Greenhouse gas fluxes from agricultural soils of Kenya and Tanzania

Knowledge of greenhouse gas (GHG) fluxes in soils is a prerequisite to constrain national, continental, and global GHG budgets. However, data characterizing fluxes from agricultural soils of Africa are markedly limited. We measured carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4) fluxes at 10 farmer-managed sites of six crop types for 1 year in Kenya and Tanzania using static chambers and gas chromatography. Cumulative emissions ranged between 3.5–15.9 Mg CO2-C ha−1 yr−1, 0.4–3.9 kg N2O-N ha−1 yr−1, and −1.2–10.1 kg CH4-C ha−1 yr−1, depending on crop type, environmental conditions, and management. Manure inputs increased CO2 (p = 0.03), but not N2O or CH4, emissions. Soil cultivation had no discernable effect on emissions of any of the three gases. Fluxes of CO2 and N2O were 54–208% greater (p < 0.05) during the wet versus the dry seasons for some, but not all, crop types. The heterogeneity and seasonality of fluxes suggest that the available data describing soil fluxes in Africa, based on measurements of limited duration of only a few crop types and agroecological zones, are inadequate to use as a basis for estimating the impact of agricultural soils on GHG budgets. A targeted effort to understand the magnitude and mechanisms underlying African agricultural soil fluxes is necessary to accurately estimate the influence of this source on the global climate system and for determining mitigation strategies

Analysis of the relationship between changes in macroeconomic variables and various sector price indices of JSE

Purpose- The purpose of this paper is to analyse the relationship between changes in domestic macroeconomic variables and various indices of the JSE during the full time period, June 1995 to December 2018 and the sub-periods, June 1995 to June 2007 and July 2007 to December 2018. Design/ methodology/ approach- The paper employs the Autoregressive Distributed Lag (ARDL) model approach to cointegration using monthly data from June 1995 to December 2018. Findings- In terms of the long run, the results show that the coincident indicator measure of domestic economic activity is positively and significantly related to the various JSE indices for all study periods. In terms of inflation, the results show no relationship between inflation rate and the various indices for both whole period and June 1995 to June 2007 sub period. However for the July 2007 to December 2018 sub period, JSE All Share Index and JSE Top 40 Index are negatively related. For the real effective exchange rate, only the Consumer Services Index is positively related to the exchange rate in terms of June 1995 to June 2007 sub period. However, JSE All Share Index and JSE Top 40 Index are negatively related to the exchange rate in all study periods. In terms of the short term interest rate, for the whole period, JSE All Share Index, JSE Top 40 Index, Health Care Index and Telecommunications Index are negatively related to interest rate. In terms of the June 1995 to June 2007 sub period, JSE All Share Index and Industrials Index are negatively related to the short term interest rate. For the July 2007 to December 2018 sub period, Telecommunications Index and Technology Index are negatively related. In terms of the short run, the coincident indicator is positively and significantly related to the various JSE indices for all study periods. Inflation is not significantly related to any index in the whole period. In terms of the June 1995 to June 2007 sub period, Industrials Index and Financials Index are positively related to inflation and in the July 2007 to December 2018 sub period, Consumer Goods Index, Health Index and Consumer Services Index are negatively related to the inflation rate. The real effective exchange rate is positively and significantly related to the various JSE indices in the different study periods. In terms of the short term interest rate, for the whole period and the June 1995 to June 2007 sub period only the Technology Index is not significantly and negatively related to the short term interest rate, but for the July 2007 to December 2018 sub period, Top 40 Index, Telecommunications Index and Technology Index are positively related to the interest rate. Only the Financial Index is negatively related to short term interest rates during this sub period. Research Limitations- Not a lot literature was found on the relationship between macroeconomic variables and the various sector indices of the JSE. Most previous work, in the South African context focused just on the JSE All Share Index. Practical Implications- The findings can help investors diversify their portfolios into indices that benefit from expected changes in macroeconomic variables, such as recessions, rising interest rates, rising inflation or a weakening exchange rate. Alternatively, they can hedge themselves against the negative implications of such macroeconomic changes on portfolio performance. In addition, the findings are important for the monetary authorities to better understand the implications of their policy changes on financial markets

Nitrous oxide emissions from European agriculture - An analysis of variability and drivers of emissions from field experiments

