Dynamics of plant nutrients in organically and conventionally managed soils extracted by different analyze methods

The goal of this work was to research what kind changes in the soil agrichemical parameters occur depending on different farming methods. The field experiment was established on sandy loamy soil at Olustvere (58° 33΄ N, 25° 34΄ E) during 2008-2014. The following treatments were carried out: organic (ORG), organic with farmyard cattle manure (ORGFYM) and conventional with farmyard cattle manure and mineral fertilizers (CONFYM). Every year in September the soil samples (0-20 cm) on the crop rotation fields were collected and analysed for P, K, Mg and Ca by the Mehlich 3 (Me3) method. In parallel, ammonium lactate extractable P and K (AL-method), and ammonium acetate extractable Mg and Ca (NH4OAc-method) were determined. In all the treatments, no significant changes in soil Corg content were established over seven years. A significant (p < 0.05) decrease in soil pH was shown for the CONFYM treatment. For the ORG treatment there revealed considerable decrease of the available K content in the soil. The application of manure in the both organic and conventional treatments sustained the status of available nutrients in the soil. The Pearson correlation coefficients (at the significance p < 0.01) between the Mehlich 3 method and alternative methods were the following: for P - 0.770, for K - 0.922, for Mg - 0.951 and for Ca - 0.841. The PMe3/PAL quotient was inversely proportional with the CaMe3 values