Modeling N-response of field vegetable crops grown under diverse conditions with N_ABLE: A review

The development of advice on the use of nitrogen (N) fertilizers for vegetable crops in the UK is complicated by the numerous crops and the widely different ways in which they are grown. Modeling approaches have been adopted to provide cost effective means of solving the problem. It is based on fundamentally derived equations for groups of processes that dominate plant nutrition. The equations include ones for the decline in critical %N with increase in plant mass, for the dependence of growth rate on sub-optimal %N, and for the development of roots systems and their ability to extract nitrate from soil. They have been combined with those for soil processes into a model, N_ABLE, which calculates daily increments in N-uptake, growth, changes in the distributions of water and nitrate down the soil profile and the amounts of N leached out of the profile. It requires only readily available inputs; it has been calibrated for different crops and its validity tested against the results of field experiments. User-friendly versions have had an impact on commercial practices in the UK. An internet version enables simulations to be made for 22 different crops, grown on different soils, using either a user's own daily weather or best estimates of daily weather for any of 134 sites throughout the world. The model runs interactively at: http://www.qpais.co. uk/nable/nitrogen.htm.