Below are the results from a trial conducted in three locations in 2019. Varieties were PHY 480 W3FE, which has resistance to root-knot nematode (RKN), and DP 1646 B2XF, an industry standard. Given RKN-resistance, the hypothesis is that such varieties might have a superior root system and thereby more readily take up N. Nematode levels at the outset were unknown.
Samples were taken in mid-October concurrent with rainfall that relieved a sustained late season drought. Application of N varied by locations. At Headland, all except the 0-N plots received an at-plant application of 30 lbs N, with the remaining N applied at sidedress. At the other sites, all N was applied shortly after planting.
Overall yields were highest at Headland and comparable for Shorter and Tallassee. At the two locations where root-knot nematode levels were low to moderate, DP 1646 B2XF had superior yield compared to PHY 480 W3FE. Yields of the two varieties were similar at shorter which had high levels of RKN. At Headland, 90 lb/A N was clearly sufficient for maximum yield.
Rates responses at the other locations were somewhat scattered. At two locations, season-end RKN levels were significantly lower following PHY 480 W3FE as compared to DP 1646 B2XF.