Efeito de fertilizantes à base de BioNiK-Phos e Fósforo na produção de girassol híbrido no Norte de Uganda

The sunflower oil seed industry is one of the promising business sectors in Uganda for both domestic and export markets. Both open-pollinated varieties and hybrids are grown in Uganda. Average yields of open-pollinated varieties in farmers’ fields range from about 750-900 kg ha-1 and hybrids about 2,000 kg/ha. For high production and productivity, sunflower requires fertilizers. The objective of this study was to establish the effects of BioNik-Phos and di-ammonium phosphate (DAP) fertilizers micro-dosing on yield of sunflower hybrid (PAN 5057) in Northern Uganda in 2021b and 2022a seasons. Field experiments were laid using a randomized complete block design (RCBD) with 4 replications per location in 3 locations in Alebtong District (Abako, Aloi and Angeta). There were significant (P < 0.05) differences in sunflower yields across treatments in all the three locations (Abako: 1,250-3,524 kg ha-1, Aloi: 1,274-3,488 kg ha-1 and Angeta: 1,238-3,369 kg ha-1) in 2021 with or without micro-dosing with BioNiK-Phos and DAP fertilizer. A similar trend was recorded for 2022a season (Abako: 1,268-3,500 kg ha-1, Aloi: 1,357-3,607 kg ha-1 and Angeta: 1,286-3,417 kg ha-1). The effect of DAP fertilizer micro-dosing on sunflower hybrid productivity was three folds in both years. BioNiK-Phos effect was, however, not significantly different (P < 0.05) from the control. This is the first report of the effect of BioNiK-Phos and DAP fertilizers micro-dosing of sunflower in Northern Uganda.A indústria de sementes de óleo de girassol é um dos sectores empresariais promissores no Uganda, tanto para o mercado interno como para o de exportação. Tanto variedades de polinização aberta como híbridos são cultivados em Uganda. Os rendimentos médios das variedades de polinização aberta nos campos dos agricultores variam entre cerca de 750-900 kg ha-1 e os híbridos cerca de 2.000 kg ha-1. Para alta produção e produtividade, o girassol necessita de fertilizantes. O objetivo deste estudo foi estabelecer os efeitos da microdosagem de fertilizantes BioNik-Phos e fosfato diamônico (DAP) no rendimento do híbrido de girassol (PAN 5057) no Norte de Uganda nas temporadas 2021b e 2022a. Os experimentos de campo foram realizados usando um desenho de blocos completos aleatórios (DBCA) com 4 repetições por local em 3 locais no distrito de Alebtong (Abako, Aloi e Angeta). Houve diferenças significativas (P < 0,05) na produção de girassol entre os tratamentos em todos os três locais (Abako: 1.250-3.524 kg ha-1, Aloi: 1.274-3.488 kg ha-1 e Angeta: 1.238-3.369 kg ha-1) em 2021 com ou sem microdosagem com BioNiK-Phos e fertilizante DAP. Uma tendência semelhante foi registada para a época 2022a (Abako: 1.268-3.500 kg ha-1, Aloi: 1.357-3.607 kg ha-1 e Angeta: 1.286-3.417 kg ha-1). O efeito da microdosagem de fertilizante DAP na produtividade do híbrido de girassol foi três vezes maior em ambos os anos. O efeito BioNiK-Phos, no entanto, não foi significativamente diferente (P < 0,05) do controle. Este é o primeiro relato do efeito da microdosagem de fertilizantes BioNiK-Phos e DAP em girassol no Norte de Uganda

Effect of plant spacing on pigeonpea grain yield in Northern Uganda

The aim of crop production is to achieve the highest possible yield per unit area. One way of increasing productivity per unit area is through plant spacing optimization. The effect of plant spacing (90 cm x 60 cm, 150 cm x 120 cm and 150 cm x 180 cm) on yield of three pigeonpea genotypes (KAT 60/8, ICEAP 00540 and ICEAP 00554) was investigated on-station in a small-plot field experiments in 2018. Significant differences were recorded in grain yield of all the three genotypes. The highest yield for all the three genotypes was recorded for row spacing of 90 cm and inter plant spacing of 60 cm, and the lowest for row spacing of 150 cm and inter plant spacing of 180 cm. Plant spacing effect on other yield parameters (number of pods per plant and 100 seed weight) were not significant. Similar effects were recorded for plant growth parameters (plant height and number of primary branches). Thus, it can be concluded that row spacing of 90 cm and interplant spacing of 60cm is appropriate for pigeonpea grain production in Uganda

