Response of Eggplant to Integrated Approaches for Sustainable Reclamation and Improvement of a Cheringa Hot Spot of Acid Sulfate Soil

The application of basic slag (BS20 and BS30: basic slag 20 and 30 t ha-1) and aggregate size (A20 and A30: aggregate sizes of soil less than 20 and 20-30 mm) and different techniques (Tech 1: pyrite at top, jarosite at middle, and top soil at the bottom of ridge; Tech 2: top soil at top, pyrite at middle, and jarosite layer at the bottom of ridge) exerted significant (p≤0.05) positive effects on the growth and yield of eggplants cultivated under field condition and the effects varied not only with the kinds and amounts of amending materials but also with the techniques applied. The soil showed a silty clay loam texture, initial pH value of 4.1, pyrite content of 55 g kg-1, base saturation of 47%, ECe value of 3.6 dS m-1, high exchangeable Fe3+ and Al3+ contents of 1.47 and 5.29 cmolc kg-1, respectively. The pH value of the average soil data obtained from all the treatments during fruit set (95 days after transplantation) of eggplants was found to be increased in pH by 1.2 units higher compared with the control (i.e. initial pH value). The contents of P, K, Ca and Mg in the average soil data during fruit set were found to be increased (IOC = increased over control) by 41 to 127% IOC, while the contents of Al3+, Fe3+, Na+, Cl- and SO4 2- in the soil were found to be decreased by 28 to 92% IOC. The different treatments on eggplants grown under the modified-plain-ridge-ditch techniques in the Cheringa acid sulfate soil significantly (0≤0.05) increased the fresh yield of eggplants, and the increment was more pronounced with Tech 2. The maximum yield of 17.8 t ha-1 of eggplant for Tech 1 and 20.1 t ha-1 for Tech 2 were recorded by the application of BS30 in the soils of smaller aggregates (A20) at the ridges of Tech 2, followed by the A30BS30 treatments in both the techniques. The lowest quantity of 1.7 t ha-1 yield was recorded by the control treatment. The eggplants grown in the ridges of both the techniques exhibited the best responses on N, P, K, Ca and Mg contents in eggplant tissues during fruit set. As expected, the lowest contents of these nutrients in the eggplants were recorded in the control treatment. Sulfur content of the eggplants grown in the control plots was 3.6 g kg-1 and was in the range of adequate S content (4 g kg-1). However, the S contents in the eggplants grown in different treatments were significantly (p≤0.01) lower compared with the adequate level. The effectiveness of the treatments for the reclamation of the soil in relation to the growth of eggplants was: Tech 2 > Tech 1, BS30 > BS20, and A20 > A30. The results suggest that the physicochemical properties of the soil, and the growth, yield and nutrition of eggplants were strikingly improved by the application of flash leaching followed by BS30 and A20 treatments in the ridges of Tech 2, and are regarded as the best reclamation measures for this acid sulfate soil.