ABSTRACT

Field plot experiments were used to study the response of soybean (Glycine max (L.) Merrill var. TGX 1485-ID) to application of lime and potassium fertilizer in a tropical ultisol in 1999 and 2000 cropping seasons. In each year, the experiment was laid out as a 4 x 4 factorial arranged in randomized complete block design. Treatments comprised four lime rates of 0, 1.5, 3.0 and 4.5 t/ha and four potassium levels of 0, 40, 80 and 120 kg k 201ha and there were three replications. The soils of the experimental site were texturally sandy clay loam, moderately high in potassium content, low in organic matter and nitrogen contents and were acidic. On the average, lime always significantly increased soil pH, and increased the number of nodules produced per plant at 8 WAP, root dry weight at 4 WAP and grain yield, especially in 2000 cropping season, but had no significant effects on root dry weight, plant height, shoot dry weight, number of pods per plant, number of seeds per pod and 100-seed weight. The use of 1.5-3 t/ha lime rate proved satisfactory and is recommended. Potassium fertilizer application on the other hand, significantly increased 100-seed weight in 2000 cropping season but, in general had no effect on soil pH, number of nodules per plant, root dry weight, shoot dry weight, number of pods per plant, number of seeds per pod and grain yield. There were generally no statistically significant effect of lime and potassium fertilizer interactions on soybean crop growth and yield. However, grain yield seemed best when lime at 1.5-3 t/ha was combined with potassium at 40 kg K20/ha.