|Roof, Mitchell - CLEMSON UNIV, FLORENCE|
Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 13, 2003
Publication Date: March 1, 2004
Citation: Bauer, P.J., Roof, M.E. 2004. Nitrogen, aldicarb, and cover crop effects on cotton yield and fiber properties. Agronomy Journal. 96:369-376. Interpretive Summary: Thrips are a serious insect pest of cotton, especially when the cotton plants are small early in the season. We were interested to learn if different winter cover crops affected the attractiveness of cotton to thrips. We were also curious whether cover crops and nitrogen fertilizer rate affected the ability of the plants to recover from thrips damage. We found little difference among cover crops for thrips populations or thrips damage. We also found that the predominant effect of cover crops on yield and quality was through their influence on the soil nitrogen supply, and the cotton yield and quality loss from early season insect damage generally became greater as the total nitrogen available to the crop increased. Researchers and extension personnel will use this research as they develop sustainable cotton production practices.
Technical Abstract: Conservation tillage with cover crops is gaining wide acceptance for cotton (Gossypium hirustum L.) production, but little is known about the effects of habitat manipulation on thrips (Frankliniella sp.) populations and the effects of thrips damage on cotton yield and quality. The objectives of this study were to determine the effect of winter cover crops on thrips populations in cotton seedlings and to assess the yield and fiber quality response of cotton 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) near Florence, SC, from 1996 through 1998. Treatments were cover crops, N fertilizer rate, and aldicarb rate. Cover crops evaluated were rye (Secale cereale L.), crimson clover (Trifolium incarnatum L.), a clover + rye mixture, and winter fallow. Nitrogen fertilizer levels were 0, 78, and 112 kg N/ha. Aldicarb levels were 0 and 1.18 kg a.i./ha. The main influence of cover crops on cotton yield and quality was on the N supply to the crop. Summing the total N in the cover crop with fertilizer N applied and using that value as a dependant variable in quadratic regression equations provided good descriptions for yield and some fiber properties each year. Aldicarb reduced thrips populations and increased yield by 9% in 1996, 48% in 1997, and 35% in 1998, but the response of cotton to aldicarb was dependant on N level. Similarly, many fiber properties were dependant on both total N and aldicarb level each year. Improved integrated pest management strategies for this important pest in conservation tillage systems will need to include agronomic practices in their assessment of control measures.