Periodical changes in soil reaction due to incorporation of green manure to a degraded tea soil of the mid-country of Sri Lanka

Abstract

Some of the lands under tea in the mid-country of Sri Lanka were abandoned since three decades as marginaUdegraded lands due to their poor performances. Soil acidity has been identified as a decisive factor for low soil fertility. For reclamation of such lands, application of liming is frequently advocated. However, as much of these lands are allocated to poor settlers , the procedure of liming is less appropriate.

This study has attempted to evaluate the effect of green manures in reducing the acidity of a degraded tea soil in view of reducing the cost of liming. A pot incubation experiment was conducted by treating the soil separately with Cao, Ipil-Ipil (Leucaena /eucocepha/a) , Gliricidia (Gltricidia sepium) and WiJdsunflower (Tithonia diversifolia) green manure at a rate representing 5 t ha -1. The duration of the incubation was 12 weeks and soil samples were drawn at 1Sl, 2nd, 3rd, 4th ,8th and 12th week sub~uent to incorporation of materials.The samples were checked for pH. W- and Al +- saturations as well as pH buffering fluctuations.

Based on the results it could be concluded that the green manures used have made a significant contribution in reducing the acidity of the soil including the Al3+-saturation. However, there were hardly differences between the green manures. No change was recorded pertaining to the pH buffering behavior of the soil as well. The overall effect in increasing the pH by green manure was around 1 unit where as the effect by Cao was 1.6 units. Hence there is a possibility of partial substitution of liming materials with appropriate green manures. It is useful to study the effectiveness of such combinations in the future.