| In order to explore the integrated management system of drip irrigation for water and fertilizer in the fruit-crop alley cropping system in the loess area of western Shanxi,the apple-soybean alley cropping system was taken as a typical research object.Under different drip irrigation water and fertilizer control measures,the effects of two conditions of irrigation and fertilization on soil nutrient and water spatial distribution,physiological growth characteristics of apple and soybean,yield and water and fertilizer utilization efficiency were analyzed.The experiment was irrigated in four key water-requiring periods of soybean.Fertilizers were applied with irrigation water,and different irrigation ceilings and fertilization levels were set each time.The four irrigation ceiling levels were:60%of field capacity（Fc）（W1）,70%（W2）,80%（W3）and 90%（W4）,three nitrogen levels:pure N 59.40 kg·hm-2（F1）,92.00 kg·hm-2（F2）,124.32 kg·hm-2（F3）,and the control treatment（CK）-no irrigation and no fertilization during the whole growth period,only the base fertilizer was applied before sowing.（1）The results indicated that:the soil water content of each experimental treatment in the two years have increased by 7.52%-24.59%and 1.20%-21.94%compared with CK,respectively.In the horizontal direction,the average soil water content of the 0-60 cm soil layer decreased first and then rised with the increase of the distance from the tree row,and the minimum value appears at 1 m;In the vertical direction,the soil water content of the 0-60 cm soil layer in different growth periods increased with the increase of soil depth.Water and fertilizer control measures had a greater impact on the soil water content of the 0-30 cm soil layer.Water consumption was most affected by the amount of irrigation water.The water consumption of each test treatment increased by 13.8%-30.10%and 3.53%-35.53%compared with CK during 2 years.（2）Drip irrigation and fertilization effectively increased the contents of soil ammonium nitrogen,nitrate nitrogen and organic matter.The effect of fertilization was greater than irrigation and the interaction between the two.In general,the experimental treatments of soil ammonium nitrogen,nitrate nitrogen and organic matter were significantly higher than the control treatments,which were increased by 37.40%-68.53%,23.83%-63.52%and 1.97%-26.95%,respectively.In the horizontal direction,soil nutrients gradually increased with the distance from the tree row.In the vertical direction,the soil ammonium nitrogen and organic matter both gradually decreased with the increase of the soil depth,and the soil layer where the maximum value of the soil ammonium nitrogen appeared at the W3 and W4irrigation levels showed a downward trend.Soil nitrate nitrogen gradually accumulated to the lower layer under the treatment of high water and high fertilizer,and leaching occurred.It shows that too much water and fertilizer will aggravate the leaching of soil nitrate nitrogen,which is not conducive to crop growth.（3）The water and fertilizer regulation under drip irrigation increased the chlorophyll content（SPAD）,net photosynthetic rate（Pn）and transpiration rate（Tr）of soybean and apple,and the maximum value was W3F2 treatment.The daily changes of Pn and Tr of apples and soybeans were single-peak curves,and leaf water use efficiency（LWUE）generally showed a"U"curve.In general,the SPAD value,Pn and Tr of soybean and apple increased first and then decreased with the increase of irrigation and fertilization.W3 irrigation level and F2 fertilization group performed better.Pn was significantly positively correlated with the distance from the tree row and changed significantly as the distance from the tree row increased;SAPD values and Tr were positively correlated with the distance from the tree row;LUUE gradually decreased with the increase of the distance from the tree row,but there was no significant correlation.During two years,the plant height,stem diameter and leaf area index of soybean decreased gradually with the growth period.Except for the pod setting period in 2019,the maximum plant height,stem thickness and leaf area index of soybeans all appeared in W3F2 treatment,and the response to water and fertilizer was the same as the SPAD values,Pn and Tr of soybeans and apples.Drip irrigation and fertilizer control increased the root length density of soybean and apple,and the maximum root length density was W3F2treatment.Apple root was mainly distributed in the 0-40 cm soil layer and 0.5-1.0 m from the tree line;soybean root was mainly distributed in the 0-20 cm soil layer and 1.75-2.5 m from the tree line.Slight water stress promoted the separation of root niche,and the root length density of apple increased from 40to 60 cm.（4）During the two-year test period,the W3F2 treatment yield and water use efficiency（WUE）were the best.The two growth seasons combined showed that the treatment increased by 10.88%-99.37%and8.00%-70.02%compared with the other treatments.The maximum value of Partial Fertilizer Productivity（PFP）in two years occurred in W3F1 and W4F1 treatments,respectively and the results of PFPs were similar to those of output.In 2019,each test treatment increased to a different degree than in 2018,indicating that with the increase of the test period,the effect of fertilizer production increased gradually.This study showed that excellent drip irrigation and fertilizer control measures can effectively promote the physiological growth of apple and soybean,and ease interspecies competition.However,excessive irrigation and fertilization leaded to leaching of nutrients in the root zone,resulting in waste of resources and environmental pollution.According to the comprehensive evaluation method of intercropping system,the upper limit of irrigation is 80%of field water holding capacity,and the nitrogen fertilizer amount of 92.00 kg·hm-2 can improve the crop yield while promoting the sustainable development of the agroforestry system. |
