The importance of environmental factors in soil fertility assessments. II.* Nutrient concentration and uptake

Abstract

Lettuce plants were grown in two soils under a wide range of controlled conditions in the glasshouse. Assessments were made of the effect of soil temperature, incident light and season, in terms of the nutrient concentration and nutrient uptake in the plant tissue, which was analysed for nitrogen, phosphorus, potassium, magnesium, calcium and sodium. Both the concentration and the uptake of each nutrient were affected significantly by soil temperature and incident light, both between and within seasons. The type of soil had an effect on these estimations, but its significance could not be tested statistically. A considerable number of first and second order interactions between components of the physical environment affected the quantities being examined. These interactions were statistically significant. The value of each nutrient analysed, which is an aspect of plant performance, reflected changes in the physical environment independently of the other nutrients. Often a particular nutrient showed no coincident pattern of responses to the environment when these were measured in terms of dry weight, nutrient concentration in the tissue, or total nutrient uptake. Each nutrient concentration and each nutrient uptake varied as micrometeorological factors in the glasshouse changed. Hence, ambiguous assessments of soil fertility were obtained with all measured plant responses. ____________________ *Part I, Aust. J. Agric. Res., 25: 299 (1974).