Abstract
Soil acidity and phosphorus (P) deficiency are some of the major causes of low maize yields in Kenya. Although considerable work has been done to establish liming rates for acid soils in many parts of the world, information on the effects of the lime-Al-P interactions on maize growth and yield is limiting. A green house pot experiment was conducted at Waruhiu Farmers Training Centre, Githunguri to evaluate the effects of lime-Al-P interactions on maize growth and yield in acid soils of the Kenya highlands. Extremely acidic (pH 4.48) and strongly acidic (pH 4.59) soils were used for the study. Four lime (CaO) rates and phosphorus (Ca (H2PO4)2 rates were used. The liming rates were: 0, 2.2, 5.2 and 7.4 tonnes ha-1 for extremely acidic soil and 0, 1.4, 3.2, and 4.5 tonnes ha-1 for the strongly acidic soil. Phosphorus applications rates were: 0, 0.15, 0.30 and 0.59 mg P kg-1 soil for the extremely acidic soil and 0, 0.13, 0.26, and 0.51 mg P kg-1 for strongly acidic soil. The experiments were a 42 factorial laid down in a Randomized Complete Block Design (RCBD) and replicated three times. Data collected included: plant height, number of leaves, P-uptake and maize dry matter yield. Lime-Al-P interaction significantly (P≤ 0.05) increased P concentrations in maize tissues, maize height, dry matter yields. Use of 7.4 tonnes ha-1 in extremely acidic soils and 4.5 tonnes ha-1 in strongly acidic soils significantly (P≤ 0.05) increased maize height compared to lower lime rates. Phosphorus uptake and dry matter yields did not however, vary when 7.4 tonnes ha-1 lime was combined with either 0.59 mg P kg-1 or 0.3 mg P kg-1 in extremely acidic soils, and 4.5 tonnes ha-1 was combined with either 0.51 mg P kg-1 or 0.26 mg P kg-1 in strongly acidic soils. It was, therefore, concluded that lime and P positively interact to reduce Aluminium toxicity in the soils and improve maize growth, P uptake and yields in acid soils in the Kenya highlands. However, further research is required to evaluate long term effects of the interactions on crop yields, uptake of plant nutrients under field conditions.
Highlights
In highly weathered, acid soils around the world, P, Ca, and Mg deficiencies and aluminum (Al) and manganese (Mn) toxicities are the most important nutritional and/or element disorders that limit crop yields [1,2]
Aluminium toxicity can interfere with active ion uptake processes across the root-cell plasma membrane [7]
Liming rates were chosen to obtain 0, 30, 70 or 100% reduction in amounts of M KCl-extractable Al originally present in the soil while the phosphorus levels added were: 0, 0.5, 1 or 2 times the standard phosphorus requirement (SPR) of the tested soils (Table 1)
Summary
Acid soils around the world, P, Ca, and Mg deficiencies and aluminum (Al) and manganese (Mn) toxicities are the most important nutritional and/or element disorders that limit crop yields [1,2]. Phosphorus deficiency in such soils is attributed to adsorption of P by Al/Fe oxides and hydroxides, such as gibbsite, hematite, and goethite [3]. Aluminium toxicity can interfere with active ion uptake processes across the root-cell plasma membrane [7]
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