African Journal of Agricultural Research, Jun 30, 2007
Pigeonpea is one of the few crops with a high potential for resource-poor farmers due to its comp... more Pigeonpea is one of the few crops with a high potential for resource-poor farmers due to its complementary resource use when intercropped with maize. A three year comprehensive comparative study on the performance of six pigeonpea (Cajanus cajan) varieties on farmers' fields in Eastern and Southern Africa where intercropping with maize is normal practice, was undertaken. The varieties were tested for accumulation of dry matter (DM), nitrogen (N) and phosphorus (P) in all above-ground organs for three years under farmers' conditions. The study revealed that the latest introduced ICEAP 00040 outperformed all the other tested varieties (ICP 9145; ICEAP 00020, ICEAP 00053, ICEAP 00068, and a local variety called "Babati White") under farmer-managed conditions. The harvest indices (HI), ranging from 0.08-0.15 on dry matter (DM) basis, were relatively low and unaffected (P>0.05) by the environmental variation. The N harvest index (NHI) was 0.28 and P harvest index (PHI) was 0.19. The better responses of ICEAP 00040 to favourable conditions could however only be realised in a minority of cases as yields generally were low. These low yields are still a major challenge in African smallholder agriculture as pulses play an important role in soil fertility maintenance as well as in the household diets.
Analysis of rainfall variability and trends for better climate risk management in the major agro ... more Analysis of rainfall variability and trends for better climate risk management in the major agro ecological zones in Tanzania. CCAFS Working Paper no. 363. Wageningen, the Netherlands: CGIAR Research Program on Climate Change, Agriculture and Food Security (CCAFS) About CCAFS Working Papers Titles in this series aim to disseminate interim climate change, agriculture, and food security research and practices and stimulate feedback from the scientific community. About CCAFS The CGIAR Research Program on Climate Change, Agriculture and Food Security (CCAFS) is led by the International Center for Tropical Agriculture (CIAT), part of the Alliance of Bioversity International and CIAT, and carried out with support from the CGIAR Trust Fund and through bilateral funding agreements. For more information, please visit https://ccafs.cgiar.org/donors.
In Malawi the parasitic weeds (witchweeds) for cereals and legumes exist simultaneously. The pred... more In Malawi the parasitic weeds (witchweeds) for cereals and legumes exist simultaneously. The predominant species for cereals is Striga asiatica, while for legumes it is Alectra vogelii, which causes damage in groundnuts (Arachis hypogea L.), cowpeas (Vigna unguiculata) and soybeans (Glycine max.). Growing legumes is a control measure for S. asiatica in cereal crops. Studies were initiated in 2000/2001 at
Conservation agriculture (CA) based on minimum mechanical soil disturbance, permanent organic soi... more Conservation agriculture (CA) based on minimum mechanical soil disturbance, permanent organic soil cover and crop rotation is increasingly promoted to overcome problems associated with conventional tillage (CT) such as soil fertility decline, low and unstable crop yields and high production costs. Because of the resilience of the CA farming system, CA may be a tool to assist farmers as they adapt to variable and erratic rainfall resulting from the influence of climate change in sub-Saharan Africa (SSA). This study evaluates the agronomic and economic benefits of CA and constraints to its widespread adoption among smallholder farmers in Malawi. This study draws its empirical data from collaborative work between the International Maize and Wheat Improvement Centre (CIMMYT); the regional nongovernmental organisation, Total Land Care (TLC); Agricultural Research and Development Programme (ARDEP); the Malawi Government extension services; the Department of Agricultural Research Services ...
