Effects of mulching on the growth and fruit quality of apple trees

Abstract: 【Objective】In order to reveal the different responses of leaf photosynthetic parameters, tree growth and fruit quality of‘Wang Shan Hong'Fuji apple to different mulching materials, the present experiment was conducted to provide references for the reasonable selection of mulching materials for the orchard soil management.【Methods】The sample trees were 4 years old‘Wang Shan Hong'Fuji on‘Liaozhen 109'dwarf rootstocks, which were bred by Liaoning Institute of Pomology. The ground mulching materials were horticultural fabric, agricultural carpets, wood chips with no-mulching as a contrast. The differences in soil temperature, soil moisture content, leaf photosynthetic parameters, tree growth and fruit quality were investigated.【Results】The orchard ground was covered by horticultural fabric, agricultural carpets and wood chips with clean tillage as the control, and the different soil layer temperatures showed a trend of‘rising first and then decreasing'in 2016 and 2017. The peak values appeared in August 19, 2016 and August 16, 2017, respectively. With the increase of soil depths, soil temperatures decreased. Compared with the no-mulching treatment, soil temperatures increased with horticultural fabric, and reduced with agricultural carpets or wood chips. In 2016 and 2017, soil moisture contents also showed a trend of‘rising first and then decreasing', and soil moisture contents increased with the increase of soil depths. After the orchard ground was covered by horticultural fabric, agricultural carpets and wood chips, the soil water contents at different soil layers were improved. Among them, the stable effect of soil moisture contents was obvious after the ground was covered with horticultural fabric but the effect was the worst with no-mulching. Compared with no-mulching, after the ground was covered with horticultural fabric, agricultural carpets and wood chips, the leaf net photosynthetic rate, water use efficiency and relative chlorophyll contents increased. There were significant differences in photosynthetic parameters among different treatments. After the ground was covered with horticultural fabric, the coefficient of variation with leaf net photosynthetic rate, water use efficiency and relative chlorophyll contents were the smallest and the stability was better than other treatments. After the ground was covered with wood chips, the net photosynthetic rate, water use efficiency and relative chlorophyll contents were significantly improved in the midium and late period of 2017, but the coefficient of variation was the highest, and the stability was the worst. After the orchard ground was covered with horticultural fabric, agricultural carpets and wood chips, the leaf fresh weight, leaf thickness, tree height, coverage rate and the amount of total branches increased. The composition proportion of different types of branches was affected. In 2016 and 2017, after the ground was covered with agricultural carpets, the leaf fresh weight, leaf thickness, tree height, coverage rate, total branche amounts and the ratio of medium-length shoots to spurs were the highest, and the ratio of long shoots was the lowest. In spring, the length of new shoots was the longest after the ground was covered with horticultural fabric, and in summer, the growth rate of new shoots was the faster after it was covered with agricultural carpets or wood chips. The fruit mass, firmness, soluble solids, TSS/TA, fruit color (a and b) setting increased, titratable acidity and fruit color (value L) decreased after it was covered with agricultural carpets or wood chips.Among them, the fruit mass, firmness, soluble solids and TSS/TA were the highest after it was covered with horticultural fabric, followed by wood chips. After the ground was covered with horticultural fabric, agricultural carpets and wood chips, the red color on fruit surface was significantly improved, but the brightness was slightly worse. There were differences in the contents of soluble sugar and organic acid in fruits after the ground was covered with different types of materials. The contents of glucose, fructose, sucrose and shikimic acid increased, but the contents of malic acid and citric acid reduced.【Conclusion】The effects of three different mulching materials on soil moisture contents, soil temperatures, leaf photosynthetic parameters, tree growth and fruit quality were compared. The comparative effects showed in a descending order: agricultural carpet, wood chips and horticultural fabric.