Evaluating Added Benefits from Combined Cattle Manure and Fertilizer Application in a Maize Cropping System

A field experiment was conducted at Kpongu in the Upper West region of Ghana to determine the added benefits in grain yield of maize derived from the concurrent use of manure and mineral fertilizer, and their cost effectiveness. Factorial combinations of cattle manure and mineral fertilizer each at 0, 50 and 100% of their recommended rates were evaluated in both the field and the laboratory studies. The treatments were applied in a randomized complete block design with three replications on the field. The same treatments were applied in the incubation study in a completely randomized design. The use of 100% NPK （Nitrogen, Phosphorus, Potassium） ＋ 5 t manure gave the highest grain yield of 4,678 kg·ha^-1. Synergistic interactions resulting in added benefits in grain yield were observed in all the combined nutrient inputs except 50% NPK ＋ 2.5 t manure which accrued an added disadvantage of 44 kg·ha^-1. Economic analysis proved that 100% NPK ＋ 2.5 t manure and 50% NPK ＋ 5 t manure were the most economically viable combined treatments in terms of grain yield. Based on the results from this study, resource poor farmers in the Upper West region of Ghana may reduce mineral fertilizer recommended rates by 50% and supplement it with 5 t quality （N 〉2.5%） cattle manure without compromising yield and profit.

Soil carbon stock and emission: estimates from three land-use systems in Ghana

Background:Land-use systems that sequester carbon and reduce CO_(2) emissions are key in the global mitigation strategies of climate change.Greenhouse gas emission from agro-ecosystems in sub-Saharan Africa is little studied.Here,we quantified soil carbon stock(SCS)and CO_(2) emissions from three land-use systems viz.arable land,oil palm plantation and forestland in the semi-deciduous forest zone of Ghana.Results:Soil organic carbon concentration at the 0–15 cm layer in the forestland was 62 and 23%greater than that in the arable land and palm plantation,respectively.The SCS along the 1.0-m profile was 108.2,99.0 and 73.5 Mg ha^(−1) in the forestland,palm plantation and arable land,respectively.Arable land emitted 30–46%more CO_(2) than palm plantation and forestland.In the dry season,CO_(2) emissions were respectively 0.93,0.63 and 0.5 kg ha^(−1) h−1 from the arable land,palm plantation and forestland.Positive relationships were observed between CO_(2) emissions and SCS,soil temperature,and moisture.The SCS greatly influenced CO_(2) emission in the dry season more than in the wet season in the relatively higher carbon-input systems(forestland and palm plantation).Soil temperature accounted for more than 55%of CO_(2) emissions in both seasons,which has implications in the era of rising global temperatures.Conclusions:The study provides relevant information on carbon storage abilities of the three land-use types in tropical climate and calls for drastic climate change actions to reduce degradation of forest cover and soil disturbance in agro-ecosystems in sub-Saharan Africa.