Zinc reactions and availability in soil
The requirement of zinc (Zn) for normal plant growth was first recognized in the late nineteenth century, but acceptance of this element as an essential plant nutrient did not occur until the early 1930s. Since then, Zn deficiency has been identified throughout the world on numerous crops grown on widely varying soils under a variety of management practices. Many soils contain appreciable amounts of Zn that plants are unable to utilize. The addition of Zn compounds to soils can also prove to be of limited benefit, as most of the Zn becomes "fixed" by soil components. The mechanisms responsible for Zn "fixation" or "release" have not been fully elucidated. An understanding of the controls on the concentration of Zn in soil solutions is of great significance to the art of maintaining and improving the fertility of soils, and is of rapidly growing importance in understanding the development of Zn deficiency in plants. Certainly a better understanding of soil Zn chemistry and availability, and plant-soil relations will help improve agronomic practices for efficient crop production. With a better understanding of the Zn-deficiency problem in crops in mind, a project has been undertaken on 'zinc reactions and availability in soil'. The work in the project concentrates mainly on evaluation of zinc extractants, identification of soil variables responsible for Zn unavailability, mechanisms involved in Zn fixation at elevated pH and response of barley to Zn and Cu application.