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