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Mapanda F.,Chemistry and Soil Research Institute | Wuta M.,University of Zimbabwe | Nyamangara J.,International Crops Research Institute for the Semi Arid Tropics | Rees R.M.,Scottish Agricultural College
Plant and Soil | Year: 2011

Optimizing a three-way pact comprising crop yields, fertility inputs and greenhouse gases may minimize the contribution of croplands to global warming. Fluxes of N 2O, CO 2 and CH 4 from soil were measured under maize (Zea mays L.) grown using 0, 60 and 120 kg N hm -2 as NH 4NO 3-N and composted manure-N in three seasons on clay (Chromic luvisol) and sandy loam (Haplic lixisol) soils in Zimbabwe. The fluxes were measured using the static chamber methodology involving gas chromatography for ample air analysis. Over an average of 122 days we estimated emissions of 0.1 to 0.5 kg N 2O-N hm -2, 711 to 1574 kg CO 2-C hm -2 and-2.6 to 5.8 kg CH 4-C hm -2 from six treatments during season II with the highest fluxes. The posed hypothesis that composted manure-N may be better placed as a mitigation option against soil emissions of GHG than mineral fertilizer-N was largely supported by N 2O fluxes during the wet period of the year, but with high level of uncertainty. Nitrogen addition might have stimulated both emissions and consumption of CH 4 but the sink or source strength depended highly on soil water content. We concluded that the application of mineral-N and manure input may play an important role with reference to global warming provided the season can support substantial crop productivity that may reduce the amount of N 2O loss per unit yield. Confidence in fluxes response to agricultural management is still low due to sporadic measurements and limited observations from the southern African region. © 2011 Springer Science+Business Media B.V. Source

Manyanga M.A.,Chemistry and Soil Research Institute | Mafongoya P.L.,University of KwaZulu - Natal | Tauro T.P.,University of Zimbabwe
African Journal of Ecology | Year: 2014

Sustainable crop production is dependent on improvement of soil health using different management strategies. A study was conducted in the 2008/09 cropping season to investigate soil macrofauna order diversity and abundance under organic matter transfer system and improved fallows in a high rainfall (>800 mm year-1) area of Zimbabwe. Macrofauna were sampled using monoliths to a depth of 25 cm and Shannon-Wiener diversity was used for diversity testing. Order diversity varied significantly with treatment under both systems. Under improved fallows, Leucaena trichandra had the highest fauna orders (6) followed by Calliandra colorthysus (5), then Acacia anguistissima (4) while Leucaena pallida and miombo forest had the least orders. Crotalaria juncea had the highest faunal orders (5), among organic material transfer system while other treatments had ≥3 orders. Unfertilized maize had one order. Calliandra colorthysus had the highest order diversity followed by maize stover > cattle manure > Cr. juncea > fully fertilized maize > unfertilized maize. Major groups identified were termites, earthworms, beetles, millipedes and ants. All taxa combined, cattle manure and miombo forest had the highest macrofauna abundance. This study showed that application of organic nutrient resources and use of improved fallows significantly influenced soil macrofauna order diversity and abundance. © 2014 John Wiley & Sons Ltd. Source

Mapanda F.,Chemistry and Soil Research Institute | Mapanda F.,University of Zimbabwe | Mavengahama S.,Stellenbosch University
Scientific Research and Essays | Year: 2011

The levels of selected nutrients in soils and chemical composition of irrigation water were investigated in 16 villages from the dryland areas of Chivi District in Zimbabwe. The objective was to generate a biophysical knowledge base on the soil fertility status across different villages, and to relate it to site history, management and quality of surface and groundwater used for irrigation. Soil samples were collected from the fields, gardens, cultivated vleis, and virgin land while irrigation water samples were collected from rivers, vlei and shallow wells used to irrigate horticultural crops. Results revealed medium to deficient levels of nitrogen (N) and phosphorus (P) (>75% of the sampled units), and to a lesser degree, potential soil acidity problems on selected fields. The considerably higher soil pH and exchangeable bases in the irrigated gardens and vleis than in the fields and virgin land reflected the impact of management and land utilization. The chemical quality of the sampled water used for irrigation of horticultural crops all showed high chloride hazard. There was need to ascertain the magnitude of crop productivity against applied soil fertility inputs to establish the level and rate of nutrients mining from the soils. © 2011 Academic Journal. Source

