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 limi ted by low phosphorus (P) availability. Breeding for P uptake and P utiliza tion efficiency may reduce this problem. This study was conducted to determ ine 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 tw o experiments in Mexico, each on an acid Andisol under rainfed conditions a nd 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 ca lcareous soil. With P fertilization, this range was even larger. Under cond itions of P deficiency, i.e. in the acid soil at - P and (P thigh P adsorpt ion) and calcareous soil at - P (P-depleted soil), P uptake explained 71-10 0% of the variation in grain yield, and was highly correlated with grain yi eld (r = 0.79-0.95). In contrast, at + P in the calcareous soil, P utilizat ion 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 yiel d, irrespective of the P level. In the acid soil, post-anthesis P accumulat ion was important. It was positively correlated with grain yield, whereas i n the calcareous soil, no post-anthesis-P accumulation occurred. Here, grai n 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 unde r both high and low-P conditions. (C) 2001 Elsevier Science B.V. All rights reserved.