Typology-based evaluation of Nutrient Expert® for sustainable maize intensification in smallholder farms of eastern India

Smallholder maize systems in South Asia face challenges of low productivity, inefficient fertilizer use, and rising environmental footprints. Decision-support tools (DST) such as Nutrient Expert® (NE®), built on 4R nutrient stewardship principles, offer promise for achieving sustainable intensification (SI), yet their performance across diverse farm types remains poorly understood. This study assessed NE®-guided fertilization against farmer fertilizer practices (FFP) across 112 farms in four agro-climatic zones of southern West Bengal, India. Farm typologies were delineated using principal component and cluster analysis, resulting in seven distinct farm types (FT) reflecting socio-economic and biophysical heterogeneity. Paired on-farm trials compared NE® and FFP for multiple indicators, including yield, economics, energy use, and greenhouse gas (GHG) emissions. Results show that NE® reduced N, P, and K use by 66%, 93%, and 56%, respectively, while increasing yields across all farm types, with the highest gains in FT-4 (71.1%), FT-2 (63.0%), and FT-7 (60.3%). Gross return above fertilizer cost (GRF) improved in nearly all cases, with FT-2 achieving a 90% gain. Energy productivity and net energy gain increased in most farm types, while yield-scaled GHG emissions declined in 88.4% of farms. However, benefits were uneven: FT-3 and FT-5, constrained by setting higher yield targets, coupled with poor resource endowment and weak yield response, showed limited improvements. Thin-plate spline regression further identified farm-type–specific sustainability frontiers, indicating untapped potential for SI beyond current NE® yield targets. Overall, the findings demonstrate the utility of NE® in tailoring realistic yield targets for DST and nutrient management across heterogeneous farm systems, while also highlighting the importance of typology-based scaling strategies. • NE improved maize yield, profit, and energy efficiency and reduced GHG emissions compared to farmer fertilizer practices • Fertilization using NE achieved highest energy efficiency and lowest GHG emissions in input intensive, resource-rich farms • NE® tool largely achieved normative standards of economic and environmental outcomes from maize • NE® can further improve maize yield across all farm types • Typology-based scaling is vital for sustainable intensification in South Asia