Perennial Grain Crops for African Smallholder Farming Systems Grant #OPP

Transcription

1 Executive Summary Perennial Grain Crops for African Smallholder Farming Systems Grant #OPP Overview...2 Next Steps...3 Summaries By Research Group Snapp Group...5 Richardson Group...7 Schmitt-Olabisi Group...8 Basso Group...9 Messina Group...12 Weltzien and Cox Group...19

2 Overview Cultivation of perennial grain crops such as perennial forms of sorghum, wheat and pigeonpea potentially have many benefits for smallholder African farmers, such as alleviation of soil degradation, reclamation of marginal land, gains in soil productivity, and increased crop profitability. However, there has been little research devoted to the development of such crops for use in the tropics, particularly for marginal lands. This report reviews evidence on the values, benefit and constraints associated with development of perennial grains for small-scale African farms. The crop profiles reported on here include field experimentation results, which provide insights for future plant breeding efforts and systems research. Farmers to this day use perennial systems despite strong emphasis of extension and research on annual systems, despite no improved varieties of perennial grain crops, and despite a dearth of research on ratooning grain crops. We found evidence that farmers are interested in the soil fertility benefits from perennial grain crops more than the seed or labor saving potential, with the notable exception of women in Mali who did appreciate labor saving. This suggests that a continued focus on perennial grain crops for marginal lands as well as perennial legume crops is appropriate. We conducted a comprehensive bibliographic review which highlighted considerable advancement in genetic understanding of how to develop perennial grains, most notably in the case of perennial rice. Research on farming systems has been much more limited, including the scope for adoption and potential impact of perennial grains on multiple ecosystem services, including profitability and long-term sustainability. We used a wide range of approaches to develop two case studies, investigating the demand for perennial grains in West Africa and in East Africa. Scenario visioning and participatory action research documented strong concerns with sustainable resource management in Malawi, and corresponding interest in a perennial grain legume, such as ratooned pigeonpea. Evidence of interest included the persistence of perennial management: the practice of ratooning pigeonpea and production as two to three year stands is widespread in Malawi. This was a surprising finding, given that no pigeonpea varieties have been developed for ratooning, and technical advice as well as policies have only considered annual pigeonpea. Indeed, there is no mention of ratooning in any Ministry of Agriculture extension recommendation that we could find across Africa, nor are there research efforts to develop superior ratooning or perennial production of pigeonpea either through genetic improvement or agronomic aspects. Our bibliographical review found few research papers that address the topic of perennial or ratoon pigeonpea either, despite it being a wide-spread farming practice. We also found evidence for perennial sorghum production as a common drought management mitigation strategy fifty years ago in Southern Africa, but government policy has since suppressed ratooning and perennial sorghum, primarily as a disease management measure. Farmers expressed interest in perennial crops in the main as a means to build soils. Choice experiments, systems dynamic modeling and farmer participatory research all were consistent with acceptance of Page 2

3 short-term reductions in grain yield, if substantial soil fertility gains were realized. We documented a marked demand by farmers for perennial crops as a means to rehabilitate marginal soils: this was observed among male and female farmers, in Malawi and Mali, across quite different farming systems and market contexts. The extent of marginal lands across West, East and Southern Africa, and evidence of biophysical and management drivers of marginal maize performance was systematically documented as well. Directions for agricultural development varied by country, with Malawi concerns centering around environmental issues whereas Mali stakeholders envisioned different futures, and often prioritized market linkages, with sustainable management of the environment as a secondary concern. The wide range of tools and approaches we used to evaluate the demand for perennial grains, and assess the types of plant traits valued by farmers, converged to suggest the almost universal interest in soil conserving crops that also provided multiple products such as fodder and fuelwood, to complement intensification of annual crops. Specific traits such as grain quality, regrowth patterns and yield of fodder and grain will vary with context as we also found smallholder farms to be highly complex, and influenced by community, country and regional environment. Conceptually, sustainable farming systems rooted in perennial grains is not a hypothetical future scenario in the African context; perennial grain cultivation and harvesting is both a historic legacy and a present-day strategy in many regions of Africa. We demonstrated here how farmers have historically used perennial grains to improve their food security and enhance the resilience of their farming systems under marginal environmental conditions by studying the elements of existing perennial grain production from the regionally-specific contexts of Mali and Malawi. Next Steps Based on the findings from the current research project, our research groups are motivated to carry perennial grains research for sub-saharan Africa forward in several important areas. Perennial legume crop breeding and systems development, as well as attention to plant traits that enhance soils are key priorities that came out of this research. Perennial pigeonpea clearly is a viable option for many areas of East Africa as a soil fertility and climate resilience strategy and also a labor saving strategy for certain labor-constrained households. In West Africa, browsing-tolerant legumes such as perennial cowpea may potentially provide soil fertility benefits and overcome the livestock grazing issues that farmers encounter. Perennial rice may be a promising option for women farmers in West Africa who are labor constrained due to the social norms that prevent them from accessing labor and animal traction. There is also a need for more research on perennial grain crops as a soil erosion strategy. Perennial cowpea genotypes exist and could be developed, as does ratooning ability in pigeonpea. Perennial legumes that can be harvested at the ground level and regrow from tubers or other underground structures would be highly adapted to integration with smallholder farming systems that have a prominent livestock presence, as is common in West Africa. Page 3

