Relationships between leaf water potential and soil water potential in grasses subjected to water stress

Abstract

For grasses and other crops in general, soil water potential has been widely studied to determine if there is a deficit or excess of water content in the soil. However, the plant water absorption process is not only modulated by soil water potential but also by the combination of meteorological, soil depth, and crop canopy factors, which could be elucidated through water relations responses. The objective of this work was to compare the water relations of grass species established in different soil depths and subjected to water stress. Santo Agostinho (Stenotaphrum secundatum), Esmeralda (Zoysia japonica), Tanzania (Panicum maximum) and Tifton 85 (Cynodon spp.) were used in this trial. The four species of grasses were tested in four different soil rooting depths: 10, 20, 30 and 40 cm. The grasses were irrigated at soil moisture field capacity level, until the time of imposing the water stress period. Soil depth had a direct influence on leaf water potential and soil water potential. Moreover, correlation coefficients are higher in deeper soil profiles. The strongest correlations between leaf water potential and soil water potential were found in the deeper soil depth treatments. Therefore, for the soil depth treatment of 40 cm, the average R² for the four species was 0.55, the highest being 0.70 in Tanzania grass. It is possible to relate leaf water potential and soil water potential independently of the grass species used or the depth of soil available to the roots, which would allow the creation of new irrigation management strategies.

Yield and quality responses of Megathyrsus maximus and Cynodon spp. forage grasses to irrigation

“…The experiments were carried out in a rain out shelter at the University of São Paulo, Brazil (22°46'39"S, 47°17'45"W, altitude of 570 m). The rain out shelter had 160 m² of internal area, and 48 pots with a volume of 0.1 m³ and dimensions of 0.60 × 0.40 × 0.45 m were used (Tapparo et al, 2019;Chaves et al, 2021;Almeida et al, 2022;Tapparo et al, 2022).…”

“…The use of transparent film prevented compression and allowed integration of an area of approximately 0.06 m 2 . It was much faster and easier to mark the average height on the film than to measure a sufficient number of points to reach the same average height (Tapparo et al, 2019;Tapparo et al, 2022). For dry matter (DM) determinations, aboveground biomass was obtained within an area of 0.24 m², dried for 48 h at 65 °C, and weighed.…”

“…When the irrigation depth is calculated using data collected from only one rotational grazing plot (reference plot), one can underestimate or overestimate the water consumption of pastures that present a leaf area index (LAI) different from the reference plot (Tapparo et al, 2022). The application of incorrect irrigation depth can increase the operational cost of the system, reduce the net revenue, and influence the quality of the grasses (Tapparo et al, 2019;Liao et al, 2021).…”