First things first: Widespread nutrient deficiencies limit yields in smallholder oil palm fields

CONTEXT: Indonesia is the most important oil palm producing country. Nearly 40% of planted area is managed by smallholders, with yields well below the potential. Efforts to increase productivity have focused on the source of planting material, with little attention paid to plant nutrition. OBJECTIVE: To assess the degree to which current productivity in smallholder oil palm fields is limited by nutrients in scenarios with distinct sources of planting material. METHODS: We collected detailed data on leaf nutrient concentration from 30 fields to derive minimum sampling size needed to diagnose nutrient status. Subsequently, we collected data on yield and palm type from 973 smallholder fields to assess the importance of nutrient status and planting material in the determination of yield. RESULTS AND CONCLUSIONS: Potassium (K) deficiency was widespread (88% of fields) and often severe. Nearly two thirds of fields were also deficient for nitrogen (N) and boron (B), half were phosphorous (P) deficient, and one third were magnesium (Mg) deficient. Nutrient imbalances, especially between K and N, were also common. Fields with sufficient N, P, and K levels yielded 47% more (equivalent to 1.2 t oil ha⁻¹) than deficient fields across the entire range of planting materials. We conclude that improved plant nutrition increases fresh fruit yields in smallholder fields irrespective of the source of planting material. The advantage of certified planting material is reflected in the higher oil extraction rates. SIGNIFICANCE: Increased smallholder oil palm yields on existing plantations through improved plant nutrition offers the opportunity to improve smallholder profits and livelihoods, whilst at the same time increasing total oil production without bringing new areas into cultivation.