Conservation Agriculture in Eastern and Southern Africa PATRICK C. WALL,1 CHRISTIAN THIERFELDER,2... more Conservation Agriculture in Eastern and Southern Africa PATRICK C. WALL,1 CHRISTIAN THIERFELDER,2 AMOS NGWIRA,3 BRAM GOVAERTS,4 ISAIAH NYAGUMBO2 AND FRÉDÉRIC BAUDRON5 1Independent International Consultant, Bahías de Huatulco, Oaxaca, México; 2International Maize and Wheat Improvement Center (CIMMYT), Harare, Zimbabwe; 3Department of Agricultural Research Services, Chitedze Research Station, Lilongwe, Malawi; 4International Maize and Wheat Improvement Center (CIMMYT), México DF, México; 5International Maize and Wheat Improvement Center (CIMMYT), Addis Ababa, Ethiopia
A study was conducted from 2014 to 2017 in Malawi to elucidate the short-term effects of maizeleg... more A study was conducted from 2014 to 2017 in Malawi to elucidate the short-term effects of maizelegume intercropping and rotation systems under conservation agriculture (CA) and conventional tillage (CT) on crop productivity and profitability. Twelve farmers hosted on-farm trials per district, in three districts, with each farmer having six plots. The design of the study was randomised complete block design arranged in a split plot fashion with tillage as main plot and cropping systems as subplots, with each farmer acting as a replicate. CA had 1400 and 3200 kg ha −1 more maize grain yield in the second and third seasons, respectively compared with CT. In the first two seasons, CT had 310, 180 and 270 kg ha −1 more cowpea, soybean and pigeon pea grain yields in Salima, Mzimba and Mangochi districts, respectively, compared with CA. Similarly, CA had 1100 and 950 kg ha −1 more groundnut grain yields than CT in Salima and Mzimba districts in the second and third seasons, respectively. Over the three-year study period, partial land equivalent ratio for maize ranged from 0.78 to 1.24. Largest net returns were achieved by intercropping maize with pigeon pea in Mangochi and rotating maize and groundnut in Mzimba and Salima districts.
Conservation agriculture (CA) is increasingly promoted among smallholder farmers of sub-Saharan A... more Conservation agriculture (CA) is increasingly promoted among smallholder farmers of sub-Saharan Africa in a quest to improve food security while sustaining the natural resource base of the agro-ecosystems where agriculture is based. The aim of this study was to investigate the effects of CA and traditional tillage on soil organic carbon (SOC) and selected hydraulic properties in two contrasting agro-ecological zones of Malawi. Six farmers hosted on-farm trials in each location, with each farmer having the following treatments: CA with continuous sole maize (CA-SM), CA with maize–legume intercrops (CA-ML), and traditional tillage with continuous sole maize (CT-SM). Soil samples were randomly collected in October 2015, from farmers’ fields located in Chipeni, Chinguluwe, Lemu, and Zidyana where CA had been implemented for 10 years (2005–2015) at six depth intervals: 0–10, 10–20, 20–40, 40–60, 60–80, and 80–100 cm. Bulk density, soil water characteristics, and pore size distribution we...
SUMMARYConservation agriculture (CA) was introduced to farmers in Malawi to address soil degradat... more SUMMARYConservation agriculture (CA) was introduced to farmers in Malawi to address soil degradation, declining crop productivity and the need to adapt to climate variability and change. This research from 2005 to 2014 aimed at analysing the effects of CA on longer-term productivity and profitability compared with conventional systems as practiced in two communities of Central Malawi. CA treatments outyielded conventional ridge tilled control plots in Mwansambo and Zidyana on average by between 22 and 31%, respectively. An economic analysis from 2011 to 2014 found that, on average, income was 50 and 83% greater in CA systems than in conventional systems. The crops were produced with 28 -39 less labour days ha−1 compared with the conventional practice, leading to greater net benefits. Despite the higher returns with CA, there are still challenges with residue retention, weed control, adequate rotations, management of pests and diseases as well as other socio-economic constraints. At ...
ABSTRACT Declining soil fertility is a major constraint limiting African agriculture. In a four-y... more ABSTRACT Declining soil fertility is a major constraint limiting African agriculture. In a four-year (2007–2011) on-farm study in Malawi, we compared the effects of compost (bokash and liquid manure) and compost (bokash) in combination with low doses of inorganic fertilizer with recommended inorganic fertilizer rates on the performance of three maize genotypes. Compost use resulted in increases in soil organic carbon, total nitrogen, available phosphorus, and soil pH. Chemical analysis of both bokash and liquid manure indicated the need to improve compost quality. In low rainfall areas and sites characterized by poor soils but with good quality compost, maize yields did not show significant differences between chemical fertilizer and bokash plus urea. Although it was not possible to quantify soil-water balance studies in these on-farm trials, it can be assumed that bokash helped in soil-water conservation in low rainfall areas, thereby, improving the ability of maize to withstand conditions of water stress compared with the effects of NPK fertilizer. While SC627 gave 29% higher yields under chemical fertilizer compared with bokash and urea, yields of both local and ZM621 were similar between the two treatments, suggesting that local and ZM621 are less responsive to fertility inputs. Our study showed that for maize hybrid variety, SC627, lower vulnerability to low yields is obtained from the application of chemical fertilizer. For both local maize and OPV variety ZM621, less risk of a lower yield is obtained when the plots received applications of a combination of bokash and urea rather than a total reliance on chemical fertilizer. The results of this study call for a more nuanced approach than the current recommendation permits.
