The influence of NPK fertilization on Lolium perenne L. forage quality

S. Bumane

Priekuli Plant Breeding Institute, 1a Zinatnes St., Priekuli, LV 4126, Latvia;
e-mail: skbumane@inbox.lv

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. ‘Spidola’ 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 N₀P₀K₀ + absolute MAX N₁₂₀P₁₂₀K₁₆₀. The totalplot area was 17.5 m², harvested area 13.5 m². In the trial, five levels of fertilizer werecompared: – 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^-1of K₂O. The goal of current research was to clarify the influence of mineral fertilizer optimization on forage quality formation in perennial ryegrass cv. ‘Spidola’ 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).

Key words:

Nitrogen uptake at various fertilization levels and cutting frequencies of Lolium species

R. Aavola¹ and M. Kärner²

¹Jõgeva Plant Breeding Institute, Aamisepa 1, 48309 Jõgeva, Estonia;e-mail: rene.aavola@jpbi.ee
²Institute of Agricultural and Environmental Sciences, Estonian University of Life Sciences,Kreutzwaldi 5, 51014 Tartu, Estonia; e-mail: malle.karner@emu.ee

Abstract:

A field trial was carried out in 1999–2000 to identify optimal combinations of compound fertilizer rates and defoliation frequencies in perennial ryegrass cv. Raidi (diploid) and Raite (tetraploid) and Italian ryegrass cv. Talvike (tetraploid), to enable the nitrogen (N) requirements of dairy cows to be met. The study aimed at estimating the N utilization in the swards subjected to 6 cycles of simulated grazing or cutting 4 times for silage. N application rates were changed from 0–500 kg ha-1 by 100 kg in the former and from 0–400 by 80 kg ha-1 in the latter harvest regime. Increasing the rate of fertilizer increased the N concentrations and yields. Applying N 300 to ryegrasses defoliated at tillering to stem elongation stage allowed assuring minimum N content in the forage dry matter (2.2%) while at N 500 the upper level (2.7%) was exceeded. The ryegrass plants took up less N than was applied with the compound fertilizer. Increasing the defoliation frequency of grass had a positive effect on N content of the forage, but had inconsistent or no effect on improving N uptake from fertilizer and soil. Perennial ryegrass cultivars were more efficient than Italian ryegrass in taking up N from the soil and fertilizer at simulated grazing. Cutting 4 times a year at moderate to high fertilizer rate applications did not reveal a distinct superiority in N absorption of a particular cultivar, but Italian ryegrass had the best N uptake potential from N deficient soil.

Key words:

defoliation, Italian ryegrass, nitrogen, perennial ryegrass, uptake