Fructan to nitrogen ratio as an indicator of nutrient stress in wheat crops

Abstract

Wheat stems serve as a store for fructans to buffer the plant against nutritional and environmental influences. It has been suggested that fructan storage influences yield stability and tolerance of environmental factors. Near infra-red spectroscopy (NIR) analysis provides a rapid and accurate assessment of the fructan content of the wheat stem, as well as allowing detection of growth-limiting nutrient stresses, and so is proving to be a useful technique for making crop management decisions. Commercial laboratories using NIR analysis have been tissue-testing crops in the eastern Australian wheat belt since 1993. In healthy, normally developing crops not under stress there is a predictable relationship between nitrogen and fructan. Investigation of the nitrogen and fructan concentrations in commercial crops has confirmed an inverse relationship between these two constituents. The function: Fructan (%)=a+bN%+cN%² accounted for up to 81% of variation in tissue fructan concentration. In commercial tissue-testing this relationship is used to detect crops under stresses other than nitrogen deficiency. If the fructan concentration deviates by more than 4%, cereal growers are advised that their crop might be subject to other stresses which might reduce its response to applied nitrogen.