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

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%

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

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

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

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

LAND-USE AND LAND-USE CHANGE EFFECTS ON NITROUS OXIDE EMISSIONS IN THE SEASONALLY DRY ECOSYSTEMS OF ZIMBABWE: A REVIEW

Nitrous oxide (N2O) is a greenhouse gas (GHG) with a considerable warming potential and involvement in the destruction of stratospheric ozone. The conversion of savannas to agricultural land has the potential of changing the characteristics and gas exchange of the ecosystems dramatically. The savanna woodlands cover over 95% of Zimbabwe\u2019s forest area, and are divided into five woodland types: Acacia, miombo, mopane, teak Baikiaea Plurijuga and Terminalia Combretaceae . This review is aimed at exploring the effects of land-use changes and land management practices on N2O emissions in Zimbabwe. Available data on N2O emission were collected from standing and deforested miombo woodlands, grasslands and agricultural lands. Estimated mean annual N2O emissions from savanna ecosystems in Zimbabwe were 17.1 Gg N2O, while annual fluxes from arable land (cultivated and fallow) was 3.19 Gg N2O. Biogenic N2O emissions were mainly concentrated in the wet season as N2O production is strongly enhanced by high soil moisture. During the dry season pyrogenic emissions were also important sources of N2O, contributing, an estimated 6.7 Gg N2O annually. Land use change in the form of biomass burning and conversion to grassland or arable land may be considerable source of N2O, whereas current agricultural practices do not seem to provide a large source of N2O in Zimbabwe. Seasonally dry savanna ecosystems, thus, constitute an important source of N2O, which should not be ignored in national and regional estimates of emissions of N2O. Land-use change from savanna to agricultural production results in an immediate increase in N2O emissions. However, the emissions will decrease with time. The current estimates are associated with large uncertainties, thus, there is need for more detailed studies on the effects of land-use change on N2O emissions and on spatial and temporal variations in N2O emissions from the different savanna ecosystems.L\u2019oxyde nitreux (N2O) est un gaz \ue0 effet de serre (GES) avec un potentiel de r\ue9chauffement et une implication dans la destruction de la couche stratosph\ue9rique d\u2019ozone. La conversion des savanes en terres agricoles induit le changement radicales des caract\ue9ristiques et \ue9changes gazeux des \ue9cosyst\ue8mes. Les savanes bois\ue9es couvrent plus de 95% de la couverture foresti\ue8re au Zimbabwe et sont subdivis\ue9es en cinq types de boisements : Acacia, miombo, mopane, teak ( Baikiaea Plurijuga ) et Terminalia Combretaceae . Cet article visait \ue0 examiner la contri- bution potentielle des \ue9cosyst\ue8mes \ue0 savanes non perturb\ue9es et les effets des changements dans l\u2019utilisation des terres sur les \ue9missions de N2O. Les donn\ue9es disponibles sur les \ue9missions de N2O \ue9taient collect\ue9es des r\ue9gions bois\ue9es de Miombo, r\ue9gions de bois\ue9es de miombo, les prairies et des terres agricoles. La moyenne des flux de N2O des \ue9cosyst\ue8mes \ue0 savane estim\ue9e \ue0 17.1Gg pendant que les flux annuels \ue0 partir des terres arables (cultiv\ue9es et en jach\ue8re) \ue9tait de 13.9Gg. Les flux \ue9taient principalement concentr\ue9s dans la saison humide du fait que les \ue9missions de N2O sont fortement influenc\ue9es par l\u2019humidit\ue9 \ue9lev\ue9e du sol. Les \ue9missions pyrog\ue9niques de la saison s\ue8che constituaient d\u2019importantes sources de N2O, avec un niveau annuel d\u2019\ue9mission de 6.7Gg. Les \ue9cosyst\ue8mes de savane en saison s\ue8che constituent ainsi une importante source de N2O \ue0 ne pas n\ue9gliger dans des estimations nationales et r\ue9gionales des \ue9missions de gaz. Les estimations actuelles sont associ\ue9es \ue0 de grandes incertitudes, ainsi, la n\ue9cessit\ue9 d\u2019\ue9tudes plus d\ue9taill\ue9es sur les variations spatiales et temporelles des \ue9missions produites dans diff\ue9rents \ue9cosyst\ue8mes \ue0 savane, et les effets du changement dans l\u2019utilisation des terres sur les \ue9missions de N2O