Auteur: Bussink D.W., Van Middelkoop J.C., Holshof G. and Van der Draai H.
Jaar van uitgifte: 2015
Optimal potassium (K) fertilisation stimulates grassland production. In 2011 and 2012 fertiliser trials on grassland were executed to update the 40-year-old recommendations. Farm field trials were executed on 24 locations on sand, clay and peat soils with varying K-availability and buffering capacity. There were three treatments on each site: with or without cattle slurry application, two nitrogen (N) levels (60 and 120 kg N ha‑1) and two K fertiliser levels (0 and 60 kg K2O ha‑1). Uptake of K in the first and second cut (to account for any residual effect) was determined to derive the optimal K-application rate. In parallel there was a seasonal trial with different N and K levels to test the interaction of K with N. Fertilisation with 60 kg K2O ha‑1 resulted in extra yield of the first cut of 200 to 650 kg DM ha‑1. The fertiliser increased the yield in the seasonal trials up to 2 tons DM ha‑1 year‑1. The experimental data were used to develop a new recommendation system based on the soil parameters of cation exchange capacity and available K determined in 0.01 M CaCl2. The new recommendation results, on average, in a lower K application rate than the previous recommendation.