*Gobal CA-CoP* *CONSERVATION AGRICULTURE COMMUNITY OF PRACTICE* *for sustainable production intensification and land management* Dear Subscribers, Please see herebelow two documents shared by Krishna Naudin of CIRAD documenting work done on CA in Madagascar. However, with reference to the first publication, it seems that there are still some researchers who wrongly state the definition of CA as comprising of minimum tillage. *Amir Kassam * *Moderator* e-mail: [log in to unmask] URL: www.fao.org/ag/ca ---------- Forwarded message ---------- From: Krishna NAUDIN <[log in to unmask]> Date: Mon, Sep 4, 2017 at 1:41 PM Subject: 2 articles about CA To: [log in to unmask] Dear Amir Please find attached below news about two articles from our (current and ex) PhD students in Madagascar. Regards Krishna ---------------------- *Agro-ecological functions of crop residues under conservation agriculture. A review* - Lalaina RanaivosonEmail author <[log in to unmask]> - Krishna Naudin - Aude Ripoche - François Affholder - Lilia Rabeharisoa - Marc Corbeels Agronomy for Sustainable Development August 2017, 37:26 https://link.springer.com/article/10.1007/s13593-017-0432-z Abstract Conservation agriculture, which is based on minimum tillage, permanent soil cover and crop rotations, has widely been promoted as a practice to maintain or improve soil quality and enhance crop productivity. To a large extent, the beneficial effects of conservation agriculture are expected to be provided by permanent soil cover with crop residues. Surface crop residues play an important role for crop growth through their benefits on soil-related structural components and processes in the agro-ecosystem, referred to in this study as agro-ecological functions. Through a meta-analysis of the literature, we have studied the relative effects of surface crop residue levels on the performance of a set of agro-ecological functions compared with a no-till bare soil, i.e., without surface residues. The selected agro-ecological functions were soil water evaporation control, soil water infiltration, soil water runoff control, soil loss control, soil nutrient availability, soil organic carbon (SOC) stocks and gains, weed control and soil meso- and macrofauna abundance. The potential effects of crop residue cover were quantified using boundary line models. Our main findings were (1) 8 t ha−1 of residues were needed to decrease soil water evaporation by about 30% compared to no-till bare soil. (2) To achieve the maximum effect on soil water infiltration, water runoff and soil loss control, residue amounts of at least 2 t ha−1 were required. (3) The effect of increasing the amounts of surface crop residues on soil nutrient supply (N, P and K) was relatively low; the boundary line models were not significant. (4) The average annual SOC gain increased with increasing amounts of residues, with a mean of 0.38 t C ha−1 year−1 with 4 to 5 t ha−1 of residues. (5) Weed emergence and biomass can be reduced by 50% compared to a no-till bare soil with residue amounts of 1 t ha−1 or more. (6) There was a weak response in soil meso- and macrofauna abundance to increasing amounts of surface crop residues. The maximum effect corresponded to an increase of 45% compared to a no-till bare soil and was reached from 10 t ha−1 of residues. Our findings suggest that optimal amounts of surface residues in the practice of conservation agriculture will largely depend on the type of constraints to crop production which can be addressed with mulching. *Can conservation agriculture improve crop water availability in an erratic tropical climate producing water stress? A simple model applied to upland rice in Madagascar* Bruelle, G., Affholder, F., Abrell, T., Ripoche, A., Dusserre, J., Naudin, K., Tittonell, P., Rabeharisoa, L., Scopel, E. Agricultural Water Management http://www.sciencedirect.com/science/article/pii/S0378377417 302500?via%3Dihub Abstract Family farms in the tropics mainly rely on rainfed agriculture. Water availability is limited to rainfall and is one of the main constraints to crop productivity. Conservation agriculture (CA) is promoted as an alternative that, among other functions, enhances water infiltration and limits evaporation from the soil thanks to a mulch of crop residues left on the soil surface. These functions are assumed to reduce the water availability constraint by limiting water stress during crop growth. But the variability of rainfall distribution combined with the wide range of agroecological conditions and the variety of crop husbandries in the tropics makes it difficult to evaluate the efficiency of mulching. The aim of this study was to capture the variability through a simple modeling approach using the crop growth model PYE-CA, which requires a limited set of parameters and a virtual experiment (VE). We applied our approach to a case study of upland rice in the Lake Alaotra region in Madagascar, where rainfall distribution is highly variable. The VE used a 17-year series of weather data with a range of soil water conditions, sowing dates, and growth and yield limitations that cover the variability of agroecological conditions and management systems in the study area. The VE revealed that variable successions of wet and dry episodes during the rainy season resulted in both water stress and an increase in deep drainage. In the majority of conditions simulated, enhancing water infiltration through CA mainly increased water loss through drainage. However, better water infiltration may also reduce the production risks involved in early sowing or crop intensification, thereby offering new opportunities to farmers. As an alternative to time consuming and labor intensive experimentation, we propose a suitable modeling approach to identify the main drivers of rainfall × crop interactions that could be extrapolated to other regions in the tropics. ######################################################################## To unsubscribe from the CA-Cop-L list, click the following link: &*TICKET_URL(CA-Cop-L,SIGNOFF);