Phenological responses of upland rice grown along an altitudinal gradient

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Due to land expansion and an increase in productivity, rice production in sub‐Saharan Africa has been growing at a rate of 6% in the past decade. Rainfed rice production systems have accounted for a large share of this expansion. In these systems, the potential growing period not only depends on the length of the rainy season and thus water availability, but is often, especially in the highlands of East Africa, bordered by the onset of the cool period of the year, when low minimum temperatures compromise rice yields. The objective of this study was to investigate the yield potential of 30 rice varieties contrasting in crop duration and cold tolerance in the highlands of East Africa, with its limited length of growing period. A field trial was conducted in the cropping seasons in 2016 and 2017 at the Fogera rice research station, Ethiopia. As a function of the onset of rains, rice was sown mid‐July in 2016 and early July in 2017. Early sowing in 2017 led to an extended crop duration and significantly lower yields of the short‐duration varieties, and to a shortened duration and significantly higher yields of the medium‐ and long‐duration varieties, when compared to late sowing in 2016. Late sowing compromised yield of the medium‐ and long‐duration varieties because of low temperatures during booting stage, which led to high spikelet sterility. Early sowing resulted in low yields of the short‐duration varieties, probably due to low solar radiation during the cloudy rainy season, which coincided with the vegetative stage. Therefore, choice of variety should be a function of the variable onset of the rainy season and related sowing date. However, crop models precisely calibrated for potential varieties and the respective environmental conditions could fully support the selection of a suitable variety, depending on the date of sowing, for example with the help of online tools or smartphone applications.

Section: Discussionsupporting

confidence: 70%

Season‐specific varietal management as an option to increase rainfed lowland rice production in East African high altitude cropping systems

Abera

Stuerz

Senthilkumar³

et al. 2020

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“…In a study on upland rice varieties conducted in the same region but with fewer sowing dates, Shrestha et al. (2013) found that in low and mid‐altitude, grain yield was mainly influenced by sowing date, whereas in high altitude, genotype and sowing date were influencing grain yield to the same extent. If only one crop per year is cultivated, rice can be grown without temperature constraints in the rice‐growing regions of Madagascar and high‐yielding varieties can be selected.…”

Section: Discussionmentioning

confidence: 99%

“…Since at the high‐altitude site, plants matured more than one month later during these favourable periods than at the mid‐altitude site, sowing in December was not suitable for many varieties anymore, because the reproductive stage was exposed to low temperature which strongly affected the spikelet fertility. The threshold of the mean daily minimum temperature between booting and heading for spikelet fertility has been defined to be 18°C, with severe effects on fertility below 15°C (Shrestha et al., 2013). At the high‐altitude site, mean minimum temperature between booting and heading never exceeded 18°C, and exceeded 15°C only after sowing between September and November during the first year of the experiment.…”

Section: Discussionmentioning

confidence: 99%

“…The number of spikelets per panicle was found to be highly dependent on temperature between panicle initiation and booting (Stuerz, Sow, Muller, Manneh, & Asch, 2014). During the same period, spikelet fertility is strongly affected by low temperatures, which can lead to a large share of sterile spikelets in high‐altitude locations (Dingkuhn, Sow, Samb, Diack, & Asch, 1995; Shrestha et al., 2013). Nevertheless, there is a difference in varietal response to low temperature.…”

Section: Introductionmentioning

confidence: 99%

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Genotypic yield responses of lowland rice in high‐altitude cropping systems

Razafindrazaka

Stuerz

Cotter

et al. 2020

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Rising global mean temperatures open opportunities in high‐altitude production systems for temperature‐sensitive crops such as lowland rice. Currently, the cropping window for rice in higher altitudes is still narrow, and thus, genotypes that tolerate a certain degree of chilling are needed to achieve their potential yield. Final yield depends on the interaction between genotype and environmental conditions. Exposing the genotype to a wide range of environments is a way to evaluate its adaptability into an expanding cropping calendar. Over a 2‐year period, an experiment was conducted in lowland rice systems in Madagascar at two locations differing in altitude. Twenty genotypes with contrasting levels of tolerance to low temperature were sown monthly in a non‐replicated rice garden trial. Plant development was monitored and yield and yield components were determined. Yield stability across the different growing environments was investigated. While crop duration was affected by sowing dates and altitude, yield was mainly determined by sowing date. Panicle number per m2 and number of spikelets per panicle were the most limiting factors for yield potential in mid‐altitude, while in high altitude, yield was mainly limited by spikelet fertility. Resulting cropping calendar and genotype recommendations are discussed.

“…Van Oort and Zwart (2018) have shown that climate change can be expected to have a strong impact on rice cultivation in Africa and have highlighted that regional differences in these impacts require regional adaptations strategies such as improved nutrient management strategies or shifts in cropping calendars. Climate change‐related adaptation and mitigation measures do also offer new possibilities to intensify agricultural production particularly in temperature‐limited environments such as high altitudes or seasonally hot regions (Jagadish et al., 2012; Shrestha, Asch, Brueck, et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

Creating the data basis to adapt agricultural decision support tools to new environments, land management and climate change—A case study of the RiceAdvice App

Cotter

Asch

Abera

et al. 2020

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Increasing demand for land to ensure human food security in the future has already impelled agricultural production into marginal areas. The environmental conditions found there have a more pronounced impact on agricultural productivity than in the systems used so far under favourable conditions. In addition to this challenge, climate change is expected to increase the unreliability of weather conditions (through increased variability and occurrence of extremes) for farmers considerably. This unreliability is even more serious in developing countries’ farming system where food security is vulnerable. Current efforts in digitalization offer great possibilities to improve farmers` decision‐making processes. A wide range of online tools and smartphone applications is available to support both agricultural extension services and smallholder farmers alike. These apps are often parameterized and validated to certain environments and are troubled when applied to new geographical locations and different environmental conditions. We have conducted field trials to demonstrate potential methods to close knowledge gaps in the data background for one of these apps, RiceAdvice, concerning three key aspects: shifting of cropping calendar, adjustment of fertilizer management and genotype selection. Sites in Ethiopia, Madagascar and Rwanda were selected to represent altitudinal gradients, with overlapping elevations reflecting differences in temperature to enable cross‐country comparisons. Planting dates were distributed throughout three calendar years, with continuous iterative planting dates taking place in Madagascar, in‐ and off‐season planting dates in Rwanda with different fertilizer applications, and one planting date during each rainy season in Ethiopia with different management options. With these trials, we have been able to identify key data sets needed for the adaptation of agricultural decision support tools to new environments. These include the assessment of climatic constraints on innovations to cropping calendars (e.g. double cropping), informed selection of alternative varieties able to complete crucial parts of their phenological development to avoid temperature‐related stress inducing, for example spikelet sterility in rice in late development stages and the effectivity of potential innovations in fertilizer management strategies.