BARLEY NUTRIENT-UPTAKE, ROOT-GROWTH AND DEPTH DISTRIBUTION IN 2 SOIL TYPES IN A RHIZOTRON WITH VERTICAL AND HORIZONTAL MINIRHIZOTRONS

Barley was cultivated in a rhizotron with 1-m-deep windows facing a sa ndy or clayey soil. The plants were irrigated/fertilized at 3-day inte rvals, to minimize water and nutrient constraints for the crop. Vertic al minirhizotron tubes were installed in both soil types, and horizont al tubes were installed at three depths in the sandy soil. Roots were counted (minirhizotrons) and their total length was measured (rhizotro n windows) seven and ten times, respectively, during the growing seaso n. Soil moisture was monitored from the minirhizotrons using a capacit ance method. At harvest, above-ground parts were cut, and roots were s ampled by soil coring and biomass, root length and contents of N, P an d K were measured. The soils were sampled for mineral N and water-solu ble P and K before and after the growing season. Total crop dry mass a t harvest in the sand was similar to that in the clay, but the crop gr own on sand contained more N and P than the crop grown on clay. In the soil cores, root biomass did not differ between soil types, but root length was higher in the sand. Root numbers, root length and mean dept h were greater in the sand than in the clay when observed with vertica l minirhizotrons or rhizotron windows. The reasons for these differenc es are discussed in relation to soil water and soil nutrient condition s. The apparent vertical distribution of roots differed greatly depend ing on the method used, being deepest for the vertical tubes and shall owest for soil cores. The causes for these differences are discussed b riefly.