Phosphorus (P) Uptake Mechanisms of Crops Grown in Soils with Low P Status : I. Screening of Crops for Efficient P Uptake

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Phosphorus (P) uptake by pot-grown plants of buckwheat (Fagopyrum esculentum Moench.), castor (Ricinus communis L.), cotton (Gossypium spp.), groundnut(Arachis hypogaea L.), maize (Zea mays L.), pigeonpea (Cajanus cajan L.), rice (Oryza sativa L.), sorghum (Sorghum bicolor L.), soybean (Glycine max L.), and sunflower (Helianthus annuus L.) was examined. Two kinds of Andosols (Minori, Kawatabi) and a red-yellow soil (Taketoyo) were used. In all the soils the content of available P was very low, and most of inorganic P was either iron (Fe)- or aluminum (Al)-bound. Phosphorus uptake by rice, pigeonpea, and groundnut was much higher than that by other crops. Upland rice took up more P than other crops especially in the Kawatabi soil (high humic non-allophanic Andosol). Such a high P uptake ability in rice plant was presumably associated with its tolerance to Al. Exchangeable Al concentration decreased after liming of Kawatabi soil, and P uptake by groundnut and pigeonpea was markedly enhanced. The results suggest that pigeonpea, groundnut, and rice can take up Fe- or Al-bound P. The superior P uptake ability of pigeonpea and rice was confirmed in another experiment in which vermiculite treated with FePO_4 or AlPO_4 was used as the potting medium.