Role of cultivars and grass in the stability of soil moisture and temperature in an organic vineyard

Abstract

[Abstract:] Soil water content (SWC) and temperature (ST) are main parameters in agriculture, but are difficult to predict due to the numerous processes involved. To find stability patterns, this study evaluated the soil hydro-thermic response in a rainfed organic vineyard with humid climate, a permanent grass cover and under no-tillage and homogeneous soil and topographic conditions. The differences between the rows (R) and inter-row areas (IR) and two cultivars (Agudelo –Ag– and Blanco Legítimo –BL–) were assessed. SWC and ST were measured with 12 probes every 15 min at 5, 15 and 25 cm depth over the crop cycle (242 days). On average, wetter (+2.2%) and cooler (−1.4%) values appeared in Ag than in BL that may be associated with differences in vine water demand. IR had wetter (+5.9%) and cooler (−0.7%) conditions than R due to higher water consumption by vines. Significant differences appeared when time-series analysis was split into three periods: drying and warming (spring), dry and warm (summer), and wetting and cooling (autumn). SWC and ST correlated well in R, but moderate correlations appeared in IR, showing a more complex pattern in this zone. In general, the most stable conditions appeared at 15 cm depth, with drier and warmer conditions in the deepest layer in spring and autumn. This vertical pattern did not vary over time for ST, but IR had the most stable and moistest conditions in summer at 25 cm. The relative differences among zones and cultivars revealed that Ag had moister, but less representative, conditions than BL at the three soil layers in spring, and this pattern kept in summer at 15 and 25 cm, but only in autumn at 15 cm. Regarding ST, the pattern was very stable, and cooler and representative conditions prevailed in Ag. BL has been rarely cited in the literature, and these results contributed with new insights about the SWC and ST dynamic on this cultivar. Cooler conditions always appeared in IR, compared with R; and R always had more representative values of SWC than IR. The pattern of ST was more variable and R only had more representative values than IR at 15 cm in summer and at 25 cm in spring and summer. This article represents the first study that calculated the index of temporal stability (ITS) for SWC and ST in any type of woody crop. Our findings allowed to identify the most representative areas of the hydro-thermic response of the soil in the vineyard, which is of interest to save time and resources during long-term monitoring tasks in commercial vineyards.