Potential of Crop Rotation Using Forages in the Tropics

Soil fertility is a fundamental biophysical root cause of food insecurity sub-Saharan Africa. Low quality crop residues and grasses during the dry season also limit animal productivity. Forage legumes (herbaceous and tree legumes) have great potential to increase crop animal productivity. Technologies have been developed over the past 3 decades to fully integrate forage legumes into farming. Most of these technologies are still on shelves with low adoption by farmers. Rhe role of forage legumes in nutrient cycling is reviewed in this paper. The factor limiting adoption will also be discussed. Innovative dissemination pathways to increase adoption will be suggested

Differences in Chemical Composition Among Provenances of Tree Fodder Species in a Subhumid Environment: Relation to use as Supplements

Studies were initiated in a subhumid Southern African environment to assess the chemical composition and nutritive value of Acacia angustissima (Mill.) Kuntze, Calliandra calothyrsus Meiss. and Leucaena species. The objective was to determine variability in crude protein (CP) concentration, acid detergent fibre (ADF), neutral detergent fibre (NDF), and soluble and insoluble proanthocyanidins from fodder samples of species, subspecies and provenances. A wide range was found in these parameters. The implications of these chemical composition factors, especially proanthocyanidins, on the use of these browse fodders in livestock feeding systems are discussed

Fodder Production of Multipurpose Trees in a Maize Farming System of Subhumid Southern Africa

Ways to integrate fodder production into maize production systems under Southern Africa’s subhumid conditions have been studied. One way involves the planting of tree and grass fodder hedges along soil conservation contour-bunds in maize fields. Management factors that influence the productivity of maize and fodder components in the system are fodder spp., side-pruning and deferment of wet season cutting. The other option involves interplanting tree fodders with maize through the use of a coppicing tree such as Acacia angustissima. Practical applications of these methods in mixed crop-livestock production systems are discussed

Differences in Chemical Composition Among Provenances of Browse Species in a Subhumid Environment: Relation to use as Supplements

Studies were initiated in a subhumid Southern African environment to assess the chemical composition and nutritive value of Acacia angustissima (Mill.) Kuntze, Calliandra calothyrsus Meiss. and Leucaena species. The objective was to determine variability in crude protein (CP) concentration, acid detergent fibre (ADF), neutral detergent fibre (NDF), and soluble and insoluble proanthocyanidins from fodder samples of species, subspecies and provenances. A wide range was found in these parameters. The implications of these chemical composition factors, especially proanthocyanidins, on the use of these browse fodders in livestock feeding systems are discussed

Contextual vulnerability of rainfed crop-based farming communities in semi-arid Zimbabwe: A case of Chiredzi District

Purpose The purpose of this paper is to assess smallholder farmers’ vulnerability to climate change and variability based on the socioeconomic and biophysical characteristics of Chiredzi District, a region that is susceptible to the adverse effects of climate change and variability. Design/methodology/approach Vulnerability was assessed using the Vulnerability to Resilience and the Climate Vulnerability and Capacity frameworks. Findings The major indicators and drivers of vulnerability were identified as droughts, flash floods, poor soil fertility and out-migration leaving female- and child-headed households. From sensitivity analysis, it was shown that different areas within the district considered different biophysical and socioeconomic indicators to climate change and variability. They also considered different vulnerability indicators to influence the decisions for adaptation to climate change and variability. Originality/value The results of this study indicate that the area and cropping systems are greatly exposed and are sensitive to climatic change stimuli, as shown by the decline in main cereal grain yield. These results also showed that there is a need to define and map local area vulnerability as a basis to recommend coping and adaptation measures to counter climate change hazards

Building climate change resilience through adaptation in smallholder farming systems in semi-arid Zimbabwe

Purpose This study aimed to determine factors that increase resilience and cause smallholder farmers to adapt better to climate change and vulnerability. Design/methodology/approach In this study, the authors used the vulnerability to resilience model and binary logit model to analyse the factors influencing household decisions to adapt. Findings Households with increased access to climate information through extension services were likely to have better adaptation abilities. It was also shown that younger farmers were likely to adapt to climate change given their flexibility to adopt new techniques and their access and use of modern information and technology. Larger households were found to have higher probability of adapting as most adaptation strategies are labour intensive. Household’s possession of livestock and access to credit significantly enhanced adaptation. However, households with higher farm income have lesser incentives to adapt to because their current farming practices might already be optimum. Research limitations/implications Given that most of the smallholder farmers are vulnerable, such as women-headed households and the elderly, who are labour constrained, there is need for research and development of labour saving technologies to increase resilience to climate change and vulnerability. Originality/value These findings underscore the importance of enabling farmer access to information and better technologies which enable them to increase adaptive capacity and resilience

Organic matter technologies for integrated nutrient management in smallholder cropping systems of southern Africa

