Photosynthesis and growth of young grapevines intercropped with native grasses in soils contaminated with copper
De Conti L
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High copper (Cu) contents in vineyard soils characterized by long-term use of Cu-containing fungicides may cause physiological and nutritional disorders in young grapevines, limiting plant growth and sometimes compromising plant survival. This problem is particularly evident in viticultural areas of southern Brazil. The aim of the present work was to assess if intercropping of vines with native grasses of southern Brazil can contribute to reducing phytoavailabity of soil Cu and consequently limiting the onset of toxicity symptoms (i.e. impairment of photosynthetic and growth parameters). To this purpose, a natural grassland soil of the Pampa Biome, southern Brazil, was collected, air-dried, treated to correct for acidity and P and K levels, and incubated. Three Cu levels were imposed- control (no added Cu), 40 mg Cu kg-1, and 80 mg Cu kg-1. Such Cu concentrations occur frequently in vineyard soils of the region. The experimental design was completely randomized with three replications. At each Cu level, we carried out the combination of a single crop (grapevine), a consortium with Paspalum plicatulum (grapevine + Paspalum plicatulum) and another one with Axonopus affinis (grapevine + Axonopus affinis). In the consortium treatments, two grass seedlings were transplanted into each experimental unit, 35 days before transplanting the vines. The experiment was conducted for 70 days. At 41 days after transplanting the plants, gas exchange (IRGA) was measured. At 70 days, plant height and total dry matter production were determined and the growth rate was quantified. Copper caused phytotoxicity in the grapevine-only crop, evidenced by the reduction of the photosynthetic rate, plant height and total dry matter production. The cultivation of grapevines intercropped with grasses favored the growth of the grapevines in the control soil as well as in Cu-contaminated soils with plants showing increased photosynthetic rates, total dry matter yield and growth rate.