The soil is the natural habitat of cultivated plants. It is where they take root and mainly derive water and nutrients from. When the soil is frozen, the soil water containing nutrients for the plants also remains frozen.
Applying fertilisers to frozen soil is pointless, as the plant will not be able to take them up. Plant protection products applied while the soil remains frozen also remain on the soil surface. During thawing, there is a high risk of fertilisers and plant protection products running off with surface run-off into depressions in the ground or beyond the field and crop they were intended to fertilise or protect. This is a major financial loss and a significant environmental risk.
During the period when the soil remains flooded, there is a so-called free water table on the soil surface. The application of any chemicals during this period results in excessive dilution of the active substance on the one hand, and high losses on the other, whether through surface run-off or ground run-off. The application of any chemicals to the field surface, as well as organic fertilisers, during these periods remains ineffective for the crop, economically unjustified and environmentally damaging.
Detailed guidelines for fertiliser application on flooded and frozen soils can be found in the Code of Good Agricultural Practice.