Effects of Rotation, Irrigation and Cultivar on Cotton Yield with Root-Knot Nematode.

Irrigated cotton is produced on the Texas High Plains under varying levels of deficit irrigation. The performance of new cotton cultivars under different irrigation levels is an important factor in cultivar selection. Additionally, pest problems such as root-knot nematode or Verticullium wilt are important factors in cultivar performance. Field studies were conducted in 2014 near Lamesa, Texas in order to evaluate effects of five cultivars, three irrigation levels, and crop rotation on cotton yield and fiber quality in a root-knot nematode infested field and to determine effects of crop rotation, cultivar, and irrigation levels on nematode reproduction and root galling. Five varieties were planted using a randomized complete block design at three water levels--low, base and high. Results indicate that increased irrigation level increased yields for both Wheat – Cotton rotation and Continuous Cotton, but had only limited effect on lint quality as measured by loan value. No differences in yields among cultivars was found in the system. The Wheat – Cotton rotation produced 28-39% higher yields compared to Continuous Cotton system across irrigation level, but had little effect on fiber quality. Early season root galls indicated that the Wheat rotation did reduce the root-knot nematode population density over the Continuous Cotton system. Overall density of root-knot nematode was low to start 2014, and nematode buildup during the season was affected by cultivar, but not by rotation. Low initial nematode pressure was insufficient to cause substantial yield losses, so the susceptible check was able to yield similar to the cultivars with some nematode resistance. However, the root-knot nematode buildup in the susceptible cultivar should eventually result in a more damaging nematode density in the future.