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We established a greenhouse study on five different Venezuelan soils to evaluate the external phosphorus (P) requirement of cowpea (Vigna unguiculata var. Tuy). The external requirement for the various soils was almost identical (approximately 1.00 μg/ml) and independent of edaphic factors, such as texture and mineralogy. The values differ greatly from those previously reported for the same species growing in a high P-fixing Hawaiian soil. We propose that pot effect, variety differences, and the presence (or absence) of my-corrhizal associations influence the differences between these external P requirements.

This paper reports the results of studies concerning phosphate sorption variability. Two kinds of soil populations were studied, a large soil population that includes most of the orders of Soil Taxonomy(British and tropical soils), and a less diverse collection of soil samples corresponding to four different soils series (three from Britain and one from Malaysia)