Impact of precision nutrient management on yield, quality and economics of rice-based cropping systems

Abstract:

Policy statement: national fertilizer subsidy programmes across much of Angola and comparable rice-growing regions continue to promote a single blanket recommended dose regardless of field-specific soil status, a policy this two-season research set out to test against four precision nutrient management approaches that adjust fertilizer application to actual crop and soil need. Five nutrient management strategies, farmer practice (no formal recommendation), blanket recommended dose of fertilizer (RDF), soil test crop response (STCR)-based recommendation, Leaf Color Chart (LCC)-guided nitrogen management, and Nutrient Expert decision-support tool recommendation, were compared for rice grain yield, nitrogen use efficiency, grain quality, and net economic return. The Nutrient Expert-guided treatment produced the highest grain yield at 6.9 t per hectare, exceeding farmer practice by 41% and blanket RDF by 18%, while also delivering the highest nitrogen use efficiency and net economic return among the five approaches tested. Leaf Color Chart-guided management, a considerably simpler and lower-cost precision approach than either STCR or Nutrient Expert, still captured most of the yield and efficiency benefit, reaching 94% of Nutrient Expert's yield and 91% of its net return, suggesting this simpler tool offers a strong practical entry point for precision nutrient management where more sophisticated decision-support tools are not readily accessible. Yield response to nitrogen status, measured through Leaf Color Chart readings, followed a curvilinear rather than linear pattern, with yield gains diminishing and eventually reversing at the highest chart readings, confirming that nitrogen application beyond crop need reduces rather than continues raising yield. These findings challenge blanket fertilizer recommendation policy and support precision nutrient management, even in its simpler and more accessible forms, as a genuinely superior alternative on yield, efficiency, and economic grounds simultaneously.