Effects of plant density and mepiquat chloride application on cotton boll setting in wheat–cotton double cropping system

Sowing cotton directly after harvesting wheat in the Yangtze River Valley of China requires early mature of cotton without yield reduction.Boll-setting period synchronisation and more yield bolls distributed at the upper and middle canopy layers are also required for harvesting.The objective of this study is to quantify the individual and interaction effects of plant density and plant growth regulator mepiquat chloride(MC)on temporal and spatial distributions of yield bolls,as well as yield and yield components.During the 2013–2016 cotton growing seasons,the experiments were conducted on a shortseason cotton cultivar CRRI50 at Yangzhou University,China.Various combinations of plant density(12.0,13.5 and 15.0 plants m^(–2))and MC dose(180,270 and 360 g ha^(–1))were applied on cotton plants.The combination of 13.5 plants m^(–2)and 270 g ha^(–1)MC resulted in the greatest boll number per unit area,the highest daily boll setting number and more than 90%of bolls positioned within 45–80 cm above the ground.In conclusion,appropriate MC dose in combination of high plant density could synchronize boll-setting period and retain more bolls at the upper and middle canopy layers without yield reduction in the system of direct-seeded cotton after wheat harvest,and thus overcome the labor-intensive problem in current transplanting cropping system.

Cotton-harvester-flow simulator for testing cotton yield monitors

An experimental system was developed to simulate the pneumatic flow arrangement found in picker-type cotton harvesters.The simulation system was designed and constructed for testing a prototype cotton yield monitor developed at Mississippi State University.The simulation system was constructed to approximate the pneumatic cotton flow system of a cotton picker,and was capable of operating with varying cotton flow rates.The simulator was tested with different cotton flow rates,and the relationship between feeder rate and amount of conveyed seed cotton was found to be consistent.Further,the simulator was used to conduct tests with the novel optical cotton yield monitor,which proved accurate at measuring the amount of seed cotton flowing through the simulator.Finally,some differences between laboratory testing and field-testing were noted:seed cotton becomes fluffed and twisted when recycled through the simulator,and seed cotton stored in the laboratory tends to be of lower moisture content than cotton during harvest.These differences should be considered when using a laboratory simulator to test cotton yield monitors.