Study On Water-nitrogen Coupling Mechanism On Cotton Plant In Condition Of Film Mulch And Drip Irrigation

Drip irrigation underfilm mulch is an advanced technique combined by the trickle irrigation technique and the polyethylene film planting technique, which have the advantages of saving water, enhancing yields, upgrading quality of product and high water utility. Compared with conventional irrigation and cultivation mode, the soil moisture and fertile environment, water-nitrogen requirement pattern are changed by drip irigation under film mulch. However, The mechanism of these advantages is not awared till now, A coupled irrigation plus fertilization experiment was conducted to explore the impact on biological characteristics and cotton yield in term of water-nitrogen coupling. The demonic of cotton plant's nitrogen uptake and apparent evapotranspiration under film mulch and drip irrigation was studied as well. The main results were as follows:1. Apparent evapotranspiration of cotton field in different growth stages was strongly influenced by irrigation quota. With the increase of the quota of irrigation the cotton plant water consuming capacity is increased as well.The average apparent water consuming capacity is 5.8mm from planting to emergence, 37.3mm in days after emergence 24, 113.3mm in days after emergence 24 to 60, 237.5mm in days after emergence 61 to 112,40.0mm in days after emergence 113 to 157 respectively, the whole water consuming capacity in cotton whole life cycle was 433.7mm in the condition of film mulch and dip irrigation.2. Nitrogen uptake was appear in days after emergence 60 (earlier flowering, about 30, June) to 100 (full boiling about 10, August) 39days, whereas over 70% nitrogen was absorbed during this period. This suggested that it is reasonable to distribute most of the nitrogen fertilizer in form of top-dressing would fit to cotton physiological demands. Our results illustrated that nitrogen absorbed 206kg N/hm~2 during 60-100 days after emergence, thereinto 54 kg N/hm~2 was absorbed days after emergence 61 to70, 60 kg N/hm~2 was absorbed days after emergence 71 to 80, 54 kg N/hm~2 was absorbed days after emergence 81 to 92, 38 kg N/hm~2 was absorbed days after emergence 71 to 80 respectively.3. An emperical model between cotton yield and irrigation/fertilization was established, we calculated that the maximum yield was 5253kg/hm~2, the maximum yield irrigation was 4190m~3/hm~2, and the maximum yield N application was 224 kg/hm~2.4. Yield composition factor analysis demonstrated that nitrogen fertilization is the main factor that affected cotton yield, the mechanism was higher nitrogen fertilization could yield bigger boll as compared to lower nitrogen fertilization, higher irrigation quota could yield higher economic yield and biomass as compared to lower irrigation quota. While water product efficiency and water usage efficiency was lowed.