In all the soils types of the world a phosphate deficiency was observed, especially in the poorly countries, where the fertilisation level are inadequate. On the other hand, in one of the rich countries the phosphate level in soils are much more than it is necessary for the crops needs, so the environment is polluted. The crops dependence on the soil’s phosphate level in the soils and plants growth interaction is materialized. To these, a predictive model is necessary, model in which the essential processes of plants growth being presented in equations form. One of these models is the PHOSMOD model. This model was developed by Greenwood et al. (2001a), mainly for vegetable crops. After some adjustments, the model is able to reproduce the observed responses to band placed P and starter fertilizer in plant dry matter, and to predict differences between soil types in the responses to applied fertilizer. The model calculates the effects of soil phosphates, starter fertiliser phosphates and granular fertiliser phosphates on daily crop growth, phosphates concentration in the plants, and the changes in the different forms of soil phosphates. It is considered that the fertilisers are applied immediately after the seeding and the phosphate from the soil is represented by the interaction between the soil type and their evolution. All others nutrient, including N and K, it is considered that are in sufficient quantities for the maximal plant growth. The phosphate transport in soils is by diffusion and takes account of soil type, buffer capacity and soil water content. Mass flow transport is ignored. The interchange between solution, labile and non-labile forms of phosphate are recalculated for each day in the phosphate depleted regions around each segment of root and in the fertilised and unfertilised regions of soil into which no roots have penetrated.

phosphates accessibility; fertiliser; daily crop growth

Presentation: oral