Fertilizer micro dosing and timing of weeding for improved agronomic efficiency in finger millet production in eastern Uganda
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Finger millet (Eleusine coracana (L.) is a major food crop mostly for the semi-arid tropics of Sub-Saharan Africa. In Uganda, finger millet is rated third after maize and sorghum in order of production, among smallholder farmers. However, finger millet productivity and production are on the decline due to among other things, low soil fertility and weed proliferation. The recommended finger millet fertilizer rates have largely not been adopted by farmers because of the high cost of fertilizer. The objectives of the study were to (i) evaluate the effect of fertilizer micro-dosing on N and P use efficiency for improved finger millet performance; (ii) determine the optimum combination of fertilizer micro-dosing and timing of weeding on finger millet production, and (iii) determine the profitability of fertilizer micro-dosing and timing of weeding on finger millet production in eastern Uganda. A field experiment was conducted at Kuju Technology Verification Center (TVC) in Amuria district, in eastern Uganda. The Center is located at 02002‘N 33039‘E of the equator. The experiment was conducted during the short and long rains of 2016. Treatments included: microdose application of N at 16.6 kg ha-1 and P at 10.6 kg ha-1; and a full dose of N at 83 kg ha-1 and P 52 kg ha-1 (recommended rates as the control). Also, weeding was done at 20, 30, and 45 DAS, and double weeding at 20 and 45DAS. A randomized complete block design in a split-plot treatment structure was conducted, treatments were replicated three times. The variety of finger millet used for this study was SEREMI II (high yielding, early maturing, and farmer preferred). Pest and disease control were not necessary since these were not prevalent during the study. Data were collected on tiller number, growth vigor, days to flowering, weed biomass, weed species’ number and diversity, plant height, grain yield, and agronomic efficiency. Also, data were collected on production costs and returns per treatment, for profitability assessment. Finger millet plant growth parameters and grain yield were analyzed using Analysis of Variance (ANOVA) of GenStat, 14th edition, and means were separated by LSD at 5%. Correlation analysis was done on weed biomass and finger millet grain yield. Also, regression analysis was conducted on fertilizer micro-dosing and agronomic efficiency, and gross margin analysis was used for the determination of profitability of fertilizer micro-dosing and weeding time. The results revealed that N and P micro-dosing (16.6 kg N ha-1 and 10.6 kg P ha-1) reduced weed pressure (biomass) in finger millet by 83.5%, especially when combined with weeding at 20 DAS. The agronomic efficiency of P was clearly greater (43.8 kg kg-1) than that of N, implying that in this study soil, P was more limiting than N for finger millet production. Furthermore, utilization of N by finger millet was boosted by the application of P as a microdose, compared to the full dose. In terms of economic benefits, fertilizer micro-dosing (N and P) and single weeding at 20 DAS was the most profitable, as it led to a percentage gross margin of 264. This study has demonstrated the value of fertilizer micro-dosing in reducing fertilizer wastage that is usually incurred by applying the recommended full doses. Therefore, fertilizer micro-dosing (16.6 kg N ha-1 and 10.6 kg P ha-1) should be adopted and scaled out for use by finger millet producers in eastern Uganda, to be able to make maximum economic and environmental gains. However, prior to scaling out the results of this study to the farming communities, further research is necessary on-farm to integrate the socio-economic and biophysical interfaces in order to achieve more realistic and practical recommendations for finger millet producers.