Variation in nitrogen, sulfur, selenium, cobalt, manganese, copper and zinc contents of grain from wheat and two lupin species grown in a range of Mediterranean environments

Abstract

Grains of Lupinus angustifolius, Lupinus albus and Triticum aestivum were sampled from 23 sites selected on the basis of three major rainfall categories (annual average greater than 450 mm; 325- 450 mm; less than 325 mm), and four soil types (infertile sands, sandy loams, sand over clay, and alkaline). The variation in concentrations of most nutrients were as great within rainfall or soil categories as between these categories, although selenium concentrations tended to be lower in grain from the highest rainfall zone. Lupin seed contained higher concentrations of nitrogen, sulfur, selenium, copper and zinc than wheat. The concentration of manganese varied between species and sites, with L. albus containing levels of up to 2000 ¦g/g at several sites. There was a positive correlation between manganese and cobalt concentrations in grain of L. angustifolius and L. albus at sites where manganese concentrations were above 50 and 500 ¦g/g respectively. The grain of L. angustifolius contained significantly lower concentrations of nitrogen, manganese, cobalt and copper than did L. albus, although there were considerable site differences. Nitrogen/sulfur ratios were wider in lupins (24/l for L. albus and 20.5/l for L. angustifolius) than in wheat grain (15.4/l). The ratios showed up to twofold range over all sites, which suggests that limitations in sulfur supply occurred at sites with a wide ratio. The concentrations of selenium, copper, zinc and cobalt were below the recommended dietary allowance for livestock at many sites, while the manganese concentrations in white lupin at several sites were at potentially toxic levels for animals. The nitrogen/sulfur ratio of grain was also outside the optimum for protein utilization by livestock. These findings highlight the need for some form of trace element and protein monitoring to avoid potential deficiency and toxicity problems in livestock consuming the grain.