Soil greenhouse gas fluxes following tropical deforestation for fertilizer-intensive sugarcane cultivation in northwestern Uganda

Deforestation followed by fertilizer intensive agriculture is widely recognized as a significant contributor to anthropogenic greenhouse gas emissions (GHG), particularly carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). However, empirical studies focusing on soil GHG flux dynamics from deforestation hotspots in the tropics are still limited creating major uncertainties for constraining global GHG budgets. In this study, we investigated how deforestation for fertilizer intensive sugarcane cultivation in Uganda affects soil-borne GHGs. Therefore, soil GHG fluxes were measured in a primary forest and in a completely randomized experiment premised in the neighboring sugarcane fields with different fertilizer regimes, representing both smallholder and industrial-scale sugarcane farm management. Despite the use of different fertilization rates (low, standard, and high) as treatments for the sugarcane CRD experiment, neither auxiliary controls nor soil GHG fluxes significantly differed among the CRD treatments. Soil respiration was higher in the sugarcane than in the forest, which we attribute to the increased autotrophic respiration from the sugarcane’s fine root biomass and the likely exposure of the sugarcane’s larger soil organic carbon stocks to microbial decomposition through ploughing operations. The forest soils were a stronger net sink of CH4 than the sugarcane soils despite forest soils having both higher bulk densities and larger water-filled pore space (WFPS), and we suspect that this was due to alteration of the methanotroph abundance upon the conversion. Soil N2O emissions were smaller in the sugarcane than in the forest, which was surprising, but most likely resulted from the excess N being lost either through leaching or uptake by the sugarcane crop. Only seasonal variability in WFPS, among the auxiliary controls, affected CH4 uptake at both sites and soil CO2 effluxes in the sugarcane. Noteworthy, soil N2O fluxes from both sites were unaltered by the seasonality-mediated changes in auxiliary controls. All the findings put together suggest that forest conversion for sugarcane cultivation alters soil GHG fluxes by increasing soil CO2 emissions and reducing both soil CH4 sink strength and soil N2O emissions

Yield advantage and profitability of selected climate-smart technologies: Findings from demonstration plots in Northern Uganda

Climate-smart agriculture (CSA) is viewed as a potentially effective intervention to address low agricultural productivity in Sub-Saharan Africa (SSA), while strengthening farmers’ capacity to adapt to the effects of climate change. We therefore conducted a study to examine maize yield response to three CSA practices – ripping, permanent planting basins and alley cropping. The profitability of their use with and without fertiliser application was also evaluated. It was deduced from the study that ripping, planting basins and alley cropping with Gliricidia (Gliricidia sepium) gave the greatest yield advantage. of 457.1 kg/acre, 456.7 kg/acre and 437.2 kg/acre respectively. Fertiliser application significantly increased the yield advantage, but this increment did not necessarily translate into cost-effectiveness due to the associated costs. In fact, minimum tillage interventions were more profitable without fertiliser application, and at some locations responded poorly to fertiliser application. These variable responses indicate the need for developing site-specific CSA interventions for improved maize productivity and profitability

Yield advantage and profitability of selected climate-smart technologies: Findings from demonstration plots in Northern Uganda

Climate-smart agriculture (CSA) is viewed as a potentially effective intervention to address low agricultural productivity in Sub-Saharan Africa (SSA), while strengthening farmers’ capacity to adapt to the effects of climate change. We therefore conducted a study to examine maize yield response to three CSA practices – ripping, permanent planting basins and alley cropping. The profitability of their use with and without fertiliser application was also evaluated. It was deduced from the study that ripping, planting basins and alley cropping with Gliricidia (Gliricidia sepium) gave the greatest yield advantage. of 457.1 kg/acre, 456.7 kg/acre and 437.2 kg/acre respectively. Fertiliser application significantly increased the yield advantage, but this increment did not necessarily translate into cost-effectiveness due to the associated costs. In fact, minimum tillage interventions were more profitable without fertiliser application, and at some locations responded poorly to fertiliser application. These variable responses indicate the need for developing site-specific CSA interventions for improved maize productivity and profitability

