*2.2. Spatiotemporal Rainfall Data Collection*

Rainfall data were collected from November 2016 to May 2018, which included two growing seasons. Season one was from November 2016 to May 2017 (SES1) and season two was from November 2017 to May 2018 (SES2). We collected the data from 38 rain gauges randomly located in a rectangular section of Idifu (Figure 2). The rain gauge positions were defined using the K-means clustering algorithm method [25], then displayed in quantum geographic information system (QGIS) and modified onsite depending on the site conditions and features. Distances between rain gauges were limited to a minimum of 150 m between any pair of rain gauges and varied as shown in the rectangular area of 2.5 by 6 km (1500 ha) to cover a portion that contained many of the village farmers. We recorded the daily rainfall using manual rain gauges. Farmers living close to each location were identified, and at least one farmer was trained how to record the daily rainfall at 8:00 a.m. daily with the supervision of an agricultural field officer. The numbers of rainy days (events) were counted as any nonzero readings from an accumulated rainfall measurement recorded each day throughout the season.

**Figure 2.** Soil pattern and rain gauge positions at the Idifu study site.
