Linking liming and soil nutrients availability: bridging the gap on knowledge of the effect of liquid liming agents as soil pH correction tools for improved yields and quality of flue-cured tobacco in Malawi
Malawi soils are highly weathered and acidic resulting in fixation of Phosphorus (P), Potassium (K) and Nitrogen (N) into insoluble forms with iron (Fe) and aluminium (Al) which are inaccessible by plants. Soil pH correction through liming to neutralise acidity to amenable levels for plant growth is an important cultural practice for improved productivity. But currently, the standard cumbersome method of ploughing and immediately manually applying of dry-calcitic-lime at two tons/ha as a blanket recommendation nine months before transplanting poses implementation challenges amongst resource challenged small-holder farmers who channel all their energies to current crop rather than the future one. With unavailability of tractors in such small-holdings, liming is almost non-existent. The adoption rate of liming is 2% this affects productivity per unit area. As a mitigation measure targeting small-holder farmers, two liquid-liming agents, MAG-LIME-FLO and CAL-LIME-FLO, with two controls: the standard dry-calcitic practice and plot with no lime, were investigated for their efficiency in correcting pH, improving nutrient availability, on increasing yields and quality in a trial laid out in randomised complete block with six replications. Data collection was on pH at transplanting, 6, 10, 14 weeks after transplanting and assessed for yield and quality. The results showed that liquid-limes started correcting pH as early as six weeks after transplanting with MAG-LIME-FLO and CAL-LIME-FLO increasing soil pH by 15% at six weeks and by 25% five months later. Liquid-limes increased P availability by 70%, K by 56%, Ca by 79% and Mg by 77%. Liquid-limes had 94% yield advantage over non-limed plots and significantly outperformed the dry-calcitic-lime by 50%. Handling costs showed that liquid-limes had reduced application and transportation costs of 70% over dry-calcitic-lime. These findings are of significant benefit to Malawi small-holder farmers who are yet to embrace pH correction initiatives through liming as an integral part of good agricultural practices.