4 More research overall is needed on perennial crops, especially in breeding as well as the social and environmental implications of these crops. In Malawi, farmers in the northern and central regions were interested in more research to develop local markets for pigeonpea and field trials of new varieties, such as sorghum (Photo 1). In the southern region, the farmers who grow perennial crops would benefit from research on strategies for soil fertility and grain disease management in perennial sorghum systems. The quality of extension services plays an important role in the adoption of such crops and linking farmers to emerging markets. In Mali, sorghum is not by any means a minor or marginal crop and therefore deserves much more emphasis in breeding efforts, including of perennial varieties. Farmers are interested in perennial grain crops for numerous reasons, but felt that research would be need to be targeted on resistant crops to the extended dry season and to grazing by livestock. They also imagined that soil fertility and weed management strategies would differ for perennial crops, which would also require more research. Another priority topic for future systems research that we suggest is perennial rice, to scope out the potential within upland and paddy rice in Africa. Improved varieties have been developed at the School of Agriculture, Yunnan University with support from the Land Institute (Drs. Fengyi Hu, Eric Sacks and Stan Cox). This perennial rice germplasm developed in Asia shows tremendous potential for high grain yield from both first and second year crops grown at field scale. The findings from our literature review document the development of this new germplasm at IRRI, which was recently taken to the next level in China as reported at our Perennial Grain meeting with FAO in Mali. Findings from our participatory research in Mali documented the widespread labor shortages that are faced particularly by women farmers, who are also responsible for rice production. This is motivation for pursuing a systems analysis of the benefits, challenges and potential associated with developing perennial rice for smallholder farmers in Africa. Photo 1. Pigeonpea growing in Malawi during the dry season. Page 4

5 Summaries By Research Group Snapp Group We created a website on perennial grains that provides a portal to product profiles and a supporting database documenting benefits and risks associated with perennial grain crops for sub-saharan Africa.1 Our database on perennial grains research includes approximately 1000 journal articles and books that may be viewed and downloaded from the PGrainsForAfrica website, as well as from the public Zotero group.2 In reviewing the perennial grains literature, we found that: research on perennials is increasing overall. Specialist Photo 2. Second season regrowth on a journals play an important role in supporting early research ratooned pigeonpea plant. efforts. Existing cropping systems managed for perenniality are foundations for breeding efforts on truly perennial crops. Primary research is lacking for crops that are produced on a smaller scale globally. The concept of a perennial grain only became widely used since the 1990s. The limited amount of research on perennial sorghum and pigeonpea has focused more on ratoon systems than on breeding efforts (Photo 2). These ratoon systems and the varieties might provide an excellent starting point for perennial breeding programs. We found in Malawi that fallowing was still practiced in the northern region, but not much in the central and southern regions. Farmers innovated with the introduction of pigeonpea as an annual crop by growing it in a ratoon system for up to three years to enhance the soil quality benefits of the crop. However, the ratooning of sorghum was not as widely practiced by farmers. Most farmers earned income from the sale of agricultural products, and a strong export market for pigeonpea exists in the southern region. Animal husbandry is an issue for the production Photo 3. Pigeonpea protected from animal damage of perennial pigeonpea in the northern and central in a fenced home garden in Mali. regions but less so in the southern region where pigeonpea has been grown historically Page 5

