Effects of potassium fertiliser and dolomite on the dry matter yield and forage quality of signal grass (Brachiaria decumbens) grown on Korat soil series (Oxic Paleustults) in Northeast Thailand

This experiment was carried out to investigate the effects of potassium and dolomite on dry matter yield and quality of signal grass (Brachiaria decumbens Stapf.). It was laid out in a 4x3 factorial arranged in a randomized complete block design (RCBD) with four replications. Application rates of potassium sulphate fertiliser (K) were 0, 125, 250 and 500 kg K2O/ha and dolomite rates (D) were 0, 625 and 2,500 kg/ha. Total dry matter yield (DM yield) of four cuts significantly increased (p<0.01) with an increase in K only up to 125 kg K2O/ha. Dolomite application did not show any significant effect (p>0.05) on DM yield. There was no significant (p0.05) K x D interaction for DM yield and forage quality. K did not affect (p>0.05) crude protein (CP), neutral detergent fibre (NDF) and acid detergent fibre (ADF) contents except for CP and NDF in rainy season. K at 125 kg K2O/ha slightly increased CP content cf. control in rainy season. D did not affect (p0.05) CP, NDF, ADF and dry matter degradability (DMD) in rainy and dry seasons. The highest K application rate significantly decreased (p<0.01) DMD in both seasons.