Prediction of effects of nitrogen management on barley quality for malting

Consistent high quality barley (Hordeum vulgare L.) for malting is difficult to achieve in high fertility sites and on soils with low water holding capacity. Poor quality grain may result from excessive nitrogen (N) uptake and consequently high amounts of N translocated to the grain, or incomplete filling of kernels in drought situations, especially on light soils. A mechanistic model which has the capacity to predict grain quality variables such as grain N concentration and grain size was validated with a field experiment. The validation crop was grown in the North Island of New Zealand under four N management treatments without irrigation and compared with a simulated crop for growth responses. Dry matter (total and grain) yield and crop N uptake agreed closely with the simulation results. There was also close agreement between the simulated and the observed variables for grain characteristics, although prediction of grain N concentration was higher than the observed values across the range of N treatments. The model sensitivity for grain N and grain size was evaluated over an extended range of N applications and for variable soil moisture conditions simulated by calculated deviations from long term mean rainfall. These simulations provided guidelines for improved N management during the growing season to achieve more consistent grain quality.