Selection for phosphorus efficiency in corn

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Abstract
A total of 73 USA corn (Zea mays L.) inbreds and hybrids were grown in the greenhouse for 2-4 wk in low and high available P nutrient solutions and soils to select for P efficiency based on yield differences in a low available P medium. Variation in growth in the low P medium was partially explained by differences in early growth vigor (especially when inbreds and hybrids were compared in the same trial), but not by any apparent differences in P absorption characteristics. Hybrids (17) with high yields in the adequate P medium and contrasting yields in the low P cultures were grown to maturity in a very low available P (5 ppm Bray 1) Berks soil (a Typic Dystrochrept) in the field with and without added fertilizer P but with other nutrients and lime adequately supplied to both treatments. The relative growth rate of these hybrids in a low P medium in the greenhouse was not correlated with their yield in the low available P soils in the field. This may be due to the relatively small differences in yield in the low P soil in the field and the strong influence of seedling vigor on early growth in the greenhouse. Screening corn for P efficiency in the field is much more likely to succeed than short term greenhouse screenings. Seven corn lines from Colombia and Mexico were also tested in the field for relative P efficiency. One of these (''La Posta'', from Mexico) appeared to be superior to any of the other USA or Latin American corn lines in its ability to absorb P from the soil.