6 In Mali, we found that complex social structures and norms mean that a perennial crop would either have to resist animal grazing or be managed in such a way that minimizes the potential for damage since changing social norms could take on the order of generations (Photo 3). Sorghum is most frequently grown on the more preferred fields by farmers that are also more fertile and moist (Figure 1), which indicates that sorghum is not by any means a minor or marginal crop. The majority of farmers, who had never grown a perennial grain crop before, were interested in perennial grain crops and easily envisioned ways that they could fit into their farming systems. Figure 1. The percentage of times that crops are placed in plots with high soil moisture, high soil fertility, and plots that farmers generally prefer. Page 6

7 Richardson Group Choice experiments were used to study farmers preferences for various attributes of perennial pigeonpea in Malawi: perenniality, soil fertility, biomass, pigeonpea yield, and maize yield. Farmers reported several alternative uses of pigeonpea. The most widespread alternative use was as a soil amendment, and farmers in Zomba, reported the highest rates of alternative uses of the pigeonpea plant (particularly as fuelwood, Table 1). Results suggest that perenniality is positive and significant. Soil fertility is twice as important to farmers as biomass production from pigeonpea. Yield is positive for both pigeonpea and maize, but maize yield is valued by farmers approximately twice as much as pigeonpea yield. Results suggest that farmers would accept a 2% reduction for perenniality but as much as 20% to have higher soil fertility and 7% to have higher biomass production (Table 2). Demand for perenniality is generally positive but farmers place a low value on it. Soil fertility improvement is by far the most appealing attribute to farmers. The curve is steeper than the other attributes indicating that a portion of the sample (about 25%) would trade a large maize yield loss for the benefits of soil fertility improvement. Table 1. Percent of farmers by District who ranked the importance of pigeonpea attributes, other than grain yield. Dedza Ntcheu Zomba Fuelwood 44% 80% 95% Soil amendment 74% 85% 89% Forage 40% 38% 51% N Table 2. Willingness-to-pay estimates of random parameters for attributes of perennial pigeonpea, in kilograms of maize yield. Attribute kg/ha % of average yield** Time in field (perennial=1) % Soil fertility (high=1) % Biomass (high =1) % Pigeonpea yield 0.57* N/A * pigeonpea yield is a continuous variable so the parameter estimate is a dimensionless rate of substitution (eg. ratio of pigeonpea yield to maize yield). ** average yield is defined as the average yield across the three districts as reported by district extension officers (1500KW/ha). Choice experiments were also used to study farmers preferences for various attributes of a perennial sorghum crop in Mali. Cropping system attributes used in the choice experiments included seed requirements, labor requirements, forage quantity, soil improvement, and sorghum yield. The sorghum yield attribute serves as a substitute for a cost or price variable when evaluating tradeoffs associated Page 7

8 with the benefits of other attributes. Results suggest that seed and labor requirements were not necessarily important determinants of the choice between an annual and perennial sorghum variety. Farmers would accept approximately a 25% yield reduction for the benefits of soil improvement (Table 3). Results of separate models for men and women reveal that women care more about labor, forage and soil improvement, and less about seed requirements and yield. Table 3. Willingness-to-pay estimates of random parameters for attributes of perennial sorghum, in percentage of sorghum yield. Attribute All Men Women Seed requirements Labor requirements Forage quantity Soil improvement Schmitt-Olabisi Group Participatory scenario visioning workshops in Mali and Malawi revealed that the future of agriculture in Malawi is seen as being driven by a response to environmental degradation and resource pressure, while the agricultural future in Mali is expected to be determined by the empowerment (or lack of empowerment) of smallholder farmers in the face of technological advancement and agricultural intensification. Perennial pigeonpea in Malawi might therefore be promoted for its environmental benefits, while perennial sorghum in Mali, in order to have long-term benefits for smallholder farmers, would have to be promoted in tandem with land security, market and credit access, and other support systems that would allow smallholders to remain central to the agricultural development trajectory. We also developed system dynamics models that combine elements from sociological and economic theories of change to simulate the potential demand for perennial pigeonpea and perennial sorghum. The models were parameterized using the marginal utility values from the choice experiments and literature from agronomic experiments. Where free-range livestock are not a problem the perennial pigeonpea model shows significant demand from existing pigeonpea farmers due to the potential for improved soil fertility resulting in increased maize production; adoption is faster in lower potential areas. This is because the marginal benefits of perennial pigeonpea over annual pigeonpea for soil improvement are greater in areas where maize yields are lower. When annual climatic variability is factored into the model and Monte Carlo analysis is used, the pattern of adoption is lower because disadoption after a poor rainfall year results in a loss of trust in the perennial system for both crops (Figure 2, blue line). While perennial pigeonpea outperforms annual pigeonpea under the full range of climatic conditions, the amount by which it outperforms annual Page 8