SUMMARYAn on-farm study was conducted from 2009 to 2012 with communities in the Manjawira, Mpingu... more SUMMARYAn on-farm study was conducted from 2009 to 2012 with communities in the Manjawira, Mpingu and Zidyana Extension Planning Areas in the Ntcheu, Lilongwe and Nkhotakota districts of central Malawi. The aim of the study was to evaluate the effects of the principles (no-tillage and mulching) and components (fertilization and weeding) of conservation agriculture (CA) on crop productivity and weeds, and the interactions between principles and components, and to suggest strategies for introducing CA to smallholder farmers. The treatments consisted of tillage, fertilizer application, residues management and weed control strategies. While combined analysis showed that mulching is as effective as tillage in controlling weeds, the interaction between site and treatment revealed that in the more humid environment of Zidyana, weed dry matter obtained under no-tillage and residues plus fertilizer (NT+F+R) was 0.6 mg ha−1lower than under CP+F. Results suggest that about 6.0 mg ha−1of mulch ...
ABSTRACT Adoption of conservation agriculture (CA) is increasingly being promoted as a way of ada... more ABSTRACT Adoption of conservation agriculture (CA) is increasingly being promoted as a way of adapting agricultural systems to increasing climate variability, especially for areas such as southern Africa where rainfall is projected to decrease. The DSSAT crop simulation models can be a valuable tool in evaluating the effects of CA which are viable both economically and environmentally. Our objectives were: (1) to evaluate the ability of DSSAT to predict continuous maize (Zea mays L.) yield for conventional tillage (CT) and CA systems as well as maize yield for a CA maize–cowpea (Vigna unguiculata) rotation on an Oxic rhodustalf (2) to use DSSAT to project weather effect of climate change on yield, economic returns and risk in CT and CA systems. The DSSAT model was calibrated using data from 2007–2008 season and validated against independent data sets of yield of 2008–2009 to 2011–2012 seasons. Simulations of maize yields were conducted on projected future weather data from 2010 to 2030 that was generated by RegCM4 using the A1B scenario. The DSSAT model calibration and validation showed that it could be used for decision-making to choose specific CA practices especially for no-till and crop residue retention. Long term simulations showed that maize–cowpea rotation gave 451 kg ha�1 and 1.62 kg mm�1 rain more maize grain yield and rain water productivity, respectively compared with CT. On the other hand, CT (3131–5023 kg ha�1) showed larger variation in yield than both CA systems (3863 kg ha�1 and 4905 kg ha�1). CT and CA systems gave 50% and 10% cumulative probability of obtaining yield below the minimum acceptable limit of 4000 kg ha�1 respectively suggesting that CA has lower probability of low yield than CT, thus could be preferred by risk-averse farmers in uncertain climatic conditions. Using similar reasoning, Mean-Gini Dominance analysis showed the dominancy of maize–cowpea rotation and indicated it as the most efficient management system. This study therefore suggests that CA, especially when all three principles are practiced by smallholders in the medium altitude of Lilongwe and similar areas, has the potential to adapt the maize based systems to climate change. Use of DSSAT simulation of the effects of CA was successful for no-till and crop residue retention, but poor for crop rotation. Refinement of crop rotation algorithm in DSSAT is recommended.