Giller K.E.,Wageningen University | Giller K.E.,University of Zimbabwe | Murwira M.S.,Soil Productivity Research Laboratory | Dhliwayo D.K.C.,Chemistry and Soil Research Institute | And 2 more authors.
International Journal of Agricultural Sustainability | Year: 2011

Maize is the dominant staple crop across most of southern Africa - it is so dominant in some areas that more than 80 per cent of the smallholder land area is planted with maize. Soyabean was identified as the crop with a potential to address the need for diversifying the cropping systems, which could assist in overcoming the pervading soil fertility constraints and could provide smallholder farmers with an opportunity to earn income while also addressing the nutritional security of households. An initiative was launched in the 1996/97 cropping season in Zimbabwe, to test soyabean as a potential smallholder crop. From an initial 55 farmers in the first year, soyabean production expanded rapidly to an estimated 10,000 farmers three years later. Since then, soyabean has diffused spontaneously to most smallholder farming areas in the higher rainfall zones of Zimbabwe. Thus, the initiative has assisted a large number of smallholders to grow soyabean, and exploded a long-held belief in Zimbabwe that soyabean is not a suitable crop for smallholders. © 2011 Earthscan. Source

Mapanda F.,Chemistry and Soil Research Institute | Mapanda F.,University of Zimbabwe | Mupini J.,University of Zimbabwe | Wuta M.,University of Zimbabwe | And 3 more authors.
European Journal of Soil Science | Year: 2010

Land used for agricultural production can contribute significantly to greenhouse gas (GHG) emissions; however, there is very little information on the role of management and land use change in influencing these emissions in Africa. Thus, exploring GHG emissions that occur at the soil-atmosphere interface is an essential part of the effort to integrate land management strategies with climate change mitigation and adaptation in southern Africa. We measured soil emissions of carbon dioxide (CO 2), methane (CH 4) and nitrous oxide (N 2O) from rain-fed perennial tropical grassland, wastewater-irrigated perennial tropical pastureland, recently cleared woodland, miombo woodland, a Eucalyptus plantation, regular cropland and recently cleared-and-cropped land, on two contrasting soils at five sites in one cropping season in Zimbabwe. Gas samples were collected using static chambers and analysed by gas chromatography. Considerably high GHG emissions were found on sewage effluent-irrigated pastureland (means, 190 mg CO 2-C m -2 hour -1, 102 μg CH 4-C m -2 hour -1 and 6 μg N 2O-N m -2 hour -1 from sandy soil) and altered woodlands (mean ranges, 38-70 CO 2-C m -2 hour -1, 12-43 μg CH 4-C m -2 hour -1 and 20-31 μg N 2O-N m -2 hour -1 from deforested and cultivated woodland on clay and sandy soils). Relatively low and less variable emissions were found among the rain-fed perennial tropical grasslands, regular croplands and Eucalyptus plantations (mean ranges, 19-39 mg CO 2-C m -2 hour -1, -9.4-2.6 μg CH 4-C m -2 hour -1 and 1.0-4.7 μg N 2O-N m -2 hour -1). Variability in CO 2, CH 4 and N 2O emissions from soils was to the greatest extent influenced by soil temperature, but soil moisture, mineral-N and pH were also important. The increased N 2O emissions from cleared woodland on clay soil were attributed to increased mineralization and N availability when no tree could take up that N, while the N mineralized on the sandy soil could have been largely leached due to the soil's poor nutrient holding capacity, resulting in a relatively lower N 2O emission response to clearing. We concluded that the alteration of woodlands by deforestation and cultivation increased soil temperature, resulting in increased soil respiration, while the establishment of Eucalyptus plantations may provide an option for reduction in soil emissions of CO 2 and N 2O and a sink for CH 4. © 2010 The Authors. Journal compilation © 2010 British Society of Soil Science. Source

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