture,mixed planting of melilotus and rape between rows,and timely mowing and tilling in the loess hilly and gully region of Northern Shaanxi. |
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