MODELING THE WATER BALANCE COMPONENTS OF THE SOYBEAN CANOPY BY SOIL-VEGETATIONATMOSPHERE TRANSFER MODEL - Soybean and Wheat Crops: Growth, Fertilization, and Yield - page 41

soil water extraction occur in the top 0.61 m to 0.91 m of the soil profile. Irrigation water
should thus be limited to a 0.91 m penetration depth to avoid leaching nitrates into the local
aquifer [1-4].
Figure 1. Soybean field at Rimski Sancevi (Serbia) [5].
1.2. Modeling Soybean Water Balance
The soybean water balance and its components can be considered and modeled for
different purposes. For example, CROPGRO is a process-oriented model that simulates a crop
carbon balance, a crop and soil water balance, and a crop and soil nitrogen balance. State
variables are the amounts, masses and numbers of tissues, and rate variables are the rates of
inputs transformations and losses from state variables [6,7]. This model as a stand alone, in
modified versions, can be used for (i) determining the productivity levels, potential yields,
yield gaps [8], (ii) simulating soybean growth in controlled environments [9], (iii) simulating
phasic temperature and photo period control for soybean [10], etc.
Water balance components and related hydrological variables of the soybean field can be
simulated by a Soil-Vegetation-Atmosphere Transfer (SVAT) model that is forced by the
products of RegCM (Regional Climate Model) for both present and future (warm-up)
conditions. This is important for the projection of the climate change impact on the regional
hydrological cycle that is a basis to start the discussion on the vulnerability of agricultural
production system and to see the performance and usefulness of the RegCM products. While
changes in atmospheric composition are expected to exert an increasing radiative forcing of