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Title: Weed competition with soybean in no-tillage agroforestry and sole-crop systems in subtropical Brazil

item DEISS, LEONARDO - Universidade Federal Do Parana
item MORAES, ANIBAL - Universidade Federal Do Parana
item PELISSARI, ADELINO - Universidade Federal Do Parana
item Franzluebbers, Alan
item SKORA NETO, FRANCISCO - Universidade Federal Do Parana
item DA SILVEIRA PONTES, LAISE - Universidade Federal Do Parana
item SANTIAGO BARRO, RAQUEL - Federal University Of Rio Grande Do Sul
item SILVESTRI SZYMCZAK, LEONARDO - Universidade Federal Do Parana

Submitted to: Planta Daninha
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/5/2016
Publication Date: 10/20/2017
Citation: Deiss, L., Moraes, A., Pelissari, A., Franzluebbers, A.J., Skora Neto, F., Da Silveira Pontes, L., Santiago Barro, R., Silvestri Szymczak, L. 2017. Weed competition with soybean in no-tillage agroforestry and sole-crop systems in subtropical Brazil. Planta Daninha. 35:.

Interpretive Summary: Agroforestry systems are designed to integrate timber and agricultural operations in the same field. Although such systems have been used in the tropics for a long time for ecological efficiency, development of systems in the more temperate and mechanically industrialized regions is rather new and implications unknown on many aspects of production and the environment. A soil scientist at USDA-Agricultural Research Service in Raleigh NC teamed with a group of scientists from the Federal University of Parana, Agronomic Institute of Parana, and Federal University of Rio Grande do Sul in Brazil to analyze the effects of agroforestry on weed growth and competition with soybean production. The presence of trees inhibited soybean growth as a result of several possible factors associated with trees, but not due to greater weed pressure. Suppression of weeds enhanced soybean production in an open field without trees, but suppression had no effect on soybean production in alleys between tree lines. The results of this research suggest that trees growing as borders with crops can limit both weed and soybean growth potential. In the future, it will be important to quantify the balance of negative and positive effects of agroforestry systems to achieve greatest resource efficiency.

Technical Abstract: Weed competition on soybean [Glycine max (L.) Merr.] growth and yield was expected to be different when managed in an agroforestry system as compared with solecropping without trees. Therefore agronomic practices to control weeds might need to be modified in agroforestry systems. We analyzed weed competition effects on soybean growth and yield components at different distances from 4-year-old eucalyptus (Eucalyptus benthamii) in an alley cropping system, as well as in a sole-crop system in southern Brazil. Above-ground soybean biomass was collected throughout the growing season and a logistic function was used to model crop growth. Grain yield and yield components were evaluated using regression analysis across positions between tree lines, and results compared to those without influence of trees. Soybean yield components were mostly reduced between tree lines compared with sole-cropping without trees. Soybean growth and yield within the eucalyptus agroforestry system was not affected by weed competition. However, weeds reduced soybean growth and yield in sole-cropping without trees. Reduction in soybean yield in the agroforestry system was rather caused by competition from trees. These results suggest that tree interference may limit both weed and soybean growth potential.