Determination of the water supply available in soils for crops is important for both the calculation of water balance and the prediction of water stress. An approach to calculations of available water content in layers of the root zone, depletion of water during growth, and water balance, with limited access to data on farms, is presented. Soil water retention was calculated with simple pedotransfer functions from the texture of soil layers, root depth, and depletion function were derived from observed data; and the potential evapotranspiration was calculated from the temperature. A comparison of the calculated and experimental soil water contents showed a reasonable fit.

In a three-year experiment (2019–2021), the roots of 7-year-old apple trees (Malus domestica cv. ‘Red Jonaprince’) grown under drip irrigation were studied. The aim of the study was to determine the effect of irrigation on root density at different depths and distances from the trunk. The working hypothesis assumed that irrigation significantly affects the total length of apple roots. The irrigation treatments corresponding to the calculated water evapotranspiration (ET100), 50% of the calculated ET (ET50), a control (ET0, no irrigation, under rainfed conditions), and a treatment using double-drip lines (2Drops) were monitored. Soil cores were collected in spring and autumn. The total length of the roots (TRLt) and the length of new vital roots (TRLv) to a depth of 80 cm were evaluated. The effects of treatments were mostly insignificant for the TRLt; only in the dry season in 2019 were the TRLt values of the irrigated treatments (ET50 and ET100) significantly higher, 18.67 km·m⁻² and 17.45 km·m⁻², in comparison to 11.16 km·m⁻² for the ET0, at a 10 cm distance from the tree trunk. The irrigation treatments had a statistically significant effect on the TRLv values near the trunk in 2019 and 2020, while in autumn 2020 and 2021, irrigation significantly affected the TRLv at greater distances from the tree trunk. In summary, the irrigation treatments mostly had no significant effect on the total root length. However, an effect of irrigation on the root length of new vital roots was observed at certain sampling dates and distances from the trunk.

The purpose of this study was to determine the effect of sixty years of contrasting fertilization treatments on the roots of winter wheat (Triticum aestivum L.) at sites with different soil and climate conditions. The depth and length density distribution of the wheat roots were determined between 2014 and 2016 in a crop rotation experiment established in 1955 at three sites: Lukavec, Čáslav, and Ivanovice (Czech Republic). Three fertilization treatments were examined: Zero fertilization (N0), organic (ORG) fertilization, and mineral (MIN) fertilization. The fertilization, site, and year all had a significant effect on the total root length (TRL). The average TRL per square meter reached 30.2, 37.0, and 46.1 km with the N0, ORG, and MIN treatments at Lukavec, respectively, which was the site with the lightest soil and the coldest climate. At Čáslav and Ivanovice (warmer sites with silt and loamy soils), the average TRL per square meter reached 41.2, 42.4, and 47.7 km at Čáslav and 49.2, 55.3, and 62.9 km at Ivanovice with the N0, MIN, and ORG treatments, respectively. The effect of fertilization on the effective root depth (EfRD), the depth at which the root length density dropped below 2.0 cm cm⁻³, was significant, while the maximum root depth (RMD) was only marginally affected. With the sites and years averaged, the MIN-treated plants showed a greater EfRD (102.2 cm) in comparison to the N0 (81.8 cm) and ORG (93.5 cm) treatments. The N0 treatment showed no signs of an adaptive reaction to the root system, with potential improvement for nutrient acquisition, while optimal fertilization contributed to the potential for resource depletion from the soil profile.

Knowledge of the spatial variability of soil hydraulic properties is important for many reasons, e.g., for soil erosion protection, or the assessment of surface and subsurface runoff. Nowadays, precision agriculture is gaining importance for which knowledge of soil hydraulic properties is essential, especially when it comes to the optimization of nitrogen fertilization. The present work aimed to exploit the ability of vegetation cover to identify the spatial variability of soil hydraulic properties through the expression of water stress. The assessment of the spatial distribution of saturated soil hydraulic conductivity ($K_s$) and field water capacity ($FWC$) was based on a combination of ground-based measurements and thermal and hyperspectral airborne imaging data. The crop water stress index (CWSI) was used as an indicator of crop water stress to assess the hydraulic properties of the soil. Supplementary vegetation indices were used. The support vector regression (SVR) method was used to estimate soil hydraulic properties from aerial data. Data analysis showed that the approach estimated $K_s$ with good results (R${}^2$ = 0.77) for stands with developed crop water stress. The regression coefficient values for estimation of $FWC$ for topsoil (0–0.3 m) ranged from R${}^2$ = 0.38 to R${}^2$ = 0.99. The differences within the study sites of the $FWC$ estimations were higher for the subsoil layer (0.3–0.6 m). R${}^2$ values ranged from 0.12 to 0.99. Several factors affect the quality of the soil hydraulic features estimation, such as crop water stress development, condition of the crops, period and time of imaging, etc. The above approach is useful for practical applications for its relative simplicity, especially in precision agriculture.

The suitability of two exponential distribution functions for the description of winter wheat root length distribution in a soil profile was examined. The impact of use of both the observed and fitted distribution functions as input parameters for simulation of wheat growth with the Crop Environment Resource Synthesis-Wheat crop model was determined. The fit between the observed and root distribution predicted with exponential functions was significant in all cases (R² > 0.79, p < 0.01); in 8 of the 12 cases the fit was tight (R² > 0.9). The simulation of the wheat crop growth was performed with 20 years’ daily meteorological data for clay-loam and loamy-sand soils. The impacts of using the observed or fitted exponential root distributions on growth and root distribution simulated with the crop model was negligible in those cases with a fit over about R² > 0.9. In two cases with the worst fit (R² = 0.79 and 0.82), the available water was reduced especially in sandy-loam soil, on average of years by 15 mm. On average, wheat yields decreased by 304 and 60 kg ha⁻¹ for sandy-loam and clay-loam soils when the fitted exponential distributions were used compared with the observed ones.