A greenhouse study indicated that high levels of soil potassium could not overcome the deleterious effect of high reniform nematode populations on cotton yield and maturity. Reniform nematodes affected plant height and weight but did not affect root mass. Reniform nematodes did delay crop maturity by as much as 2 to 3 weeks. Results suggest that reniform nematodes may adversely affect cotton growth by inhibiting cotton roots from extracting potassium from the soil efficiently.