Godsteven Maro^1,, Suzana Mbwambo¹, Epafra Mosi¹

Three lime requirement algorithms were calibrated against the standard lime incubation in the acid coffee soils of Tanzania using three topsoil samples from Masama Sawe (Hai District), Mfiriga (Njombe Rural District) and Msia (Mbozi District), all of pH<5.0. A total of 54 dishes (500g) were arranged in split plot RCD with three replications in the screenhouse. Main factors were locations, while sub-factors were different dosages (0, 0.023, 0.045, 0.091, 0.227 and 0.454 g) of pure CaCO₃ equivalent to 0, 0.5, 1.0, 2.0, 5.0 and 10.0 tons CaCO₃ per ha. These were mixed with 100g of soil per dish and incubated for six weeks at room temperature and near field capacity. At the end of week 1, 2, 4 and 6, 10g of each was mixed with 25ml of distilled water, shaken for 30 minutes in an end-to-end shaker and the pH of the soil (1:2.5) was read. The amount of CaCO₃ added was then plotted against pH, and a LR determined graphically. Three liming algorithms were suggested for sandy loam, loam and clay soils that use ΔpH (target pH – initial pH; the former set at 5.5) and percent organic matter. They were validated using a separate database and compared against similar algorithms developed in Brazil, Nigeria and China. The results suggest the Brazilian algorithm LR = 0.0699*(ΔpH*OM)^0.9225, being closest to the incubation algorithms, to be tentatively adopted in Tanzania, pending further validation. The discussion touches the concerns about acidity and liming in Tanzania, alternatives available, and a potentially lucrative lime industry based on locally available lime deposits.

Acid coffee soils, calibration, lime estimation, Tanzania