Nitrous oxide emissions from a network of agricultural experiments in Europe were used to explore the relative importance of site and management controls of emissions. At each site, a selection of management interventions were compared within replicated experimental designs in plot-based experiments. Arable experiments were conducted at Beano in Italy, El Encin in Spain, Foulum in Denmark, Logården in Sweden, Maulde in Belgium, Paulinenaue in Germany, and Tulloch in the UK. Grassland experiments were conducted at Crichton, Nafferton and Peaknaze in the UK, Gödöllö in Hungary, Rzecin in Poland, Zarnekow in Germany and Theix in France. Nitrous oxide emissions were measured at each site over a period of at least two years using static chambers. Emissions varied widely between sites and as a result of manipulation treatments. Average site emissions (throughout the study period) varied between 0.04 and 21.21 kg N₂O-N ha⁻¹ yr⁻¹, with the largest fluxes and variability associated with the grassland sites. Total nitrogen addition was found to be the single most important determinant of emissions, accounting for 15% of the variance (using linear regression) in the data from the arable sites (<i>p</i> < 0.0001), and 77% in the grassland sites. The annual emissions from arable sites were significantly greater than those that would be predicted by IPCC default emission factors. Variability of N₂O emissions within sites that occurred as a result of manipulation treatments was greater than that resulting from site-to-site and year-to-year variation, highlighting the importance of management interventions in contributing to greenhouse gas mitigation

Closing maize yield gaps in sub-Saharan Africa will boost soil N2O emissions:Cropland N2O emissions in Africa

In sub-Saharan Africa (SSA) the most important staple crop is maize, the production of which is dominated by smallholder farming systems using low external inputs (&lt;10 kg N ha-1) resulting in low crop yields and large yield gaps (difference between actual and potential yields). To assess increases in soil N2O emissions when closing maize yield gaps by increased fertilizer use, we reviewed the literature, developed a relationship between yield gaps and soil N2O emissions, and used it to scale across SSA. According to our analysis, N2O emissions from maize production will increase from currently 255 to 1755 ± 226 Gg N2O-N yr-1 (+589 %) if existing maize yield gaps are closed by 75 %, increasing total anthropogenic N2O emissions for SSA by c. 50 %

Closing maize yield gaps in sub-Saharan Africa will boost soil N2_{2}O emissions

In sub-Saharan Africa (SSA), the most important staple crop is maize; the production of which is dominated by smallholder farming systems using low external inputs (<10 kg N ha$^{−1}$) resulting in low crop yields and large yield gaps (difference between actual and potential yields). To assess increases in soil N$_{2}$O emissions when closing maize yield gaps by increased fertilizer use, we reviewed the literature, developed a relationship between yield gaps and soil N$_{2}$O emissions, and used it to scale across SSA. According to our analysis, N$_{2}$O emissions from maize production will increase from currently 255 to 1755 ± 226 Gg N$_{2}$O-N year$^{−1}$ (+589%) if existing maize yield gaps are closed by 75%, increasing total anthropogenic N$_{2}$O emissions for SSA by c. 50%

GREENHOUSE GAS EMISSIONS FROM SAVANNA (MIOMBO) WOODLANDS: RESPONSES TO CLEARING AND CROPPING

Natural vegetation represents an important sink for greenhouse gases (GHGs); however, there is relatively little information available on emissions from southern African savannas. The effects of clearing savanna woodlands for crop production on soil fluxes of N2 O, CO2 and CH4 were studied on clay (Chromic luvisol) and loamy sand (Ferric acrisol) soils in Zimbabwe. Maize ( Zea mays L.) was the test crop. Gas samples were measured from undisturbed, cleared and cultivated woodlands using the static chamber methodology involving gas chromatography for ample air analysis. Site and climatic variables were particularly important determinants of GHG emissions. Over an average of 154 days emissions of O.8 \u2013 2.5 kg N2O-N ha-1, 1146 \u2013 2847 kg CO2-C ha-1 and 7.4 \u2013 38.5 kg CH4-C ha-1 were estimated during a season that followed a relatively drier one. Fertiliser-N significantly increased GHG emissions on cropped plots (clay soil). The undisturbed woodland with a relatively higher tree density (loamy sand) was an important GHG source. The high CH4 fluxes from woodlands provide ground based validation of satellite observations of CH4 hotspots in sub-Saharan Africa, and have considerable implications on regional GHG balance.La v\ue9g\ue9tation naturelle repr\ue9sente une source importante de gaz \ue0 effet de serre (GES) ; Par ailleurs, il existe relativement peu d\u2019informations disponibles sur les \ue9missions dans les savanes sud africaines. Les effets du d\ue9boisement de la savane pour la production agricole sur le flux du sol de N2O, CO2 et de CH4 ont \ue9t\ue9 \ue9tudi\ue9s sur les sols argileux (luvisol chromique) et sablo limoneux (acrisol ferrique) au Zimbabwe. La plante test consid\ue9r\ue9e \ue9tait ma\uefs ( Zea mays L.). Des \ue9chantillons de gaz \ue9taient collect\ue9s des for\ueats non perturb\ue9es, d\ue9frich\ue9es et cultiv\ue9es en utilisant la m\ue9thode de la Chambre statique impliquant le gaz chromatographie pour l\u2019analyse de l\u2019air. Le site et les variables climatiques \ue9taient particuli\ue8rement des d\ue9terminants importants des \ue9missions de gaz \ue0 effets de serre. Sur une moyenne de 154 jours des \ue9missions de O.8 \u2013 2.5 kg N2O-N ha-1, 1146 \u2013 2847 kg CO2 -C ha-1 et 7.4 \u2013 38.5 kg CH4-C ha-1 \ue9taient estim\ue9es au cours d\u2019une saison qui a suivi celle relativement la plus s\ue8che. L\u2019engrais N significativement augment\ue9 les \ue9missions de gaz \ue0 effets de serre sur les parcelles cultiv\ue9es (sol argileux). Le sol (sablo-limoneux) sous for\ueats non perturb\ue9es avec relativement une plus grande densit\ue9 d\u2019arbres \ue9tait une source importante de gaz \ue0 effets de serre. Les flux \ue9lev\ue9s de CH4 en condition de v\ue9g\ue9tation naturelle fournit une base de validation des observations satellitaires du CH4 en Afrique subsaharienne, et ont une des implications sur la balance r\ue9gionale des gaz \ue0 effets de serre

