Reduced Cotton Growth and Yield Under Foliar Application of Mepiquat Chloride Was Not Due to Less Nitrogen and Phosphorus Acquisition Under an Innovative Cropping Model in Yangtze River Valley of China

Sustainable cotton production has been an everlasting challenge due to multiple measures. An innovative cotton cropping system characterized by late sowing, once fertilization and higher density has been successfully practiced in China. But, it is still unsure that mepiquat chloride (MC) application is an essential input in this cropping model or not. We hypothesized that MC application might reduce the cotton growth and yield and thus can be ignored to increase the net farm income. To test this hypothesis, a 2-year field experiment was performed where cotton was sown in late-May at 10 plants m planting density and with 225 kg N ha single fertilization. Foliar application of MC was done thrice with 5 leaf intervals which were initiated from the 6th leaf stage in 5 dosages (0, 30, 60, 90, and 120 g ha). Cotton growth attributes including leaf area index and leaf area duration were drastically reduced and control treatments (MC0) showed maximum increase by 28–35% and 28–36% across 2 years. Besides this, cotton nitrogen and phosphorus acquisition was not significantly influenced by MC application especially the uptake in reproductive organs from MC0 to MC120 of 57.13 to 53.24 kg N ha and 19.69 to 19.33 kg P ha, respectively. Moreover, lint yield was reduced by 5–29% as MC dosage increased due to reduced photosynthesis and disturbed source-sink relationship under MC application. Overall, the results suggested that MC application is not required in this innovative planting model and can be ignored to increase the net return.