Abstract
Extensive livestock production in Mediterranean climate conditions and acidic soils requires animal feed supplementation. This occurs during the summer and, frequently, also in the autumn and winter, depending on the prevailing rainfall patterns. The purpose of this study was to evaluate the effect of dolomitic limestone application and of tree canopy on availability, quality, and floristic composition of a permanent pasture, grazed by sheep. At the end of autumn, winter, and spring of 2018/2019 and 2019/2020 pasture green and dry matter production (GM and DM, respectively), crude protein (CP), and fiber (neutral detergent fiber) were monitored in 24 sampling points. Half of these points were located in areas amended with dolomitic limestone (COR) and half in unamended areas (UCOR). In each of these, half of the sampling points were located under tree canopy (UTC) and half outside tree canopy (OTC). Pasture floristic composition was monitored in spring 2020. The results show, in autumn, a positive and significant effect (i) of soil pH amendment on pasture DM and CP daily growth rate (kg·ha−1·day−1) (+28.8% and +42.6%, respectively), and (ii) of tree canopy on pasture CP daily growth rate (+26.4%). Both factors affect pasture floristic composition. Pasture species were identified as potential bio-indicators, characteristic of each field area. These results show the practical interest of the soil pH correction to reduce the animal supplementation needs in the critical autumn period in the Mediterranean montado ecosystem.
Highlights
Montado is an agro-silvo-pastoral ecosystem characteristic of the southern region of the Iberian Peninsula [1], with an important role in natural resource conservation and carbon sequestration, reducing soil erosion, and mitigating the effects of climate change [2]
Taking as reference the soil data obtained in October 2015 and in March 2020 (Table 1), there was a slight increase in pH. This improvement in pH was significantly more evident, as expected, in the areas where the dolomitic limestone was applied and accentuates the pattern of improvement that the October 2018 results evidenced. These results show that the surface application of amendments has a slow positive effect on the soil pH
Apart from the two aforementioned species (Erodium botrys and Hordeum murinum), two other species, Avena barbata (25.6 ± 31.5% in COR areas and 16.7 ± 23.9% in UCOR areas) and Geranium molle, are prevalent in under tree canopy (UTC) areas, only in uncorrected areas (17.8 ± 18.1%). These results show that vegetation cover is clearly higher in outside tree canopy (OTC) areas than in UTC areas, but very similar in COR areas and UCOR areas (Figure 9a)
Summary
Montado (dehesa in Spain) is an agro-silvo-pastoral ecosystem characteristic of the southern region of the Iberian Peninsula [1], with an important role in natural resource conservation and carbon sequestration, reducing soil erosion, and mitigating the effects of climate change [2]. In this ecosystem, pasture, considered a low-cost feed [3], is the main food resource for extensive livestock production [4]. The Mediterranean climate is a bioclimatic variant of the temperate climate with a marked seasonal and inter-annual variability, characterized by winter cold stress and summer drought stress. Ruminants that depend solely on natural pasture start the grazing period with forage of high quality (low levels of fiber and high levels of protein), but after the blooming period and the peak biomass production in late spring, there is a sharp drop in pasture quality associated with a decrease of the pasture feed value (reduction in the proportion of leaves and high tissue lignification) which may lead to the worsening of the animal’s corporal condition [5]
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