Calcium Requirement in the Background Nutrient Solution on Growth of Wheat Plants Using the Relative Addition Rate Technique

Abstract

The growth of a cultivar of wheat (Triticum aestivum L.), “Atlas 66,” was studied under conditions of low background nutrient concentrations and a daily nutrient-addition rate controlled by a computer program. Different calcium (Ca) concentrations were supplied by a daily delivery stock solution and by a background nutrient solution. When Ca was supplied by a delivery solution, plant mass production increased as Ca concentrations increased, but the rate of plant growth was lower than the theoretical production. In addition, solution pH decreased and electrical conductivity (EC) increased over time. On the other hand, when Ca was supplied as a background solution, plant growth was similar to theoretical production at a Ca concentration ranging from 100 to 800 μM. In this range, solution pH increased, but solution EC remained stable over time. Calcium supply only by a delivery stock solution was found to be inadequate to support optimal growth of wheat plants. However an initial nutrient solution constituted only by Ca (100 to 200 μM) plus daily delivery nutrient additions at 0.20 day^{− 1} was demonstrated to be a good protocol for wheat. The culture solution EC was low and constant over the experimental period, simulating natural soil-solution concentrations.