| One solution to the correction of P problems in agricultural soils is to identify, select, breed and develop plant species or cultivars which produce well on soils considered to be low in available P or which efficiently use applied P fertilizer.; A series of greenhouse experiments using a Tilsit silt loam (mixed, mesic, Typic Fragiudult) were conducted to investigate the response of winter wheat cultivars to different P sources and the interactive effects of P source, N nutrition, and soil acidity; and to try to identify possible mechanisms responsible for cultivar response differences.; In general, it was observed that dry matter (DM) and P uptake (PUP) of the wheat cultivars were positively correlated with greater P source solubility and NH{dollar}sb4sp+{dollar}-N nutrition. Ammoniacal-N sources improved P availability from phosphate rock (PR) sources and were associated with higher root length density (RLD), higher root cation exchange capacity (RCEC), and lower soil pH. Cultivar response differences in DM and PUP existed especially with limed and unfumigated soil. Such differences, however, tended to be larger with the more soluble P source, DCP, suggesting that the wheat cultivars were not as responsive when P availability (solubility) was lower. Lack of cultivar differences in DM and PUP under moderately acidic to neutral soil conditions indicates that differences in P absorption were not brought about by differences in Al tolerance among the wheat cultivars. The greater cultivar differences found with unfumigated soil suggests that soilborne factors, such as rhizosphere microbial activity, might have played a role in the expression of those differences. |
