Eco-Study And Simulation Of Boll Development And Fiber Quality Formation In Cotton

It is of key importance to simulate the boll growth and fiber quality formation and to predict yield and fiber quality in cotton based on the effects of eco-factors on boll growth and fiber quality. In this study, a series of field experiments with different cotton cultivars, nitrogen and water management practices, temperature, light intensity, sunlight duration were carried out in two years, the relationships of boll growth and fiber quality to eco-factors were determined, and a simulation model of boll growth and fiber quality was developed basing on boll physiological development time. This work would provide theoretical base and key techniques for improving cotton growth & quality simulation and realizing precise growth and quality management.The results of field experiment in four typical eco-sites within three main cotton regions of China with different sowing dates showed that boll weight, fiber length and soluble sugar contents (SSC) in fiber increased, and fiber strength and micronaire value decreased with the latitude increase from the Yangtze River to Northern Xinjiang. The rank of meteorological factors affecting boll weight was successively total sunlight hours (TSLH), total effective temperature accumulation above 15 (TETA15), and daily temperature difference (DTD). The optimal temperatures of boll growth were 24.7 of daily mean temperature (DMT) and 13.7癈 DTD. From the Yangtse River to North Xinjiang cotton region, the restraining effect of TETA15 and DMT on boll weight enhancement gradually changed to promotive effect, while the promotive effect of DTD changed to restraining effect, and promotive effect of TSLH changed to no effect on boll weight enhancement, the relationships between eco-factors and fiber strength, micronaire value and SSC were quantified and used to analyze the optimal range or critical values of temperatures during boll period. DMT and minimum temperature (Tmin) during boll period should be 21.2 ?29.7 and 10.7-21.3, respectively, and DTD should not be over 15.2 if the highquality fiber is required, while fiber length is the longest when DMT is 25.4. DMT and Tmin should not be lower than 15.5 and 10.7, respectively, and DTD should not be over 17.9癈 during boll period if the lowest fiber quality standard can be accepted by textile industries.The relationships of boll growth and fiber quality to light intensity were analyzed on the experiment data on bolls per plant, boll final weight, relative growth rate. The results indicated that the opening bolls per plant decreased, the values of theoretically maximum boll weight, relative growth rate and maximum accumulation rate of boll dry matter all decreased, and the time of the boll dry matter accumulation was postponed with the decrease of light intensity. The rank of contribution of light intensity reduction to the boll components was fiber weight, seed weight and hull weight.By analyzing the dynamic relationships between cotton development and environmental factors, a simulation model of cotton development stages based on physiological development time (PDT) was established. In calculation of relative thermal effectiveness, the impact of diurnal temperature differences in different regions on cotton development was incorporated, and the enhancement of plastic mulching on air temperature was quantified. For simulation of development stages, fruiting initial node index (FINI), sunlight hours factor (SHF) and solar radiation index on fruiting branch (FBRI) were introduced besides earliness factor of a given genotype. Validation of the model with data sets from different years, ecological zones, genotypes and cultural practices indicated a high goodness of fit between the simulated results and observed values. The root mean square error (RMSE) of days between simulated and observed from sowing to emergence, from squaring to anthesis, from anthesis to boll opening, from sowing to boll opening were 0.9, 2.2, 2.3, and 1.7d, respectively, averaging 2.Id. The RMSE between simulated and observed days of all fruiting sites from squaring to bol...