Nitrogen, aldicarb, and cover crop effects on cotton yield and fiber properties

Thrips, primarily Frankliniella spp., can damage cotton (Gossypium hirsutum L.) seedlings. The objectives of this study were to determine the effect of winter cover crops on thrips populations in cotton and to assess the yield and fiber quality response to cover crops and N fertilizer rate with and without thrips protection. A field experiment was conducted on a Bonneau loamy sand soil (loamy, siliceous, thermic, Arenic Paleudult) from 1996 through 1998. Treatments were cover crops, N fertilizer rate, and aldicarb rate. Cover crops were rye (Secale cereale L.), crimson clover (Trifolium incarnatum L.), a clover + rye mixture, and winter fallow. Nitrogen levels were 0, 78, and 112 kg N ha(-1). Aldicarb levels were 0 and 1.18 kg a.i. ha(-1). Aldicarb reduced thrips populations. For plots without aldicarb, differences among winter covers occurred at one sampling time in 1998 when fallow had more thrips than the other three winter covers. Aldicarb increased yield by 9% in 1996, 48% in 1997, and 35% in 1998. In 1997 and 1998, yield increases with aldicarb were greater in the winter cover and N treatment combinations that provided higher total N to the crop. The 0 kg N ha(-1) rate tended to have lower yield, fiber length, length uniformity, fiber strength, micronaire, and Hunter's +b than the other two N rates. Aldicarb generally increased the value of these fiber properties each year. Including agronomic practices in assessing control measures may improve integrated pest management strategies for thrips in conservation tillage systems.