TABLE CONTENTS

Relationships between Soil Electrical Conductivity and NDVI for Sitespecific
Rotylenchulus reniformis Nematode Evaluations and Yield
Potential in Cotton
Lawrence, K.S., G.W. Lawrence, E. van Santen, A. Winstead, S. Norwood, C. Burmester & C.
Overstreet
Auburn University, Alabama, USA
The test was conduced on a 20 acre producer cotton field naturally infested with the reniform
nematode in north Alabama. Before planting, soil electrical conductivity data (EC) was
collected utilizing the Veris 3100 mapping system measuring both shallow (0-1foot) and deep
(0-3feet) electrical potential. The field was placed on 0.25 acre grids (160 targets per field) at
30 days after planting (DAP) using the GIS Site Mate system. Corresponding nematode soils
samples were collected at each grid intersect 30 and 45 DAP. Real-time NDVI was
determined using the Greenseeker technology. Yield estimates were collected with a yield
monitor system and placed into four low to high yielding categories. EC shallow and deep,
NDVI, nematode numbers, and cotton root mass were then analyzed with the SAS ®
CANDISC procedure and the resulting phenotypic correlations (r) were used to determine the
relationship of these response variables with yield classes. There was a significant separation
of the highest yielding areas from the lower three yield classes along the 1 st canonical axis,
which accounted for 50% of the multivariance. High yielding areas were distinguished from
the low yielding regions by cotton root mass (r = -0.80), R. reniformis per gram of root (r =
0.93), and NDVI at 45 DAP (r = -0.93). The 2 nd canonical variate discriminated among the
three lower yielding areas. These differences were best described by EC values and the R.
reniformis extracted from the soil. Regression analysis indicated a significant (P = 0.06)
relationship of reniform counts with NDVI at 45 DAP, although the coefficient of
determination was very small.
5 th International Congress of Nematology, 2008 312