Effects of sodium sulphate and potassium chloride fertilizers on the nutritive value of timothy grown on different soils

Third harvest samples from a pot experiment were analysed to study the effe cts of sodium (Na) (0, 200 and 400 mg dm(-3) of soil in a single applicatio n as Na2SO4. 10H(2)O) and potassium (K) application (0, 100 and 200 mg dm(- 3) applied at each harvest as KCI) on the nutritive value of timothy grown on three different soil types (clay, loam and organogenic soil). The effect s of fertilization on concentrations of crude protein, neutral detergent fi bre (NDF) and non-structural carbohydrates, although statistically signific ant, were relatively minor in absolute terms. Na applications increased and K applications decreased sulphur and phosphorus concentrations, the magnit ude of which was dependent on soil type. The increase in sulphur concentrat ion can be attributed to sulphate in Na-fertilizer. The effects of fertiliz ers on in vitro organic matter digestibility and the potential extent of dr y matter (DM) and NDF digestibility were small. Digestion kinetic parameter s estimated from fermentative gas production measured using a fully automat ed system were used in a rumen simulation model to estimate digestibility. Total gas volume and the rate of gas production from the rapidly digestible fraction were negatively correlated with timothy S and N concentrations. N a application had no effect, but K application increased true rumen DM dige stibility, the effect being most profound on organogenic soil. The results suggest that Na application does not elicit substantial positive effects on the nutritive value of timothy which has often been reported for perennial ryegrass, but K application can improve the nutritive value of timothy gro wn on K deficient soil.