Sustainable and resilient cropping systems are required in southern Africa to arrest declining so... more Sustainable and resilient cropping systems are required in southern Africa to arrest declining soil fertility and offset the future negative effects of climate change. Conservation agriculture (CA) has been proposed as a potential system for improving soil quality and providing stable yields through minimum soil disturbance, surface crop residue retention (mulching) and crop rotations or associations. However, concerns have been raised about the lack of evidence of the benefits of CA for small-scale farmers in southern Africa. This research was carried out in two communities and one on-station site in Zambia to provide more scientific evidence about the effects of CA on soil quality, infiltration, soil moisture and crop performance. Results from Kayowozi showed that maize yields in a direct seeded CA treatment, using cowpea seeded with a dibble stick in full rotation, increased by up to 78% after four cropping seasons in comparison to a conventional control using a ridge and furrow system. At Malende, maize yields for animal traction rip-line seeded and direct seeded plots were, on average, 75% and 91% higher than a conventionally tilled control plot after six cropping seasons. Detailed studies undertaken at the Monze Farmer Training Centre revealed that CA treatments, especially that using cotton in rotation, increased water infiltration and soil moisture. In some years, infiltration was five times higher on CA fields than on those using conventional tillage. Carbon increases were only found at the on-station longterm trial, where, over time, CA plots outperformed conventional practice leading to an overall increase of 12% carbon in the first 30 cm, compared with decreases of 15% in the conventional control. Comparative analyses between the on-farm and on-station trials point to a lack of adequate mulching, which might be the reason for lower carbon at the on-farm sites. We conclude that the effects of CA can build up on different soil types in most systems, but that scaling up and out requires the whole community to be targeted, rather than relying on individual farmers to overcome constraints related to the setup in rural communities.
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 medi...
Conservation agriculture (CA) systems are based upon minimal soil disturbance; crop residue reten... more Conservation agriculture (CA) systems are based upon minimal soil disturbance; crop residue retention and crop rotation and/or intercrop association are increasingly seen to recycle nutrients, increase yield and reduce production costs. This study examines the effects of CA practices on crop productivity, profitability and soil quality under the conditions encountered by smallholder farmers in two farming communities from 2005 to 2011 in Malawi, as part of the contribution to remedy a lack of supporting agronomic research for these relatively new systems. The drier agroenvironment of Lemu of Bazale Extension Planning Area (EPA) is characterized by sandy clay loam soils and lower rainfall. Here, CA showed positive benefits on maize yield after the first season of experimentation, with highest increases of 2.7 Mg ha−1and 2.3 Mg ha−1more yield in CA monocrop maize and CA maize–legume intercrop, respectively, than the conventional tillage in the driest season of 2009/10. In the high rai...
Conservation agriculture (CA) characterised by minimal soil disturbance, permanent soil surface c... more Conservation agriculture (CA) characterised by minimal soil disturbance, permanent soil surface cover by dead or living plants and crop rotations is one way of achieving higher soil organic carbon (C) in agricultural fields. Sandy loam and loamy soil samples from zero tillage (ZT) and conventional tillage (CT) plots were taken from farmers' fields during the dry season in August 2006. Soil organic carbon (SOC) and soil organic nitrogen (SON), microbial biomass carbon (MB-C) and microbial biomass nitrogen (MB-N), C mineralization and SOC distribution in particle size fractions in 0-20 cm layer were evaluated. Forty eight farmers' fields were randomly sampled at four different locations in Central and Northern Malawi, representing ZT plots maintained for a different number of years, and ten fields under CT with similar soil type and crop grown were selected. SOC and SON in ZT fields were 44 and 41 % (4 years ZT) and 75 and 77 % (5 years ZT) higher, respectively, than CT plots. MB-C and MB-N in ZT fields were 16 and 44 % (4 years ZT) and 20 and 38 % (5 years ZT) higher, respectively, than CT plots. However, MB-C and MB-N in ZT fields were 27 and 25 % (2 years ZT) and 17 and 9 % (3 years ZT) lower than in CT plots. The proportion of the total organic C as microbial biomass C was relatively higher under CT than ZT treatments. The higher SOC and MB-C content in the ZT fields resulted in 10, 62, 57 % higher C mineralization rate in ZT plots of 3, 4 and 5 years of loamy sand soils and 35 % higher C mineralization rate in ZT plot of 2 years than CT of sandy loam soils in undisturbed soils in the laboratory. Simulating plough from the undisturbed soils that were used for C mineralization experiment resulted in linear curves indicating that all organic C was already depleted during the first incubation period. The relative distribution of soil organic matter (SOM) in silt and clay size fractions was strongly correlated (r = 0.907 and P B 0.01) with silt percentages. Easily degradable carbon pool (C A,f) was correlated (r = 0.867 and P B 0.05) with organic carbon in sand size fraction. In developing viable conservation agriculture practices to optimize SOC content and long-term sustainability of maize production systems, priority should be given to the maintenance of C inputs, crop rotations and associations and also to reduced soil disturbance by tillage.
