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

联合国前总干事科菲·安南呼吁“非洲独特的绿色革命”。这一声明中隐含的是承认，第一次绿色革命为现代集约农业提供了模板，并主导了欧洲、亚洲大部分地区和北美的景观，但从长远来看，这一革命可能是不可持续的。第一次绿色革命始于20世纪60年代，其基础是培育少数几种作物的高产品种，并大量投入肥料和作物保护产品。这种耕作方式的一个新问题是，严重依赖无机肥料和化学农药导致“开放式渗漏”系统，对环境产生影响，包括扩散污染和生物多样性丧失。还有证据表明，从农业的角度来看，这些系统可能是不可持续的，因为土壤健康状况下降，害虫、杂草和疾病对杀虫剂产生抗药性。相比之下，撒哈拉以南非洲的大部分地区仍然以小得多的规模种植，投入较低，作物种类较多，但生产力低得多。可以说，因此，英国和撒哈拉以南非洲地区处于加剧光谱的两端，但两者都是不可持续的（无论是在粮食生产方面还是在环境方面）我们预计，在种植不同作物的数量和采用各种作物管理做法方面，一个更加多样化的系统将更可持续地提供粮食和营养，因为不同的作物或多或少会受到变异性的影响。在这几年的天气里。由于作物如何利用土壤中的养分存在差异，因此更多样化的作物混合物也有望提高效率并减少对环境的影响。我们将研究撒哈拉以南非洲现有种植系统多样性的重要性。通过这样做，我们将能够推荐增加产量的方法，保持适当的作物和管理多样性水平，以确保系统具有弹性。为了量化非洲种植系统多样性的价值，我们将使用在非洲和英国运行了几十年的长期实验（LTE）的数据。这些实验将用于比较多年来以不同方式耕作如何在土壤健康、粮食供应稳定和自然资源利用方面促进可持续性。在考虑“可持续性”或“复原力”等概念时，重要的是要有这样的实验，这些实验不仅着眼于实践改变的短期影响，而且能够捕捉到只有在中长期才明显的影响-管理对土壤健康的影响就是如此。长期试验的工作结果将与对撒哈拉以南非洲四个地区（尼日利亚北部、卢旺达东部、马拉维部分地区和肯尼亚西部）农场的调查相结合，以收集有关现有作物种类和种植方式的数据。我们将特别感兴趣的是当地使用的作物，而不是大规模种植。通过将这些信息与我们从长期试验中了解到的种植系统多样性与可持续性之间的关系相结合，我们将能够比较不同的系统，并确定在提供食物和保护环境之间取得最佳平衡的系统。这项工作将得到计算机模型的支持，这些模型能够预测新组合如何提供食物和营养益处。

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.