Abstract
Alternative methods to control invasive fodder grasses are necessary to reduce the use of herbicides in forest restoration, which has been carried out primarily in riparian zones. We sought to investigate if inter-row cultivation of crotalaria (Crotalaria breviflora DC) or pumpkin (Cucurbita moschata Duschene ex. Poir) with native tree species is an efficient strategy to control invasive fodder grasses in restoration plantings. We tested five treatments in a randomized block design, namely (1) control of brachiaria grass (Urochloa decumbens (Stapf.) Webster) with glyphosate in the implementation and post-planting grass control of the reforestation, (2 and 3) glyphosate use in the implementation and inter-row sowing of crotalaria (2) or pumpkin (3), and control of brachiaria by mowing in the post-planting phase, (4 and 5) mowing in the implementation and inter-row sowing of crotalaria (4) or pumpkin (5), and control of brachiaria by mowing in the post-planting phase. Post-planting grass control was carried out four and nine months after tree seedling planting. Throughout 13 months, we evaluated the percentage of ground cover by brachiaria grass, pumpkin production, and native tree seedling mortality, height and crown cover. The exclusive use of glyphosate, without inter-row sowing of pumpkin or crotalaria showed the most favorable results for controlling brachiaria grass and, consequently, for tree seedling development. Hence, inter-row cultivation of green manure or short-lived crop species is not enough to control invasive grasses in restoration plantings, and complementary weeding is necessary to reduce the highly competitive potential of C4 grasses for supporting native species seedlings growth.
Highlights
A remarkable increase in tropical forest restoration efforts has been recently observed in the Brazilian Atlantic Forest, as a result of large-scale restoration programs (Rodrigues et al, 2009), public policies (Wuethrich, 2007), and growing involvement of agro-industry companies (Rodrigues et al, 2011)
In the fifth month after planting, one month after maintenance intervention, treatments 1 and 3 had lower invasive grass coverage when compared to other treatments (Figure 2)
In the months, treatment 1 had lower grass coverage (p < 0.05) than all other treatments, which did not differ among themselves (F4,19 = 13.91, p < 0.0001)
Summary
A remarkable increase in tropical forest restoration efforts has been recently observed in the Brazilian Atlantic Forest, as a result of large-scale restoration programs (Rodrigues et al, 2009), public policies (Wuethrich, 2007), and growing involvement of agro-industry companies (Rodrigues et al, 2011). While there is no consensus on the use of herbicides in riparian areas as a safe strategy of weed control in forest restoration, alternative, non-chemical methods of weed control are especially demanded and necessary (Pywell et al, 2010). Following this trend, in Brazil, legal instruments have allowed inter-row cultivation of green manures and short-lived crops with native tree species, such as the São Paulo state environmental office (SMA) resolution no 8 of 2008
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