Effects Of Split-root Irrigation Methods On Protected Cucumber Growth,Physiological Characteristics And Water Use Efficiency

In order to investigate the mechanism of split-root irrigation on cucumber growth, physiological characteristics and water-saving, we uesed ’Jinyou3’ as the test material, and planted under the cultivation conditions of PVC pipe, plastic greenhouses and greenhouse respectively. Three drip irrigation patterns were setted with randomized block design: alternate partial root-zone drip irrigation (APDI), fixed partial root-zone drip irrigation (FPDI), and conventional drip irrigation (CDI). Effects of split-root irrigation methods on protected cucumber growth, physiological characteristics and water-saving were researched, the results showed as follows:1. Compared with CDI, FPDI severely inhibited the growth of cucumber, but APDI can stimulate the compensation growth of cucumber root, significantly improve root activity, and increase cucumber root shoot ratio. It was conducive to the growth of cucumber root elongation and absorption area increase;2. Under the CDI, APDI and FPDI treatments, cucumber leaf relative water, water potential and osmotic potential decreased with the decreasing irrigation, but the cell sap increased significantly. CDI supplied water adequately, the cucumber physiological metabolism was vigorous, free water and bound water ratio was significantly higher than APDI and FPDI treatments. While APDI and FPDI treatments were affected on the irrigation quantity and area, so free water and bound water ratio significantly decreased, metabolic weakened, but the resistance had been improved;3. Compared with CDI, chlorophyll a, chlorophyll b and carotenoid content in cucumber increased with decreasing irrigation significantly under the processing of APDI and FPDI, but the chlorophyll a/b decreased. There was no significant difference between APDI and CDI, but there was significant difference between FPDI and CDI. It indicated that FPDI reduced the light-harvesting ability of cucumber leaves and then affected photosynthesis of cucumber;4. FPDI reduced the photosynthetic gas exchange capacity and cucumber leaf photochemical efficiency significantly. The APDI maintained proper moisture condition of the blade, and also maintained relatively suitable photosynthetic gas exchange capacity and higher photochemical efficiency; and the crop stomatal conductance reduced, thus leaf transpiration water consumption reduced, so redundancy of vegetative growth can be controlled;5. FPDI and APDI reduced the amount of irrigation, resulting in crop osmotic adjustment substances such as soluble sugar, proline content increased, SOD, POD, CAT and other antioxidant enzyme activity increased, thus enhanced the adaptability to drought stress;6. Compared with CDI, APDI improved the content of soluble protein fruit and vitamin C, also improved some of the quality of cucumber, but FPDI reduced quality of cucumber;7. APDI significantly reduced the soil moist layer of deep percolation of irrigation water, thus improving the efficiency of irrigation water use. Solar greenliouse cultivation experiment results showed that the reduction in the amount of17%of APDI irrigation, and water use efficiency increased18.6%. Greenhouse cultivation experiment results showed that the water use efficiency of spring crop APDI and FPDI treatment increased1.24and2.23times respectively, autumn crop increased0.82and0.63times. However, compared with the yield of CDI, there was a decrease of26.9%and16.3%of FPDI treatment under spring and autumn respectively, while the APDI ensured no significant reduction in yield.In conclusion, the alternate partial root-zone drip irrigation (APDI) can stimulate cucumber root compensation growth, improve the quality of the fruit, and improve water use efficiency greatly without production reduction. So it can be used in protected horticulture as a water-saving irrigation mode and has a broad application prospect.