Allelopathic Effect Of Fruit Tree Leaf Litter Decomposition On Crops In Fruit-crop Intercropping In Southern Xinjiang

The young orchards in southern Xinjiang have vigorously developed the agroforestry management model with intercropping as the main body,and have formed the pattern of fruit tree-crop intercropping agriculture,which is of great significance to alleviate the contradiction between forest farmers and land,increase farmers’income and promote sustainable agricultural development.However,in the process of intercropping,the allelochemicals produced by plants through volatilization can affect the normal growth of crops,resulting in crop yield reduction or quality reduction.In this study,based on the extensive investigation of common fruit tree-crop intercropping types in southern Xinjiang,eight kinds of common fruit tree litter in southern Xinjiang were used as the object.The mother liquor of the extract was obtained by decomposing the litter in the laboratory,and then diluted into the corresponding concentration as the culture matrix of the test material.The germination and growth experiments were carried out in the laboratory with wheat,soybean,rapeseed,cotton and sunflower as the receptor plants to study the effect of the extract of fruit tree litter on the germination and seedling growth of these crops.The allelopathy of five crops was preliminarily discussed.It has certain reference value for the selection of optimal matching species and the adoption of reasonable configuration mode of intercropping system.The main conclusions are as follows:（1）The effects of litter extracts from Malus pumila and Pyrus bretschenideri on seedling height,fresh weight,catalase（CAT）and superoxide dismutase（SOD）activities of wheat seedlings were generally promoted,and the allelopathic comprehensive effect index SE>0.10.The extract of Prunus persica litter could inhibit the germination of wheat seeds,inhibit the dry matter accumulation of wheat seedlings,and reduce root activity,chlorophyll content and peroxidase（POD）activity.The other low concentration of fruit tree litter extract could promote the germination and growth of wheat seeds,while the high concentration showed inhibition.In summary,Malus pumila and Malus pumila can be used as the best tree species for wheat intercropping.Young Ziziphus jujube,Prunus armeniaca,Prunus avium L.and Amygdalus communis L.can also be intercropped with wheat,so as to avoid intercropping of Prunus persica and Juglans regia with wheat.（2）The leaf litter extracts of Amygdalus communis L.,Juglans regia and Prunus armeniaca can generally shorten the germination time of soybean seeds,promote the growth of root length of soybean seedlings,increase dry matter accumulation and catalase（CAT）activity,and the comprehensive allelopathic effect index SE>0.Malus pumila litter extract can significantly inhibit the chlorophyll and protective enzyme activity of soybean seedlings.With the increase of the concentration of the extract of fruit tree litter,the comprehensive effect index of the other treatments on soybean also decreased,even became negative,indicating that the effect on soybean gradually changed from promotion to inhibition.In summary,Amygdalus communis L.,Juglans regia,and Prunus armeniaca can be intercropped with soybeans.Ziziphus jujube,Prunus persica,Prunus avium L.,and Pyrus bretschenideri can be intercropped with soybeans during the young tree period to avoid Malus pumila and soybeans.（3）The allelopathic comprehensive effect index of Prunus armeniaca leaf litter extract on rape was SE>0.10;the effects of Ziziphus jujube,Prunus persica and Pyrus bretschenideri on rape gradually changed from promotion to inhibition with the increase of the concentration of fruit tree litter extract.The allelopathic comprehensive effect index of other fruit tree litter extracts on rape was SE>0,but the overall was small.In summary,Prunus armeniaca can be used as the most suitable intercropping tree species for rapeseed.Juglans regia,Prunus avium L.,Malus pumila and Amygdalus communis L.can be used as alternative tree species for rapeseed intercropping.Ziziphus jujube,Prunus persica and Pyrus bretschenideri should fully consider tree age or remove litter in time during intercropping with rapeseed.（4）The extracts of the fallen leaves of Amygdalus communis L.and Prunus armeniaca can significantly shorten the germination time of cotton seeds,promote the dry matter accumulation of cotton seedlings,increase the chlorophyll content,and increase the catalase（CAT）activity.The allelopathic comprehensive effect index SE>0.10,there is a significant promotion effect on cotton,so Amygdalus communis L.and Prunus armeniaca can be used as the optimal choice for cotton intercropping tree species.The allelopathic comprehensive effect index（SE）of Prunus avium L.and Malus pumila litter extracts at low concentration was more than 0.10,which significantly promoted the germination and growth of cotton seeds.Therefore,Prunus avium L.and Malus pumila should be used as intercropping tree species of cotton in young period.The effects of other tree species on cotton showed a significant concentration effect.In summary,the selection order of cotton intercropping tree species is:Amygdalus communis L.>Malus pumila>Prunus avium L.>Prunus armeniaca.Other young tree species can be intercropped with cotton,or the litter should be properly cleaned during the intercropping process to avoid inhibiting the normal growth of cotton.（5）Low concentration(1 mg·mL^-1)of Amygdalus communis L.and Prunus armeniaca leaf litter extracts could significantly increase the seedling height of sunflower seedlings,promote the increase of fresh weight of sunflower seedlings,and increase the activity of catalase（CAT）.The comprehensive effect index SE>0.10,which had a significant effect on sunflower.The allelopathic comprehensive effect index SE<0of Ziziphus jujube and Prunus avium L.on sunflower significantly inhibited the germination and growth of sunflower seeds.In summary,the young trees of Prunus persica,Prunus armeniaca,and Malus pumila can be intercropped with sunflowers,but the intercropping density is fully considered during the intercropping process or the litter is cleaned in time to avoid inhibiting the normal growth of sunflowers.Try to avoid Ziziphus jujube and Prunus avium L.intercropping with sunflower.