Effect Of Different Mulching Methods On Changes Of Soil Nutrients In Dryland Apple Orchards

Mulching,an important measure for soil management in agriculture,has been widely used as one of the soil management techniques in many countries and regions.This study takes dwarf apple trees planted in dry-land in Weibei,Shannxi Province as the study object,and aims to explore the effect of different mulching techniques applied in various developmental stages of apple trees on the changes of soil nutrients in the orchards through field experiment and laboratory analysis,in order to provide basis for the management of soil nutrients with orchard mulching and the improvement of the effectiveness of orchard mulching.The main results are as follows:1.In different developmental stages of apples,different mulching techniques had different effects on the soil organic matter in the orchards.In the spring shoot growth period,straw mulching significantly improved the content of organic matter in 0–30cm soil layer;straw mulching during the autumn shoot growth significantly improved the content of organic matter in 0–20cm soil layer;during the ripening of fruits,soil layers in depth of 0-80 cm demonstrated increasing content of organic matter after straw mulching.In particular,the 0-10 cm soil layer had the most significant increase;polypropylene film mulching in different developmental stages of apples decreased the content of organic matter in the soil,especially in orchard of late maturing apple varieties;both straw and polypropylene film mulching in different developmental stages of apples significantly increased the total nitrogen in 0-20 cm soil layer.2.The effect of different mulching techniques in different developmental stages of apples on the soil organic matter in the orchards: straw mulching > clean tillage > polypropylene film mulching;effect on soil total nitrogen: polypropylene film mulching > straw mulching > clean tillage.3.In different developmental stages of apples,different mulching techniques had different effects on the available nutrients in the orchards.The effects of ammonium nitrogen on spring shoot growth stage and autumn shoot growth stage were the same: straw mulching > ground cloth mulching > clean tillage,while the effect of nitrate nitrogen on spring shoot growth stage was: ground cloth mulching > clean tillage > straw mulching.The effects of nitrate nitrogen on the autumn shoot growth stage and fruit mature stage were the same: ground cloth mulching > straw mulching > clean tillage and the effect of ammonium nitrogen on the fruit mature stage was: ground cloth mulching > straw mulching > clean tillage;while polypropylene film mulching increased the content of nitrate nitrogen in 0–40cm soil layer and the content of ammonium nitrogen in 0–60cm soil layer,had no significant effect on readily available phosphorus,and improved the content of readily available potassium in 0–60cm soil layer in the orchard of late maturing apple varieties.During the autumn shoot growth,straw mulching improved the content of ammonium and nitrate nitrogen in 0–40cm soil layer and the content of readily available potassium in 0–60cm soil layer;while polypropylene film mulching increased the content of nitrate nitrogen in 0–20cm soil layer and the content of readily available potassium in 0–30cm soil layer;both straw and polypropylene film mulching had no effect on the content of readily available phosphorus in soils.During the ripening of fruits,straw mulching improved the content of readily available potassium in 0–30cm soil layer and the content of ammonium nitrogen in 0–10cm soil layer,and had no effect on the content of nitrate nitrogen in soils;while polypropylene film mulching increased the content of ammonium nitrogen in 0–20cm soil layer and the content of nitrate nitrogen in 0–30cm soil layer,and improved the content of readily available potassium in 0–40cm soil layer in the orchard of medium maturing varieties;both straw and polypropylene film mulching had no effect on the content of readily available phosphorus in soils.4.In different developmental stages of apples,different mulching techniques had different effects on the available nutrients in soils: effect of mulching during the Spring shoot growth on the content of ammonium nitrogen: straw mulching > polypropylene film mulching > clean tillage,and on the content of nitrate nitrogen: polypropylene film mulching > clean tillage > straw mulching;effect of mulching during the autumn shoot growth and ripening of fruits on the content of ammonium and nitrate nitrogen: polypropylene film mulching > straw mulching > clean tillage;effect on the content of readily available phosphorus of mulching during the spring shoot growth: straw mulching > polypropylene film mulching > clean tillage,and effect on the content of readily available phosphorus of mulching during the autumn shoot growth and the ripening of fruits: not significant;effect of mulching in different developmental stages of apples on the content of readily available potassium: straw mulching > polypropylene film mulching > clean tillage.5.Statistical analysis suggested that mulching promoted the root development by improving soil nutrients and affected the growth and development of overground parts of apple trees.In the spring and autumn period,the root system in surface soil is more easily affected by soil nutrients and that readily available potassium and phosphorus,organic matter and total nitrogen had a strong effect on root length density and root activity,and had a weak effect on root biomass density and nitrate reductase.