Soil acidity challenges and the significance of liming and organic amendments in tropical agricultural lands with reference to Ethiopia

摘要

Globally, about 30% of the ice-free land, comprising large proportion of agricultural land, is affected by soil acidity which is potentially limiting agricultural productivity and causing environmental challenges. On the other hand, it is well documented that liming can curb the situation and boost agricultural production when appropriately applied. However, it is not well understood why the tendency of farmers toward liming is generally poor in tropical smallholder farming systems. Thus, this review is aimed to critically evaluate the effect of liming on crop yield, analyze the significance of organic amendment as an alternative to liming to treat acid soils and identify the socioeconomic challenges obstructing the implementation of soil acidity treatment. With this review, the possible link of land management and soil acidity is also evaluated to showcase if approaches to any other land management could have negative or positive effects on soil acidity. To understand the effect of management on soil acidity, a logistic regression was run using soil data from the Harmonized World Soil Database, taking soil organic carbon (SOC) as an explanatory variable and pH as a dependent variable. With this review, studies from science, socioeconomics and policy focusing on soil acidity and its management were assessed. The literature showed liming can increase crop yield up to 0.5 t ha~(-1). The regression analysis to support this review also revealed a positive relationship between SOC and pH, implying the strong effect of land management on soil acidity. This further reveals that a bad management of soil organic matter can lead to an exacerbation of soil acidity. In other words, effective soil acidity management in the region requires an integrated approach that involves combined application of organic amendments, liming and applying optimum inorganic fertilizers. In short, the principle of integrated soil fertility management can be applicable to mitigate soil acidity problems in the region. This, however, needs to be complemented with improved policies that incorporate effective incentive mechanisms.