The importance of environmental factors in soil fertility assessments. I. Dry matter production

Abstract

The importance of environmental factors on assessments of soil fertility was examined by means of pot experiments in the glasshouse. A preliminary experiment showed, over the course of 12 months of testing, that the fertility ratio varied with the season. In the main experiment each of two soils received nine chemical treatments in an omission-type experimental design. All chemical treatments were subjected to three different light regimes obtained by shading and to three soil temperatures. They were repeated at three different seasons of the year. Plants growing under acute mineral deficiency responded to changes in the environmental conditions and the deficiency became less acute the more the physical conditions favoured plant growth. Changes in environmental conditions were able to eliminate a marginal deficiency of plant nutrient. Because the results show many first and second order interactions between root temperature, light intensity and season, and because of the different yield responses to these factors for different soils and for different nutrients, an assessment of fertility by means of fertility ratios under one set of pot culture conditions cannot easily be applied to other situations.