| Mineral elements are important factors affecting the growth of fruit trees.Different model of fertigation can directly affect the distribution of soil mineral elements in time and space,affect the growth and distribution of roots,and then affect the absorption and utilization of mineral elements by trees.Therefore,different technical parameters of fertigation and nitrogen fertilizer form tests were carried out in Luochuan apple experimental station of Northwest A& F University from October 2018 to October 2020.Three factors and two levels of drip line layout(one pipe for a row and two pipes for a row),dripper spacing(30 and 50 cm)and fertilization cycle(15 and 30 d)were completely combined.Two treatments of urea(U)and urea ammonium nitrate solution(UAN)were set up in nitrogen fertilizer.Leaf samples were collected at flowering stage,spring shoot growing stage,young fruit period,early expansion period,late expansion period,coloring stage and maturity stage.Fruits samples were collected at maturity stage.The effects of fertigation mode on the content and ratio of mineral elements in apple leaves and fruits were analyzed,and the relationship between the content of mineral elements and yield and quality was explored,in order to provide a theoretical basis for the optimization of fertigation mode in low-stock and densely planted apple orchards in this area.The main results are as follows:(1)The influence of different fertigation modes on the leaf mineral elements in apple trees was revealed.The leaf contents of N,P,K and Cu under different treatments generally decreased with the growth period,while the contents of Ca and Mn generally increased,the contents of Mg generally increased first and then decreased,and the contents of Zn fluctuated.Compared with one pipe for a row,two pipes for a row could effectively increase the contents of P,Mg,Fe,Cu and Zn in apple leaves,but reduce K content.The dripper spacing of 30 cm could effectively increase the contents of K,Mg,Fe,Cu and Zn in apple leaves than 50 cm.Fertilization cycle of 15 d could effectively increase the contents of P,K,Ca,Mg,Fe,Mn,Cu and Zn in apple leaves than 30 d,but reduce N content.The effects of drip line layout and dripper spacing on N content in leaves varied in growth periods,and the effect on leaf Ca content did not show significant difference throughout the growth periods.Compared with different treatment combinations,the combination treatment of two pipes for a row,the dripper spacing of 30 cm and fertilization cycle of 15 d could make the contents of P,Ca,Mg,Fe,Cu and Zn in apple leaves at a higher level,which was beneficial to the accumulation of mineral elements in apple leaves.The effects of nitrogen forms on apple leaf mineral elements varied with years.In 2019,most of the effects of nitrogen forms did not show significant difference.In 2020,the contents of N,P,Mg,Fe and Mn in leaves of UAN treatment was higher than that of U treatment in most cases,and reached significant level at some growth stages.(2)The influence of different fertigation modes on the mineral elements in apple fruits was revealed.Two pipes for a row could effectively increase the apple fruit N,Mg,Fe,Cu,Zn content.The dripper spacing of 30 cm could effectively increase the apple fruit P,Mg,Cu,Zn.Fertilization cycle of 15 d could effectively increase the apple fruit N,P,Ca,Mg,Fe,Cu,Zn.Compared with different treatment combinations,the combination treatment of two pipes for a row,the dripper spacing of 30 cm and fertilization cycle of 15 d could make the contents of N,P,Ca,Mg,Cu and Zn in apple fruits at a higher level,which was beneficial to the accumulation of mineral elements in apple fruits.The contents of all mineral elements in apple fruits treated with UAN were higher than those treated with U.(3)The influence of different fertigation modes on the ratio of mineral elements in apple fruits was revealed.The ratios of P/Ca,K/Ca,K/(Ca+Mg)and(K+Mg)/Ca in apple fruits treated with one pipe for a row were higher than two pipes for a row.The ratios of K/Ca,K/Mg,K/(Ca+Mg)and(K+Mg)/Ca in apple fruits treated with 50 cm of the dripper spacing were higher than 30 cm.The ratios of P/Ca,K/Ca,K/Mg,K/(Ca+Mg)and(K+Mg)/Ca in apple fruits treated with30 d of fertilization cycle were higher than 15 d.The combination treatment of one pipe for a row,the dripper spacing of 50 cm and fertilization cycle of 30 d could increase K/Ca,K/(Ca+Mg),(K+Mg)/Ca in apple fruits.The effect of nitrogen forms on the ratio of mineral elements in apple fruits varied with years.In 2019,the ratio of mineral elements in fruits treated with U were higher than those treated with UAN.In 2020,the ratio of mineral elements in fruits treated with UAN were higher than those of U treatment.(4)The relationship between leaf mineral elements and apple yield and quality was revealed.There was a significant negative correlation between yield and leaf Zn content at coloring stage.Soluble solid content was significantly positively correlated with leaf K content at flourishing stage,leaf Ca content at flowering stage,leaf Fe content at fruit expansion stage,leaf Zn content at coloring stage.There was a significant positive correlation between VC content and leaf Mg at flourishing stage,and between soluble sugar and leaf Mn content at coloring stage.The content of titratable acid showed a significant negative correlation with leaf N content at maturity stage.The ratio of sugar to acid was significantly negatively correlated with leaf Ca content at coloring stage and maturity stage,and positively correlated with leaf Mn content at fruit expansion stage and coloring stage.Fruit hardness was significantly positively correlated with leaf Fe content at flowering stage.Fruit shape index was significantly negatively correlated with leaf P content at fruit expansion stage,leaf K content at flourishing stage,leaf Ca and Mg content at flowering stage,and positively correlated with leaf Mn content at coloring stage.(5)The relationship between fruit mineral elements and apple quality was revealed.Fruit N content was significantly positively correlated with VC content,and fruit P content was significantly positively correlated with soluble solids and titratable acid.The Ca,Mg and Zn content of apple fruits were significantly positively correlated with fruit hardness.There was a significant negative correlation between fruit shape index and fruit Cu content,and between the ratio of sugar to acid and fruit Mn content. |
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