The 13C Discrimination of Crops Identifies Soil Spatial Variability Related to Water Shortage Vulnerability

Abstract

Spatial variability of crop growth and yields is the result of many interacting factors. The contribution of the factors to variable yields is often difficult to separate. This work studied the relationships between the 13C discrimination (Δ13C) of plants and the spatial variability of field soil conditions related to impacts of water shortage on crop yield. The 13C discrimination, the indicator of water shortage in plants, 15N (δ15N) discrimination, and nitrogen (N) content were determined in grains of winter wheat, spring barley, and pea. The traits were observed at several dozens of grid spots in seven fields situated in two regions with different soil and climate conditions between the years 2017 and 2019. The principles of precision agriculture were implemented in some of the studied fields and years by variable rate nitrogen fertilization. The Δ13C significantly correlated with grain yields (correlation coefficient from 0.66 to 0.94), with the exception of data from the wetter year 2019 at the site with higher soil water capacity. The effect of drought was demonstrated by statistically significant relationships between Δ13C in dry years and soil water capacity (r from 0.46 to 0.97). The significant correlations between Δ13C and N content of seeds and soil water capacity agreed with the expected impact of water shortage on plants. The 13C discrimination of crop seeds was confirmed as a reliable indicator of soil spatial variability related to water shortage. Stronger relationships were found in variably fertilized areas.

Identification of Infiltration Features and Hydraulic Properties of Soils Based on Crop Water Stress Derived from Remotely Sensed Data

“…This resolution is probably sufficient for soil assessment in most cases. On the other hand, as shown by Haberle et al [27,28], soil properties can change suddenly within units of meters. In this perspective, UAV technology with a very high resolution appears to be potentially applicable in practice.…”

“…extreme values) for a relatively small FWC range (see Figure 4a), [88]). As shown by Haberle et al [28] for the lower Jizera river area, soil vulnerability to leaching given by texture (loamy-sand and sandy-loam soil) and the resulting low water capacity is amplified by high spatial variability of soil properties, which is often manifested visually by water stress impacts, when non-irrigated crops are grown in the area.…”

“…The texture ranged from loam to sandy loam and sandy soil with skeletons, especially in the subsoil. The spatial variability of soil types corresponds to the great variability of the moisture-holding capacity of the topsoil and subsoil [28]. The two experimental sites near the villages Sojovice (three field blocks) and Kochánky in the lower Jizera River region were monitored (Figure 1).…”

“…The use of irrigation systems that mask the hydropedological properties of soils is problematic in this regard; see, for example, the Sojovice locality (see Table 3). The reason for the worse FWC estimate in the topsoil layer in Kochánky was probably a sudden spatial change (in the order of 1-2 m; see [28]) of soil hydraulic properties and thus the impact of water stress on vegetation. The effects of drought here were mainly influenced by subsoil, as confirmed by the high R 2 values (see Table 4 and Figure 6b)).…”

“…This approach assumes a continuous change in soil properties between points. Haberle et al [27,28] show that soil properties can change abruptly, and consequently, the use of interpolation methods provides results with limited accuracy. A suitable approach for assessing soil hydraulic properties is offered by remote sensing (RS), which has considerable potential, especially for precision agriculture and, by extension, for protecting surface waters from eutrophication [29,30].…”