On-farm measurement of electrical conductivity for the estimation of ammonium nitrogen concentration in pig slurry

Abstract

Pig (Sus scrofa domesticus) slurry (PS) is commonly applied as fertilizer to agricultural fields. Knowledge of PS nitrogen content is essential for good management, but PS nitrogen content is highly variable not only between farms but also within a farm. Laboratory analysis of animal slurries is often expensive and impractical for routine farmer use. Therefore, when slurry is spread on land its fertilizer value is generally unknown resulting in risk of pollution. In this work, two rapid and suitable for field use, methods for determining PS ammonium-N (NH4 +-N) concentration (Quantofix® and conductimetry) are evaluated. The electrical conductivity of a dilution 1 PS: 9 distilled water (EC1:9) had better results than Quantofix®, did not need reagents and in addition, gave a direct value of NH4 +-N concentrations (range 1.0 - 7.6 kg NH4 +-N m-3). The conductimetry method allows the use of alternative waters with EC < 1.9 dS m-1 for dilution. The method is being introduced to farmers in northeast Spain in order to improve PS management and has been well received due to its low cost and ease of use in practical application.