Uptake of N, P and S in fertilized pasture herbage and herbage yield response to fertilizer as affected by soil nutrients

Abstract

Uptake of N, P and S nutrients in the herbage of different pasture species were determined at eight sites within pastures located on Luvisolic soils in northeastern Saskatchewan, Canada. Also, the nutrient status of the soil was related to herbage yield response to N, P and S fertilizers. Soil tests would be used to establish the initial response to ferilizer and thereafter, nutrients removed from the soil could be replaced by fertilizer. Experiments in the study included one site with bromegrass (Bromus inermis Leyss.) and alfalfa (Medicago media Pers.), six sites on a pasture mixture (Bromus inermis Leyss., Festuca rubra L., Poa pratensis L. and Medicago media Pers.) and one site with Russian wildrye (Psathyrostachys juncea (Fisch.) Nevski) at both Pathlow and Pleasantdale pastures. Nitrogen and P fertilizers were applied at 0, 45 and 90 kg N ha−1 in combination with P at 0 and 20 kg ha−1. Sulphur treatments included 90N–20P–2-S (sulphate source, kg S ha−1) on pasture mixture sites and two treatments of 90N–20P–23S and 90N–20P–45S (elemental source, kg S ha−1) on bromegrass and alfalfa. Maximum uptake of nutrients were 103.6 kg N, 11.5 kg P and 5.2 kg S ha−1 with the application of 90N–20P–45S (kg ha) on the bromegrass–alfalfa pasture. The controls resulted in the lowest uptake of 20.2 kg N, 1.9 kg P (pasture mixture) and 1.5 kg S ha−1 (bromegrass and alfalfa). Yield response to N and P fertilizers (percentage yield over control) was related to soil tests for N, P and S (r2 = 0.42). Herbage yield increase (log10 mean of years) from S fertilizer over the control was negatively related to the soil test for S on six sites (r2 = 0.77). Uptake of N, P and S in herbage gave an adequate estimate of nutrient removal and the amount of fertilizer to apply to maintain soil nutrient levels. Key words: pasture, N, P, S, herbage, soil tests, yield