1991 Annual Report for LS91-040
Utilization of Winter Legume Cover Crops for Pest and Fertility Management in Cotton
Summary
Objectives
The general concern with winter cover crops has involved a perception that pest problems in the summer crop would increase due to the cover crop, in particular legume cover crops. On the other hand, cover crops or attractive field borders may enhance the number and diversity of natural enemies reducing pest problems. Seven sites examined the benefits and risks from pests as a result of the use of winter legume cover crops in cotton production systems.
Approach
The two long-term sites were Clarkedale, Arkansas, established in 1972, and Bossier City, Louisiana, established in 1955. All sites had the cover crop treatments hairy vetch and winter fallow. Tillage comparisons, conservation and conventional, were included at four sites. The entomology sites, Edisto and Foreman, included two hairy vetch treatments; 1) all cover crop incorporated, and 2) strips of hairy vetch allowed to mature.
Results
The data indicates that cover crops are generally pest neutral for insects, weeds, soilborne plant pathogens, and nematodes. The hairy vetch cover crop reduced populations of Thielaviopsis basicola, the causal agent of black root rot, compared to the winter fallow treatment.
Data also suggested that maintained strips of hairy vetch in the cotton crop are serving as a trap crop for thrips. The root knot nematode, Meloidogyne incognita, increased by the use of legume cover crops in 1992, but this response was not consistent over years.
These data are quite encouraging for the use of cover crops in commercial cotton production systems. Additional research is needed to quantify Meloidogyne incognita damage and develop management solutions, including timing of incorporation of the cover crop or identifying resistant legume cover crop species.
Improved soil and plant nitrogen status was detected from the use of a legume cover crop. The economic analyses of the sites indicate that the use of a hairy vetch winter cover crop under conventional tillage resulted in higher net returns than traditional winter fallow at five sites.
In addition, cotton production under conventional tillage was more profitable than the reduced tillage practices employed at two of the sites in this study. Cotton using winter fallow in combination with reduced tillage was more profitable than cotton production with hairy vetch-reduced tillage. This research has established that an environmentally sound production system does not appear to increase pest problems and is economically sound.
December 1995.