Papers by Walter Mupangwa
Smallholder farming in Zimbabwe is increasingly
affected by dwindling maize (Zea mays L.) yields ... more Smallholder farming in Zimbabwe is increasingly
affected by dwindling maize (Zea mays L.) yields due to
declining soil fertility and the negative effects of climate
variability and change. A long-term on-farm study was
established between 2004 and 2013 at the Zimuto Communal
Area near Masvingo, Southern Zimbabwe to test the feasibility
and viability of conservation agriculture (CA) systems
under the circumstances of low fertility and erratic rainfall.
CA seeding systems based on animal traction excelled and
significantly increased maize productivity by up to 235%
(1761 kg ha-1) and legume productivity by 173%
(265 kg ha-1) as compared to the conventional control treatment.
Soil quality indicators such as infiltration and soil
carbon improved 64-96% and 29-97 %, respectively, over
time. However, a direct link between increased infiltration
and grain yield could not be established. Increased plant
population, because of greater precision and moisture conservation
during direct seeding as well as an improved response
to fertilizer application due to gradually increasing soil carbon
could be the reasons why yields on CA systems outyielded the
conventional control. CA systems were more economically
viable than planting crops under the normal conventional
practice with mouldboard ploughs and removal of crop residues.
Farmers generally rated important crop characteristics of
maize planted under CA as high but weed control was rated as
low, due to the lack of an appropriate herbicide under the
prevailing environment. The results of this study show that
CA is a potential option even in areas of climate risk and low
soil fertility. However, the adoption of CA was low amongst
members of the rural farming community due to the perceived
risk of crop failure, lack of appropriate and accessible inputs
and markets for farm produce, and lack of appropriate information
and knowledge about alternative agricultural methods.
This highlights the need for better resource and input availability
as well as more vibrant and efficient extension services.
Successful CA promotion requires that the systems are
adapted to farmers’ circumstances. However, CA cannot expand
where farmers depend on remittances, are donor dependent,
and where crop production in general is doubtful. Land
uses such as extensive livestock production or game ranching
may be better and more profitable alternatives for farmers in
these situations.
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International Journal of Agricultural Sustainability, 2013
ABSTRACT Livestock and crops are key components of mixed farming systems and are a source of hous... more ABSTRACT Livestock and crops are key components of mixed farming systems and are a source of household food and income. However, mixed farming systems face livestock feed shortages and low soil productivity challenges. Conservation agriculture (CA) systems based on minimum soil disturbance, crop residue retention and crop rotations offer an opportunity to grow both fodder and food crops on the available land to improve productivity and crop output per-unit area. A four-year experiment involving maize monocropping as control treatment and four relay or intercropping treatments with different legume and fodder crops was set up on contrasting soils in Zimbabwe. Lablab was superior in biomass production compared with radish on both soil types. On the clay soil, continuous maize, sole lablab, sole radish, maize/lablab relay and radish/common beans relay treatments produced similar biomass when soil moisture was adequate. When soil moisture was limiting, lablab produced more biomass than continuous maize, radish, maize/lablab relay and radish/beans relay treatments on clay soil. On sandy soils, lablab produced more biomass than continuous maize, radish, maize/lablab relay and radish/beans relay treatments. Leguminous and non-leguminous fodder crops can be grown successfully in CA systems that are being promoted in the mixed crop/livestock farming systems of southern Africa.
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The increasing demand for food from limited available land, in light of declining soil fertility ... more The increasing demand for food from limited available land, in light of declining soil fertility and future threats of climate
variability and change have increased the need for more sustainable crop management systems. Conservation agriculture
(CA) is based on the three principles of minimum soil disturbance, surface crop residue retention and crop rotations, and
is one of the available options. In Southern Africa, CA has been intensively promoted for more than a decade to combat
declining soil fertility and to stabilize crop yields. The objective of this review is to summarize recent advances in
knowledge about the benefits of CA and highlight constraints to its widespread adoption within Southern Africa.
