The Assessment of Crop Water Productivity Behaviour in Humid Climate Region for Nasho Irrigation Scheme and Rainfed Area in Rwanda

Abstract. The study quantified and analysed Agricultural Crop Water Productivity Indicators such as Transpiration, Actual Evapotranspiration and Interception, Net Primary Productivity, Total Biomass Production, and Gross Biomass Water Productivity. And Crop Water Productivity (CWP) of irrigated crops was normalised from climate constraints to evaluate the level of climate effects for C3 (are the plants which fix carbon dioxide using Calvin cycle and producing a 3-carbon molecule) and C4 (plants fix carbon dioxide into a 4-carbon molecule) crops. Comparative analysis indicated that the beans as C3 crops are more affected by the climate than maize, the C4 crops in both seasons which has a significant meaning due to the different biological properties of both beans and maize. The findings indicate that the average seasonal transpiration values for maize and beans during the winter season are 364 and 420 mm/season, respectively, while during the summer season, they are 306 and 323 mm/season. During the summer, the average seasonal evapotranspiration for maize and beans is 415 and 399 mm/season, respectively, and during the winter, it is 493 and 538 mm/season. Also, summer beans and maize produced 2.50 and 2.43 kg/m3 of crop water productivity, whereas beans and maize produced 2.67 and 2.70 kg/m3 as gross crop water production for winter. For the summer beans and maize, the average seasonal Total Biomass Production (TBP) was 10534 and 11169 kgDM/ha/season; for the winter crops, it was 12440 and 13349 kgDM/ha/season. Additionally, summer crops such as beans and maize have gross crop water productivity of 2.67 and 2.70 kg/m3, respectively, whereas winter crops have 2.50 and 2.43 kg/m3. During the evaluation of climate effects on crop water productivity, the climatic normalization of crop water productivity technique was examined for irrigated beans and maize. For winter beans, the average CWP and CWPc values are 2.5 and 3.2 kg/m3, while for summer beans, they are 3.0 and 3.0 kg/m3. Additionally, the 2.4 and 2.4 kg/m3 of CWP and CWPc are indicated for winter maize, whereas 2.7 and 2.0 kg/m3 are for summer maize.