Pillars and challenges of a three-scale approach for designing innovative agroecological cropping systems – Case-study of the Diagnosis, Assessment, Training and Extension (DATE) approach
Introduction:
Shifting from conventional to agroecological based cropping systems faces differerent issues, mostly methodological and technical (Steiner, 1985, Malézieux et al., 2009). This paper aims to present the Diagnosis, Assessment, Training and Extension (DATE) approach used in different tropical contexts aiming to scale-out innovative and locally adapted farming systems. This approach has been used in in different tropical countries under small farming contetxs e.g. Madagascar, Laos, Cameroon, to design innovative cropping systems based on Conservation Agriculture principles (Séguy et al., 2006). The pillars and the challenges of this DATE approach are to work simultaneously at three scales i.e. field, farm, territory integrating two main concepts of cropping system designing, the de-novo and the step-by-step approaches (Meynard et al., 2012).
High altitude upland rice production systems are expected to benefit from climate change
induced increase in temperatures. The potential yield of rice genotypes is governed by the thermal
environment experienced during crop development phases when yield components are determined.
Thus, knowledge on genotypic variability in phenotypic responses to variable temperature is required
for assessing the adaptability of rice production to changing climate. Although, several crop models are
available for this task, genotypic thermal constants used to simulate crop phenology vary strongly
among the models and are under debate. Therefore, we conducted field trials with ten contrasting
upland rice genotypes on three locations along an altitudinal gradient with five monthly staggered
sowing dates for two years in Madagascar with the aim to study phenological responses at different
temperature regimes. We found that, crop duration is equally influenced by genotype selection, sowing
date and year in the high altitude. In contrast, in mid altitudes genotype has no effect on crop duration
but year and sowing date strongly affect crop duration. At low altitudes crop duration is more affected
by sowing date and less by genotype and year. Every 1°C increment in mean air temperature decreases
crop duration (germination to flowering) by 5 to 9 days depending on genotype. Using a wide range of
environments for estimating thermal constants (Tbase and Tsum) allowed for more accurate results
under field conditions. Whereas the mid altitudes represent favorable conditions for upland rice, grain
yield is strongly affected by low temperatures at high altitudes and severly influenced by frequent
tropical cyclones at low altitudes. In high altitude, genotype explained 68% of variation in spikelet
sterility, whereas in mid and low altitudes environment explained more than 70% of the variation. The
phenological responses determining crop duration and yield, the reported basic genotypic thermal
constants, and the analyses of genotypic thermal responses with regard to spikelet sterility reported
here, provide valuable information for the improvement of rice phenological and growth models
urgently needed to develop new genotypes and better adapted cropping calendars.