Nitrogen leaching and indirect nitrous oxide emissions from fertilized croplands in Zimbabwe

Agricultural efforts to end hunger in Africa are hampered by low fertilizer-use-efficiency exposing applied nutrients to losses. This constitutes economic losses and environmental concerns related to leaching and greenhouse gas emissions. The effects of NH4NO3 (0, 60 and 120 kg N ha-1) on N uptake, N-leaching and indirect N2O emissions were studied during three maize (Zea mays L.) cropping seasons on clay (Chromic luvisol) and sandy loam (Haplic lixisol) soils in Zimbabwe. Leaching was measured using lysimeters, while indirect N2O emissions were calculated from leached N using the emission factor methodology. Results showed accelerated N-leaching (3–26 kg ha-1 season-1) and N-uptake (10–92 kg ha-1) with N input. Leached N in groundwater had potential to produce emission increments of 0–94 g N2O-N ha-1 season-1 on clay soil, and 5–133 g N2ON ha-1 season-1 on sandy loam soil following the application of NH4NO3. In view of this short-term response intensive cropping using relatively high N rate may be more appropriate for maize in areas whose soils and climatic conditions are similar to those investigated in this study, compared with using lower N rates or no N over relatively larger areas to attain a targeted food security level

Short-term responses of selected soil properties to clearing and cropping of miombo woodlands in central Zimbabwe

Clearing and cultivation of indigenous woodlands for agriculture may be among the most important mechanisms of physical, chemical and biological land degradation in Zimbabwe, and southern Africa in general. The objective of the study was to determine the effects of clearing miombo woodland and converting the land to maize (Zea mays L.) cropping on selected soil properties on clay (Chromic luvisol) and loamy sand (Ferric acrisol) soils in central Zimbabwe. Soil samples were collected from undisturbed, cleared and cultivated woodlands after four cropping seasons and analyzed for soil organic C, total N and P, exchangeable bases, cation exchange capacity, infiltration rate, aggregate stability and microbial biomass C and N at 0–5, 6–10 and 11–20 cm depths. Results showed that clearing and conversion of miombo woodlands to croplands reduced soil nutrients, cation exchange capacity (range: 9.6–21.0 cmolc kg−1 in clay; 7.0–15.5 cmolc kg−1 in loamy sand), and microbial C (range: 0.06–0.54% in clay; 0.02–0.37% in loamy sand). The extent and nature of change was variable, depending on the soil type and depth. Clearing of trees and leaving soil surface covered with grass did not always translate to a significant decline in soil organic C after four seasons (range: 0.69–2.24% in clay; 0.24–1.43% in loamy sand), unless the clearing was followed by successive cultivation and cropping without N fertilization. The reduced soil quality under cultivation was attributed to a potential pulse in decomposition and mineralization processes caused by soil disturbance, followed by leaching of released nutrients to lower horizons. This could be aided by nutrient removal in crop parts during harvest, without adequate soil nutrient replenishment. Under the woodland ecosystem, litter-fall may help to maintain steady-state infiltration rate (range: 45–126 cm h−1 in clay; 32–97 cm h−1 in loamy sand) by protecting the soil surface from damage and ensuring the formation of stable aggregates which preserve pore continuity. It was recommended that when miombo woodlands are to be cleared, management decisions that reduce tillage intensity and maximize residue retention should be put into practice; otherwise the clearing is strongly discouraged

