THE EFFECT OF TEMPERATURE ON THE GROWTH AND COMPOSITION OF THE STUBBLE AND ROOTS OF PERENNIAL RYEGRASS

Abstract

in about six weeks. At 800 F top growth was rapid but no new roots were produced and shoots from the rhizomes appeared above ground only under conditions of low nitrogen nutrition. Although no analyses were made of these plants it is assumed that the rapid top growth, combined with frequent clipping, soon depleted the carbohydrate reserves and led to their exhaustion. At 60F growth was more normal for the species. According to LOVVORN (7), when four species of grasses were cut frequently, the yields were lower at 80than at 65F. BROWN (3) grew four grasses at a num- ber of constant temperature levels between 40and 1000 F. In some species the optimum temperature for top growth was not the same as the optimum for root and rhizome production. For three grasses having lower optimum temperatures (70-90for herbage, 50-70for roots and rhizomes), namely Kentucky bluegrass, Canada bluegrass and orchard grass, an increase in tem- perature was associated with increased fiber and decreased nitrogen-free extract contents in above-ground and below-ground parts. Protein was at a minimum at 60or 70and was greater at both lower and higher tempera- tures. In Bermuda grass, which had an optimum growth temperature of 1000, fiber and nitrogen-free extract increased with rising temperature, the former to reach a limit of increase at 700, the latter at 100. The protein minimum was at 80-90, somewhat higher than with the other grass species.