| The mountainous apple region in Northern Shaanxi is the main and excellent apple producing area in China.However the rainfall in this region is less and uneven,and the transpiration of apple trees is strong,which causes the contradiction between water supply and demand in apple orchard is very prominent,and seriously affects the apple yield and quality in this region.Mulching and deficit irrigation are often used to alleviate the contradiction between water supply and consumption in arid and semi-arid areas.The field experiment was carried out in Qingshuigou modern agricultural professional cooperative of Zizhou County,Yulin City,Shaanxi Province from 2019 to 2020 and taking the mountain apple orchard in Northern Shaanxi as the research object.The experiment included two factors:mulching and deficit irrigation.There three mulching methods—horticultural fabric mulching(FM),corn straw mulching(SM),and clear tillage treatment with no mulching(TL),and three irrigation strategies—full irrigation(W1),moderate deficit irrigation(W2),and severe deficit irrigation(W3).The local rain fed cultivation as control(CK),so there are 10 treatments in total.The conclusions of this study can provide scientific basis and technical support for the regulation of soil moisture and water-saving and high-efficiency production of orchards in northern Shaanxi under limited water resources.The main conclusions are as follows:(1)Soil microenvironment can be effectively improved by mulching.The mulching significantly reduced the soil bulk density and increased the soil porosity of 0-40 cm soil layer.The SWC decreased first and then increased with the growth period.The mulching significantly increased the SWC.FM treatments had higher SWC in the early growth period,while SM treatment had higher SWC in later growth period.In the two years,the SWC of FM increased 6.3%compared with TL and CK,and the SWC of SM increased4.7%and 5.7%compared with TL and CK respectively.Under the same mulching,the SWC decreased with the increase of degree of deficit,but it was mainly reflected in the early stage of growth,and in the later stage decreased with the increase of precipitation.SM treatment significantly reduced soil temperature during the whole growth period,and with the development of growth period,the temperature reduction range gradually decreased.Compared with TL treatment,the soil temperature at the bud development and flowering stage,the leaf expansion stage,the fruit expansion stage,and the fruit maturing stage,the temperature was 5.24℃,4.19℃,2.49℃and 1.31℃lower.SM also greatly buffered the soil temperature change.FM treatment did not have a significant impact on soil temperature.(2)Mulching can effectively control soil evaporation and increase infiltration after irrigation or rainfall,and improve soil water environment.After irrigation,the SWC of0-40 cm soil layer increased significantly,and the WSC of 40-60 cm soil layer increased slightly under mulching treatment.The SWC below 60 cm soil layer was not affected by irrigation,while the SWC below 40 cm soil layer under TL treatment was not affected by irrigation.Mulching increased water infiltration after irrigation.When heavy rain occurred,compared with TL treatment,mulching treatment significantly increased soil infiltration,and SM treatment was better.However,when thin rain occurred,the infiltration of SM treatment is lower than that of TL treatment.By analyzing the relationship between soil relative evaporation rate and SWC,we found that the threshold of SWC(22.09%-22.75%)between energy-limited stage and falling-rate stage.When the SWC was above the threshold,the relative soil evaporation changed little with SWC,and there was no significant correlation between them.when the SWC was below the threshold,the relative soil evaporation rate decreased linearly with the decrease in SWC.In the whole evaporation process,SM treatment could significantly reduce soil evaporation,while FM treatment could only significantly reduce soil evaporation in the energy-limited stage.(3)Both irrigation and mulching can effectively improve the physiology and growth of apple trees.Mulching had a significant effect on flowering phenology,FM improved the flowering potential of apple trees,the SM treatment can effectively control the flower bud abscission,delay the flowering phenology of apple,and improve the ability of anti freezing injury of apple flowers.Mulching significantly improved photosynthetic efficiency(P_n),the daily average P_nof FM and SM was 14.4%and 18.6%higher than that of TL,and32.7%and 37.6%higher than that of CK,respectively.SM effectively inhibited the midday depression of P_n.FM showed the same trend,while the effect was not significant.In different water deficit treatments,the P_ndecreased with the increase of degree of deficit.Mulching can significantly increase the shoot length and stem diameter,and enhance the growth of apple trees.The effect of water deficit on the growth of apple trees was mainly reflected in the stem diameter.Compared with CK,irrigation treatment effectively increased apple yield,and the combination of mulching and irrigation treatments expanded this trend,and the increase of yield was mainly by increasing and maintaining the number of fruits..The average yield of two years showed that the yield of FM and SM treatments increased by 30.0%and 27.3%compared with TL treatment.Mulching significantly increased WUE,while deficit irrigation had no significant effect on WUE.In summary,straw mulching and horticultural fabric mulching are suitable ground management methods for apple orchards in northern Shaanxi.Straw mulching has a better effect on regulating soil temperature and improving apple tree photosynthesis.The combination of mulching and drip irrigation can effectively alleviate the contradiction between water supply and demand in this area,and can effectively guarantee the sustainable development of the local apple industry. |
