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

联合国前总干事科菲·安南呼吁进行一场“非洲独一无二的绿色革命”。这一声明隐含着对第一次绿色革命的承认，这场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，从长期来看可能无法持续。这场始于20世纪60年代的第一次绿色革命是以培育几种作物的高产品种为基础的，同时还投入了大量化肥和植保产品。这种耕作方式的一个新出现的问题是，对无机肥料和化学杀虫剂的严重依赖导致了对环境的影响，包括扩散污染和生物多样性的丧失。也有证据表明，从农业的角度来看，这些系统可能是不可持续的，因为土壤的健康状况下降，害虫、杂草和疾病对杀虫剂产生抗药性。相比之下，撒哈拉以南非洲大片地区的种植规模仍然小得多，投入更少，作物种类更多，但生产率要低得多。因此，可以说，英国和撒哈拉以南非洲地区处于强化光谱的两端，但两者都是不可持续的(无论是在粮食生产还是环境方面)。我们预计，在种植不同作物的数量和所使用的作物管理做法方面更加多样化的系统将更可持续地提供食物和营养，因为不同的作物将或多或少地受到不同年份天气变化的影响。由于作物如何利用土壤中的养分存在差异，更多样化的作物混合预计也将更有效，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制度多样性的重要性。通过这样做，我们将能够推荐保持适当水平的作物和管理多样性的增产方法，以确保系统具有弹性。为了量化非洲种植制度多样性的价值，我们将使用在非洲和英国已经运行了几十年的长期实验(LTE)的数据。这些实验将被用来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。在考虑诸如“可持续性”或“恢复力”之类的想法时，重要的是要有这样的实验，这些实验不仅要着眼于实践变化的短期影响，而且能够捕捉到只有在中长期才明显的影响--就像管理对土壤健康的影响一样。关于LTES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)农场的调查结合起来，以收集有关作物类型和种植方式的现有品种的数据。我们将对当地使用未大规模种植的作物特别感兴趣。通过将这些信息与我们从LTES了解到的种植制度多样性和可持续性之间的关系结合起来，我们将能够比较不同的制度，并确定在提供粮食和保护环境之间取得最佳平衡的制度。这项工作将得到计算机模型的支持，这些模型能够预测潜在的新颖组合将如何带来食品和环境效益。

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.