Andrews Opoku

DETERMINANTS OF FERTILIZER MICRODOSING-INDUCED YIELD INCREMENT OF PEARL MILLET ON AN ACID SANDY SOIL

Recent studies have reported the benefits of fertilizer microdosing in increasing crop yields in low input cropping systems. Little information is however available on the mechanisms underlying this effect. The objective of this study was therefore to explore the root-based mechanisms governing the growth enhancing phenomena of the fertilizer microdosing technology. A two-year experiment was conducted at the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), Research Station in Niger. Four treatments comprising (i) 2 g hill−1 of diammonuim phosphate (DAP), (ii) 6 g hill−1 of compound fertilizer NPK, (iii) broadcasting of 200 kg ha−1 of compound fertilizer NPK (recommended rate) and (iv) unfertilized control was arranged in a randomized complete block design with four replications. On average, fertilizer microdosing treatments (2-g DAP hill−1 and 6-g NPK hill−1) achieved 86% and 79% of the grain yields recorded from broadcasting of 200-kg NPK ha−1, respectively, in 2013 and 2014. The leaf area index and leaf chlorophyll content significantly increased with fertilizer microdosing at the early stage of millet growth. At the same stage, fertilizer microdosing enhanced the lateral root length density in the topsoil (0–20 cm) by 72% and 40% at respective lateral distances of 25 cm and 50 cm from the centre of the hill compared with broadcast of 200-kg NPK ha−1. Fertilizer microdosing did not significantly change soil pH in the root zone. It is concluded that the positive effect of fertilizer microdosing in increasing millet yield results from the better exploitation of soil nutrients due to early lateral roots proliferation within the topsoil.

Neem seed oil: a potent nitrification inhibitor to control nitrate leaching after incorporation of crop residues

The effect of neem seed oil and neem leaf extract as organic nitrification inhibitors (NIs) on the accumulation of and , and nitrification inhibition after incorporation of crop residue was investigated in an incubation experiment. Dicyandiamide (DCD) applications of 15 and 30 kg active ingredient ha− 1 were used as low and high doses of a synthetic NI. Soil samples were amended with 21 g kg− 1 cauliflower leaves and treated with NIs at a rate of 30 kg ha− 1 of neem seed oil, 60 kg ha− 1 of neem leaf extract, 15 kg ha− 1 of DCD, and 30 kg ha− 1 DCD. Samples were incubated at temperatures corresponding to field temperatures during fall and winter in Flanders, Belgium. Neem seed oil increased accumulation by 8.9 mg kg− 1 and decreased by 13.5 mg kg− 1 within a month. High and low doses of DCD increased accumulation by 48.2 and 1.6 mg kg− 1, respectively. Nitrification was inhibited by 29% for 30 days by the low dose of DCD, 58% in 30 days by neem seed oil, and 42% in 45 days by the high dose of DCD. Nitrification was not inhibited by the neem leaf extract.

Fertilizer micro-dosing increases crop yield in the Sahelian low-input cropping system: A success with a shadow

ABSTRACT Over the years, a scarcity of information on nutrient gains or losses has led to overemphasis being placed on crop yields and economic income as the direct benefits from fertilizer micro-dosing technology. There is increasing concern about the sustainability of this technology in smallholder Sahelian cropping systems. This study was designed in the 2013 and 2014 cropping seasons to establish nutrient balances under fertilizer micro-dosing technology and their implications on soil nutrient stocks. Two fertilizer micro-dosing treatments [2 g hill−1 of diammonium phosphate (DAP) and 6 g hill−1 of compound fertilizer Nitrogen-Phosphorus-Potassium (NPK) (15-15-15)] and three rates of manure (100 g hill−1, 200 g hill−1 and 300 g hill−1) and the relevant control treatments were arranged in a factorial experiment organized in a randomized complete block design with three replications. On average, millet (Pennisetum glaucum (L.) R.Br.) grain yield increased by 39 and 72% for the plots that received the fertilizer micro-dosing of 6 g NPK hill−1 and 2 g DAP hill−1, respectively, in comparison with the unfertilized control plots. The average partial nutrients balances for the two cropping seasons were −37 kg N ha−1yr−1, −1 kg P ha−1yr−1 and −34 kg K ha−1yr−1 in plots that received the application of 2 g DAP hill−1, and −31 kg N ha−1yr−1, −1 kg P ha−1yr−1 and −27 kg K ha−1yr−1 for 6 g NPK hill−1. The transfer of straw yields accounted for 66% N, 55% P and 89% K for removal. The average full nutrient balances for the two cropping seasons in fertilizer micro-dosing treatments were −47.8 kg N ha−1 yr−1, −6.8 kg P ha−1 yr−1 and −21.3 kg K ha−1 yr−1 which represent 7.8, 24.1 and 9.4% of N, P and K stocks, respectively. The nutrient stock to balance ratio (NSB) for N decreased from 13 to 11 and from 15 to 12 for the plots that received the application of 2 g DAP hill−1 and 6 g NPK hill−1, respectively. The average NSB for P did not exceed 5 for the same plots. It was concluded that fertilizer micro-dosing increases the risk of soil nutrient depletion in the Sahelian low-input cropping system. These results have important implications for developing an agro-ecological approach to addressing sustainable food production in the Sahelian smallholder cropping system.

Corralling, planting density, and N fertilizer rate effect on soil properties, weed diversity, and maize yield

ABSTRACT The interaction effect of stocking density of sheep and goat corralling (SDSG), maize planting density (MPD), and N fertilizer rate (NFR) on soil properties, weed diversity, and maize yield were evaluated on-farm in a smallholder maize-livestock farming system of Northern Ghana during the 2014 and 2015 cropping seasons. A split-split plot design replicated on eight farms was used to study the effect of three SDSG (0, 70, and 140 head ha−1), three MPD (66 667, 100 000, and 133 333 plants ha−1), and three NFR (0–40-40, 60–40-40, and 90–40-40 NPK kg ha−1). The SDSG at 70 and 140 head ha−1 increased (P < 0.01) soil chemical and biological properties and weed diversity compared with the control in both cropping seasons. Maize growth, yield and yield components, and weed biomass were affected (P < 0.05) by the SDSG, MPD, and NFR interactions. Maize-livestock farmers with smaller flock size could use SDSG at 70 head ha−1 with NFR at 90 kg ha−1, whilst those with large flock size could stock at 140 head ha−1 with NFR at 60 kg ha−1 and MPD at 133 333 plants ha−1 for increased maize yield and weed management.

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. 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. 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.