African Journal of Agricultural Research, Jun 30, 2007
Pigeonpea is one of the few crops with a high potential for resource-poor farmers due to its comp... more Pigeonpea is one of the few crops with a high potential for resource-poor farmers due to its complementary resource use when intercropped with maize. A three year comprehensive comparative study on the performance of six pigeonpea (Cajanus cajan) varieties on farmers' fields in Eastern and Southern Africa where intercropping with maize is normal practice, was undertaken. The varieties were tested for accumulation of dry matter (DM), nitrogen (N) and phosphorus (P) in all above-ground organs for three years under farmers' conditions. The study revealed that the latest introduced ICEAP 00040 outperformed all the other tested varieties (ICP 9145; ICEAP 00020, ICEAP 00053, ICEAP 00068, and a local variety called "Babati White") under farmer-managed conditions. The harvest indices (HI), ranging from 0.08-0.15 on dry matter (DM) basis, were relatively low and unaffected (P>0.05) by the environmental variation. The N harvest index (NHI) was 0.28 and P harvest index (PHI) was 0.19. The better responses of ICEAP 00040 to favourable conditions could however only be realised in a minority of cases as yields generally were low. These low yields are still a major challenge in African smallholder agriculture as pulses play an important role in soil fertility maintenance as well as in the household diets.
Analysis of rainfall variability and trends for better climate risk management in the major agro ... more Analysis of rainfall variability and trends for better climate risk management in the major agro ecological zones in Tanzania. CCAFS Working Paper no. 363. Wageningen, the Netherlands: CGIAR Research Program on Climate Change, Agriculture and Food Security (CCAFS) About CCAFS Working Papers Titles in this series aim to disseminate interim climate change, agriculture, and food security research and practices and stimulate feedback from the scientific community. About CCAFS The CGIAR Research Program on Climate Change, Agriculture and Food Security (CCAFS) is led by the International Center for Tropical Agriculture (CIAT), part of the Alliance of Bioversity International and CIAT, and carried out with support from the CGIAR Trust Fund and through bilateral funding agreements. For more information, please visit https://ccafs.cgiar.org/donors.
In Malawi the parasitic weeds (witchweeds) for cereals and legumes exist simultaneously. The pred... more In Malawi the parasitic weeds (witchweeds) for cereals and legumes exist simultaneously. The predominant species for cereals is Striga asiatica, while for legumes it is Alectra vogelii, which causes damage in groundnuts (Arachis hypogea L.), cowpeas (Vigna unguiculata) and soybeans (Glycine max.). Growing legumes is a control measure for S. asiatica in cereal crops. Studies were initiated in 2000/2001 at
Conservation agriculture (CA) based on minimum mechanical soil disturbance, permanent organic soi... more Conservation agriculture (CA) based on minimum mechanical soil disturbance, permanent organic soil cover and crop rotation is increasingly promoted to overcome problems associated with conventional tillage (CT) such as soil fertility decline, low and unstable crop yields and high production costs. Because of the resilience of the CA farming system, CA may be a tool to assist farmers as they adapt to variable and erratic rainfall resulting from the influence of climate change in sub-Saharan Africa (SSA). This study evaluates the agronomic and economic benefits of CA and constraints to its widespread adoption among smallholder farmers in Malawi. This study draws its empirical data from collaborative work between the International Maize and Wheat Improvement Centre (CIMMYT); the regional nongovernmental organisation, Total Land Care (TLC); Agricultural Research and Development Programme (ARDEP); the Malawi Government extension services; the Department of Agricultural Research Services ...
