Uncertainty in nutrient loads from tile-drained landscapes: Effect of sampling frequency, calculation algorithm, and compositing strategy

•Uncertainty in nutrient load estimates from tile-drained landscapes was assessed.•Linear interpolation of nutrient concentration yielded the least amount of uncertainty.•Uncertainty in annual load estimates increased with increasing sampling interval.•Sample frequencies of 13–26h for DRP and 2.7–17.5d for NO3-N are recommended.