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.

Fluctuations in precipitation and higher evapotranspiration due to rising temperatures are reflected in reduced wheat yields, even in areas with a low historical incidence of drought. In this study, the effects of drought (S) and irrigation (IR) on spelt, einkorn wheat, and two common wheat cultivars were assessed in a field experiment in the years 2018–2021. Water availability was differentiated from the flowering stage using a mobile cover and drip irrigation. Grain yield, canopy temperature, and discrimination of ¹³C in grain (Δ ¹³C) were monitored. Drought reduced the average grain yield of common wheat to 5.24 t.ha⁻¹, which was 67.00% of the rain-fed control (C) yield, and 62.09% of the irrigated wheat yield. For spelt and einkorn wheat, the average grain yield from stressed plants was 2.02 t.ha⁻¹; this was 79.97% of the C-variant yield, and 70.82% of the IR-variant yield. Higher stand temperatures were an excellent indicator of water deficit in the stressed crops. The relationship between temperature and final grain yield in the monitored variants was always negative. In all years, discrimination of ¹³C in grain corresponded to water availability; in its effect on yields, the correlation was always positive. Between 2018 and 2020, spelt and einkorn exhibited lower Δ ¹³C in comparison with common wheat in all variants, suggesting a greater impact of differentiated water supply. The results of the experiment conclusively demonstrated systematic effects of drought after flowering upon yields and other studied characteristics.

The carbon (C) fixed by crops, which is exported with harvest and retained as postharvest residues in a field, is important for calculating the C balance. The aim of this study was to determine the effect of water availability on the C content in whole wheat plants. In a three-year field trial, the weights of grain, straw, chaff, stubble, and roots of two cultivars of winter wheat (Triticum aestivum L.) and one cultivar of einkorn wheat (Triticum monococcum L.) and their carbon contents were determined in water stress, irrigation, and rain-fed control treatments. The water availability, year, and cultivar had a significant influence on the C content in aboveground plant parts, but the effect of water on grain C was weak. The C content decreased with irrigation and increased with drought, but the differences were small (at most, 3.39% in chaff). On average, the C contents of grain, straw, chaff, and roots reached 45.0, 45.7, 42.6, and 34.9%, respectively. The amount of C exported with grain and left on the field in the form of postharvest residues depended on the weight of the total biomass and the ratio of grain to straw and residue. Whole plant C yield reached 8.99, 7.46, and 9.65 t ha⁻¹ in rain-fed control, stressed, and irrigated treatments, respectively, and 8.91, 9.45, and 7.47 t ha⁻¹ in Artix, Butterfly, and Rumona, respectively. Irrigation significantly increased the C content in grain and straw (but not in chaff, stubble, and roots) in comparison with water shortage conditions. On average, a grain yield of 1 t ha⁻¹ corresponded to an average export of 0.447–0.454 t C ha⁻¹ in the grain of all cultivars and inputs of 0.721, 0.832, and 2.207 t C ha⁻¹ of residue to the soil in the form of straw and postharvest residue in the two cultivars of common wheat and one of einkorn. The results of the study provided reliable data for the calculation of the C balance of wheat under conditions of different water availability.

¹³C discrimination (Δ¹³C) has been used in research as an indicator of water availability in crops; however, few data are available concerning fruit trees. The aim of this study was to examine the effect of irrigation on the Δ¹³C values of apple leaves. We assumed that Δ¹³C would increase with irrigation intensity. The Δ¹³C of apple trees (Malus domestica) cv. ‘Red Jonaprince’ was determined in the years 2019–2022. Leaf samples were collected in spring, in June, at the beginning of the irrigation campaign, and in autumn, in September, following the harvest. The irrigation doses were applied to replenish the water consumption, 0% (ET0), 50% (ET50), 75% (ET75), and 100% (ET100), of the calculated evapotranspiration (ET) levels. In November, the leaves collected from different positions on the shoots were sampled, assuming the Δ¹³C signature would reflect the changes occurring in the water supply during their growth. The irrigation rates had a significant effect on the Δ¹³C of the leaves when the data for the spring and summer months were pooled. On average, Δ¹³C increased from 20.77‰ and 20.73‰ for ET0 and ET50, respectively, to 20.80‰ and 20.95‰ for ET75 and ET100, respectively. When the data obtained for the spring and summer months were analysed separately, the effect of irrigation was weak (p < 0.043). The Δ¹³C value was always higher for treatment ET100 than treatment ET0, for individual experimental years and terms; however, the differences were minor and mostly insignificant. The leaf position had a strong significant effect on Δ¹³C; the values gradually decreased from the leaves growing from two-years-old branches (22.50‰) to the youngest leaves growing at the top of the current year’s shoots (21.07‰). This order was similar for all the experimental years. The results of the experiment suggest that ¹³C discrimination in apples is affected not only by water availability during growth, but also by the use of C absorbed in previous years.