Impacts des systèmes de culture en semis direct avec couverture végétale (SCV) sur la dynamique de l'eau, de l'azote minéral et du carbone du sol dans les cerrados brésiliens.

Under the humid tropical climate of the Brazilian cerrados, new cropping systems have become necessary to ensure sustainable agricultural production. Direct-sowing mulch-based cropping systems (DMC) introduce a cover crop before or just after the commercial crop. They help farmers enhance natural resources and produce more total biomass during the year. Crop residues protect the soil and increase organic restitution to the system. In 1999, a Franco-Brazilian collaborative project began scientific studies aimed at quantifying the impact of DMC, especially on the dynamics of water, carbon and nitrogen. DMC systems significantly decrease water runoff. In this way they effectively fight against soil erosion, even if additional infiltrated water can sometimes saturate the system and escape by drainage. The cover crop can then recycle some of that drainage loss and protect and use water resources better throughout the year. DMC systems also provide more favourable conditions that ensure the more intensive and more regular mineralisation of soil organic matter during the rainy season. Some of the organic mulch mineralises at the same time, providing the commercial crop with the benefit of a higher pool of inorganic nitrogen. The additional cover crop can recycle part of the nitrogen not used by the commercial crop and some of the nitrogen mineralised before or after this commercial cycle. Under DMC high microbial activity is responsible for higher CO2 emissions to the atmosphere, but the soil carbon balance is nonetheless positive because of the large biomass production and organic input from the introduction of the cover crop. Even under the hot and humid conditions of the cerrados, soil carbon content increases under the more productive DMC systems

Impactos do sistema de plantio direto com cobertura vegetal (SPDCV) sobre a dinâmica da água, do nitrogênio mineral e do carbono do solo do cerrado brasileiro.

Nas regiões tropicais, principalmente no cerrado brasileiro, para assegurar uma produção agrícola sustentável, é preciso recorrer a novos sistemas de cultura. Por isso, foi desenvolvido o Sistema de Plantio Direto com Cobertura vegetal, que preconiza o não-revolvimento do solo e o cultivo de plantas de cobertura, antes ou depois da cultura comercial, para produzir mais biomassa e proteger permanentemente o solo

Upland cropping systems to produce staple food and milk on the Malagasy highlands

International audienc

Identification of the main constraints for upland rice crop in direct-seeding mulch-based cropping systems under the high altitude conditions of the Madagascar highlands

International audienceIn the Madagascar highlands, increasing demand for rice combined with increasing land pressure in the lowlands led to the development of upland rice. To tackle the sustainability problem of upland crop production systems, Centre de coopération internationale en recherche agronomique pour le développement (CIRAD, an international governmental organization) and TAFA (an NGO) have developed direct-seeding mulch-based cropping systems (DMC), which not only decrease soil erosion but also increase soil fertility. To understand the mechanisms underlying the performance of upland rice DMC, an experiment was set up in 2003. The yield components of upland rice were studied under high-altitudinal conditions during six rainy seasons from 2003/04 to 2008/09. Treatments compared were two soil management techniques: conventional tillage with removal of most of the crop residues, associated with plowing ('plowing'); and a no-till system with direct seeding under mulch made of crop residues ('no-till'). The rice yields obtained were often better from plowing than from no- till, except in the last season. This difference was due to blast disease, which was significantly lower in no-till with low fertilization (best percentage of full grains and better weight of grain). The differences in yields obtained between no-till and plowing were mainly explained by problems of crop installation. The plant densities and plant growth were lower in no-till. This was particularly linked to slower root development in no- till. Overall, the biomass production of rotations of rice seemed too low in the highland conditions (low temperature) for the no-till system to be successful in the early years (low soil protection and slower restructuring of the soil)

Cotton as an entry point for soil fertility maintenance and food crop productivity in savannah agroecosystems-Evidence from a long-term experiment in southern Mali

Given the scarcity of manure and the limited land available for fallowing, cotton cultivation with its input credit schemes is often the main entry point for nutrients in cropping systems of West Africa. In an experiment carried out during 25 years in southern Mali, the crop and soil responses to organic fertilizer (=OF), inorganic fertilizer (=IF), and a combination of both (=OIF) were quantified and compared to a control treatment for a typical cotton-sorghum-groundnut rotation. From 1965 to 1979 (15 years, period 1), fertilizers were only applied on cotton and the control treatment was not fertilized. From 1980 to 1989 (10 years, period 2), the amount of manure applied was split between cotton and sorghum, and inorganic fertilizers were applied to the three crops. Inorganic fertilizers were also applied to plots with cotton and sorghum that were previously unfertilized control treatments. In favorable rainfall seasons maximum yields of fertilized treatments reached ca. 3.5 t ha−1 in the case of cotton and groundnuts, and ca. 2 t ha−1 in the case of sorghum. During period 1, cotton yields were steady (ca. 1 t ha−1) when no fertilizers were added. Cotton yields were 20% higher in the OF and OIF treatments than in the IF treatment. Sorghum and groundnut benefited from residual effects of fertilizer application on cotton leading to a 200% and 50% yield increase respectively compared to the control treatment. During period 2, yields of the three crops were similar across fertilized treatments. Groundnut yields in the OF treatment, and cotton yields in the OF and IF treatments were respectively 45%, 30% and 20% significantly higher than those in the respective control treatments. No added benefit on crop yields was observed from the combined use of inorganic and organic fertilizer. Soil nutrient contents (SOC, N, P, K) did not significantly change in any of the treatments after 25 years. Soil pH decreased in treatments receiving inorganic fertilizer. Despite low level of soil organic matter, crops responded to organic or inorganic fertilization and crop productivity over time was mostly influenced by the interaction between fertilization and rainfall variability. Our results highlight the role of cotton in West African landscapes as an entry point of nutrients via fertilization, which impacts positively on the productivity of the other crops in the rotation. Credit schemes by the cotton company for farmers to purchase fertilizer to which they would otherwise not have access are thus crucial for sustained crop productivity.Fil: Ripoche, Aude. Centre de Coopération Internationale en Recherche Agronomique pour le Développement. Agroécologie et Intensification Durable des cultures Annuelles; FranciaFil: Crétenet, M. Centre de Coopération Internationale en Recherche Agronomique pour le Développement. Agroécologie et Intensification Durable des cultures Annuelles; FranciaFil: Corbeels, Marc. Centre de Coopération Internationale en Recherche Agronomique pour le Développement. Agroécologie et Intensification Durable des cultures Annuelles; Francia. Empresa Brasileira de Pesquisa Agropecuária. Cerrados; BrasilFil: Affholder, François. Centre de Coopération Internationale en Recherche Agronomique pour le Développement. Agroécologie et Intensification Durable des cultures Annuelles; FranciaFil: Naudin, Krishna. Centre de Coopération Internationale en Recherche Agronomique pour le Développement. Agroécologie et Intensification Durable des cultures Annuelles; FranciaFil: Sissoho, F. Institut d’Economie Rurale. Programme Coton; MaliFil: Douzet, Jean-Marie. Centre de Coopération Internationale en Recherche Agronomique pour le Développement. Agroécologie et Intensification Durable des cultures Annuelles; Francia. African Conservation Tillage Network; Burkina FasoFil: Tittonell, Pablo Adrian. Wageningen University and Research Centre; Holanda. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Bariloche; Argentin