Abstract
• Rice crop modelling since 1990 at AfricaRice addressed thermal and hydric stresses. • Applied foci are breeding support, thermal stress risks, crop calendars and yield gaps. • Leaf and panicle transpirational cooling sustain photosynthesis and spikelet fertility under heat. • Phenology and yield prediction require simulating floodwater and crop temperature. • Scarce soil and hydrology data in diverse systems hamper water-limited yield gap modelling. Rice is cultivated throughout Africa in a vast array of environments. Crop growth modelling at AfricaRice seeks to develop an understanding of genotype, management and environment interactions to inform research and development. This paper reviews progress made over thirty years of modelling, as well as the knowledge gaps remaining. Major advances were made in modelling phenology and heat- and cold-induced sterility. This crucially took into account the crop-generated microclimate via transpirational cooling in irrigated rice. On this basis, the RIDEV model and its successors provided effective support to applied breeding, genetics, agronomy and cropping systems research. As a major learning, rice very effectively avoids heat stress if it can transpire water abundantly. For water-limited systems, ORYZA2000 based yield gap, climate-change impact and drought mapping projects gave direction to AfricaRice’s applied research agenda. But large gaps remain in modelling capabilities and underlying knowledge, particularly regarding biotic stresses, inland valley hydrology, and rice-based cropping sequences, e.g. including vegetable crops. In terms of understanding the physiology, more research is needed to accurately model spikelet number, thermal acclimation, photosynthesis response to extreme temperatures, and variation in rooting depth. This will require enhanced collaboration between AfricaRice and advanced research centers to resolve the scientific and technical bottlenecks in crop modelling.
Highlights
The second section (§3) addresses crop modelling conducted at AfricaRice since 2005, when the center temporarily moved to Cotonou in Benin – again due to civil unrest that started in Ivory Coast in 2002
Crop Modelling expertise first came to AfricaRice in late 1990 as a new breeder-ecophysiologist team (Kouame Miezan and Michael Ding kuhn) were posted to the Sahel irrigated rice program based near Saint Louis, Senegal
These observations were the rationale for developing in 2012 a new RIDEV V2 model in 2012, simulating, in addition to the variables already simulated in RIDEV, diurnal dynamics of panicle temperature and the time of day of anthesis
Summary
Crop modelling is not an end in itself. In the context of applied research for the development of the rice sector in Africa, pertinent agricultural technologies and knowledge must be generated and trans ferred to stakeholders involved in rice production, extension, research or policy. East African countries gradually joined AfricaRice, including Madagascar in 2010 This development added the cool highlands of East Africa to the already large diversity of rice agroecologies on which the center works. When crop modelling first started in 1990, the center’s research was focused on (1) the mostly rainfed “upland-inland-valley continuum” systems in the humid zones and (2) the river-fed irrigated rice systems in the Sahel. The second section (§3) addresses crop modelling conducted at AfricaRice since 2005, when the center temporarily moved to Cotonou in Benin – again due to civil unrest that started in Ivory Coast in 2002. Much work was done on soil fertility modelling (Haefele et al, 2000, 2003; Segda et al, 2005; Saito et al, 2015) and turning this work into freely available decision support tools (www.riceadvice.info). RIDEV: a simple crop model assisting rice breeders and agronomists in the Sahel
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