Research results from Southern Africa showed that CA generally increased water infiltration, reduced soil erosion and
run-off, thereby increasing available soil moisture and deeper drainage. Physical, chemical and biological soil parameters
were also improved under CA in the medium to long term. CA increased crop productivity and also reduced on-farm
labor, especially when direct seeding techniques and herbicides were used. As with other cropping systems, CA has
constraints at both the field and farm level. Challenges to adoption in Southern Africa include the retention of sufficient
crop residues, crop rotations, weed control, pest and diseases, farmer perception and economic limitations, including
poorly developed markets. It was concluded that CA is not a ‘one-size-fits-all’ solution and often needs significant
adaptation and flexibility when implementing it across farming systems. However, CA may potentially reduce future soil
fertility decline, the effects of seasonal dry-spells and may have a large impact on food security and farmers’ livelihoods if
the challenges can be overcome.
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Climate resilient cropping systems are required to adapt to the increasing threats of climate cha... more Climate resilient cropping systems are required to adapt to the increasing threats of climate change projected for Southern Africa and to better manage current climate variability. Conservation agriculture (CA) has been proposed among technologies that are climate-smart. For a cropping system to be labelled Bclimate-smart^ it has to deliver three benefits: a) adapt to the effects of climate and be of increased resilience; b) mitigate climate effects by sequestering carbon (C) and reducing greenhouse gas emissions (GHG); and c) sustainably increase productivity and income. Research on smallholder farms from Southern Africa was analysed to assess if CA can deliver on the three principles of climate-smart agriculture. Results from Southern Africa showed that CA systems have a positive effect on adaptation and productivity, but its mitigation potential lags far behind expectations. CA systems maintain higher infiltration rates and conserve soil moisture, which helps to overcome seasonal dry-spells. Increased productivity and profitability were recorded although a lag period of 2–5 cropping seasons is common until yield benefits become significant. Immediate economic benefits such as reduced labour requirements in some systems will make CA more attractive in the short term to farmers who cannot afford to wait for several seasons until yield benefits accrue. The available data summarizing the effects of CA on soil organic C (SOC) and reductions in greenhouse gases, are often contradictory and depend a great deal on the agro-ecological environment and the available biomass for surface residue retention. There is an urgent need for more research to better quantify the mitigation effects, as the current data are scanty. Possible co-interventions such as improved intercropping/ relay cropping systems, agroforestry and other tree-based systems may improve delivery of mitigation benefits and need further exploration.
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SUMMARY Multilocation experiments were established to determine the best strategy for using inorg... more SUMMARY Multilocation experiments were established to determine the best strategy for using inorganic fertilizer in conservation agriculture (CA) systems that use green manure cover crops, namely sunhemp, velvet bean and cowpea grown in rotation with maize. The objectives of the study were to determine (i) the effect of half and full rates of basal fertilizer on maize and legume biomass yields, (ii) the residual effects of unfertilized, half and fully fertilized green manure legumes on maize grown after the legumes, and (iii) the residual effect of unfertilized, half and fully fertilized green manure legumes combined with basal and topdressing fertilizer on maize yields. Experimental design was a randomized complete block with basal fertilizer as a treatment in the green manure legumes phase. Previously, in the maize phase, green manure legume species were the main treatment with basal fertilizer as a subtreatment (sunhemp, velvet bean and cowpea: 0, 75, 150 kg ha −1 and 0, 50, 100 kg ha −1 , respectively). Nitrogen was applied in the maize phase at 0, 23, 46, 69 kg N ha −1 as a sub-subtreatment in Malawi. Results showed that inorganic fertilizer is the most effective when applied to the maize, not green manure legumes. Biomass of green manure legumes, sunnhemp 8084 kg ha −1 , velvet bean 7678 kg ha −1 and cowpea 4520 kg ha −1 , was not significantly affected by application of basal fertilizer. Maize production increased after the application of green manure legumes with maize-after-maize, maize-after-velvet bean, maize-after-sunnhemp and maize-after-cowpea, yielding 3804, 5440, 5446 and 5339 kg ha −1 , respectively. Nitrogen increased maize yield regardless of the previously used green manure legumes species. Our results suggest that farmers should apply fertilizer to maize and grow green manure legumes on residual soil in CA systems. Despite growing green manure legumes, smallholders should apply nitrogen topdressing to maize grown using the green manure legumes in some agro-ecologies.
