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Influence of Lime and Phosphorus Application Rates on Growth of Maize in an Acid Soil 时间:2017-06-15 12:42 来源:未知作者:admin 点击: 次 Abstract:The interactive effects of lime and phosphorus on maize growth in an acid soil were investigated in a greenhouse experiment. A completely randomized design with 12 treatments consisting of four lime levels, 0, 2, 10, and 20 t ha−1, in a factorial combination with three phosphorus rates, 0, 30, and 100 kg ha−1, was used. Maize was grown in pots for six weeks and its heights and dry matter yield were determined and soils were analyzed for available P and exchangeable acidity. Liming significantly reduced the exchangeable acidity in the soils. The effect of lime on available P was not significant but available P increased with increasing P rates. There was a significant effect of lime, P, and P by lime interactions on plant heights and dry matter. Without lime application, dry matter increased with increasing P rates but, with lime, dry mattes increased from 0 to 30 kg P ha−1 but declined from 30 to 100 kg P ha−1. The highest dry matter yield (13.8 g pot−1) was obtained with a combined 2 t ha−1 of lime with 30 kg P ha−1 suggesting that lime application at low rates combined with moderate amounts of P would be appropriate in this soil.
1. Introduction
The problem of acid soil infertility in the tropics has been recognized for a long time [1, 2]. In acid soils with pH < 5.5, the solubility of aluminium increases to toxic levels that severely restrict root systems and reduce plant growth [3, 4]. In addition, phosphorus reacts with iron and aluminium in soil solution under acidic conditions to form insoluble phosphates hence reducing its availability to plants [5]. Phosphorus deficiency often, therefore, occurs simultaneously with aluminium toxicity in these soils [6]. Efforts to ameliorate the deleterious effects of soil acidity must therefore be accompanied by measures to increase available phosphorus in soils.
Addition of lime to agricultural acid soils has been widely adopted as an amelioration strategy for many years as a means of improving crop production [7, 8] but is rarely used in western Kenya. Failure to use lime, together with the increased use of acidifying fertilizers such as urea and diammonium phosphate, which are used to correct N and P deficiencies, has resulted in a marked increase in acidity of many of these soils [9]. Changes in soil pH brought about by liming may have profound effects on the availability of many elements absorbed by crops. Liming increases soil pH and therefore eliminates aluminium toxicity at pH > 5.5 by precipitating Al thus making it unavailable for plant uptake [10]. It also improves Ca supply and Mo availability and ensures optimal bacterial nitrogen fixation [11]. But its effect on availability of P is controversial [12].
Conflicting reports suggest that the prior liming of highly weathered acid soils can result in an increase, a decrease, or no change in the availability of applied phosphate. These effects appear to be dependent on the rates of lime and P fertilizer applied and their interactions [13]. For example, at high lime rates, the soil pH increases to >6 and the soluble P forms a complex with Ca, and consequently P availability is decreased [14] while low lime rates are insufficient to eliminate soluble Al and Fe which fix P at low pH. Appropriate combination of lime and P is therefore an important strategy for improving crop growth in acid soils [15]. There is however paucity of information on interactive effects of lime and phosphate fertilizers on crop performance in western Kenya and this limits the ability of farmers to make informed decisions on the appropriate rates of lime and P fertilizer to be combined. The objective of this study was therefore to investigate the interactive effects of lime and phosphate fertilizer on exchangeable acidity, P availability, and maize growth in an acid soil of western Kenya.