Influence of a grass layer on vineyard soil temperature

Abstract

Vineyard grass cover can modify soil variables such as temperature and water content, which in turn influence berry quality at harvest. Such effects require further documentation and this study was conducted to determine how a grass layer could change soil thermal behaviour compared to bare soil. Soil temperature, soil water content and net radiation were measured in a Médoc vineyard, Château Talbot (France). The field used for the experiment was divided into two parts, one with a bare ploughed soil and the other with a partial grass cover. The same measurements were taken on both parts. Bare soil temperatures were generally higher, and the difference between the two treatments was greater in the middle of the inter-row, just under the grass layer. Nevertheless, net radiation above the vegetation, which represents the radiative available energy, was the same for the two plots. Soil conduction heat flux (G) was calculated from temperature measurements. Under the grass layer, the horizontal component of G was barely detectable, whereas under bare soil, G was essentially vertical. The grass layer was therefore acting as an insulating layer, preventing exchanges between soil and atmosphere. Soil temperature and thermal behaviour are heavily influenced by soil surface management practices. The field experiment provided a large data set of measurements which will be used to calibrate a heat and mass transfer model.