| Traditional theory suggests that, continuous cropping will lead to negative effects on crop growth, and which may bring low production and quality, diseases and pests. Xinjiang is one of the three main cotton bases in China, and continuous cotton in Xinjiang is very common. With increasing time following cotton plantations, seed cotton yield in Xinjiang increased steadily with the process of "the initial development-slowly increasing-rapid growth". Years of practice proves that agricultural technology such as fertilizers, pesticides, farm machinery, irrigation, breeding has been providing a way to improve cotton productivity, thus compensate for the adverse effects of continuous cotton cropping in Xinjiang. Therefore, agricultural technology has been becoming a new kind of productivity to overcome the drawbacks of continuous cropping.This paper describes a case study of the Manas River Valley, which was the largest oasis agricultural area in Xinjiang and contains a typical oasis suitable for study. We using spacial substitutes and laboratory analysis to evaluate effects of continuous cropping on soil properties, and then to provide an early warning of changes in soil quality in advance. Method of fixed position experiments and crop growth model was used to analyze the effect of cultivation and farming systems on ecological environment in cotton field, and then to quantify the compensation efficiency of agricultural technology on continuous cotton productivity in Xinjiang. By systematically analyzing the various cultivation technologies on cotton productivity, the optimizing allocation of light, heat, water, soil and other resources in agro-ecosystem was discussed for a better productivity, resource use efficiency and environmental quality.The synthetic evaluation of cotton production showed upward trend during the past 20 years in the Manas River Valley, and which transite to positive in the year of 1997. Soil sample at the depth of 0-20 cm was collected from the cotton fields with an age sequence of 0,5,10,15 and 20 years. Results showed that the content of soil organic carbon, soil total N, soil available N, soil microbial biomass C, soil microbial biomass N, and activities of urease, invertase and cellulose were increased with increasing plantation age but decreased with increasing soil depth. The cumulative rate of soil organic carbon, soil microbial biomass C, soil total N, and soil microbial biomass N reached the maximum value at 13.2,11.3,17.0 and 14.6 years after plantation, respectively. By systematically analyzing the various indices of soil quanlity, an early warning of changes in soil quality can be provided 10 years in advance.Accumulated temperature of plastic mulching cultivation and open field cultivation were compared to clarify the warming effect of plastic mulching. The compensation coefficient (K) was 0.66 and 0.25 during emergence-squaring stage and squaring-flowering stage of plastic mulching cotton cultivation respectively. Plastic mulching cultivation shortened the duration of vegetative stage and longer the duration of reproductive growth, which ensures sufficient dry matter accumulation for yield formation.Relationship between dry matter production and amount of solar radiation intercepted by the canopy was studied of different cotton stand densities, result showed that light extinction coefficient (0.98) and effective radiation efficiency (3.2g/MJ) was similar of different cotton stand densities, which suggested these two parameters were not affected by stand density, and solar radiation interception was enhanced by stand density which adjusted the flowering-boiling stage in accordance with light-heat abundant month of June-August in cotton cultivation of Xinjiang.Evapotranspiration was estimated by crop coefficient method and Penman-Montieth model of drip and furrow irrigation. Result showed there was no significant difference of total evapotranspiration between drip and furrow irrigation. Compared with furrow irrigation, the value of stage evapotranspiration and average daily evapotranspiration were higher under drip irrigation before flowering and became lower after flowering. Seed cotton yield, irrigation water use efficiency and water use efficiency was increased by 13%,77% and 56% respectively of drip irrigation.Soil organic C and total N content at 0-20 cm were influenced significantly by residue incorporations and fertilizer application amounts, the content of soil organic C at 0-20 cm increased while total N decreased with cotton residue incorporation, soil organic C content at 0-20 cm decreased while soil total N increased with N fertilizer application. Soil organic C and N density was 4.48 kg/m2 and 0.37 kg/m2 respectively with average residue incorporation and average inorganic N fertilization, which compared to 2.87 kg/m2 and 0.21 kg/m2 respectively with no-residue incorporation and no-inorganic N fertilization. And the soil organic C, N sequestration rate was 0.19 kg C/ha/year and 0.05 kg N/ha/year with average residue incorporation and average inorganic N fertilization.According to ANOVA, the contribution for cotton production of single technology such as drip irrigation, plastic mulching, residue incorporation and plant density was 58.61%,35.44%,20.11%,24.03% respectively. The interaction effect of coupling of different techniques for cotton production showed that the combination of high-density & plastic mulching & drip irrigation got the best interaction effect (281.57 kg/ha) while drip irrigation & residue incorporation got the lowest interaction effect (24.99 kg/ha).This paper quantified the compensation effect of agricultural technologies on cotton productivity, and which of great significance for enriching the theory of crop cultivation and farming systems in oasis. Compensation coefficient (K) was provided of plastic mulching for cotton cultivation. And light extinction coefficient and effective radiation efficiency was confirmed of high density cotton cultivation in Xinjiang. Indices of soil microbial biomass and soil carbon and nitrogen density were put forward to reflect the changes in soil quality of continuous cotton fields, contribution of technologies were quantified on cotton productivity. Crop growth model (SUCROS-COTTON) was used to reflect crop productivity, which provides a new idea to evaluate the compensation effect of cotton productivity.
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