Browsing by Author "Alhonoja, Katja"

Phosphorus (P) plays a major role in cereal production. Total P content is high in Finnish soils but only a fraction of it is available to plants. This phenomena led to generous P fertilization since 1940 increasing the P concentration in fields as well as P balances. Reduced P fertilization since 1970 has decreased soil P concentration, resulting in negative P balances almost in entire Finland. Accumulation of P in the top soil is a result of chemical reactions occurring in the soil. Reactions of P in soils and the ability of the plants to take up P from soil affects the efficiency of P fertilization. P fertilization is most effective when the application rate replaces P removed from the soil in harvested yield. In this theses, results of the long-term fertilization trial (1973-2013) are compiled. The trial included spring wheat (Triticum aestivum L.), barley (Hordeum vulgare L.) and oat (Avena sativa L.). The data gathered was analyzed to investigate crop yield, P concentration of soluble P in soil and the effect of plant species on the concentration of soluble P in soil within 40 years. Rate of P fertilization and plant species affected soluble P concentration in soil. The higher the P fertilization rate was, the higher the soluble P concentration in soil was. The concentration of soluble P did not decrease during the years when the P fertilization rate was reduced. Among all cereals studied, the P balance decreased during the years following the decrease in P fertilization rates. Changes in P balance does not explain chances in soluble P concentration in soil.