Research On Fertigation Models Of Jujube Under Bubble-Root Irrigation

Bubble-root irrigation was a new water-saving irrigation technique. In order to investigate high yield and high quality fertigation models under bubble-root, three years old jujube trees and quadratic orthogonal regressive rotation design with four factors of irrigation amount, N fertilizer, P fertilizer and K fertilizer were used in this study to respectively establish seven regression models on water-fertilizer and stem increment, new branch growth, percentage of fertile fruit, fruit quality, single fruit weight, and yield of jujube. Single and coupling effects on growth, quality and yield of jujube were analyzed. The main research findings were as follows:(1) If other factors were zero codes, stem increment, new branch diameter, new branch length, percentage of fertile fruit, fruit quality, single fruit weight, and yield of jujube decreased firstly but then increased with water-fertilizer rate, which showed exorbitant irrigation amount and fertilizer rates would go against growth of jujube, and quality and yield improvements of jujube fruit.(2) The order of effects on the growth of jujube stem was N(X2)>W(X1)>K(X4)>N(X3); The order of effects on the growth of new branches was W (X1)>N(X2)>K(X4)>P(X3); the order of effects on the percentage of fertile fruit and the single fruit of jujube was K(X4)> N(X2)>W(X1)>P(X3); the order of effects on the diameter and yield of jujube fruit was K(X4)>W(X1)>N(X2)>P(X3).(3) Interaction effects between irrigation amount and N fertilizer rate and between N fertilizer rate and P fertilizer rate on stem increment, new branch diameter, percentage of fertile fruit, fruit quality, single fruit weight, and yield of jujube, interaction effects between irrigation amount and P fertilizer rate on stem increment and percentage of fertile fruit of jujube, interaction effects between irrigation amount and K fertilizer rate on stem increment, percentage of fertile fruit, fruit quality, single fruit weight, and yield of jujube, interaction effects between N fertilizer rate and K fertilizer rate on new branch diameter, percentage of fertile fruit, fruit quality, single fruit weight, and yield of jujube, and between P fertilizer rate and K fertilizer rate on percentage of fertile fruit of jujube were all presented positively, while interaction effect between P fertilizer rate and K fertilizer rate was presented negatively, which showed that interaction effects between irrigation amount and N fertilizer rate, between irrigation amount and K fertilizer rate, between N fertilizer rate and P fertilizer rate, and between N fertilizer rate and K fertilizer rate could promote jujube growth and improve the quality and yield of jujube fruit, while interaction effect between P fertilizer rate and K fertilizer rate went against the growth of new branches.(4) Based on an overall consideration of growth, quality and yield of jujube, under the condition of bubble-root irrigation, moisture content of soil should be keep at55-72.5%, while the recommended N rate was0.715-1.072kg/plant, the recommended P rate was0.173-0.259kg/plant, and the recommended K rate was0.297-0.446kg/plant.