A comparison of two modified Kjeldahl digestion techniques for multi‐element plant analysis with conventional wet and dry ashing methods

Abstract The efficiency of two modified Kjeldahl procedures (H2SO4‐H2‐O2‐Li2SO4‐Se and H2SO4‐Na2SO4) for digestion of plant tissue for analysis of P, K, Ca and Mg contents was compared with a conventional wet (HNO3‐HClO4) and a dry ashing procedure. Six plant tissues were chosen as test material: leaves of Malus pumila Mill., Medicago sativa L., Dactylis glomerata L., fruit and wood tissue of M. pumila and Nothofagus mensiesii Oerst. leaf litter. Apart from low P contents of M. pumila wood tissue by dry ashing, the mean P, K, Ca and Mg contents as determined after the four digestion procedures were in good agreement. Furthermore, the precision of the data for each element was generally quite similar for each of the digestion methods. The N contents determined by the two modified and a conventional Kjeldahl procedure (H2SO4‐K2SO4‐CuSO4‐Se) also agreed closely.