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PRECISION AGRICULTURE INITIATIVE FOR TEXAS HIGH PLAINS
FIRST BIENNIUM REPORT, 1998 - 1999
Texas Agricultural Experiment Station
Texas Agricultural Extension Service
Texas A&M University System
Name
Title/agency
Location
Investigators:
T. A. Wheeler
Assist Prof/TAES
Lubbock
S. Searcy
Prof/TAES, TAEX
College Station
H. W. Kaufman
Assoc Prof/TAEX
Lubbock
K. Siders
IPM/TAEX
Hockley, Castro Co.
P. Kidd
IPM/TAEX
Terry, Yoakum Co.
Project Title:
Indirect methods for determination of root-knot nematode density for use in precision agriculture
Primary Location: AG-CARES
Objectives:
1) Develop methodologies for mapping the location and severity of nematode infestations in cotton fields in the High Plains of Texas.
2) Evaluate interactions between nematode density and weed, insect and seedling disease problems on growth of cotton.
A. Reporting Period: Sept. 1997 - Aug. 1999
B. Summary of Progress
Objective 1: Determine spatial and temporal variability of factors that can be addressed by precision agriculture practices.
A total of fourteen fields have been intensively sampled for root-knot nematode in the following counties: Dawson, Gaines, Hockley, Lamb, Lubbock, and Terry. These counties represent the majority of root-knot nematode acreage in the High Plains of Texas. The spatial variability of root-knot nematode in individual fields ranged from low (Figure 1A) to high (Figure 1B-E).
Figure 1
Objective 2: Develop and evaluate instrumentation and software to measure and analyze variability in crop production and plant response to that variability.
i) Determine if cover crops can be used to detect density differences in root-knot nematode, before planting of cotton.
Corn was planted as a cover crop in three locations in 1998 and 1999. One location was lost in each year before the cotton crop was harvested. A single transect covering 1000-2000ft. was divided into either 20ft or 40ft areas. Corn height, cotton yield and root-knot nematode density was measured in each plot. Sunflower was also planted as a cover crop in 1999 at two sites, and was measured similarly to corn height. In 1999 at Ag-Cares, an experiment was conducted using three cover crops, corn, wheat, and sunflower. These treatments were replicated three times in a randomized complete block design. The additional purpose of this experiment was to determine if root-knot nematode densities were increased by corn or sunflower cover crops in comparison to the wheat cover crop. Data was analyzed with regression analysis to determine if the height of the cover crop just before planting was an indicator of root-knot nematode density and cotton yield. The height of the corn cover crop was positively correlated with root-knot nematode density at the Hockley county site in 1998 (Figure 2B), Hockley county site in 1999 (different than the 1998 site, Figure 2E) and Terry county site in 1999 (Figure 2G). The 1999 Hockley county site was lost to the heavy rains soon after planting of cotton. Sunflower height was negatively correlated with root-knot nematode density at the 1999 Hockley county site (Figure 2F). There was no correlation between cover crop height and root-knot nematode density at either year in the AG-CARES site (Figure 2A,C, D). At the Ag-Cares site in 1999, root-knot nematode midseason density was not significantly different (P=0.05) between any of the cover crops. Cover crop height was not associated with cotton yields except at the Hockley county site in 1998 (Figure 3). It was concluded that the height of corn was not a negative indicator of areas high in root-knot nematode. In fact it appeared to be a positive indicator or root-knot nematode density. This led to speculation that corn was increasing the root-knot nematode population, though that increase was not higher in corn than with wheat or sunflower (tested in AG-CARES during 1999). The affect of a corn cover crop versus no cover crop on root-knot nematode density was not tested. The negative relationship between corn height and cotton yield at the Hockley county site may have also been due to water use by the corn rather than an increase in root-knot nematode density.
Figure 2