| Shortage of water resources and agricultural area-source pollution are two main factors that restrict the sustainable development of agriculture in North Xinjiang. In recent years, Xinjiang cotton production has developed rapidly. Cotton planting area and total output are both the first of nation. The cotton planting industry is the main agricultural industry in the northern areas of Xinjiang. The local management practice with high irrigation and frequent fertilization not only increases the production costs for farmers, but also intensifies the lack of water resources and the deteriorates the ecological environment. The main planting technology of cotton production is mulched drip irrigation technology. The technology played an important role to promote water-saving irrigation of cotton. With the development of modern agriculture, fertigation is the most effective water and fertilizer saving technology. How to implement the cotton drip irrigation fertilization technology effectively in water shortage area such as Xinjiang, will be very important to improve the yield and quality of cotton, water and fertilizer saving.This study use cotton (Gossypium hirsutumcv, Xinluzao 33) as the research material. Two-year experiments (2012 and 2013) were conducted to evaluate the effects of different fertigation regimes on cotton growth, physiology, yield and its components, water use efficiency, partial factor productivity, nutrient uptake, nutrient use efficiency, soil water content and so on of fertilizers in Shihezi areas of Xinjiang. The fertilization treatment was based on different ratios of N-P2O5-K2O and the irrigation treatment was based on the crop evapotranspiration (ETc). Five fertilizer treatments were designed including 60%(F0.6), 80(F0.8),100%(F1.0),120%(F1.2) and 140%(F1.4) of recommended rates with N (250)-P2O5 (100)-K2O (50) kg/hm2, and three irrigation treatments included 60%ETc (Wi),80%ETc (W2) and 100% ETc (W3). Irrigation amount was decided by a 20-cm inner diameter evaporation pan. Evaporation pan-crop coefficient in seedling, budding period and flowering period, boll opening period were 0.2,0.4,0.7 and 0.25, respectively. On the basis of model improvement, research and exploration were conducted on cotton growth, dry mass accumulation, soil water distribution under deficit irrigation. The results of the study are as follows:(1) The results showed that compared to W3F1.0, plant height, LAI, effective bolls number per plant, seed cotton yield and quality of dry matter and WUE of W1Fo.6, W1F0.8, W1F1.0, W1F1.2 and W1F1.4 treatments have dropped significantly. Besides W2F0.6 in 2013, W2 and W3 irrigation level under various fertilizer treatments, plant height were between 60 and 71 and LAI were between 3.4 and 4.2. The effective bolls number per plant of W3F1.0, W3F1.2 and W3F1.4 treatments were above 6.8 per plant. Cotton effective bolls number per plant was more sensitive than the 100-boll weight. In 2012 and 2013, the irrigation amount ranged from 291 to 445 mm and from 267 to 392 mm, cotton ET ranged from 277 to 419 mm and from 316 to 438 mm, WUE ranged from 1.27 to 1.65 kg/m3and from 1.27 to 1.52 kg/m3 in 2012 and 2013, respectively. The highest seed cotton yield was obtained in the combination treatments of W3F1.2 and W3F1.0 with the value of 5896 and 5888 kg/hm2 in 2012 and 2013, respectively. W2F1.0 combination treatment had the highest WUE. W3F1.0 combination treatment had the highest net return. PFP decreased with the increase of fertilization rate but increased with the increased irrigation amount and W3F0.6 combination treatment had the highest PFP. Considering the water shortage condition in the northern Xinjiang Uygur Autonomous Region, the treatment of 80%ETc combined with 250-100-50 kg/hm2 (N-P2O5-K2O) was suggested to be optimal for cotton production since the treatment could save 63 to 77 mm irrigation amount while keeping 95%seed cotton yields compared with the treatment of 100%ETc combined with 250-100-50 kg/hm2 (N-P2O5-K2O).(2) Under the condition of different irrigation and fertilization, the question is that usually yield, WUE and net income are difficult to balance. On the basis of binary quadratic regression, through normalization in addition to the dimension of the target variables, finally through different combination based on yield, WUE and net income multi-objective comprehensive benefit maximization of drip irrigation water fertilizer consumption was obtained. The irrigation water amount in 2012 and 2013 was 412 and 348 mm, respectively. Fertilizer rate was 278-111-56 and 258-111-52 kg/hm2 (N, P2O5, K2O) in 2012 and 2013, which can make the yield, WUE and net income of the comprehensive benefit maximization.(3) The canonical correlation analysis was used between plant height, stem diameter, branch number, leaf area index, aboveground dry mass, root dry mass and seed cotton yield and its composition of cotton shows that plant height, leaf area index, branch number, aboveground dry mass and root dry mass have positive correlation with seed cotton yield and effective boll number, but boll weight was negatively correlated with the branch number. The result of grey correlation degree analysis shows that there has a close relationship between Plant height, LAI, dry matter yield and yield. This may be root zone nutrient and water is relatively abundant under drip fertigation which do not need have strong root system of arid farmland.