Long-Term Water Balance of Selected Field Crops in Different Agricultural Regions of the Czech Republic Using Fao-56 and Soil Hydrological Approaches

Long-term water balance (WB) of four selected crops (winter wheat, oilseed rape, silage maize, semi-early potatoes) was determined at the field block scale in the Czech Republic for all agricultural growing areas (AGAs): maize-, beet-, potato- and mountain-AGAs for the 1981–2010 period. A novel approach for the calculation of WB was employed, which combined the FAO-56 method for crop water requirements (CWRs) with sources of available water from precipitation, soil, and groundwater. The computed WB was divided into four categories of soil water availability based on soil hydrolimits and crop features: Categories 1 and 2 with zero or mild occurrence of crop water stress; categories 3 and 4 with intermediate and severe occurrence of crop water stress. The winter crops were affected by water stress to a lesser extent (the area of categories 3 and 4: wheat 20.1%, oilseed rape 14.5%) as compared with spring crops (the area of categories 3 and 4: maize 39.6%, potatoes 41%). The highest water deficit was recorded for all crops in the maize-AGA due to low precipitation and high CWRs. Most available water was revealed to occur in the mountain-AGA. A strong need for the adoption of measures towards the optimization of water regimes on agricultural land was indicated. The present study shows a promising approach for evaluating and proposing changes of area of cultivated crops with the appropriate tillage and agricultural water management in terms of satisfactory crop water requirements.