Greenhouse gas emissions from savanna (miombo) woodlands. Responses to clearing and cropping

ABSTRACT Natural vegetation represents an important sink for greenhouse gases (GHGs); however, there is relatively little information available on emissions from southern African savannas. The effects of clearing savanna woodlands for crop production on soil fluxes of N 2 O, CO 2 and CH 4 were studied on clay (Chromic luvisol) and loamy sand (Ferric acrisol) soils in Zimbabwe. Maize (Zea mays L.) was the test crop. Gas samples were measured from undisturbed, cleared and cultivated woodlands using the static chamber methodology involving gas chromatography for ample air analysis. Site and climatic variables were particularly important determinants of GHG emissions. Over an average of 154 days emissions of 0.8 -2.5 kg N 2 O-N ha -1 , 1146 -2847 kg CO 2 -C ha -1 and 7.4 -38.5 kg CH 4 -C ha -1 were estimated during a season that followed a relatively drier one. Fertiliser-N significantly increased GHG emissions on cropped plots (clay soil). The undisturbed woodland with a relatively higher tree density (loamy sand) was an important GHG source. The high CH 4 fluxes from woodlands provide ground based validation of satellite observations of CH 4 hotspots in sub-Saharan Africa, and have considerable implications on regional GHG balance. Key Words: Carbon dioxide, methane, nitrous oxide, Zimbabwe RÉSUMÉ La végétation naturelle représente une source importante de gaz à effet de serre (GES) ; Par ailleurs, il existe relativement peu d&apos;informations disponibles sur les émissions dans les savanes sud africaines. Les effets du déboisement de la savane pour la production agricole sur le flux du sol de N 2 O, CO 2 et de CH 4 ont été étudiés sur les sols argileux (luvisol chromique) et sablo limoneux (acrisol ferrique) au Zimbabwe. La plante test considérée était maïs (Zea mays L.). Des échantillons de gaz étaient collectés des forêts non perturbées, défrichées et cultivées en utilisant la méthode de la Chambre statique impliquant le gaz chromatographie pour l&apos;analyse de l&apos;air. Le site et les variables climatiques étaient particulièrement des déterminants importants des émissions de gaz à effets de serre. Sur une moyenne de 154 jours des émissions de 0.8 -2.5 kg N 2 O-N ha -1 , 1146 -2847 kg CO 2 -C ha -1 et 7.4 -38.5 kg CH 4 -C ha -1 étaient estimées au cours d&apos;une saison qui a suivi celle relativement la plus sèche. L&apos;engrais N significativement augmenté les émissions de gaz à effets de serre sur les parcelles cultivées (sol argileux). Le sol (sablo-limoneux) sous forêts non perturbées avec relativement une plus grande densité d&apos;arbres était une source importante de gaz à effets de serre. Les flux élevés de CH 4 en condition de végétation naturelle fournit une base de validation des observations satellitaires du CH 4 en Afrique subsaharienne, et ont une des implications sur la balance régionale des gaz à effets de serre

Greenhouse gas emissions from Savanna (Miombo) woodlands: responses to clearing and cropping

Natural vegetation represents an important sink for greenhouse gases (GHGs); however, there is relatively little information available on emissions from southern African savannas. The effects of clearing savanna woodlands for crop production on soil fluxes of N2O, CO2 and CH4 were studied on clay (Chromic luvisol) and loamy sand (Ferric acrisol) soils in Zimbabwe. Maize (Zea mays L.) was the test crop. Gas samples were measured from undisturbed, cleared and cultivated woodlands using the static chamber methodology involving gas chromatography for ample air analysis. Site and climatic variables were particularly important determinants of GHG emissions. Over an average of 154 days emissions of 0.8 – 2.5 kg N2O-N ha-1, 1146 – 2847 kg CO2-C ha-1 and 7.4 – 38.5 kg CH4-C ha-1 were estimated during a season that followed a relatively drier one. Fertiliser-N significantly increased GHG emissions on cropped plots (clay soil). The undisturbed woodland with a relatively higher tree density (loamy sand) was an important GHG source. The high CH4 fluxes from woodlands provide ground based validation of satellite observations of CH4 hotspots in sub-Saharan Africa, and have considerable implications on regional GHG balance