Phosphorus and nitrogen fertiliser use efficiency of wheat seedlings grown in soils from contrasting tillage systems

Abstract

Aims: This paper assessed the effect that the vertical stratification of nutrients in conservation cropping systems of Australia has on phosphorus (P) and nitrogen (N) fertiliser use efficiency. Methods: Intact soil cores from two long-term tillage experiments, located on a Vertosol and on a Calcarosol were used to assess if tillage system (zero tillage - ZT vs conventional tillage - CT) and soil water influence fertiliser use efficiency (using 33P and 15N) of wheat under controlled growth conditions. Results: Adding P increased shoot growth and P uptake on the Calcarosol, provided the surface remained moist and N was applied. The percentage of plant P derived from fertiliser (Pdff) was greater on the Calcarosol regardless of tillage practice. Pdff increased when the soil remained wet or when N was added. The percentage of N derived from fertiliser (%Ndff) was not affected by tillage practice on the Vertosol but when the soil surface was allowed to dry, it was significantly greater under ZT than CT on the Calcarosol. Adding P increased N fertiliser recovery but tillage practice had no effect. Conclusion: The effect of tillage practice on P and N fertiliser use efficiency depends on soil and topsoil water status.