Conservation Agriculture in Eastern and Southern Africa PATRICK C. WALL,1 CHRISTIAN THIERFELDER,2... more Conservation Agriculture in Eastern and Southern Africa PATRICK C. WALL,1 CHRISTIAN THIERFELDER,2 AMOS NGWIRA,3 BRAM GOVAERTS,4 ISAIAH NYAGUMBO2 AND FRÉDÉRIC BAUDRON5 1Independent International Consultant, Bahías de Huatulco, Oaxaca, México; 2International Maize and Wheat Improvement Center (CIMMYT), Harare, Zimbabwe; 3Department of Agricultural Research Services, Chitedze Research Station, Lilongwe, Malawi; 4International Maize and Wheat Improvement Center (CIMMYT), México DF, México; 5International Maize and Wheat Improvement Center (CIMMYT), Addis Ababa, Ethiopia
A study was conducted from 2014 to 2017 in Malawi to elucidate the short-term effects of maizeleg... more A study was conducted from 2014 to 2017 in Malawi to elucidate the short-term effects of maizelegume intercropping and rotation systems under conservation agriculture (CA) and conventional tillage (CT) on crop productivity and profitability. Twelve farmers hosted on-farm trials per district, in three districts, with each farmer having six plots. The design of the study was randomised complete block design arranged in a split plot fashion with tillage as main plot and cropping systems as subplots, with each farmer acting as a replicate. CA had 1400 and 3200 kg ha −1 more maize grain yield in the second and third seasons, respectively compared with CT. In the first two seasons, CT had 310, 180 and 270 kg ha −1 more cowpea, soybean and pigeon pea grain yields in Salima, Mzimba and Mangochi districts, respectively, compared with CA. Similarly, CA had 1100 and 950 kg ha −1 more groundnut grain yields than CT in Salima and Mzimba districts in the second and third seasons, respectively. Over the three-year study period, partial land equivalent ratio for maize ranged from 0.78 to 1.24. Largest net returns were achieved by intercropping maize with pigeon pea in Mangochi and rotating maize and groundnut in Mzimba and Salima districts.
Conservation agriculture (CA) is increasingly promoted among smallholder farmers of sub-Saharan A... more Conservation agriculture (CA) is increasingly promoted among smallholder farmers of sub-Saharan Africa in a quest to improve food security while sustaining the natural resource base of the agro-ecosystems where agriculture is based. The aim of this study was to investigate the effects of CA and traditional tillage on soil organic carbon (SOC) and selected hydraulic properties in two contrasting agro-ecological zones of Malawi. Six farmers hosted on-farm trials in each location, with each farmer having the following treatments: CA with continuous sole maize (CA-SM), CA with maize–legume intercrops (CA-ML), and traditional tillage with continuous sole maize (CT-SM). Soil samples were randomly collected in October 2015, from farmers’ fields located in Chipeni, Chinguluwe, Lemu, and Zidyana where CA had been implemented for 10 years (2005–2015) at six depth intervals: 0–10, 10–20, 20–40, 40–60, 60–80, and 80–100 cm. Bulk density, soil water characteristics, and pore size distribution we...
SUMMARYConservation agriculture (CA) was introduced to farmers in Malawi to address soil degradat... more SUMMARYConservation agriculture (CA) was introduced to farmers in Malawi to address soil degradation, declining crop productivity and the need to adapt to climate variability and change. This research from 2005 to 2014 aimed at analysing the effects of CA on longer-term productivity and profitability compared with conventional systems as practiced in two communities of Central Malawi. CA treatments outyielded conventional ridge tilled control plots in Mwansambo and Zidyana on average by between 22 and 31%, respectively. An economic analysis from 2011 to 2014 found that, on average, income was 50 and 83% greater in CA systems than in conventional systems. The crops were produced with 28 -39 less labour days ha−1 compared with the conventional practice, leading to greater net benefits. Despite the higher returns with CA, there are still challenges with residue retention, weed control, adequate rotations, management of pests and diseases as well as other socio-economic constraints. At ...
ABSTRACT Declining soil fertility is a major constraint limiting African agriculture. In a four-y... more ABSTRACT Declining soil fertility is a major constraint limiting African agriculture. In a four-year (2007–2011) on-farm study in Malawi, we compared the effects of compost (bokash and liquid manure) and compost (bokash) in combination with low doses of inorganic fertilizer with recommended inorganic fertilizer rates on the performance of three maize genotypes. Compost use resulted in increases in soil organic carbon, total nitrogen, available phosphorus, and soil pH. Chemical analysis of both bokash and liquid manure indicated the need to improve compost quality. In low rainfall areas and sites characterized by poor soils but with good quality compost, maize yields did not show significant differences between chemical fertilizer and bokash plus urea. Although it was not possible to quantify soil-water balance studies in these on-farm trials, it can be assumed that bokash helped in soil-water conservation in low rainfall areas, thereby, improving the ability of maize to withstand conditions of water stress compared with the effects of NPK fertilizer. While SC627 gave 29% higher yields under chemical fertilizer compared with bokash and urea, yields of both local and ZM621 were similar between the two treatments, suggesting that local and ZM621 are less responsive to fertility inputs. Our study showed that for maize hybrid variety, SC627, lower vulnerability to low yields is obtained from the application of chemical fertilizer. For both local maize and OPV variety ZM621, less risk of a lower yield is obtained when the plots received applications of a combination of bokash and urea rather than a total reliance on chemical fertilizer. The results of this study call for a more nuanced approach than the current recommendation permits.
