Deborah A. Bossio

Smart Investments in Sustainable Food Production: Revisiting Mixed Crop-Livestock Systems

Farmers in mixed crop-livestock systems produce about half of the world’s food. In small holdings around the world, livestock are reared mostly on grass, browse, and nonfood biomass from maize, millet, rice, and sorghum crops and in their turn supply manure and traction for future crops. Animals act as insurance against hard times and supply farmers with a source of regular income from sales of milk, eggs, and other products. Thus, faced with population growth and climate change, small-holder farmers should be the first target for policies to intensify production by carefully managed inputs of fertilizer, water, and feed to minimize waste and environmental impact, supported by improved access to markets, new varieties, and technologies.

Soil Microbial Community Response to Land Use Change in an Agricultural Landscape of Western Kenya

Tropical agroecosystems are subject to degradation processes such as losses in soil carbon, nutrient depletion, and reduced water holding capacity that occur rapidly resulting in a reduction in soil fertility that can be difficult to reverse. In this research, a polyphasic methodology has been used to investigate changes in microbial community structure and function in a series of tropical soils in western Kenya. These soils have different land usage with both wooded and agricultural soils at Kakamega and Ochinga, whereas at Ochinga, Leuro, Teso, and Ugunja a replicated field experiment compared traditional continuous maize cropping against an improved N-fixing fallow system. For all sites, principal component analysis of 16S rRNA gene denaturing gradient gel electrophoresis (DGGE) profiles revealed that soil type was the key determinant of total bacterial community structure, with secondary variation found between wooded and agricultural soils. Similarly, phospholipid fatty acid (PLFA) analysis also separated wooded from agricultural soils, primarily on the basis of higher abundance of monounsaturated fatty acids, anteiso- and iso-branched fatty acids, and methyl-branched fatty acids in the wooded soils. At Kakamega and Ochinga wooded soils had between five 5 and 10-fold higher levels of soil carbon and microbial biomass carbon than agricultural soils from the same location, whereas total enzyme activities were also lower in the agricultural sites. Soils with woody vegetation had a lower percentage of phosphatase activity and higher cellulase and chitinase activities than the agricultural soils. BIOLOG analysis showed woodland soils to have the greatest substrate diversity. Throughout the study the two functional indicators (enzyme activity and BIOLOG), however, showed lower specificity with respect to soil type and land usage than did the compositional indicators (DGGE and PLFA). In the field experiment comparing two types of maize cropping, both the maize yields and total microbial biomass were found to increase with the fallow system. Moreover, 16S rRNA gene and PLFA analyses revealed shifts in the total microbial community in response to the different management regimes, indicating that deliberate management of soils can have considerable impact on microbial community structure and function in tropical soils.

Global tree cover and biomass carbon on agricultural land: The contribution of agroforestry to global and national carbon budgets

Agroforestry systems and tree cover on agricultural land make an important contribution to climate change mitigation, but are not systematically accounted for in either global carbon budgets or national carbon accounting. This paper assesses the role of trees on agricultural land and their significance for carbon sequestration at a global level, along with recent change trends. Remote sensing data show that in 2010, 43% of all agricultural land globally had at least 10% tree cover and that this has increased by 2% over the previous ten years. Combining geographically and bioclimatically stratified Intergovernmental Panel on Climate Change (IPCC) Tier 1 default estimates of carbon storage with this tree cover analysis, we estimated 45.3 PgC on agricultural land globally, with trees contributing >75%. Between 2000 and 2010 tree cover increased by 3.7%, resulting in an increase of >2 PgC (or 4.6%) of biomass carbon. On average, globally, biomass carbon increased from 20.4 to 21.4 tC ha−1. Regional and country-level variation in stocks and trends were mapped and tabulated globally, and for all countries. Brazil, Indonesia, China and India had the largest increases in biomass carbon stored on agricultural land, while Argentina, Myanmar, and Sierra Leone had the largest decreases.

An integrated agro-ecosystem and livelihood systems approach for the poor and vulnerable in dry areas

More than 400 million people in the developing world depend on dryland agriculture for their livelihoods. Dryland agriculture involves a complex combination of productive components: staple crops, vegetables, livestock, trees and fish interacting principally with rangeland, cultivated areas and watercourses. Managing risk and enhancing productivity through diversification and sustainable intensification is critical to securing and improving rural livelihoods. The main biophysical constraints are natural resource limitations and degradation, particularly water scarcity and encroaching desertification. Social and economic limitations, such as poor access to markets and inputs, weak governance and lack of information about alternative production technologies also limit the options available to farmers. Past efforts to address these constraints by focusing on individual components have either not been successful or are now facing a declining rate of impact, indicating the need for new integrated approaches to research for development of dryland systems. This article outlines the characteristics of such an approach, integrating agro-ecosystem and livelihoods approaches and presents a range of empirical examples of its application in dryland contexts. The authors draw attention to new insights about the design of research required to accelerate impact by integrating across disciplines and scales.

Analysis of gaps and possible interventions for improving water productivity in crop livestock systems of Ethiopia

Low crop and livestock productivities in the mixed farming systems of Ethiopia hamper efforts to meet the increasing food demands from a stressed natural resource base. Important reasons for the low agricultural productivity are water scarcity and poor spatial and temporal rainfall distribution. Although improving agricultural water productivity would safeguard peoples livelihoods and the environment, the lack of information on best bet interventions and strategies to achieve this impedes targeted decision making. Therefore, the aim of this study was to conduct an ex-ante evaluation of the potential effect of selected interventions on livestock water productivity (LWP) in mixed crop-livestock systems. Baseline data were collected from a water scarce area in the Ethiopian highlands. An analysis of productivity gaps and stakeholder interviews helped to identify promising interventions, which were categorized in three groups related to feed, water and animal management. A spreadsheet model was developed that was composed of the various production components of the farming system, their interactions and influencing factors. By linking water use for feed production with livestock products through the energy supplied by the feeds, the potential effect of interventions on LWP could be simulated. The evaluation showed that the various interventions targeting feed, water and animal management could result in LWP improvements ranging from 4 to 94%. Feed and energy water productivity increased particularly with interventions like fertilizer application, and the introduction of fodder trees, concentrates, improved food-feed crops, and soil and water conservation measures. Combining the different interventions led to a stronger improvement than any of the single interventions. The results of the evaluation can inform policy-makers and development actors on which best bets to promote and invest in.

