Bunch Ash as Source of Potassium and Soil pH Improvement in Alfalfa (Medicago Sativa L.)

Two consecutive field studies were conducted to evaluate the use of bunch ash of oil palm (Elaeis guineensis) empty fruit bunch as source of fertilizer and soil amendment to increase soil pH in the cultivation of alfalfa (Medicago sativa L.). In the first trial, alfalfa was given two sources of K, either muriate of potash (MOP, 60% K2O) or bunch ash (BA, 30% K2O). Four rates of K2O were applied: 0 (control), 100, 200 and 400kg K2O per hectare. The trial was carried out using the Randomized Complete Block Design (RCBD) with four replications. In addition to K, equal rates of nitrogen at 17 N kg/ha and phosphate 56 kg P2O5 per hectare were applied as basal fertilizers. Initial soil pH was 4.57 and the soil was limed at the rate of 13 t/ha to raise pH to 6.85, the optimum pH for alfalfa. The results showed that BA and MOP gave the same yield and quality of alfalfa at all rates of K2O. Both sources of fertilizers gave dry matter yield of between 3.4 t ha-1 to 7.7 t ha-1, crude protein of leaf between 18.67% - 24.27% and crude protein of stem between 13.31% - 19.26%. The mineral concentration and fibre concentration were also not significantly different between alfalfa applied with MOP and BA. Neutral Detergent Fiber (NDF) of leaves were 72.56% and 72.25%, NDFof stem were 66.5% and 68.0%, respectively for MOP and BA treated alfalfa. Similarly, acid detergent fiber (ADF) of leaves were 15.38% and 20.00%, ADF of stem were 39.31% and 39.34% respectively, while acid detergent lignin of leaves were 12.31% and 12.13%, respectively for MOP and BA. Yield and crude protein increased linearly with increasing rates of K2O with the maximum values obtained at 400 kg K2O per hectare. A second experiment was done to determine whether lime application will affect yield and quality of alfalfa when the optimum rate of BA at 400 kg/ha was used. The treatments comprised of four rates of lime: 0 (control), 1000, 2000 and 4000 kg/ha of GML. The initial acidity of the soil was 5.57. The hypothesis is that lime will not affect alfalfa growth as BA at 400 kg/ha is sufficient to increase pH to optimum level for alfalfa. Soil pH without lime application was raised to 6.05 and it increased linearly up to 7.76 at the highest rate of lime. There was no significant difference in soil pH between control and 1 tonne of lime in two months period of treatment. Dry matter yield, crude protein of leaf and stem, NDF, ADF, ADL, mineral K, P, Ca and Mg in both leaves and alfalfa stem increased with increasing lime applications. This shows that liming is beneficial even when BA is used at optimum level. In conclusion, BA can supply K to alfalfa and increase soil pH, but the use of lime with BA gave better performance of alfalfa than the use of BA alone.

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