Principally caused by soil water stress and declining soil fertility, low crop productivity results in both food and income insecurity. The effects of nitrogen and phosphorus fertilizer micro-dosing with inter-row rainwater harvesting practices for maize and pigeon-pea inter-cropping on yield and land use efciency are inadequately documented in sub humid tropics. A feld experiment on sandy loam soils in sub humid conditions using a splitsplit plot design was conducted. Plots used in situ rainwater harvesting practices of tied ridges, open ridges, and flat cultivation. Sub-plots were sole maize, sole pigeon-pea, and 1:1 maize-pigeon pea inter-cropping. The subsub plots were control, fertilizer (N and P) application at the micro-dose level, and recommended rates. Tied ridges signifcantly (p < 0.001) conserved more soil moisture than flat cultivation at 30 cm depth after ten days of rainfall. Ridges increased maize yield by 0.3 t ha−1 over flat cultivation. Fertilizer application signifcantly (p < 0.001) increased maize yield by 1.12 t ha−1 with micro-dosing and by 1.60 t ha−1 with recommended rates over the control. Combining tied ridges and fertilizer signifcantly (p < 0.040) increased maize yield by 132–156% compared to flat cultivation without fertilizer. Reflecting a land equivalent ratio, land use efciency was 67–122% higher in inter-cropping than sole crop. Tied ridges conserved more soil moisture than flat cultivation, enhancing fertilizer use efciency that improved crop yields and land equivalent ratio under intercropping. This strategy could increase food availability and income generation under smallholder farming systems in sub-humid tropic areas.