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Continuous conventional tillage coupled with unsystematic cereal/legume rotations has promoted lo... more Continuous conventional tillage coupled with unsystematic cereal/legume rotations has promoted low crop productivity on smallholder farms. A multi-locational study was established in three agro-ecoregions (AEs) of Zimbabwe. The aim of the study was to determine the effect of four tillage systems (conventional plowing, planting basins, rip-line and animal traction direct seeding systems) on maize (Zea mays L.), cowpea [Vigna unguiculata (L.) Walp] and soybean [Glycine max (L.) Merrill] yields, and evaluate the economic performance of the conservation agriculture (CA) systems relative to conventional plowing. Each farmer was a replicate of the trial over the three cropping seasons. In the high (750– 1000 mm per annum) and low (450–650 mm) rainfall AEs, conventional practice and CA systems gave similar maize grain yield. Under medium rainfall conditions (500–800 mm) planting basins, rip-line and direct seeding systems gave 547, 548 and 1690 kg ha −1 more maize yield than the conventional practice. In the high and low rainfall AEs, conventional practice and planting basins had the lowest maize production risk. Cowpea yield was 35 and 45% higher in the rip-line and direct seeding than conventional practice. Soybean yield was higher in rip-line (36%) and direct seeding (51%) systems than conventional practice. Direct seeding system gave the highest net benefits in all AEs. A combination of long-term biophysical and socioeconomic assessments of the different cropping systems tested in our study is critical in order to fully understand their performance under different AEs of Zimbabwe.
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Papers by Walter Mupangwa
affected by dwindling maize (Zea mays L.) yields due to
declining soil fertility and the negative effects of climate
variability and change. A long-term on-farm study was
established between 2004 and 2013 at the Zimuto Communal
Area near Masvingo, Southern Zimbabwe to test the feasibility
and viability of conservation agriculture (CA) systems
under the circumstances of low fertility and erratic rainfall.
CA seeding systems based on animal traction excelled and
significantly increased maize productivity by up to 235%
(1761 kg ha-1) and legume productivity by 173%
(265 kg ha-1) as compared to the conventional control treatment.
Soil quality indicators such as infiltration and soil
carbon improved 64-96% and 29-97 %, respectively, over
time. However, a direct link between increased infiltration
and grain yield could not be established. Increased plant
population, because of greater precision and moisture conservation
during direct seeding as well as an improved response
to fertilizer application due to gradually increasing soil carbon
could be the reasons why yields on CA systems outyielded the
conventional control. CA systems were more economically
viable than planting crops under the normal conventional
practice with mouldboard ploughs and removal of crop residues.
Farmers generally rated important crop characteristics of
maize planted under CA as high but weed control was rated as
low, due to the lack of an appropriate herbicide under the
prevailing environment. The results of this study show that
CA is a potential option even in areas of climate risk and low
soil fertility. However, the adoption of CA was low amongst
members of the rural farming community due to the perceived
risk of crop failure, lack of appropriate and accessible inputs
and markets for farm produce, and lack of appropriate information
and knowledge about alternative agricultural methods.
This highlights the need for better resource and input availability
as well as more vibrant and efficient extension services.
Successful CA promotion requires that the systems are
adapted to farmers’ circumstances. However, CA cannot expand
where farmers depend on remittances, are donor dependent,
and where crop production in general is doubtful. Land
uses such as extensive livestock production or game ranching
may be better and more profitable alternatives for farmers in
these situations.
variability and change have increased the need for more sustainable crop management systems. Conservation agriculture
(CA) is based on the three principles of minimum soil disturbance, surface crop residue retention and crop rotations, and
is one of the available options. In Southern Africa, CA has been intensively promoted for more than a decade to combat
declining soil fertility and to stabilize crop yields. The objective of this review is to summarize recent advances in
knowledge about the benefits of CA and highlight constraints to its widespread adoption within Southern Africa.