Nutrient limitations regulate soil greenhouse gas fluxes from tropical forests: evidence from an ecosystem-scale nutrient manipulation experiment in Uganda

Tropical forests contribute significantly to the emission and uptake of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). However, studies on the soil environmental controls of greenhouse gases (GHGs) from African tropical forest ecosystems are still rare. The aim of this study was to disentangle the regulation effect of soil nutrients on soil GHG fluxes in a tropical forest in northwestern Uganda. Therefore, a large-scale nutrient manipulation experiment (NME) based on 40 m × 40 m plots with different nutrient addition treatments (nitrogen (N), phosphorus (P), N + P, and control) was established. Soil CO2, CH4, and N2O fluxes were measured monthly using permanently installed static chambers for 14 months. Total soil CO2 fluxes were partitioned into autotrophic and heterotrophic components through a root trenching treatment. In addition, soil temperature, soil water content, and mineral N were measured in parallel to GHG fluxes. N addition (N, N + P) resulted in significantly higher N2O fluxes in the transitory phase (0–28 days after fertilization, p < 0.01), because N fertilization likely increased soil N beyond the microbial immobilization and plant nutritional demands leaving the excess to be nitrified or denitrified. Prolonged N fertilization however, did not elicit a significant response in background (measured more than 28 days after fertilization) N2O fluxes. P fertilization marginally and significantly increased transitory (p = 0.052) and background (p = 0.010) CH4 consumption, probably because it enhanced methanotrophic activity. Addition of N and P together (N + P) resulted in larger CO2 fluxes in the transitory phase (p = 0.010), suggesting a possible co-limitation of N and P on soil respiration. Heterotrophic (microbial) CO2 effluxes were significantly higher than the autotrophic (root) CO2 effluxes (p < 0.001) across all treatment plots with microbes contributing about three times more to the total soil CO2 effluxes compared to roots (p < 0.001). However, neither heterotrophic nor autotrophic respiration significantly differed between treatments. The results from this study suggest that the feedback of tropical forests to the global soil GHG budget could be disproportionately altered by changes in N and P availability in these biomes

Evaluating the role soil nutrients play in regulating soil greenhouse gas fluxes from the pristine tropical forests: evidence from a nutrient manipulation experiment in Uganda

The exchange of the climate-relevant greenhouse gases (GHGs) at the soil-atmospheric interface is regulated by both abiotic and biotic controls. However, evidence on nutrient limitations of soil GHG fluxes from African tropical forest ecosystems is still rare. Therefore, an ecosystem-scale nutrient manipulation experiment (NME) consisting of nitrogen (N), phosphorus (P), N + P, and control treatments was set up in a tropical forest in northwestern Uganda. Soil carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) fluxes were measured monthly using static vented chambers for 14 months. A root trenching treatment was also done in all the experimental plots in order to disentangle the contribution of root and microbial respiration to total soil CO2 effluxes. In parallel to soil GHG flux measurements, soil temperature, soil moisture, and mineral N were determined. Lifting the N limitation on the soil nitrifiers and denitrifiers through N fertilization significantly increased N2O fluxes in N, and N + P addition plots in the transitory phase (0-28 days after N fertilization, p < 0.01). However, sustained N fertilization did not significantly affect background (measured more than 28 days after fertilization) N2O fluxes. Alleviation of the P limitation on soil methanotrophs through P fertilization marginally and significantly increased CH4 consumption in the transitory (p = 0.052) and background (p = 0.010) phases, respectively. Simultaneous addition of N and P (N + P) significantly affected transitory soil CO2 effluxes (p = 0.010), suggesting a possible co-limitation of N and P on soil respiration. Microbial CO2 effluxes were significantly larger than root CO2 effluxes (p < 0.001) across all treatment plots so was the contribution of microbial respiration to the total soil CO2 effluxes (about 70 %, p < 0.001). Despite the fact that soil respiration was affected through N + P fertilization, neither heterotrophic nor autotrophic respiration significantly differed in either the N + P or the other treatments. Overall, the study findings suggest that the contribution of tropical forests to the global soil GHG budget could be altered by changes in N and P availability in these biomes