ROOT-ZONE TEMPERATURE AND CALCIUM EFFECTS ON PHOSPHORUS, SULFUR, AND MICRONUTRIENTS IN WINTER-WHEAT FORAGE

An understanding of how environmental factors can alter accumulation o f nutrients by plants is needed to anticipate and prevent mineral defi ciencies in both plants and grazing animals. To determine the effects of root zone temperature (RZT) and Ca level on mineral concentrations of winter wheat (Triticum aestivum L.), 'Centurk' seedlings were grown under three RZT regimes (constant 8 degrees C, constant 16 degrees C, and transferral from 8 degrees C after 23 d to 16 degrees C) and four Ca levels (0.2, 0.6, 2.0, and 5.0 mM) in nutrient solution. Plants gr own at 8 degrees C RZT had significantly lower shoot and root concentr ations and unit absorption rates of P, S, Cn, Zn, and Mn than did thos e grown at 16 degrees C. Within 2 wk after transfer from 8 degrees C t o 16 degrees C RZT, concentrations of P, S, Cu, Zn, and Mn in shoots a nd roots increased significantly. Increasing Ca levels in solution sig nificantly increased shoot and root concentrations and unit absorption rates of P and Cu. In contrast, increasing Ca levels significantly de creased concentrations and unit absorption rates of Mn and Zn. Thus, a suboptimal RZT could depress accumulation of P, S, Cu, Zn, and Mn by winter wheat forage, and possibly induce mineral deficiencies in both plants and grazing animals. A high solution Ca level could partially a meliorate this adverse effect on P and Cu accumulation by wheat, but i t also could exacerbate the problem of low Mn and Zn concentrations at a cool RZT.