Research results from Southern Africa showed that CA generally increased water infiltration, reduced soil erosion and
run-off, thereby increasing available soil moisture and deeper drainage. Physical, chemical and biological soil parameters
were also improved under CA in the medium to long term. CA increased crop productivity and also reduced on-farm
labor, especially when direct seeding techniques and herbicides were used. As with other cropping systems, CA has
constraints at both the field and farm level. Challenges to adoption in Southern Africa include the retention of sufficient
crop residues, crop rotations, weed control, pest and diseases, farmer perception and economic limitations, including
poorly developed markets. It was concluded that CA is not a ‘one-size-fits-all’ solution and often needs significant
adaptation and flexibility when implementing it across farming systems. However, CA may potentially reduce future soil
fertility decline, the effects of seasonal dry-spells and may have a large impact on food security and farmers’ livelihoods if
the challenges can be overcome.
affected by dwindling maize (Zea mays L.) yields due to
declining soil fertility and the negative effects of climate
variability and change. A long-term on-farm study was
established between 2004 and 2013 at the Zimuto Communal
Area near Masvingo, Southern Zimbabwe to test the feasibility
and viability of conservation agriculture (CA) systems
under the circumstances of low fertility and erratic rainfall.
CA seeding systems based on animal traction excelled and
significantly increased maize productivity by up to 235%
(1761 kg ha-1) and legume productivity by 173%
(265 kg ha-1) as compared to the conventional control treatment.
Soil quality indicators such as infiltration and soil
carbon improved 64-96% and 29-97 %, respectively, over
time. However, a direct link between increased infiltration
and grain yield could not be established. Increased plant
population, because of greater precision and moisture conservation
during direct seeding as well as an improved response
to fertilizer application due to gradually increasing soil carbon
could be the reasons why yields on CA systems outyielded the
conventional control. CA systems were more economically
viable than planting crops under the normal conventional
practice with mouldboard ploughs and removal of crop residues.
Farmers generally rated important crop characteristics of
maize planted under CA as high but weed control was rated as
low, due to the lack of an appropriate herbicide under the
prevailing environment. The results of this study show that
CA is a potential option even in areas of climate risk and low
soil fertility. However, the adoption of CA was low amongst
members of the rural farming community due to the perceived
risk of crop failure, lack of appropriate and accessible inputs
and markets for farm produce, and lack of appropriate information
and knowledge about alternative agricultural methods.
This highlights the need for better resource and input availability
as well as more vibrant and efficient extension services.
Successful CA promotion requires that the systems are
adapted to farmers’ circumstances. However, CA cannot expand
where farmers depend on remittances, are donor dependent,
and where crop production in general is doubtful. Land
uses such as extensive livestock production or game ranching
may be better and more profitable alternatives for farmers in
these situations.
variability and change have increased the need for more sustainable crop management systems. Conservation agriculture
(CA) is based on the three principles of minimum soil disturbance, surface crop residue retention and crop rotations, and
is one of the available options. In Southern Africa, CA has been intensively promoted for more than a decade to combat
declining soil fertility and to stabilize crop yields. The objective of this review is to summarize recent advances in
knowledge about the benefits of CA and highlight constraints to its widespread adoption within Southern Africa.
Research results from Southern Africa showed that CA generally increased water infiltration, reduced soil erosion and
run-off, thereby increasing available soil moisture and deeper drainage. Physical, chemical and biological soil parameters
were also improved under CA in the medium to long term. CA increased crop productivity and also reduced on-farm
labor, especially when direct seeding techniques and herbicides were used. As with other cropping systems, CA has
constraints at both the field and farm level. Challenges to adoption in Southern Africa include the retention of sufficient
crop residues, crop rotations, weed control, pest and diseases, farmer perception and economic limitations, including
poorly developed markets. It was concluded that CA is not a ‘one-size-fits-all’ solution and often needs significant
adaptation and flexibility when implementing it across farming systems. However, CA may potentially reduce future soil
fertility decline, the effects of seasonal dry-spells and may have a large impact on food security and farmers’ livelihoods if
the challenges can be overcome.