Does crotalaria (Crotalaria breviflora) or pumpkin (Cucurbita moschata) inter-row cultivation in restoration plantings control invasive grasses?

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.

Controlling invasive plant species in ecological restoration: A global review

“…Mowing and herbicides have been used to control invasive species in the first years of forest restoration until trees grow enough to outcompete grasses through shading (Evangelista, Michelan, Gomes, & Thomaz, 2017; Maron & Connors, 1996; Ross et al., 2019). A restoration method successfully used in Brazil to outcompete invasive grasses is sowing green manure species (usually exotic, but non‐invasive, legume shrubs for producing biomass that have positive effects on soils) in between the planting lines of native trees (César, Brancalion, Rodrigues, Oliveira, & Alves, 2013; Durigan, Guerin, & da Costa, 2013). These species grow faster than native trees and anticipate the occupation of the ecological niche of C 4 grasses, reducing the recolonization of restoration plantations by these undesirable species.…”

Suitability index for restoration in landscapes: An alternative proposal for restoration projects

“…Hence, cheap complementary services might be considered. An alternative is the cultivation of pumpkin, zucchini or other crops of economic importance that cover the ground surface, in order to control the spread of exotic grasses (César et al, 2013). In addition, these species produce flowers and fruits that might be attractive to pollinator insects and/or mammals that also act as seed-dispersers.…”

Analysis of effectiveness of three forest interventionist techniques and proposal of a new and integrated model of forest restoration

“…Although the employment of a specific chemical is considered a suitable technique [32] and some products could be effective, alternative techniques should be priority considered. For example, the cultivation of pumpkin, zucchini or other crops of economic importance that cover the ground surface [33], and…”