Abstract
Plant species differ in their ability to grow at low available P soils in other words, plant species differ in P use efficiency at low P supply. This ability can be investigated by comparing P uptake efficiency of plants and relative effective factors. A pot experiment was carried out in the growth chamber and sugar beet, maize and groundnut were grown in a low available P soil in a completely randomized design with three P fertilizer levels of low, medium and high. Three harvests were performed at two different growth periods. The results showed that at low P supply, sugar beet was the most efficient plant among three species as it showed the highest relative yield. The higher P use efficiency of sugar beet was due to a higher P uptake efficiency. Phosphorus uptake for sugar beet was 29 mg P plant-1 while those for maize and groundnut were 19 and 0.8 mg P plant-1, respectively. The main reason for higher P uptake efficiency of sugar beet was its higher P influx as compared to maize and groundnut. Under low P supply during the first growing period, P influx of sugar beet was higher than that of maize and groundnut by factor 4 and 22, respectively. Finally, the higher P use efficiency of sugar beet was due to a higher P uptake efficiency which in turn was due to a high P influx.

Keywords: Phosphorus efficiency, Phosphorus influx, Sugar beet, Corn, Groundnut