Abstract
The large variation in phosphorus acquisition efficiency of different crops provides opportunities for screening crop species that perform well on low phosphorus (P) soil. To explain the differences in P efficiency of winter maize (Zea mays L.), wheat (Triticum aestivum L.), and chickpea (Cicer arietinum L.), a green house pot experiment was conducted by using P‐deficient Typic ustochrept loamy sand soil (0.5 M NaHCO3‐extractable P 4.9 mg kg−1, pH 7.5, and organic carbon 2.7 g kg−1) treated with 0, 30, and 60 mg P kg−1 soil. Under P deficiency conditions, winter maize produced 76% of its maximum shoot dry weight (SDW) with 0.2% P in shoot, whereas chickpea and wheat produced about 30% of their maximum SDW with more than 0.25% P in shoot. Root length (RL) of winter maize, wheat, and chickpea were 83, 48, and 19% of their maximum RL, respectively. Considering relative shoot yield as a measure of efficiency, winter maize was more P efficient than wheat and chickpea. Winter maize had lower RL/SDW ratio than that of wheat, but it was more P efficient because it could maintain 2.2 times higher P influx even under P deficiency conditions. In addition, winter maize had low internal P requirement and 3.3 times higher shoot demand (i.e., higher amount of shoot produced per cm of root per second). Even though chickpea had 1.2 times higher P influx than winter maize, it was less P efficient because of few roots (i.e., less RL per unit SDW). Nutrient uptake model (NST 3.0) calculations satisfactorily predicted P influxes by all the three crops under sufficient P supply conditions (CLi 48 µM), and the calculated values of P influx were 81–99% of the measured values. However, in no‐P treatment (CLi 3.9 µM), under prediction of measured P influx indicated the importance of root exudates and/or mycorrhizae that increase P solubility in the rhizosphere. Sensitivity analysis showed that in low P soils, the initial soil solution P concentration (CLi) was the most sensitive factor controlling P influx in all the three crops.