THE EXTERNAL PHOSPHATE REQUIREMENT OFCOWPEA ON FIVE DISSIMILAR SOILS

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.