SUMMARYAn on-farm study was conducted from 2009 to 2012 with communities in the Manjawira, Mpingu... more SUMMARYAn on-farm study was conducted from 2009 to 2012 with communities in the Manjawira, Mpingu and Zidyana Extension Planning Areas in the Ntcheu, Lilongwe and Nkhotakota districts of central Malawi. The aim of the study was to evaluate the effects of the principles (no-tillage and mulching) and components (fertilization and weeding) of conservation agriculture (CA) on crop productivity and weeds, and the interactions between principles and components, and to suggest strategies for introducing CA to smallholder farmers. The treatments consisted of tillage, fertilizer application, residues management and weed control strategies. While combined analysis showed that mulching is as effective as tillage in controlling weeds, the interaction between site and treatment revealed that in the more humid environment of Zidyana, weed dry matter obtained under no-tillage and residues plus fertilizer (NT+F+R) was 0.6 mg ha−1lower than under CP+F. Results suggest that about 6.0 mg ha−1of mulch ...
ABSTRACT Adoption of conservation agriculture (CA) is increasingly being promoted as a way of ada... more ABSTRACT Adoption of conservation agriculture (CA) is increasingly being promoted as a way of adapting agricultural systems to increasing climate variability, especially for areas such as southern Africa where rainfall is projected to decrease. The DSSAT crop simulation models can be a valuable tool in evaluating the effects of CA which are viable both economically and environmentally. Our objectives were: (1) to evaluate the ability of DSSAT to predict continuous maize (Zea mays L.) yield for conventional tillage (CT) and CA systems as well as maize yield for a CA maize–cowpea (Vigna unguiculata) rotation on an Oxic rhodustalf (2) to use DSSAT to project weather effect of climate change on yield, economic returns and risk in CT and CA systems. The DSSAT model was calibrated using data from 2007–2008 season and validated against independent data sets of yield of 2008–2009 to 2011–2012 seasons. Simulations of maize yields were conducted on projected future weather data from 2010 to 2030 that was generated by RegCM4 using the A1B scenario. The DSSAT model calibration and validation showed that it could be used for decision-making to choose specific CA practices especially for no-till and crop residue retention. Long term simulations showed that maize–cowpea rotation gave 451 kg ha�1 and 1.62 kg mm�1 rain more maize grain yield and rain water productivity, respectively compared with CT. On the other hand, CT (3131–5023 kg ha�1) showed larger variation in yield than both CA systems (3863 kg ha�1 and 4905 kg ha�1). CT and CA systems gave 50% and 10% cumulative probability of obtaining yield below the minimum acceptable limit of 4000 kg ha�1 respectively suggesting that CA has lower probability of low yield than CT, thus could be preferred by risk-averse farmers in uncertain climatic conditions. Using similar reasoning, Mean-Gini Dominance analysis showed the dominancy of maize–cowpea rotation and indicated it as the most efficient management system. This study therefore suggests that CA, especially when all three principles are practiced by smallholders in the medium altitude of Lilongwe and similar areas, has the potential to adapt the maize based systems to climate change. Use of DSSAT simulation of the effects of CA was successful for no-till and crop residue retention, but poor for crop rotation. Refinement of crop rotation algorithm in DSSAT is recommended.
