EFFECTS OF DATES OF SEEDING AND LEVELS OF N FERTILIZATION ON YIELDS, CHEMICAL COMPOSITION AND IN VITRO DIGESTIBILITY OF FORAGE KALE

Abstract

Forage kale (Brassica oleracea L.) was seeded on three dates and fertilized at different levels of N as NH4NO3 for 3 yr. The highest dry matter (DM) yield was obtained with the earliest date of seeding and with levels of N fertilization of 120 kg/ha. The yield of crude protein (CP) was relatively constant among years, for the different dates of seeding and for N fertilization above 120 kg/ha. Increasing N fertilization or delaying seeding increased the leaf:stem ratio, and consequently the CP content. The levels of NO3-N in stems, leaves and whole plants were at an acceptable level for safe feeding. The cellulose, crude fiber, Ca and P contents were not affected greatly either by the dates of seeding or by the levels of N fertilization. The in vitro DM digestibility (IVDMD) was not affected markedly by any treatment.