Onset data logger

One rain gauge (HOBO® Onset data loggers, Onset Computer Corporation 470 Bourne, MA, USA), was installed at a central place in each of the four sites to collect daily rainfall: Chulaimbo County Hospital (Chulaimbo); Jaramogi Oginga Odinga Teaching and Referral Hospital (Kisumu); Msambweni County Hospital (Msambweni) and Diani Health Centre (Ukunda). Data from these rain gauges were downloaded monthly.

Climate data was recorded hourly by hobo-loggers. Two temperature loggers (HOBO^® Onset data loggers, Onset Computer Corporation, 470 Bourne, MA, USA) were installed under the eaves of two houses within each of the four study areas. Daily temperature means were obtained from the land logger data and missing data were taken from logger data obtained from the paired site where possible and otherwise imputed with publicly available data from Weather Underground (www.wunderground.com; weather station codes for the coastal and western sites are HKMO and HKKI respectively) [42 ]. Missing data were imputed by adjusting available data from the paired site or Weather Underground by the slope and intercept of a linear regression equation based on the relationship between the two datasets. For rainfall, all measurements were taken from the National Oceanic and Atmospheric Administration (NOAA) Africa Rainfall Climatology (ARC) data at 0.1° × 0.1° spatial resolution [43 (link)]. The ARC dataset is produced using a combination of rainfall gauge measurements and METEOSAT satellite data to provide gridded rainfall estimates.

To monitor rainfall at each of our sampling sites, one rain gauge (HOBO Onset data loggers, Onset Computer Corporation 470 Bourne, MA USA), was installed at each of the four sites to collect daily rainfall. The sites were: Chulaimbo Sub-District Hospital (Chulaimbo) (0°02'16.5"S, 34°38'20.1"E), Jaramogi Oginga Odinga Teaching and Referral Hospital (Kisumu) (0°05'17.5"S, 34°46'13.6"E), Msambweni County Referral Hospital (Msambweni) (4°28′12″S, 39°28′48″E) and Diani Health Centre (Ukunda) (4°16'44.5"S, 39°35'25.0"E). Data from rain gauges were downloaded monthly.

At panicle initiation stage, as described by Counce et al. (2015) , three main panicles per plant were tagged in each accession of the panel. The plants with tagged panicles were then moved to the greenhouse with the HNT stress treatment, which was maintained at a day/night temperature of 30°C (86°F)/28°C (82.4°F) for 10 h (20:00–6:00), while the control treatment was set at a day/night temperature of 30°C (86°F)/22.2°C (72°F) until harvest maturity (approximately 18–20% grain moisture content). The HOBO data loggers/sensors (Onset HOBO^® data logger, Cape Cod, MA, United States) were installed in both greenhouses (control and HNT stress treatments) for the continuous monitoring and recording of the day and nighttime temperatures until physiological maturity (Figure 1A). The data logger system was operated by the HOBOware^® Pro software/app with compatible devices. At harvesting maturity, all the panicles (under control and HNT stress treatments) for each accession of the panel were harvested separately in individual brown bags, air-dried (12–14% grain moisture content), and used for the phenotyping of GY components such as PL (cm), NSP, and many others (other components not presented here). The PL of each accession with both (control and HNT stress) treatments was measured with a plastic ruler (60 cm), while NSP of each accession was counted manually by skilled personnel.

On the 13 July 2022, eight probes were deployed in a woodland at the Wellesbourne campus of the University of Warwick (coordinates: 52.211069, −1.610663). Soil here was the same composition as deployment 1, a freely draining, slightly acid loam, with texture ranging from clay loam to sandy loam. Overstory vegetation was an equal mix of Quercus robur and Acer pseudoplatanus was the understory dominated by Hedera spp. Two devices were placed at 5 cm and 10 cm every 5 m along a 20 m transect. After 6 days, the device’s driven depth was swapped (5 cm became 10 cm and vice versa). Additionally, an Onset HOBO data logger was placed adjacent to each pair and was placed 5 cm below the surface. The HOBO units are available off the shelf and offer commercial-grade data logging and wireless connectivity. These devices serve as a suitable comparison for our probes.