One of the biggest challenges in the tropics is to develop organic matter technologies which are adopted by the farmers. Technologies must be effective within farmer resource constraints, increase food production, reduce risk and enhance the soil fertility. Results from on-farm participatory research were used to quantify the effects of agronomic practices on soil resources. Agricultural productivity is primarily nitrogen (N) limited throughout Malawi, and sub-humid Zimbabwe. Tightening economic constraints faced by farmers in the region have reduced inorganic fertilizer inputs and necessitate increased reliance on biologically-fixed N and N cycling. Three components of organic matter technology were evaluated: (1) the effects of residue quality; (2) the role of deep rooting systems; and (3) tradeoffs between legumes grown for grain versus soil regeneration. Perennial systems investigated include improved fallows, intercropping, and biomass transfer. Annual systems include intercrops and rotations of cereals with legumes. The most promising non-food legumes were Tephrosia and Sesbania. Interestingly, high quality residues of perennial legumes were most effective at supplying N in the short to medium term, whereas low quality residues immobilised N. Low quality residues were problematic for smallholder farmers who need immediately available N. Challenges to adoption of perennial system technologies include establishment costs, resource competition and delayed benefits. Farmer adoption of annual grain legumes is promoted by the simultaneous production of food; however, those species which have a high N harvest index add little to no net N to the soil. Species that combine some grain yield with high root and leaf biomass, thus a low N harvest offer a useful compromise of meeting farmer food security concerns and improving soil fertility. Promising genotypes include Arachis, Cajanus, Dolichos and Mucuna spp. On-farm N budgets indicate that legumes with high quality residues and deep root systems are effective ways at improving nutrient cycling. Areas of future research priority for smallholder farms in southern Africa were identified, including technologies which combine inorganic and organic fertilizer and improve legume growth and establishment on degraded soil

Maize productivity and profitability in Conservation Agriculture systems across agro-ecological regions in Zimbabwe: A review of knowledge and practice

Conservation agriculture (CA) is increasingly promoted in southern Africa as a strategy to improve food security and reverse soil degradation in the face of climate change. However, the performance of CA under different environments and its ability to improve ecosystem services is still unclear. The effects of the CA options; direct seeding, rip-line seeding, and seeding into planting basins on maize grain yield, soil health and profitability across agro-ecological regions in Zimbabwe were evaluated through a review of literature in combination with meta-analysis. Overall, CA improved maize yield over conventional agriculture. Compared to conventional agriculture, direct seeding, rip-line seeding, and seeding into planting basins increased yield by 445, 258 and 241 kg ha−1, respectively. However, there was an initial yield decline in the first two years. CA practices reduced soil erosion and bulk density, and increased soil water content in most studies. Under high levels of residue retention (6 Mg ha−1), CA systems exhibited greater macro fauna abundance and diversity than conventional agriculture, particularly termites. Weed pressure tended to increase labour requirement for hand-hoe weeding under CA compared to conventional agriculture. However, the use of herbicides reduced weeding labour demand during the early season. The benefits of CA are tied to the farmers’ management intensity including: time of planting, weeding, fertiliser and herbicide application, and adequate training on equipment use. Economic analysis results showed that on average, a farmer incurs losses for switching from conventional agriculture to CA in the main maize growing regions of Zimbabwe. Based on the six seasons’ data, the losses were least with the ripper in drier areas and worst with the direct seeder in wetter areas. Incorporation of chemical herbicides worsens the economic returns of CA tillage options in all the agro-ecological zones. Overall, the study showed that the rip-line seeding is more attractive in the drier areas than direct seeding. Although not costed in this study, critical is the cumulative reversal of soil degradation associated with consistent CA practice which can sustain agriculture. Results from this review suggest that the benefits of CA depend largely on the type and context of CA being practised. It is thus imperative to profile the technology, the farmer socio-economic circumstances and the bio-physical environment in which the farmer operates for proper geographical and beneficiary targeting to achieve greater impact. More longer-term studies are required to fully elucidate the benefits and context of CA options and practice

Nutrient Dynamics in Wetland Organic Vegetable Production Systems in Eastern Zambia

The aim of this study was to determine effects of organic inputs on vegetable crops and on a subsequent maize crop grown in wetlands. The following treatments were applied to cabbage (Brassica oleracea) and onion (Allium cepa) crops: Gliricidia sepium (Gliricidia) biomass (8 t ha-1), Gliricidia biomass (12 t ha-1), cattle manure (10 t ha-1) with half recommended fertilizer rate, and recommended fertilizer rate (800 kg ha-1 basal dressing and 250 kg ha-1 top dressing fertilizer). The residual effect of the treatments was tested on a subsequent maize crop. The soil at the sites had low organic matter content (average 2%) and it was acidic (average pH 4.4). Soil inorganic N increased significantly from 11 mg kg-1 in the unfertilized crop to 22 mg kg-1 in the Gliricidia treatments after cabbage, and from 10.3 mg kg-1 to 37.2 mg kg-1 after the onion crop. There were significant differences (P<0.05) in onion and cabbage yields and in subsequent maize yield in both cabbage and onion plots. This study concluded that the application of high quality Gliricidia prunings lead to rapid release of N and higher vegetable yields. However, there is a high amount of residual N that can be leached