(4)Aiming at the condition of local fertilizer use efficiency is not high, especially under the study of deficit irrigation nutrient uptake use and use efficiency is less. Nutrient accumulation of different organs and nutrient use efficiency of cotton under different drip irrigation fertilizer regimes was studied. The result shows that leaf was the highest organ of nitrogen accumulation before full bloom stage, but boll was the highest organ at the bell stage. Leaf was the highest organ of phosphorus accumulation before first flowering stage, but bell was the highest organ at full bloom stage. Stem was the highest organ of potassium accumulation before first flowering stage, but bell was the highest organ at full bloom stage. The nitrogen, phosphorus, and potassium accumulation amount of growing stage can be described by Logistic function and the precision are very high. Fast accumulation of nitrogen began in 43-52 day after sowing, and the end of the fast accumulation perid spaned very large, the earliest at the end of the 76 day after sowing, the later will end at 100 day after sowing. Fast accumulation period of phosphorus began in 42-51 day after sowing, which has the same trend as nitrogen, but the end of fast accumulation arrivaled more earlier than nitrogen, it usually end at 70-82 day after sowing. Fast accumulation of potassium began in 38-49 day after sowing,and the latest end in 90 day after sowing. Fast accumulation period of 80%ETc and 100%ETc treatment began and end usually much later than 60%ETc treatment. The amount of 100 kg lint yield uptake of NPK between 1:0.23:1.14 and 1:0.29:1.35. W2F1.0 combination treatment had the highest NPK uptake ratio.(5)Many cotton leaf area index model was established, but only a few can simulate the condition of water deficit. On the basis of this, a leaf area index simulation model was developed under full and deficit irrigation of cotton in Xinjiang.Model based on beta function of daily heat effect as time scales, considering the effect of soil water stress, used of one ordered derivative of the Logistic function to describe the change rate of leaf area index. Leaf senescence process also used one ordered derivative of the Logistic function and assumed that occurred since the early flowering. The model also considered the soil water stress and temperature on leaf senescence accelerated effect. Finally Shihezi field observations were used for model parameter calibration, evaluation and sensitivity analysis. Evaluation results show that under the condition of full irrigation the root mean square error (RMSE) is 0.22 m2·m-2, residual accumulation coefficient (CRM) is 0.01. Under the condition of 20% and 40% deficit irrigation RMSE and CRM were 0.37,0.05 and 0.05,0, respectively. In addition, the simulation results of leaf area index and 1:1 line between R2 of 0.96. Simulation results show that the model is accurate dynamic change process of cotton leaf whole growth period in Xinjiang. Sensitivity analysis results show that under the condition of sufficient water, leaf aging potential area, leaf, extension area and aging area biggest, early flowering start time is the main parameters affecting the model. The model has few parameters and the characteristics of strong practicability which can be used to establish the Xinjiang cotton growth model and evapotranspiration model for leaf area index dynamic information.(6) As WOFOST model is difficult simulate crop growth in the condition of water stress accurately, and it also counld not simulate crop evapotranspiration under plastic mulching. While AquaCrop model simulate crop growth is too simple. This study reference AquaCrop model water stress factors and soil water module, water stress factor and soil moisture module of the WOFOST model are improved. The Improved WOFOST model could not accurate simulate flowering day and maturity day very well and could not simulate the effect of water stress on this. The simulated and measured values of above ground dry mass, seed cotton yield, dry mass of every organ, WUE, evapotranspiration, soil water content were between 2.8% and 20%, d-index were from 0.56 to 0.99 and model efficiency were from-1.45 to 1.Model could simulate precision of effective boll number and 100-boll weight, but WUE and evapotranspiration could not simulate very well. Finally different irrigation interval number and different irrigation water level was set up to simulate. The result shows that the seed cotton yield decreases gradually as the irrigation water amount reduce. Seed cotton yield also gradually declin as irrigation interval extension. When irrigation water at 1.0 ETc and irrigation interval at 2 d the largest seed cotton yield can be obtained. When irrigation water at 0.8 ETc and irrigation interval at 4 d the largest WUE can be obtained. |
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