9 pigeonpea is marginal in drought years, and this marginal improvement is not enough to overcome the inherent risk aversion farmers demonstrate around a new and transformative technology. Drought years therefore suppress the adoption trajectory. Increasing the climatic variability results in faster adoption but a similar mean level of adoption (Figure 2, red line). The increased rate of adoption with increased climate variability is likely driven by the soil building benefits of the perennial system, which help mitigate losses from water stress Adopters Years Figure 2. Simulated rates of adoption of perennial pigeonpea under two scenarios: with average climate variability (blue) and with increased climate variability (red). The solid lines are the mean based on 1000 simulations and the dashed lines are the upper and lower bounds of a 95% confidence interval. Basso Group The contributions of our group to this project are: to tune the Systems Approach to Land Use Sustainability (SALUS) model for simulating perennial sorghum and pigeonpea in Africa; to use the SALUS model for evaluating the contribution of medium-duration pigeonpea to maize grain yields; and to assess the environmental benefits of pigeonpea in Malawi. Page 9

10 We present preliminary findings and interpretations that are pending further refinement with input from members of the different research groups. We found that the SALUS model is able to simulate sorghum and pigeonpea growth in African farming systems. For the sorghum simulation, the root mean square error between observed and simulated sorghum grain yield in Ghana was 264 kg/ha. For pigeonpea simulation, the simulated aboveground biomass in general agreed with the observed biomass under different soil fertility in several farms at three locations in Malawi, with average 15% underestimation for the high soil fertility trials and 6% overestimation for the low soil fertility trials. Based on 30 growing season ( ) simulations across agriculture land in Malawi with different climate-soil combinations across Malawi, maize grain yield is increased by 275 kg/ha (43%), 266 kg/ha (45%) and 951 kg/ha (249%) under maize-pigeonpea rotation, continuous maize with 500 kg/ha pigeonpea residue incorporation and continuous maize with 5000 kg/ha pigeonpea residue incorporation, respectively, when compared to that under continuous maize without agricultural inputs (Figure 3). The increase in maize grain yield is related to the increase in soil inorganic nitrogen. For both optimal and marginal maize agriculture land, maize grain yield can be increased under maize-pigeonpea systems. The increase in maize grain yield for different marginal land varies depending on the factors identified as responsible of marginality. Page 10

11 Preliminary simulation results show that average pigeonpea aboveground biomass in maize-pigeonpea rotation ranges between 735 kg/ha and kg/ha and pigeonpea fixes average kg/ha nitrogen across all agricultural land in Malawi in the simulated (Figure 4). Page 11

