Complex cropping systems based on vegetatively propagated crops in the humid tropics – Végé-Culture

In the humid tropics (rainfalls >1800 mm/yr), agroforestry systems are combining arboriculture with vegeculture (based on vegetatively propagated crops). The plot is not ploughed and plants are manipulated individually to compose complex intra- and interspecific associations. These cropping systems (SdC) are now facing a reduction of the fallow period due to human pressures and/or the establishment of perennial cash crops (Ppr : rubber, cocoa, coffee, coconut, palm), which are favoured by agricultural policies and funding agencies. Vegeculture is often considered as archaic because it is installed following slash and burn practices. However, when its productions are expressed in dry matter per unit of time and space, this system appear quite attractive compared to Ppr. Vegeculture is also directly responsible from the rich agrobiodiversity observed. Plant domestication, cultivars selection and planting materials manipulation are closely combined. Vegeculture could be optimised and recommended to respond to the rapid environmental changes. However, in order to do so, it is necessary to measure accurately its performances so that they could be compared to Ppr. Measurements have to take into consideration the agronomic, ecological, nutritional and economical aspects of the system. Ppr incomes are often used to purchase imported foods, weakening food security and health of local populations.
At present, methodologies used to measure these SdC are obtained from Ecology and use indices taking into consideration specific counts conducted at a time t. These indices do not take into consideration the length of the SdC which itself depends on the diversity of species installed. The indices measure specific diversity (i.e. Shannon) but do not integrate intraspecific diversity, neither its evolution over time. The quantification of these SdC is also important to relate questions dealing with cultural diversity and human nutrition, in quantitative or qualitative terms. The secular plants of the vegeculture systems (bananas, yams, taros) have permitted the development of important populations in difficult environments. The place of these ancient crop species is now threatened by imported cereals, abundantly and cheaply produced which are now consumed in the most isolated places on earth. However, if we observe that plant genetic erosion often results from the cultural erosion of the populations, we still don’t know how to measure them.
This project proposal aims at developing and integrative methodology, combining data from geography, agro-ecology, biochemistry, genetics and socio-economy, using different scales of time and space, to quantify these SdC and to compare their performances to Ppr. The deliverables will facilitate the development of better agricultural policies. The multidisciplinary approach is integrative and contributes to the participation of scientists from various disciplines to study common sites. The performances of SdC will be measured and analysed with farmers strategies to establish correlations between agro-ecological, genetic and nutritional factors.