Ion‐selective electrodes for quick on‐farm determination of ammonium and potassium concentrations in pig slurry.

Background: Pig slurries account for a large proportion of the organic manure available worldwide. Because of the large range of slurry compositions, farmers need fast and accurate alternatives to laboratory methods to assess nutrient concentrations in these farm‐based fertilizers. In this way, nutrient emissions into the environment can be reduced and targeted nutrition of crops can be implemented, while mineral fertilizers can be saved. Aim: The objective was to evaluate whether it is possible to rapidly determine ammonium and potassium concentrations in pig slurries on‐farm using ion‐selective electrodes (ISE) and to compare the measurement with established methods. Methods: A total of 391 pig slurry samples were collected from farms in north‐west Germany, and ammonium and potassium concentrations were analyzed in the laboratory. Then the composition of pig slurries was measured with ISE, the Quantofix‐N‐Volumeter (QV) and an electrical conductivity (EC) meter and regression models were used to evaluate the on‐farm quick tests. Results: For the 391 pig slurries studied, regressions with an R2 of 0.92 for ammonium and 0.91 for potassium were achieved for concentrations measured with the ISE in comparison with laboratory analyzes. The model fits for the electrodes were significantly higher than those based on the EC for ammonium and potassium, and it was equivalent to the QV method for the assessment of the ammonium concentration. Conclusion: Due to the simple and rapid measurement, ISE offer high potential for on‐farm quantification of ammonium and potassium concentrations in pig slurries. [ABSTRACT FROM AUTHOR]