Physiological and Yield Response to Uniform Vs Non-Uniform Plant Stands of Varying Plant Populations for Non-Irrigated Cotton.

Cotton (Gossypium hirsutum L.) yield loss can vary between a uniform and nonuniform plant stand. The objective of this experiment is to quantify the ability for cotton to compensate for poor plant stands within varying plant populations in both uniform and nonuniform plant stands during 2019. Three seed ratios were used by mixing seed of glyphosate and glufosinate resistant (GR) cultivars (DP 1612, DP 1614, DP 1646) with a glyphosate and glufosinate susceptible cultivar (GA-230). Seed ratios included 100:0 (1.0 GR), 75:25 (0.75 GR), and 50:50 (0.50 GR) mixes. Seed rates of dense (12.5 seed m^-1), medium (8.2 seed m^-1), and sparse (3.3 seed m^-1) populations were used to correspond with each mixed seed ratio. All plots were sprayed with glyphosate and glufosinate approximately 10 days after emergence to terminate the susceptible cultivar and create random gaps. Once termination was completed, gaps were assessed for each seed ratio with minimum gap measurements of 18, 25, and 31 cm to correspond with the dense, medium, and sparse populations, respectively. The plants at each edge of a representative average gap were used to quantify the ability of the plant to compensate growth into the missing row area. There was a negative linear correlation between lint yield and percentage of missing row, with a 58 kg ha^‑1 decrease in yield for every 10% increase of missing row. There was 66% more lint from the average gap edge effect with 3.3 seed m^-1 using 0.50 GR than the 12.5 seed m^-1 with 0.50 GR treatment. This illustrates the plant’s compensation for yield with a reduced stand. This information is useful for determining the threshold where yield loss occurs in a reduced plant stand. Additional research is needed for initiating replanting timing and methodology to improve upon plant populations and/or gaps where reduced yields occur.