Fertilizer response and mineral nutrition of pigeon pea (Cajanus cajan (L) Millsp.).

In a greenhouse experiment with Cunupia clay soil the effect of omitting N, P, K, Ca, Mg and S on growth of Cajanus cajan was investigated. The period of rapid vegetative growth coincided with P, Ca and Mg nutrient stress. A dilution of K content was found in the plant tissue during this time of growth and the pattern of K uptake suggested that maximum uptake took place in the early growth stages. In field experiments on St. Augustine loam, N fertilizer (NH4NO3) was applied as a top-dressing at the rate of 25 kg/ha at 40, 50, 60, 70 and 80 days from seedling emergence and a basal dose of 25 kg N/ha was given at planting. A 46 % increase in seed yield was obtained when the N was applied at 40 days; delaying application actually reduced grain yield. When the top-dressing of N at 40 days was varied (0, 20, 40, 60 to 80 kg N/ha), with a basal dose at planting of 20 kg N/ha, it was found that 60 kg N/ha gave a 71 % increase in seed-yield. Application of Triacontanol, a growth hormone, did not affect the seed yield, but had short-lived effects on plant growth and on N content in the plant tissue. When different forms of N fertilizer, NaNO3, NH4C1, CO(NH2)2 and NH4NO3, were applied, urea performed best, both in terms of plant growth and yield. Plant growth and yield of pigeon pea increased with increasing K fertilizer up to 60 kg/ha; beyond this level, both plant growth and grain yield decreased. Overall a good growth prior to flowering led to a better grain yield. A boron deficiency was diagnosed in the field and confirmed by a sand-culture greenhouse experiment. In a micro-nutrient experiment with Zn, B, Mo and Co, added Zn gave an increase of 26 % in seed yield compared to the control, and Co and Mo treatments showed an increase in N content in the plant tissue.