Abstract :
Within the framework of the research program developed at the Latvian University of Agriculture (LLU), at the Research Institute of Agriculture (ZZI), Agency of LLU field trials were established and research was conducted over the period 1999-2003. In all trials, tetraploid perennial ryegrass cv. ʹSpidolaʹ was sown to plots at a rate of 12 kg ha-1. The impact of three factors (NPK) in 17 treatments, replicated four times, were researched according to the so-called „star" scheme added to control treatment NoPoK0 + absolute MAX N120P120K160. The total plot area was 17.5 m2, harvested area 13.5 m2. In the trial, five levels of fertilizer were compared: - 0; 30; 60; 90 and 120 kg ha-1 of N, 0; 30; 60; 90 and 120 kg ha-1 of P2O5, and 0; 40; 80; 120 and 160 kg ha-1 of K2O. The goal of current research was to clarify the influence of mineral fertilizer optimization on forage quality formation in perennial ryegrass cv. ʹSpidolaʹ under agro-climatic conditions of Latvia. It is concluded that N fertilizer mostly influenced herbage yield and quality characteristics of perennial ryegrass where both, crude protein (CP) content of dry matter and total yield of CP per hectare increased. In the treatments N60 and N120, the CP content in grass dry matter increased by 0.14 and 2.66%, and CP yield per hectare by 98 and 226%, respectively, compared with N0 (at P60 K80 background).
