| The technique of plastic mulched drip irrigation which is combination of drip irrigation and plasticcultivation, contributes the field to be wetted in strip and results in temperature increasing, moistureconserving, and be in favorable air condition, so that this technique supplies favorable soil condition tocotton root growth with soil moisture, temperature, and air, and promotes cotton yields as well as water useefficiency(WUE). With the features of control and local irrigation, this technique can regulate the soilmoisture, temperature and air in a favorable condition around cotton root system, consequently can increaseWU, and can contribute to a high yield of cotton.Field experiments were carried out with three treatments of soil water content which were 90％θ_f,75％θ_f,60％θ_f(θ_f is field water-holding capacity), and three kind of Soil surface conditions, which weretransparent plastic mulching, or black plastic mulching, and no plastic film. Soil temperature, moisture andcotton growth as well as its root system were observed during cotton seedling stage and wadding stage. Bythe relations of the soil water content to soil aeration, the characteristics of soil moisture, temperature andair for cotton root system, were analyzed, as well as the impact of these facts to the water consumption ofcotton roots and the plant growth. The results of the experiments were obtained as follow:(1) With the plastic film covering, the soil water content didn't fluctuate for the treatment of 90％θ_f,while soil moisture treated in 75％θ_f and 60％θ_f was waved with irrigation frequencies and the cotton rootuptaking. The cotton was in water stress obviously when was treated in 60％θ_f moisture condition. The factthat the soil water content greatly change in 0-30 cm layer indicated that cotton root mainly consume waterin this layer. There was distinct difference in the soil water content between broad row, narrow row andoutside of films. Soil moisture in the field was distributed in strip. The soil moisture distribution in verticalwith 75％θ_f water treatment was nearly symmetrical and the soil moisture was relatively ideal. The soilwater content of 60％θ_f treatment was relatively low in deep layer, while soil water content of 90％θ_ftreatment was relatively high in upper layer.(2) Before the soil water condition was treated while cotton was in budding stage, the dailytemperature of soil surface covered with transparent film was violent fluctuation comparing with thatcovered with black film. Because of the sparse cotton canopy, the result indicated that covering filmeffected soil temperature remarkably. After water treatment, canopy of cotton was great in blooming stage,the effect of covering film on increasing soil temperature was not obtained, but the soil moisture was themainly factor which influence temperature of soil. Temperature of soil was felled with soil moistureincreasing; at the same time, soil temperature was descended with soil depth increasing.(3) The soil aerated porosity decreased with the soil volume water content increasing. The ideal soilaeration was obtained in the soil of 60％θ_f condition, the inferior soil aeration, in the soil of 75％θ_fcondition, and the worst soil aeration condition, in the soil of 90％θ_f condition, when cotton was coveredthe same the plastic film.(4) With the soil volume water content increasing, cotton water consumption was increased in cottongrowth phase. With the soil volume water content increasing, the peak of cotton water consumption put off. The cotton root system consumed water in 0-30 cm soil layer in narrow row, and the intensity of cottonwater consumption decreased with the soil depth increasing. The cotton root weight was decreasing slowlyalong the soil depth during the cotton growth. The cotton root grew quickly and was very weight in thesuitable soil water condition. The cotton root grew slowly and was less weight beyond the suitable soilwater condition. Under the soil water treatment of 75％θ_f, the cotton root weight was slowly decreasingalong soil depth increasing. The cotton root weight was decreasing hastily along the soil depth increasing inthe treatment of 90％θ_f. The cotton root weight was distributed mainly in the soil narrow row and broadrow mulched with plastic film, and distribution of root weight was small in the soil outside plastic film forall water and cover treatments.(5) Leaf area index increased with the soil volume water content. Photosynthetic rates in functionalleaves were highest during full-bloom stage and were less different in these treatments. The ratio of rootbiomass to shoot biomass was decrease with the soil volume water content, when cotton was covered thesame the plastic film.(6) Covered the same the plastic film, the soil was full very much water under the treatment of 90％θ_f,then the soil aeration was worst, and the soil temperature was very low in layer of root sucking upmoisture. Therefore, these circumstances were not in favor of the growth of cotton root. During thetreatment of 60％θ_f, and the soil aeration was ideal, the soil temperature was high in layer of root suckingup moisture. However, the soil was so dry that the cotton couldn't consume water and grow normally.Therefore, cotton yields were not high. Under the treatment of 75％θ_f, the cotton root grew in the suitablecircumstance for the soil water content and soil temperature and soil aeration, so cotton yields were high inall cover treatments. The water using efficiency reduced with the soil water content increasing.
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