*2.1. Study Area*

The experiment was conducted in Morogoro, located 200 km south west of the city of Dar es Salaam. The experimental fields were located at the research farm of Sokoine University of Agriculture (SUA) (latitude = 37◦39 26" E and longitude = 6◦51 5" S) at an altitude of 510 m above mean sea level. The average annual temperature at the site is 23 ◦C with a minimum of 15 ◦C in July and a maximum of 32 ◦C in November and December. The mean relative humidity (1971–2000) for the area is 73%. Rice is grown during two seasons, dry (September–January) and wet (February–June) seasons. These two growing seasons have different irrigation needs due to differences in rainfall (1971–2000 average wet season rainfall = 53 cm and dry season = 38 cm) and evaporative demands. The seasonal mean (1971–2000) relative humidity is 66% and 78% for the dry and wet seasons, respectively. Humidity, wind speed, solar radiation, and temperature data, measured at the SUA meteorological station, were used to calculate reference evapotranspiration (ETo) using FAO Penman-Monteith method [28] (Figure 1). The average ETo for the wet and dry seasons are 52 and 64 cm, respectively. Given this weather variability, the optimum irrigation strategy for the dry season is likely to be different from the wet season. Although water availability limits large-scale production, better yields promote rice production during the dry season.

**Figure 1.** Average daily rainfall and reference ET (1971–2000) for Morogoro, Tanzania.

The experiment was conducted during the dry and wet seasons of 2012–2013. For 2013 wet season, the experimental site was moved to another plot within the same research farm due to land availability issues. Annual rainfall was measured at the site using a standard rain gauge. Another set of rainfall measurements were taken at the meteorological station at SUA. The rainfall system is bimodal, characterized by two rainfall peaks with short rains from October to December and long rains from March to May (Figure 1). Measured rainfall at the site was 489 mm and 1379 mm during the dry and wet season, respectively. High rainfall in the wet season disrupted the AWD cycle for all the SRI treatments. The top soil (0–30 cm) at the research site is a dark brown, clay loam (47% clay, 7% silt and 46% sand). The soil is acidic with a pH of 5.6. The volumetric water content at field capacity and permanent wilting point is 40.1% and 28.7%, respectively for the top soil (0–30 cm). The saturated hydraulic conductivity of the top 30 cm soil is 0.35 mm/h. Soil texture (sand, silt and clay percent) and bulk density data obtained from collected soil samples were used to estimate soil water retention and saturated hydraulic conductivity parameters [29].
