| Agroforestry, the purposeful growing of trees and crops in interacting combinations, is nowreceiving more attention as a sustainable land-management option due to its ecological,economic and social attributes in xingjiang province. The jujube-cotton intercropping systemshave been put into practice traditionally on a large scale so that the ecological environmentcan be improved and the higher economic returns can be obtained for farmers. However, thejujube-cotton intercropping systems remain reveal potential advantages for resourceutilization. Therefore, it is meaningful for us to increase resource utilization productivity byoptimizing cotton density for jujube-cotton intercropped systems. Field experiments werecarried out in2012and2013in Hetian, Xinjiang, China. Three cotton plant densities (13.5,18.0and22.5plants m-2) were tested in6-7years old jujube plantations, in which the cottonwas grown in a6m-wide space between the tree rows. The result was shown as follow:(1) In jujube-cotton intercropped systems, cotton had a significant increasing LAI and drymatter as the plant densities increasing. The yield and components of yield had also beenaffected by cotton plant densities. There was a significant decreasing for boll numbers perplant and boll weight with plant densities, but the lint percentage wasn’t be affectedsignificantly. The highest lint yield had been found at18plants m-2, which was18.2%and6.8%higher than at13.5plants m-2and at22.5plants m-2. The plant densities and year did nothave a significant interaction to yield and components of cotton. In addition, the leaf area,plant height and dry matter per plant had a significant decreasing as the distance betweenjujube and cotton decreasing. The cotton at60cm distance from jujube had a37.4%lower leafarea,41.9%lower plant height and43.8%lower dry matter compared to that at150cm and at300cm on average.(2) The cotton at18plants m-2had a higher SPAD, actual quantum efficiency of photosystemII (ΦPSII), photochemical quenching (qP), Electronic transmission rate(ETR), netphotosynthetic rate(Pn) and transpiration rate(Tr) than that at13.5plants m-2and at22.5plants m-2in jujube-cotton intercropped systems. What’s more, the border two rows of cottonhad been affected by jujube. All the indices had a significantly decreasing except for initialfluorescence(Fo)and intercellular CO2concentration(Ci)。In addition, there was a positivecorrelationship between Pn and ΦPSII, but not Gs, which indicated that the decreasing in ΦPSIIwas the main reason to explain why the net photosynthesis rate (Pn) decreased for bordercotton.(3) The light interception showed a significantly increasing with plant densities, but therewas not significant difference for cotton at18plants m-2and22.5plants m-2at flowering andboll stage. Over two years, the LUE of intercropped cotton at18plants m-2was1.87g DMMJ(PAR)-1on average, which was6%and10%higher compared to that at13.5plants m-2and22.5plants m-2. The plant density and year did show a significant interaction on lightinterception and LUE of cotton. The cotton plant densities did have a significant effect onlight interception and LUR of jujube in the whole grown stage. In addition, the lightextinction coefficient of intercropped cotton did not differ with plant densities, except thatthere was a significant lower k for cotton at22.5plants m-2at flowering and boll stage. In conclusion, the LAI and dry matter of intercropped cotton had a significant increasingwith plant densities, but the high plant densities have had a negative effect on components ofyield and yield. The LUE and productivity of cotton in jujube-cotton intercropping can beimproved by increasing the distance between cotton and jujube and optimizing cotton plantdensity. |
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