Conserving land, protecting water.

In Molden, David (Ed.). Water for food, water for life: a Comprehensive Assessment of Water Management in Agriculture. London, UK: Earthscan; Colombo, Sri Lanka: International Water Management Institute (IWMI).

Livestock and water: understanding the context based on the 'Comprehensive Assessment of Water Management in Agriculture'

The recently completed ‘Comprehensive Assessment of Water Management in Agriculture’ (CA) assessed the benefits, costs and impacts of the past 50 years of water development. It highlighted important trends that frame the challenges in water resources management of today and into the future, and critically evaluated solutions that people have developed to cope with these challenges. Important past trends include increases in food production that have outpaced population growth, much of this due to a doubling of the global irrigated area between 1961 and 2003, and accompanying declines in the health of aquatic ecosystems resulting from demands for, and impacts of, water use in agriculture. The future will bring new pressures on water resources and ecosystems as demands from sectors other than agriculture increase (including water for biofuel production), populations rise and become more wealthy, which leads to demand for foods that are more water intensive to produce, and climate change increases uncertainty and risk in our agricultural systems. Modelling predictions and analysis of scenarios show that water demand may rise from between only 20 up to 90% over the next 50 years, depending on how we choose to manage water in agricultural systems in the future. Owing to the importance of meat in changing diets and the role of livestock in managing land degradation, livestock is central to many of the issues that will determine whether or not optimistic scenarios (minimised increased demand for agricultural water in the future) can be achieved. This paper briefly summarises the insights and results of the CA, and highlights the areas where livestock management is most closely related to major water challenges and global recommendations of the CA. The purpose of this introductory paper is to set the context within which the importance of enhancing livestock water productivity in mixed farming systems can be appreciated.

Land degradation and water productivity in agricultural landscapes

Management of land, soil and water are intimately related and complementary to each other. Land degradation, and in particular soil quality degradation, is a major factor limiting agricultural water productivity and is often neglected in water management circles. When degradation of agricultural soil resources results in productivity declines that are more limiting than water, then water productivity declines. The best existing evaluation of the extent of soil degradation worldwide is still the Global Assessment of Land Degradation (GLASOD) by Oldeman (1991). Based on this assessment we can infer that on 50% of arable land worldwide, water productivity is below what could have been expected before degradation occurred (Wood et al., 2000; see also Eswaran et al. (2001) for more detailed treatment of yield impacts from land degradation). Soil degradation limits water productivity in cases where absolute quantities of water are not the most limiting factor. This situation is widespread, considering that nutrients can be more limiting than water even in very dry areas, such as the Sahel (Penning de Vries and Djiteye, 1982; Breman, 1998). Addressing these constraints is critical if improvements in water productivity are to be achieved. Increasing awareness of a ‘global water crisis’ recognizes that the scarcity of clean water does affect food production and conservation of ecosystems. It is predicted that by 2025, most developing countries will face either physical or economic water scarcity, while at the same time global demand for food will increase (Molden, 2007). Because irrigated and rainfed agriculture is by far the largest human consumptive use of fresh water, improving the productivity of water used in agriculture can assist in increasing food production while maintaining water-related ecosystem services. Tackling human-induced degradation of agricultural lands is therefore central to addressing the ‘water crisis’. This chapter reviews a range of studies and concepts regarding options for improving water productivity through improved land management that mitigates soil degradation, and aims to highlight its importance as part of a comprehensive strategy to address global water scarcity. The focus is primarily on crop water productivity at the field scale, but the importance of taking a landscape-scale perspective when evaluating impacts of changes in water use is also discussed.

Global Sequestration Potential of Increased Organic Carbon in Cropland Soils

The role of soil organic carbon in global carbon cycles is receiving increasing attention both as a potentially large and uncertain source of CO2 emissions in response to predicted global temperature rises, and as a natural sink for carbon able to reduce atmospheric CO2. There is general agreement that the technical potential for sequestration of carbon in soil is significant, and some consensus on the magnitude of that potential. Croplands worldwide could sequester between 0.90 and 1.85 Pg C/yr, i.e. 26–53% of the target of the “4p1000 Initiative: Soils for Food Security and Climate”. The importance of intensively cultivated regions such as North America, Europe, India and intensively cultivated areas in Africa, such as Ethiopia, is highlighted. Soil carbon sequestration and the conservation of existing soil carbon stocks, given its multiple benefits including improved food production, is an important mitigation pathway to achieve the less than 2 °C global target of the Paris Climate Agreement.

Assessment of water productivity and entry points for improvement in mixed crop-livestock systems of the Ethiopian highlands

between environmental legislation and the size and geometry of their farms. Amongst the respondents, 89% said that only punitive law enforcement would be able to force them to maintain all the APP (in-farm permanent protection areas). About 88% of the farms that adopted pasture base dairy-MIG, fenced off springs and remaining forests. The use of electric fences in MIG system minimizes animals contact with water, streams and forest areas. Finally, for 91% of the famers interviewed pasture carrying capacity and milk sales increased substantially when they switch from traditional semiconfinement to pasture based dairy.