Effects of Leonardite Amendments on Vineyard Calcareous Soil Fertility, Vine Nutrition and Grape Quality

Abstract

Vineyard calcareous soils are usually low in organic matter, which makes them prone to physical, chemical, and biological degradation. Besides, these soils are also usually poor in various nutrients in plant-available form, e.g., iron. To make up for this lack of soil fertility, on the one hand, manures, and on the other, iron chelates are usually used. However, the soil application of these materials is not free from problems, and other amendments based on leonardites could be advantageously used as an alternative. Therefore, two organic amendments, one leonardite alone (1 Mg/ha), and the other leonardite (1 Mg/ha) plus ferrous sulphate heptahydrate (0.5 Mg/ha), were tested for three years in a commercial vineyard calcareous plot under Mediterranean climate. The effects of these amendments on soil fertility, plant nutrient contents, and berry quality were studied against a control of bare soil by means of a fully randomized trial with three repetitions per treatment. Soil organic matter (SOM) increased as a consequence of both leonardite treatments, but much more than expected on the basis of a simple mass transfer from the amendments. With the ferrous-sulphate-heptahydrate-supplemented leonardite, the increase in SOM was noticeably higher. This is explained on the basis of nutrient quantity and intensity-pH-related effects, which increased soil nutrient plant-availability and presumably enhanced vine root growth. In response to the higher plant availability of nutrients, the petiole nutrient concentrations were observed to increase under the leonardite treatments. However, only a trend to increase potassium in petioles and in grape must, linked to a decrease of grape must pH, was observed in harvest quality under the leonardite treatments. Leonardite and adequately supplemented leonardite seem to have potential for increasing SOM contents and nutrient plant-availability, thus improving the soil fertility of vineyard calcareous soils.

Effects of Citric Acid and Humic-like Substances on Yield, Enzyme Activities, and Expression of Genes Involved in Iron Uptake in Tomato Plants

“…Applications of humic acid purified from leonardite increased plasma membrane H + -ATPase activity in cucumber roots and shoots [54,55]. This contrasts with what was found in the present study, where a reduction in tomato root tissue H + -ATPase activity via HLS was documented; the reduction was probably derived from the promotion of soluble complexes that allowed Fe to exist in a bioavailable form in the soil [23,48] or via the acidifying effect of HLS [56]. This may also have been due to feedback control mechanisms and the concentration of NO 3 − in the medium [55].…”

“…In addition, CA can reduce abiotic stress resulting from phosphorus deficiency in plants grown in calcareous soils [45][46][47]. Likewise, it has been described that the use of humic substances in calcareous soils promotes nutrient bioavailability by generating soluble complexes with minerals [23,48] and increasing nutrient uptake [40,41], and that their combination with chelate Fe (Fe-EDDHA) can increase the yield and nutrient content of plants [49].…”

“…In our study, we found repression of LeFRO1 at 49 and 84 DAT (Figure 2c) in tomato roots with HLS application. This suggests that HLS enhances Fe bioavailability in addition to procuring soluble complexes in calcareous soil [23,48]. In the case of CA, its endogenous variations in tomato plants could be involved in the regulation of nuclear target gene expression [72].…”

“…Citric acid improves Fe bioavailability by converting Fe to its plant-available form [22]. Similarly, the application of leonardite plus ferrous sulfate heptahydrate was found to improve the fertility of calcareous vineyard soils by increasing their Fe content [23]. The application of Fe complexed with extractable humic substances in water and Fe-citrate led to the overexpression of FRO, IRT1, and NRAMP in cucumber [24] as well as a modulation of the transcripts of the gene encoding H + -ATPase in tomato [25].…”

Deep incorporation of organic amendments into soils of a ‘Calardis Musqué’ vineyard: effects on greenhouse gas emissions, vine vigor, and grape quality

“…Despite the differences in pH we observed between the three experimental variants being significant, the fluctuations in pH between the four seasons examined were much stronger, which actually was the case for all investigated leaf and berry traits of this study. Several published works regarding the effects of OA on different grapevine parameters confirm our observations, that seasonal variations were in some cases much more pronounced than the influence of amendment incorporation on the assessed traits ( Chan and Fahey, 2011 ; Mugnai et al., 2012 ; Schmidt et al., 2014 ; Genesio et al., 2015 ; Olego et al., 2022 ).…”