Yield Related Traits and Yield of Maize (Zea Mays L.) as affected by Green Manuring and Nitrogen Levels at Mizan Teferi, South-west Ethiopia.

Abstract

Soil fertility decline is a major constraint to agricultural production and productivity in the areas of Bench Maji Zone due to high rates of soil erosion, leaching of nutrients as a result of high rainfall, continuous removal of crop residues from crop fields, use of cow dung for other purposes and low inherent soil fertility. A field experiment was conducted during the main rainy season of 2009 at the Mizan ATVET College to study the effects of green manure (GM) and nitrogen (N) levels on yield related traits and yield of maize. Factorial combinations of three rates of GM (0, 5 and 10 tons/ha) and four levels of N (0, 20, 40 and 60 kg/ha) were laid out in randomized complete block design with three replications. Before incorporation of the GM, a composite soil sample was taken from the experimental plots (0-30 cm depth) to observe some selected soil physico-chemical properties. At harvest, the crop was partitioned into stover and grain for the determination of N content and N uptake, fertilizer recovery and use efficiencies were calculated. Results of the soil analysis showed that the soil of the experimental site was sandy clay loam in texture; strongly acidic in reaction (pH =4.7); very high in OM content (6.51%); low to medium in total N (0.2%); very low in available P (2 mg/kg) and medium in CEC (20 cmolc/kg). Significant effects (P <0.05) were observed on days to silking, plant height, number of grains per ear, grain yield, stover yield, 1000 kernels weight, harvest index and number of barren plants per plot and the effect of GM was also significant (P <0.05) on plant height, number of grains per ear, grain yield, stover yield and 1000 kernels weight. On the other hand, the interaction effect of N and GM was significant (P <0.05) only on plant height, number of grains per ear, grain yield and stover yield. The maximum grain yield (4625 kg/ha) was obtained from the application of the highest N and GM rate (60 kg N/ha and 10 tons GM/ha) whereas the maximum plant height (199.7 cm) was attained at 60 kg N/ha and 0 ton GM/ha. On the other hand, the highest values of thousand kernels weight (294.1 g) and harvest index (59.7%) were obtained from the application of the highest N rate. Increasing N affected grain and stover N contents and total N uptake showing increasing trend with increasing N rate in most of the grain, and decreasing trend with increasing N rate in stover. The physiological use efficiency (PUE) of N exhibited non-consistent trend to the increased application of N and GM; however, at higher rates of N and GM, it was reduced. On the other hand, the apparent N recovery (ANR) and agronomic use efficiency (AUE) responded more or less positively to the increased application levels of N and GM. Higher application rates of GM increased the ANR and AUE of N nutrient. Generally, the inorganic nutrient source applied in sole and in combination with organic have improved most of the yield related traits and yield of maize while the organic nutrient source applied in sole have improved only some of the them. However, this one season study has to be conducted through a number of seasons and locations of similar agro-ecology, soil type and crop in order to draw concrete conclusions and make recommendations.