Highly variable performance of sustainable intensification on smallholder farms: A systematic review

Agroecology Can Promote Climate Change Adaptation Outcomes Without Compromising Yield In Smallholder Systems

A critical question is whether agroecology can promote climate change mitigation and adaptation outcomes without compromising food security. We assessed the outcomes of smallholder agricultural systems and practices in low- and middle-income countries (LMICs) against 35 mitigation, adaptation, and yield indicators by reviewing 50 articles with 77 cases of agroecological treatments relative to a baseline of conventional practices. Crop yields were higher for 63% of cases reporting yields. Crop diversity, income diversity, net income, reduced income variability, nutrient regulation, and reduced pest infestation, indicators of adaptative capacity, were associated with 70% or more of cases. Limited information on climate change mitigation, such as greenhouse gas emissions and carbon sequestration impacts, was available. Overall, the evidence indicates that use of organic nutrient sources, diversifying systems with legumes and integrated pest management lead to climate change adaptation in multiple contexts. Landscape mosaics, biological control (e.g., enhancement of beneficial organisms) and field sanitation measures do not yet have sufficient evidence based on this review. Widespread adoption of agroecological practices and system transformations shows promise to contribute to climate change services and food security in LMICs. Gaps in adaptation and mitigation strategies and areas for policy and research interventions are finally discussed.

Advancing the science and practice of ecological nutrient management for smallholder farmers

Soil degradation is widespread in smallholder agrarian communities across the globe where limited resource farmers struggle to overcome poverty and malnutrition. This review lays out the scientific basis and practical management options for an ecologically based approach to sustainably managing soil fertility, with particular attention to smallholder subsistence systems. We seek to change the trajectory of development programs that continue to promote inorganic fertilizers and other high input strategies to resource constrained smallholders, despite ample evidence that this approach is falling short of food security goals and contributing to resource degradation. Ecological nutrient management (ENM) is an agroecological approach to managing the biogeochemical cycles that govern soil ecosystem services and soil fertility. The portfolio of ENM strategies extends beyond reliance on inorganic fertilizers and is guided by the following five principles: (1) Build soil organic matter and other nutrient reserves. (2) Minimize the size of N and P pools that are the most susceptible to loss. (3) Maximize agroecosystem capacity to use soluble, inorganic N and P. (4) Use functional and phylogenetic biodiversity to minimize bare fallows and maximize presence of growing plants. (5) Construct agroecosystem and field scale mass balances to track net nutrient flows over multiple growing seasons. Strategic increases in spatial and temporal plant species diversity is a core ENM tactic that expands agroecosystem multifunctionality to meet smallholder priorities beyond soil restoration and crop yields. Examples of ENM practices include the use of functionally designed polycultures, diversified rotations, reduced fallow periods, increased reliance on legumes, integrated crop-livestock production, and use of variety of soil amendments. These practices foster soil organic matter accrual and restoration of soil function, both of which underpin agroecosystem resilience. When ENM is first implemented, short-term yield outcomes are variable; however, over the long-term, management systems that employ ENM can increase yields, yield stability, profitability and food security. ENM rests on a solid foundation of ecosystem and biogeochemical science, and despite the many barriers imposed by current agricultural policies, successful ENM systems are being promoted by some development actors and used by smallholder farmers, with promising results.

Integrating RNAi Technology in Smallholder Farming: Accelerating Sustainable Development Goals

Approximately 84% of farms globally are <2 hectares; these and other smallholder farms collectively produce over one third of humanity's food. However, smallholder farms, particularly in developing countries, encounter difficulties in both production and profits due to their vulnerabilities. Sustainable intensification—increasing crop yield without significantly greater resource use—must be globally adopted in smallholder farming to achieve various Sustainable Development Goals (SDGs) endorsed by the United Nations (UN). While traditional techniques for conservation agriculture must be maintained and further promoted, new technologies will undoubtedly play a major role in achieving high yields in a sustainable and environmentally safe manner. RNA interference (RNAi) technology, particularly the use of transgenic RNAi cultivars and/or sprayable double-stranded RNA (dsRNA) pesticides, could accelerate progress in reaching these goals due to dsRNA's nucleotide sequence-specific mode of action against eukaryotic and viral pests. This sequence-specificity allows silencing of specific genetic targets in focal pest species of interest, potentially resulting in negligible effects on non-target organisms inhabiting the agroecosystem. It is our perspective that recent progress in RNAi technology, together with the UN's endorsement of SDGs that promote support in- and for developing countries, should facilitate an integrated approach to sustainable intensification of smallholder farms, whereby RNAi technology is used in combination with traditional techniques for sustainable intensification. However, the development of such approaches in developing countries will require developed countries to adhere to currently-defined socioeconomic SDGs.