Low crop yields due to erratic rainfall and deteriorating soil fertility in smallholder farmers’ fields of Sub-Saharan Africa have prompted a quest for more resource-efficient production practices. In-situ water harvesting technologies have been proposed as climate-smart agriculture coping mechanisms to alleviate these problems, however, their full potential has not been realized. A study was undertaken to evaluate selected in-situ water harvesting technologies and fertilizer on nutrients uptake, use efficiency, and yield of maize and beans at Kenya Agricultural and Livestock Research Organization (KALRO) in Katumani, Machakos County for two seasons; short rain (SR) 2019 and long rain (LR) 2020. The experiment was laid out in a randomized complete block design with a split-split plot arrangement, replicated three times with in-situ rainwater harvesting technologies as the main plots, fertilizer inputs as the split plots, and cropping systems as the split-split plots. In-situ rainwater harvesting technologies comprised: Zai pits, Ngolo pits, contour furrows, and conventional tillage. Fertilizer inputs included: Di-ammonium phosphate (DAP) (18:46:0) fertilizer, goat manure, a mixture of DAP + goat manure and control. Cropping systems were: sole maize, sole beans, and maize-bean intercrop. Data was collected on soil nutrient status, soil moisture content, yield, nutrient uptake, and use efficiency. The data were subjected to analysis of variance and mean differences determined at p ≤ 0.05 significance level using GenStat software 15th Edition. During the SR 2019, soil moisture, maize, and beans yields, nutrient (N and P) uptake and uses efficiency were significantly (p ≤ 0.05) increased by in-situ rainwater harvesting technologies, fertilizer types, and cropping systems. Overall soil moisture content was higher in Zai pits (27.3 cm3 cm-3 ) followed by contour furrows (22.6 cm3 cm-3 ), Ngolo pits (20.8 cm3 cm-3 ) and lowest in conventional tillage (19.1 cm3 cm-3 ). Ngolo pits recorded higher maize and beans yields of 4.5 and 1.6 t ha-1 and above-ground biomass of 7.43 and 1.49 t ha-1 , respectively. Application of 100 kg ha-1 DAP increased maize and beans grain yield by 44.9 and 62.3%, and 58.2 and 56.2% in maize and beans above-ground biomass; respectively, compared to control. The highest N, P, and K uptake in maize grain were 67.8, 48.2 and 24.9 kg ha-1 and 47.2, 14.5, and 64.5 kg ha-1 in stover, respectively, recorded under Ngolo pits, whereas the lowest N, P and K contents in grain were 19.5, 25.7, and 9.5 kg ha-1 and 19.3, 5.37 and 16.8 kg ha-1 in Stover, respectively recorded under conventional tillage treatment. Higher N and P use efficiency of 39.1 and 40.1 kg grain per kg N and P ha-1 , respectively, were realized under Ngolo pits treated with 100 kg ha-1 DAP fertilizer. In the LR 2020, the application of 100 kg ha-1 DAP resulted in a 71.4% and 56% maize grain and biomass increase compared to control. Intercropping maize and beans increased grain yield significantly (p ≤ 0.05) by 10.3 and 29.4% compared to sole maize and sole beans. N, P and K contents were highest under Ngolo pits following application of 100 kg ha-1 DAP. Maize and beans subjected to application of 100 kg ha-1 DAP under Ngolo pits recorded the highest N and P use efficiency at 21.1 and 26.4 kg grain kg N and P ha-1 . The results of the study show that yield response to in-situ water harvesting technologies and fertilizer was influenced by soil moisture availability, N and P uptake, and use efficiency. Ngolo pits in combination with fertilizer performed better compared to conventional tillage under no fertilizer inputs. The results demonstrate the potential of integrating Ngolo pits and DAP fertilizer at the rate of 100 kg ha-1 in improving the yield of maize and beans and resource use efficiency in semi-arid areas. Key words: In-situ rainwater harvesting technologies, Ngolo pits, Zai pits, Nutrient uptake, Nutrient use efficiency

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