Achieving permanence in sustainable agriculture is a critical yet underexplored challenge, particularly among smallholder farmers in resource-constrained and price-volatile environments. This talk presents a novel approach to incentive design that combines analytical modeling with lab-in-the-field experimentation to inform the development of more robust and cost-effective sustainability interventions. The first study develops a multi-period principal-agent model in which producers make joint production and sustainability decisions over time under price uncertainty. The model addresses key gaps in literature and highlights two key insights: (i) supply-dependent incentives can significantly outperform fixed payments by mitigating the productivity-sustainability trade-off, and (ii) simple affine contracts, such as price premiums, can closely approximate the optimal mechanism. The second study tests these insights through two-stage lab-in-the-field experiments with Indonesian oil palm farmers. The initial experiment identifies systematic behavioral deviations from rational predictions, including cost aversion, bounded rationality and pro-environmental preferences, motivating a recalibrated behavioral design framework. The second experiment empirically verifies that behaviorally informed price premiums jointly improve compliance and productivity relative to equal-cost fixed payments. Together, these studies propose a generalizable and iterative design process that bridges the gap between stylized models and real-world implementation. The results offer practical implications for designing durable, scalable sustainability programs.