Sustainable and resilient cropping systems are required in southern Africa to arrest declining so... more Sustainable and resilient cropping systems are required in southern Africa to arrest declining soil fertility and offset the future negative effects of climate change. Conservation agriculture (CA) has been proposed as a potential system for improving soil quality and providing stable yields through minimum soil disturbance, surface crop residue retention (mulching) and crop rotations or associations. However, concerns have been raised about the lack of evidence of the benefits of CA for small-scale farmers in southern Africa. This research was carried out in two communities and one on-station site in Zambia to provide more scientific evidence about the effects of CA on soil quality, infiltration, soil moisture and crop performance. Results from Kayowozi showed that maize yields in a direct seeded CA treatment, using cowpea seeded with a dibble stick in full rotation, increased by up to 78% after four cropping seasons in comparison to a conventional control using a ridge and furrow system. At Malende, maize yields for animal traction rip-line seeded and direct seeded plots were, on average, 75% and 91% higher than a conventionally tilled control plot after six cropping seasons. Detailed studies undertaken at the Monze Farmer Training Centre revealed that CA treatments, especially that using cotton in rotation, increased water infiltration and soil moisture. In some years, infiltration was five times higher on CA fields than on those using conventional tillage. Carbon increases were only found at the on-station longterm trial, where, over time, CA plots outperformed conventional practice leading to an overall increase of 12% carbon in the first 30 cm, compared with decreases of 15% in the conventional control. Comparative analyses between the on-farm and on-station trials point to a lack of adequate mulching, which might be the reason for lower carbon at the on-farm sites. We conclude that the effects of CA can build up on different soil types in most systems, but that scaling up and out requires the whole community to be targeted, rather than relying on individual farmers to overcome constraints related to the setup in rural communities.
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 medi...
Conservation agriculture (CA) systems are based upon minimal soil disturbance; crop residue reten... more Conservation agriculture (CA) systems are based upon minimal soil disturbance; crop residue retention and crop rotation and/or intercrop association are increasingly seen to recycle nutrients, increase yield and reduce production costs. This study examines the effects of CA practices on crop productivity, profitability and soil quality under the conditions encountered by smallholder farmers in two farming communities from 2005 to 2011 in Malawi, as part of the contribution to remedy a lack of supporting agronomic research for these relatively new systems. The drier agroenvironment of Lemu of Bazale Extension Planning Area (EPA) is characterized by sandy clay loam soils and lower rainfall. Here, CA showed positive benefits on maize yield after the first season of experimentation, with highest increases of 2.7 Mg ha−1and 2.3 Mg ha−1more yield in CA monocrop maize and CA maize–legume intercrop, respectively, than the conventional tillage in the driest season of 2009/10. In the high rai...
Conservation agriculture (CA) characterised by minimal soil disturbance, permanent soil surface c... more Conservation agriculture (CA) characterised by minimal soil disturbance, permanent soil surface cover by dead or living plants and crop rotations is one way of achieving higher soil organic carbon (C) in agricultural fields. Sandy loam and loamy soil samples from zero tillage (ZT) and conventional tillage (CT) plots were taken from farmers' fields during the dry season in August 2006. Soil organic carbon (SOC) and soil organic nitrogen (SON), microbial biomass carbon (MB-C) and microbial biomass nitrogen (MB-N), C mineralization and SOC distribution in particle size fractions in 0-20 cm layer were evaluated. Forty eight farmers' fields were randomly sampled at four different locations in Central and Northern Malawi, representing ZT plots maintained for a different number of years, and ten fields under CT with similar soil type and crop grown were selected. SOC and SON in ZT fields were 44 and 41 % (4 years ZT) and 75 and 77 % (5 years ZT) higher, respectively, than CT plots. MB-C and MB-N in ZT fields were 16 and 44 % (4 years ZT) and 20 and 38 % (5 years ZT) higher, respectively, than CT plots. However, MB-C and MB-N in ZT fields were 27 and 25 % (2 years ZT) and 17 and 9 % (3 years ZT) lower than in CT plots. The proportion of the total organic C as microbial biomass C was relatively higher under CT than ZT treatments. The higher SOC and MB-C content in the ZT fields resulted in 10, 62, 57 % higher C mineralization rate in ZT plots of 3, 4 and 5 years of loamy sand soils and 35 % higher C mineralization rate in ZT plot of 2 years than CT of sandy loam soils in undisturbed soils in the laboratory. Simulating plough from the undisturbed soils that were used for C mineralization experiment resulted in linear curves indicating that all organic C was already depleted during the first incubation period. The relative distribution of soil organic matter (SOM) in silt and clay size fractions was strongly correlated (r = 0.907 and P B 0.01) with silt percentages. Easily degradable carbon pool (C A,f) was correlated (r = 0.867 and P B 0.05) with organic carbon in sand size fraction. In developing viable conservation agriculture practices to optimize SOC content and long-term sustainability of maize production systems, priority should be given to the maintenance of C inputs, crop rotations and associations and also to reduced soil disturbance by tillage.
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Papers by Amos Ngwira