GLTEN Africa: Cropping system diversity, a cornerstone of sustainable intensification.

The former Director General of the United Nations, Kofi Annan, has called for a 'uniquely African Green Revolution'. Implicit in this statement is the acknowledgement that the first Green Revolution that provided the template for the modern intensive agriculture and that dominates landscapes in Europe, much of Asia and North America may not be sustainable in the long term. This first Green Revolution that began in the 1960s, was based on the breeding of high yielding varieties of a few crops coupled with high inputs of fertilisers and crop protection products. An emerging problem with this way of farming is that the heavy reliance on inorganic fertilisers and chemical pesticides results in 'open leaky' systems with impacts on the environment including diffuse pollution and losses of biodiversity. There is also evidence that these systems may not be sustainable from a farming perspective as the health of soils declines and pests, weeds and diseases evolve resistance to pesticides. In contrast, large areas of Sub-Saharan Africa are still cropped on a much smaller scale with lower inputs and a greater diversity of crops but with much lower productivity. It can be argued, therefore that the UK and Sub-Saharan Africa are at opposite ends of the intensification spectrum but both are unsustainable (either in terms of food production or the environment).

We expect that a more diverse system in terms of the number of different crops grown and variety of crop management practices used will provide food and nutrition more sustainably because different crops will be more or less affected by variability in the weather between years. Because, there are differences in how crops use nutrients from the soil, a more diverse mixture of crops would also be expected to be more efficient and reduce impacts on the environment. We will study the importance of the existing diversity in cropping systems in Sub-Saharan Africa. By doing this, we will be able to recommend ways of increasing production that retains the right level of crop and management diversity to ensure the systems are resilient.

To quantify the value of diversity of cropping systems in Africa, we will use data from Long Term Experiments (LTEs) that have been running over several decades in Africa and the UK. These experiments will be used to compare how farming in different ways over many years contributes to sustainability in terms of the health of the soil, stability of food supply and use of natural resources. When considering ideas such as 'sustainability' or 'resilience' it is important to have experiments like these that do not just look at short term effects of a change of practice but are able to capture effects that are only evident over the medium to long term - as is the case for the impact of management on soil health. The results of the work on the LTEs will be combined with a survey of farms in four regions in Sub-Saharan Africa (N-Nigeria, Eastern Rwanda, parts of Malawi and Western Kenya) to collect data on the existing variety in the types of crops and ways they are grown. We will particularly interested in the local use of crops that are not grown on a wide scale. By combining this information with what we have learnt from the LTEs about the relationship between cropping system diversity and sustainability, we will be able to compare the different systems and identify the ones that strike the best balance between providing food and protecting the environment. This work will be supported by computer models that are able to predict how potentially novel combinations would deliver food and environemntal benefits.

We contend that many of the issues emerging from current, intensive farming systems are related to the over-simplification of rotations and agricultural landscapes. This has led to the over-reliance on inorganic fertilisers and a declining range of chemical crop protection active ingredients with the associated problems of diffuse environmental pollution, declining functionality of soils and the evolution of pesticide resistance. In contrast, much of Sub-Saharan Africa is still farmed on a smaller scale with lower inputs and a much wider diversity of crops. In this project, we aim to quantify the contribution of diversity in terms of the number of crops grown and their management at a field and farm scale to a range of sustainability criteria: yield stability, resource use efficiency, crop protection and soil health. In so doing, we will develop methodologies for comparing systems in terms of the level of cropping diversity and predicting their multi-criteria sustainability with the aim of recommending novel approaches that better balance productivity and the environment.

We have three main approaches. Firstly, we will interrogate data from Long Term Experiments at Rothamsted and IITA to develop generic metrics of diversity and quantify their relationships with the four sustainability criteria from data spanning several decades. These findings will be challenged with data from a survey of the existing diversity in current farming practice in SSA to identify the best performing systems in terms of SI. Finally, we will use a combination of simulation and empirical models to explore potential novel scenarios to improve SI through innovation that draws on elements of the farming systems identified from the farm surveys.

The impact from GLTEN-Africa will be delivered via three avenues:

1. The project is part of a wider initiative, GLTEN (Global Long Term Experiment Network), that is made up largely of CGIAR Institutes (including IIRI, IITA, CIMMYT, CIAT and ICRAF) and co-ordinated by Rothamsted Research. This network will provide a vehicle for developing and disseminating the ideas generated by this project and also an infra-structure to support ongoing work arising from the analyses of the importance of cropping system diversity for SI. One outcome of WP4 will be recommendations for new or modified Long Term Experiments that trial contrasting cropping systems building on the predictions from the work done in GLTEN-Africa. We intend this to be an ongoing legacy of the project funded beyond the three years of the SASSA Call.

2. The analyses of cropping system diversity done in WP3 and 4 will draw heavily on the data on existing diversity and sustainability criteria (soil properties, yield stability, resource capture and crop protection) collected from farmers in our four study regions using existing IITA infra-structure and research sites. By analysing these data in terms of a gradient of diversity and it's association with sustainability metrics, we will identify potentially promising innovations that reconcile food production and human nutrition with sustainable management of natural resources. Our analytical framework will provide an understanding of the processes underlying these 'win-win' scenarios based on the analyses of Long Term Experiments. Our approach depends on a dialogue with small holder farmers in the four study regions throughout the project and will be maintained through farm visits and farmer workshops (in the last year of the project). Specifically, we aim to develop simple methodologies that will allow farmers to audit their systems in terms of the functional diversity of crops and practices to allow them to identify opportunities to improve system resilience through targeted innovation.

3. By consolidating and standardising under-utilised data on Long Term Cropping Experiments spanning several decades we will generate novel science on the relationship between diversity of crops and crop management on various criteria of SI. This new understanding will allow fundamental principles to do with the importance of re-diversifying agricultural systems to be elucidated that will serve as a basis for future strategies to improve the sustainability of systems with different starting points and in contrasting environments. As well as being of relevance to practitioners and advisors, we anticipate this new knowledge will serve as a catalyst for new scientific work based on novel long term cropping experiments designed at the system level.