Effects of Different Organic Amendments and Chemical Fertilizer on Plant Growth and Grain Yield of Soybean on Pakchong Soil Series

Abstract

With increasing costs of chemical fertilizers, using organic amendments is an alternative method for the improvement of crop production and soil fertility maintenance. This study aimed to determine the effects of different organic amendments on soybean plant growth and grain yield. The eight treatments were arranged in an RCB design with three replications. Treatments were a combination of chemical fertilizer (16-20-0) 60 kg ha^-1 and extracts of jatropha 20 cc, chitosan 60 cc and fish waste 40 cc in 20 l of water; chicken manure 3 ton ha^-1; jatropha cake 3 and 6 ton ha^-1; chemical fertilizer (16-20-0) 180 kg ha^-1 and control (no application). The field experiment was conducted at the National Corn and Sorghum Research Center, on a site with Pakchong series soils during the dry season in 2007 (DS) and the wet season in 2008 (WS). In DS, soybean applied with chemical fertilizer produced the highest grain yield (1755 kg ha^-1). In WS, however, amendment with 3 ton of jatropha cake substantially increased grain yield (5410.83 kg ha^-1) over other treatments, followed by jatropha cake 6 ton (4331.67 kg ha^-1) and chemical fertilizer (4190.83 kg ha-1). Other organic extract applications produced similar grain yield production as the control.