12 The differences in seasonal nitrate leaching and nitrate leaching per maize grain yield under continuous maize without inputs, maize-pigeonpea rotation, and continuous maize with 500 kg/ha pigeonpea residue incorporation and with 5000 kg/ha residue incorporation appear to be small (nearly 0 kg/ha of nitrate leaching) and negligible. Furthermore, maize-pigeonpea systems may reduce nitrate leaching, which in turn may lead to a yield response for maize. Fertilized maize systems with 69 kg/ha nitrogen and 150 kg/ha nitrogen have much higher seasonal nitrate leaching: averages of 8.5 kg/ha and 34 kg/ha, respectively. Messina Group One of the most common and most commonly overlooked development tasks is targeting. In this sense we are referring here to proactively determining the appropriate location and scaling potential for any development innovation. We faced three distinct problems with targeting and scaling perennial grains. 1) where is the agriculture, 2) where is a perennial grain innovation appropriate and scalable given biophysical constraints, current or future, and 3) how do we disentangle social factors driving poorly producing agricultural regions. Each of these questions is more complex than it might appear, and they are inseparable. Unfortunately, the vast majority of development activities focus only on question 2. For this project, we first identified agricultural lands while minimizing errors of commission. Second, we used big data time series analytic processes to identify suitable soils, climate, and production. Third, we disentangled the different drivers of marginal production into all possible combinations. This final step allows us to precisely target where to promote an innovation and to realistically project the scaling potential given the potential benefits offered by each respective perennial grain. Minimizing errors of commission forces us to focus on those areas actually in agricultural production rather than including places never suitable for agriculture. This is the core marginal land problem; ranking production histories. Once lands actually used for production are identified and ranked, it then becomes possible to extract drivers of production limits. For example, one area might have poor soils, another poor rainfall, and another high temperatures, yet all produce identical yields. There are many combinations, but focusing only on outcomes misses the underlying drivers and combinations of those drivers. Perennial grains are not the solution to all drivers of poor production, but they are solutions to some. We ve identified where. Suitability of soils and climate, coupled with production estimates, were used to generate fundamental niche maps for maize, pigeonpea, and sorghum. A comprehensive literature review was conducted in order to determine optimal climatic conditions for each crop (Table 4), and production data (NASA NPP - MOD17A3) were used to delineate agricultural areas by productivity. We developed our own models for soil suitability using a suite of existing tools and a suite of landform characteristics and soil properties: slope, erosion hazard, organic matter, cation exchange capacity, texture, ph, drainage, and depth. Page 12

13 Table 4. Optimal temperatures captured by NASA MODIS Land Surface Temperature (LST MOD11A2) data. Optimal precipitation captured by NASA/JAEA Tropical Rainfall Measuring Mission (TRMM - 3B43) data. Temperature (C ) Precipitation (mm) Maize* (Marginal) 23.8 > MM > > MM > 1217 Pigeon Pea** (Optimal) 22.7 < PO < < PO < 1267 Sorghum*** (Optimal) 24.1 < SO < < SO < 875 * ARCC (Riley, Greaves, Brown) 2013, Sánchez 2014, Pingali et al ** ARCC (Nene et al., Sardana et al., Argawal, Omanga and Summerfield) 2013, Carberry et al. 1993, Omanga et al. 1995, Sardana et al. 2010, Silim and Omanga 2001, FAO, Univ. of Hawaii *** ARCC (du Plessis, Prasad et al., House et al., Wortmann et al.) 2013, Chipanshi et al. 2003, Mishra et al. 2008, FAO, du Plessis 2008 Priority areas for perennial grain development are defined as the intersection of areas of marginal dominant crop production and optimal perennial grain production. The distinction of location by source(s) of marginality is critical for the effective targeting and successful deployment of a perennial grain solution. Target maps were produced for all combinations of crops of interest for all four countries. We present two here to illustrate the potential. Each country has a unique spatial distribution of soil and climatic suitability. In the case of Tanzania, 36% of agricultural land is both marginal for maize and optimal for pigeonpea (Table 5, Figure 5). Thirty-eight percent of agricultural land is both marginal for maize and optimal for sorghum (Figure 6). Within the intersection of marginal maize and optimal pigeonpea, 62% of marginality is attributed to soil (solely or as a combination of drivers) and 25% of marginality is attributed to temperature (solely or as a combination of drivers, Table 6). Within the intersection of marginal maize and optimal sorghum, 59% of marginality is attributed to soil (solely or as a combination of drivers); 61% of marginality is attributed to precipitation (solely or as a combination of drivers). In the case of Malawi, 66% of agricultural land is both marginal for maize and optimal for pigeonpea (Figure 7). Only 4% of agricultural land is both marginal for maize and optimal for sorghum (Figure 8), due to rainfall estimates exceeding the optimal range of values for sorghum. Within the intersection of marginal maize and optimal pigeonpea, 45% of marginality is attributed to soil (solely or as a combination of drivers); 48% of marginality is attributed to temperature (solely or as a combination of drivers). Table 5. Values represent the percentage of agricultural land where there is an intersect between marginal maize and optimal pigeonpea or sorghum. Pigeon Pea (%) Sorghum (%) Tanzania Malawi 66 4 Ghana 84 3 Mali Page 13

