Response of Sesame (Sesamum indicum L.) to Inorganic Nitrogen Application Rates and Organic Fertilizers on Grey Soil in Hochiminh City, Vietnam

The organic/inorganic fertilizers can contribute substantial N for sesame, but it is not clear that such nitrogen forms are available for plant uptake. A field experiment at agricultural farm of Nong Lam University in HCMc was conducted to study the effect of four inorganic nitrogen application rates (0, 30, 60 and 90 kg N/ha) in combination with two tons of either cow manure or commercial bio-organic fertilizer (BOF) on growth and yield of sesame. The experiment comprised of 2×4×3 factorial in a Split-plot design with three replications. The results show that two organic fertilizers with low nitrogen contents (5–10 g N/kg) and high C/N ratios (28–30) by themselves are not capable of supplying enough nitrogen for sesame requirement. The additional application of inorganic nitrogen at rate of 30 kg N/ha resulted in maximum plant height (106.4 cm), number of capsules/plant (60.13), weight of capsule (1.01 g), number of seeds/capsule (71.0), weight of 1000 seeds (2.63 g), and highest actual yield (0.85 ton/ha). The combination of organic with inorganic N fertilizer, therefore, needs to consider the effective use of nitrogen from each source to maintaining sesame yield, while avoiding undesirable environmental impacts.