NITROGEN FERTILIZER TYPE AND RATE EFFECTS ON GROWTH AND YIELD RESPONSE OF SOYBEAN VARIETIES

This research was carried to determine the effect of different types and rates of nitrogen (N) fertilizer on growth and yield response of soybean varieties under Umudike ecological conditions, Abia State, Nigeria. Pot experiment was conducted in 2008 outside the green house of Michael Okpara University of Agriculture, Umudike. The response of two varieties of soybean (Tropical Glycine Max-TGX 1440 and TGX 1740) to three different nitrogen fertilizer types (NPK 15 15 15, NPK 20 10 10 and Urea) at four different rates (0, 30, 60 and 90kgN/ha-1) were evaluated. Plant height, number of leaves, stem girth, number of branches per plant, pod number per plant, pod length, number of seed per plant, dry matter weight, dry pod weight and dry seed weight were determined in this work. It was observed that plant height, number of branches, number of seed, dry matter weight and dry pod weight differed significantly at (P < 0.05) in both varieties using different fertilizer types and at different fertilizer rates. TGX 1440 using NPK 15 15 15 at the rate of 60kg N/ha-1 gave the highest plant height than using NPK 20 10 10 and Urea and at other rates (0,30 and 90kg N/ha-1) in the same variety and in TGX 1740. Also increased application of nitrogen fertilizer rate increased plant height, dry matter weight, dry pod weight and pod length as in TGX 1440 using NPK 15 15 15 and NPK 20 10 10 but decreased pod number per plant and number of seed per plant. From the results TGX 1440 performed using NPK 15 15 15 at the rate of 60kg N/ha-1. It can therefore be recommended for optimum soybean production in Abia State, Nigeria