Importance of P uptake efficiency versus P utilization for wheat yield in acid and calcareous soils in Mexico

There are large agricultural areas in the world where wheat yields are limited by low phosphorus (P) availability. Breeding for P uptake and P utilization efficiency may reduce this problem. This study was conducted to determine the contribution of P uptake and utilization efficiency to grain yield of selected spring wheat genotypes in different environments. Thirty-eight semidwarf spring bread wheat (Triticum aestivum) genotypes were grown in two experiments in Mexico, each on an acid Andisol under rainfed conditions and on a calcareous Aridisol with irrigation, without (- P) and with 35 kg P per ha fertilized (+ P). Without P fertilization, grain yield ranged from 0.8 to 4.6 t ha(-1) in the acid soil and from 2.3 to 5.2 t ha(-1) in the calcareous soil. With P fertilization, this range was even larger. Under conditions of P deficiency, i.e. in the acid soil at - P and (P thigh P adsorption) and calcareous soil at - P (P-depleted soil), P uptake explained 71-100% of the variation in grain yield, and was highly correlated with grain yield (r = 0.79-0.95). In contrast, at + P in the calcareous soil, P utilization efficiency explained 60-63% of the variation in grain yield. Here, low grain P concentration was related to high grain yield (r = - 0.40 to - 0.59). In the calcareous soil, the harvest index was correlated with grain yield, irrespective of the P level. In the acid soil, post-anthesis P accumulation was important. It was positively correlated with grain yield, whereas in the calcareous soil, no post-anthesis-P accumulation occurred. Here, grain P accumulation at maturity was completely determined by translocation of pre-anthesis shoot P. We conclude that the combination of improved P uptake and P utilization efficiency in the same genotypes requires selection under both high and low-P conditions. (C) 2001 Elsevier Science B.V. All rights reserved.