Dolomitic lime rate effects on pH, available macro- And micro nutrient content, plant growth and plant nutrient content on peats of various degrees of decomposition

Abstract

Twelve peats of different degree of decomposition were obtained all over Europe, namely Ireland, Germany, Sweden, Finland and the Baltic states. Dolomitic limestone was applied at a rate of 0, 2, 4, 6 and 8 kg m-3. Samples were taken and analyzed for pH and Electrical Conductivity and BaCl2/DTPA extractable macro and micronutrients to investigate the effect liming on the availability of these nutrients particularly calcium and magnesium. A growing trial was conducted to determine the effect of liming and peat type on Solanum lycopersicum seedling growth and on micro and macro nutrients concentration of the plants as affected by peat type and lime rate. In addition we determined lignin and humic acid in a limited number of peats to investigate if these two parameters, lignin and humic acid were correlated with the pH regression slope obtained from lime application The regression line of the lime response was not similar, steeper with the lighter peats and less steep with the darker peats indicating that to get a pre-determined level of pH of darker peats a higher rate of lime would need to be added. The regression line (b) of Ca and Mg response to lime application did not vary greatly between the peats. However with some of the darker peats the initial levels of extractable Ca was as high as or higher than what one would get after applying 4 kg m-3 of lime in lighter peat. Increasing rates of lime increased the dry weight of the plants in the lighter peats. With some of the darker peats there was no positive response to lime and in fact a negative response at the higher levels of lime indicating that not only target pH should be taken into account regarding liming rate but also extractable Ca needs to be taken into consideration. Ca/B ratio went to very high levels indicating a possible B deficiency in these peats. In conclusion with more darker peats coming into the market from all over Europe with probability some having high levels extractable Ca, a pH response curve for determining lime rates would not be adequate as it could lead to poor plant growth. In such cases a BaCl2/DTPA extractable Ca analysis is warranted.