The influence of season, stage of maturity, harvest frequency, and climatic factors on forage yield, quality, and seed production of grass introductions

Abstract

The distribution and metabolism of 14C-1- From a nursery of 200 grass introductions six accessions were chosen for evaluation of forage and seed yield and quality in response to management practices. Species represented were Paspalum nicorae Parodi, Paspalum plicatulum Michx., Setaria macrostachya H.B.K., and Panicum coloratum L. (Klein). S. macrostachya-S107 had the highest seed yield and quality and the largest caryopsis. Management treatments consisted of six initial cutting dates (seasons) at 21-day successive intervals and four maturities. Maximum yields (kg/ha) occurred at 6 to 9 weeks of age with calculated 24-week total yields as follows: P. nicorae-Pn62, 3,296; P. nicorae-Pn68, 4,614; P. plicatulum-Pp90, 6,499; S. macrostachya-S107, 9,817; S . macrostachya-S108, 8,060; and Panicum coloratum-Klein, 12,349. Invitro digestible dry matter (IVDDM) was determined for the two Setaria and Klein. The IVDDM values when plants were cut at 3 to 12-week maturities were as follows: S107, range 74-43, mean 57.0; S108, range 69-42, mean 52.9; Klein, range 70-47, mean 58.4. Variation in IVDDM within seasons (between 3 to 12 weeks of age) was 14 units of IVDDM on the average for all three grasses. The average variation within a single maturity was 13 units of IVDDM. Thus, the average variation in quality within a maturity was as great as the variation within the season. Similar, but distinct, patterns of forage quality were observed for the three grasses. The seasonal effects on forage quality were shown to be equal in magnitude to the effects of maturation. These seasonal quality patterns suggest the existence of a maturation biorhythm within the plant which controls the rate at which forage quality declines with maturity. The rhythm appears to be reset by environmental conditions following cutting, but once reset forage quality declines with maturity at a new rate established by factors influencing quality following the initial cut.