Effect of Soil Acidity Factors on Yields and Foliar Composition of Tropical Root Crops

Abstract

Tropical root crops, a major source of food for subsistence farmers, varied in their sensitivity to soil acidity factors. Tolerance to soil acidity is an important characteristic of crops for the humid tropics where soils are often very acid and lime‐scarce and expensive. Experiments on two Ultisols and an Oxisol showed that three tropical root crops differed markedly in sensitivity to soil acidity factors. Yams (Dioscorea alata L.) were very sensitive to soil acidity with yields on a Ultisol decreasing from 70% of maximum when Al saturation of the effective cation exchange capacity of the soil was 10 to 25% of maximum when Al saturation was 40%. On the other hand, Cassava (Manihot esculenta Crantz) was very tolerant to high levels of soil acidity, yielding about 85% of maximum with 60% Al saturation. Taniers (Xanthosoma sp.) were intermediate between yams and cassava in their tolerance to soil acidity yielding about 60% of maximum with 50% Al saturation of the soil. Foliar composition of cassava was not affected by soil acidity levels and that of yams and taniers was also unaffected except for Ca content which decreased with decreasing soil pH and increasing Al saturation. Response of these tropical root crops to soil acidity components was far more striking on Ultisols than on the Oxisol. For yams, soils should be limed to about pH 5.5 with essentially no exchangeable Al3+ present whereas high yields of taniers can be obtained at about pH 4.8 with 20% exchangeable Al3+ and of cassava at pH as low as 4.5 with 60% exchangeable Al3+.

Aluminium release from acidic forest soil following deforestation and maize cultivation in Ghana, West Africa

“…Nevertheless, the ability for maize plants to be influenced by Al toxicity is quite possible due to progressive acidification and Al sat of 20-56% within Maize N (30-60 cm, Fig. 1C) and since yield reduction have been reported when Al Sat is > 30% in the surface soil (Abruña-Rodriguez et al, 1982;Marschner, 1995;Ritchie, 1989).…”

“…Examples are agro-forestry, rotational cropping or ground cover planting in combination with perennial pastures (Cregan, Hirth & Conyers, 1989). Cultivation of native species that are tolerant to Al toxicity and soil acidity is also another intervention (Abruña-Rodriguez et al, 1982;Marschner, 1995).…”

“…The physiological effects of Al toxicity at elevated Al 3+ concentrations include restricted growth of roots and stems leading to increased susceptibility to drought and decreased use of subsoil nutrients (Foy et al, 1993) and, in turn, reduced yields of agricultural crops (Collet et al, 2002;Marschner, 1995;Parker et al, 1990;Moustakas et al, 1992). A large difference exists between various plants in their tolerance to acidity and Al toxicity but generally tropical crop species are adapted to elevated Al concentrations in contrast to maize, soybeans and wheat (Abruña-Rodriguez et al, 1982;Marschner, 1995).…”

Ameliorating Effects of Leucaena Biochar on Soil Acidity and Exchangeable Ions

“…In acidic soils, crop productivity is mostly constrained by aluminum (Al) and iron (Fe) toxicity, phosphorus (P) deficiency and other acidity-related soil fertility and plant nutritional problems (Patiram, 1991;Manoj-Kumar et al, 2012). In most situations, poor crop growth in acid soils can be correlated directly with aluminum (Al) saturation (Sartain and Kamprath 1977;Abruna-Rodriguez et al 1982). Although liming of acid soils can ameliorate soil acidity, this is neither an economic option for poor farmers nor an effective strategy for alleviating subsoil acidity.…”