A Study of the Effect of Rhizosphere on the Availability of N, P, K, Zn, Cu, Fe and Mn in Soil

A pot culture experiment was conducted to study the effect of rhizosphere on the availability of plant nutrients in two soils having high organic matter and low available Zn content. Barley plants were grown to study the rhizosphere effect in soils amended with supplemental Zn, or unamended. Nutrients were analyzed in the inner rhizosphere (soil adhering to root surface), outer rhizosphere (immediateiy adjacent soil) and non-rhizosphere (plant tree soil) at three plant growth stages (tillering, booting and maturity). As plants matured, the concentrations of N, P, K, Fe, Mn and Cu declined in both inner and outer rhizosphere soils but not in the non-rhizosphere. In contrast, the concentration of Zn increased in rhizosphere soils as plants matured. The pH of rhizosphere soil increased with time while that of non-rhizosphere soil decreased. The crop yield (dry malter, grain and straw) did not respond to Zn addition, suggesting that the soils were not deficient in Zn. The result indicates that Zn concentration may increase in barley rhizosphere.