Effect of Shade and Fertility on NO3‐N Accumulation, Carbohydrate Content, and Dry Matter Production of Tall Fescue1

Abstract

AbstractNitrate‐N poisoning is a suspected cause of death among cattle grazing in tall fescue (Festuca arundinacea Schreb.) under cloudy or shade conditions. The practice of aerially seeding tall fescue into sprayed brush areas is of special concern since fescue plants grow in shade at times. The purpose of this research was to evaluate the effects of shade and N fertility levels on NO3‐N, carbohydrate content, and tall fescue production. An artificial shade study was designed in which tall fescue and a check forage (wheat, Triticum aestivum L.) were grown in containers at shade levels of 0, 30, 47, 63, 80, and 94%, using Saran shade cloth. Production was measured during three periods of the growing season.Dry matter production of tall fescue increased with some shade. Seedlings did best with 47 and 63% shade. Older plants produced best with 30 and 47% shade! As shade levels increased, there was a reduction in forage production of wheat, and water soluble carbohydrate content of both tall fescue and wheat. More than 63% shade was required to significantly increase NO3‐N content of fescue forage grown with a low level of fertility, whereas only 30% was necessary in high fertility conditions. At 80% shade, fescue forage grown at high fertility showed concentrations of NO3‐N above 9,000 ppm. Levels of NO3‐N in wheat forage were much lower, and no NO3‐N levels above 5,000 ppm were detected.