Grasspea (<i>Lathyrus sativus</i>L.) as a Green N Source Reduces the Effects of 2,4 D in Susceptible Cotton (<i>Gossypium hirsutum</i>L.) Cultivars

Cotton (Gossypium hirsutum L.) production in Oklahoma has more than tripled in the last ten years. This increase in cotton acreage in Oklahoma, a region that traditionally produces winter wheat, has led to increased incidences of 2,4 D contamination in sprayers that are used to spray cotton crops. Cotton is extremely sensitive to 2,4 D, with losses of yield and ultimately profit to the cotton producer in cases of drift or tank carryover. In this study, six cotton cultivars (three 2,4 D susceptible and three 2,4 D tolerant) were grown in combination with four N treatments to determine the benefits or drawbacks of using a green manure as N source. Seedcotton, seed, and lint yield were all negatively impacted by 2,4 D in the susceptible cultivars. Additionally, water use was increased in the susceptible cultivars compared to the tolerant cultivars. The negative effects of 2,4 D on cotton growth were partially mitigated by grasspea, though the supply of too much nitrogen increased the negative effects of 2,4 D. Applying nitrogen to a susceptible cultivar of cotton contaminated by 2,4 D is not recommended for short season environments like Oklahoma.