Nitrogen and phosphorus accumulation and remobilization of durum wheat as affected by soil gravel content

Soil gravel content affects many soil physical properties, as well as crop yield. Little is known regarding the influence of soil gravel content on growth and nutrient uptake of durum wheat (Triticum durum Desf.). The accumulation of nitrogen and phosphorous during the vegetative and reproductive periods and the contribution of pre-anthesis assimilates to grain N and P con- tent have been evaluated in two durum wheat varieties grown on soils with 0, 10, 20 and 30% gravel content. The two varieties showed similar behaviour and the increase of soil gravel de- creased plant biomass during the entire biological cycle. Nitrogen and P concentration of all plant parts was not affected by soil gravel content, while N and P content was greatly reduced, owing to the effect on dry matter yield. Post-anthesis accumulation and remobilization of N and P were greatly reduced: the decrease from gravel-free soil to 30% gravel content was about 41 kg N ha–1 and 4 kg P ha–1 for the former and 14 kg N ha–1 and 2 kg P ha–1 for the latter. The differences in growth rate were attributed to differences in development of the root system due to the restricted soil volume.