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

Authors: MIYASAKA, SUSAN - UNIVERSITY OF HAWAII; Grunes, David

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/27/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary: Phosphorus, sulfur, zinc, copper, manganese, and iron can limit plant growth, and some of these elements may also be low in forages for grazing cattle or sheep. Winter wheat forage is grazed by beef cattle in many parts of the U.S., such as Kansas, Oklahoma, Texas, and Missouri, and also in other parts of the world. Often these forages are grazed in the spring and dfall when the air and the root zone temperature (RZT) are fairly cool. The purposes of this study were to determine the effects of Ca level, and RZT on the concentrations of the above-named elements in winter wheat forage. Winter wheat forages were grown in solution culture at four levels of Ca, and at RZTs of 8 deg. C or 16 deg. C, or of changing from 8 to 16 deg. C. It was found that plants grown at 16 deg. C RZT had higher concentrations of phosphorus, sulfur, zinc, copper, manganese, and iron in the edible portions of the plants than those grown at 8 deg. RZT. When the temperature ewas changed from 8 to 16 deg. C RZT, the concentrations of these elements in the plants generally approached those in plants grown constantly at 16 deg. C RZT. Therefore, one would expect to more frequently see plant nutrient deficiencies of these elements at cool temperatures than at warmer temperatures. The same is true of deficiencies of these elements in animals grazing winter wheat forages. The level of calcium in the nutrient solution sometimes increased and sometimes decreased the concentrations of these elements in the winter wheat forage. These findings are expected to contribute to reductions in the incidence of mineral nutrition deficiencies in both plants and animals.

Technical Abstract: An understanding of the environmental factors that play a major role in altering the accumulation of nutrient elements by plants is needed to prevent nutrient deficiencies in plants, animals, and humans. To determine the effects of increased root zone temperature (RZT) and four calcium (Ca) levels on the forage quality of winter wheat (Triticum aestivum L. 'Centurk'), seedlings were grown under three RZT regimes (constant 8 deg. C, constant 16 deg. C, and increasing from 8 deg. to 16 deg. C). The plants were grown in nutrient solutions, with four Ca levels (0.2, 0.6, 2.0 and 5.0 mM). Plants grown at 16 deg. C RZT had significantly higher concentrations of phosphorus (P), sulfur (S), zinc (Zn), copper (Cu) and manganese (Mn) in both the shoots and roots compared to those grown at 8 deg. C. Plants transferred from 8 deg. C to 16 deg. C RZT showed significantly increased concentrations of P, S, Zn, Cu, and Mn in both the shoots and roots within two weeks after transfer to the higher RZT. Simila results were found for iron (Fe) concentrations in the shoots. Increasing Ca levels in solution significantly increased P and Cu concentrations in the shoots and roots, but significantly decreased Zn and Mn concentrations. Thus, RZT and solution Ca levels are two environmental factors that can alter nutrient accumulation by plants, affecting both plant growth and forage quality.