Towards enhanced agronomic diagnostics based on remote sensing-derived crop water productivity for center pivot irrigated agriculture system

Efforts to expand irrigated agriculture faces challenge of managing scarce water resources amid rising food demand and impacts of climate change especially in ASAL districts. The objectives of this study were; to monitor spatial-temporal changes in performance of irrigation production system and to relate agronomic causes of variation in productivity. The open access remotely sensed WaPOR database was applied to assess chronology of land and water productivity of maize crop. Decadal data was bulk downloaded from FAO WaPOR portal delimited to the boundary of Galana Kulalu irrigation scheme in Kilifi, Kenya for four cropping seasons, 2018 to 2022. Soil chemical properties were analyzed for hot/cold spots in the scheme. The 2018-2019 season recorded highest net primary productivity (NPP) and actual evapotranspiration (AETI) and was high in center pivots located southern side of the scheme. Irrigation equity was rated fair but deteriorated to poor rating in the 2021-2022 season. Crop water productivity ranged between 0.43 and 1.07 Kg/m3. Poorly performing center pivots were characterized by significantly high soil moisture content (p< 0.05), highly alkaline soil pH 8.6 – 8.9 and high exchangeable sodium (ES) levels. Strong negative correlation existed between water productivity and exchangeable sodium levels. Critical remedial measures are needed to restore soil health, improve efficiency of water consumption and crop yield performance.