14 It is evident from these data that soil is a common factor in marginality, and since perennial grains have unique traits in support of soil rehabilitation, the locations identified in the maps could benefit from integration of perennial technologies (Photo 4). Given the spatial extent of Tanzania, climate and soil suitability is highly variable; there is almost equal potential for Tanzania to benefit from the deployment of sorghum and pigeonpea. In Malawi, much of the country is suitable for pigeonpea, with substantial gains for the dominant maize-based systems which can benefit from soil fertility gains. On the other hand sorghum potential is limited due to rainfall excess in some years. In concordance with results from our map data, model simulations, choice experiments and farmer participatory research all point to strong interest in a perennial crop that can biologically fix nitrogen and enhance soil organic matter. The latter could be addressed through a perennial sorghum introduced in steep areas to prevent erosional losses, but pigeonpea shows broader potential in terms of combining this attribute with nitrogen fixation and phosphorus solubilization, to enhance soil organic matter and conserve soil. Table 6. Values represent the percentage within the intersect between marginal maize and optimal pigeonpea or sorghum where marginality is attributed soil, precipitation, or temperature. Pigeon Pea Sorghum Soil (%) Precipitation (%) Temperature (%) Soil (%) Precipitation (%) Temperature (%) Tanzania Malawi Ghana Mali Photo 4. Benefits of double-up pigeonpea for crop yield and biomass. Page 14

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19 Weltzien and Cox Group We experimented with two agronomic strategies, cropping system and soil fertility management, to evaluate the water use efficiency (WUE) of sorghum and pigeonpea. Our main hypothesis is that intercropping sorghum with pigeonpea will enhance water use efficiency relative to sole cropped sorghum by reducing soil moisture competition between the plant species due to spatial differentiation in roots and the hydraulic lift of pigeonpea. The trials are conducted under a wide range of conditions, high and low phosphorus (P) availability at Samanko, at Farako station in Mali and Wa station in Ghana. The perennial crops are only sown at the Samanko low P field, and are presently under observation for year two. Observations for pigeonpea from year one include that: the intercrop plots with medium duration pigeonpea was challenged by delayed flowering, severe insect attack, and the shading effect of sorghum. All pigeonpea and intercrop plots had no live weeds at final harvesting. The medium duration pigeonpea variety showed good flowering, but most were destroyed by the insects before pod formation. Both perennial and long duration pigeonpea had major problem with flower/pod drop. The pigeonpea that survived the dry season have good regrowth with thicker stems than last year. Observations for perennial sorghum for year one included that flowering started in August, much earlier than the Fadda variety, not much grain was harvested. The plots had a lot of live weeds after harvest that were removed after ratooning to simulate fodder harvest for livestock. Sorghum plots that were ratooned at ground level during harvest had better regrowth. In addition to evaluating one line of perennial sorghum in the cropping system trial, we evaluated perennial sorghum RILs from the Land Institute, Kansas, USA at the ICRISAT experimental station, Bamako, Mali. Based on the evaluation of 96 RIL lines of tetraploid sorghum derived from crosses with Sorghum halepense over a period of 16 months, including an eight month period without any rainfall we can conclude the following: some perennial sorghum lines from the Land Institute have the capacity to survive the long dry season, especially in fields that have a tendency to waterlog during parts of the season. Some of the characteristics of these lines are appropriate for use in West Africa. Unfavorable traits such as extremely early flowering date, and small grain size, and glumes that remain closed at maturity can be improved but will require large breeding populations over several cycles to improve several such genetically complex traits effectively. We crossed perennial sorghum plants with adapted sorghum germplasm from Mali. Pollen from the perennial plants that survived the dry season 2014/15 was used to pollinated male-sterile plants from S1 progenies from the Diversified Guinea Race Population, that were selected for second year testing for productivity, growing in an isolated plot. The material is not yet mature, and thus the final success of the crossing program is awaited. Page 19