Abstract:
Soil acidity is the major soil chemical constraints which limit agricultural productivity in the highlands of Ethiopia receiving high rainfall. This study was conducted to evaluate the effect of different lime application methods and different lime rate determination methods on selected soil chemical properties and yield of maize (Zea mays L.) on acidic Nitisols of Mecha woreda, Amhara Region in 2018 cropping season. The experiment had 10 treatments (0, 0.06, 0.12, 0.18, 1, 2, 3.5, 4, 7 and 14 tons ha-1 lime) which were calculated based on 3 different LR determination methods. The first four rates (0, 0.06, 0.12 and 0.18 tons ha-1) were added directly as micro-dosing. The next 3 rates (1, 2 and 4 tons ha-1) were calculated based on exchangeable acidity method and the remaining 3 rates (3.5, 7 and 14 tons ha-1) were calculated based on SMP-pH-buffer. A randomized complete block design (RCBD) with four replications was used for the experiment. The rate of N and P2O5 were 180 and 138 kg ha-1, respectively. Full dose of P-fertilizer and lime as a treatment were applied at planting. Whereas, N was applied in split, 1/2 at planting and 1/2 at knee height stage. Before planting, one composite soil sample was taken to determine the required lime rate and to know previous soil history. Post-harvest soil samples were also taken from each experimental unit to examine the effect of lime after application. Liming showed a positive significant difference on pH-H2O, pH-buffer, CEC and exchangeable bases but it had an inverse and significant effect on exchangeable acidity. Soil pH-H2O and pH-buffer showed a significant positive correlation with each other (r=0.75). Both pH-H2O and pH-buffer showed significant but negative correlations with exchangeable acidity (r=-0.78 and r=-0.77, respectively). Based on developed lime recommendation equations, the amount of calculated lime showed a decreasing trend with increasing of soil pH-H2O and pH-buffer values. But, the calculated lime amount showed an increasing trend with increase of soil exchangeable acidity. Only maize grain and above ground biomass yields showed a significant difference among treatments due to liming. The minimum (6479.1 kg ha-1) and maximum (7719.1 kg ha-1) grain yield values were recorded at the control (no lime) and treatment that received 4 tons ha-1 lime, respectively. An acceptable economical profit were found on the micro-dosing level treatment which received 0.12 tons ha-1 lime with net benefits of 60,897.6 Birr due to low total variable cost. Therefore, farmers who afford to apply much amount of lime, it is recommended to add 3.5 tons ha-1 lime in drilling application method. But, application of the micro-dosing level of 0.12 tons ha-1 lime is acceptable rate for small scale farmer.
Keywords: Lime, maize, pH-H2O, pH- buffer, Exchangeable acidity