1. Ae N, Arihara J, Okada K (1991) Phosphorus uptake mechanisms of pigeon pea grown in alfisols and vertisols. In: Johansen C, Lee KK, Sahrawat KL (eds), Phosphorus Nutrition in Grain Legumes in the Semi-arid Tropics. ICRISAT, Patancheru, pp 91–98
2. Amtmann A, Hammond JP, Armengaud P, White PJ (2006) Nutrient sensing and signalling in plants: potassium and phosphorus. Adv Bot Res 43: 209–257
3. Anderson G (1980) Assessing organic phosphorus in soils. In: Khasawneh, FE, Sample EC, Kamprath EJ (eds), The Role of Phosphorus in Agriculture. ASA/CSSA/SSSA, Madison, WI, pp 263–310
4. Asmar F (1997) Variation in activity of root extracellular phytase between genotypes of barley. Plant Soil 195: 61–64
5. Asmar F, Gahoonia TS, Nielsen NE (1995) Barley genotypes differ in activity of soluble extracellular phosphatase and depletion of organic phosphorus in the rhizosphere soil. Plant Soil 172: 117–122