Abstract
Given the importance of soybean to the global economy and as a food source, improving crop management techniques is integral to obtaining higher yields. As such, this study aimed to assess the yield of soybean cultivars as a function of different glyphosate salt formulations, doses and application times. Two field experiments were conducted simultaneously using a randomized block design and 3x4x2 factorial scheme, with three repetitions. Factor A consisted of three glyphosate formulations: isopropylamine salt (Roundup Original®), ammonium salt (Roundup WG®), and potassium salt (Zapp Qi®), factor B four application times: 0, 14, 28, 42 days after planting (DAP), and factor C two doses: the recommended dose of 720 grams of acid equivalent per hectare and twice that (1440 grams of acid equivalent per hectare). There was no difference between the glyphosate salts for the BMX Ativa RR® cultivar, but yields of BMX Apolo RR® submitted to ammonium salt were 28% higher than those recorded for the other salts studied. Glyphosate potassium salt resulted in lower soybean yields. Potassium salt application between 14 and 28 DAP caused greater toxicity in both the soybean cultivars analyzed.
Highlights
Soybean (Glycine max (L.) Merrill) is the main commodity in Brazilian agribusiness (CONAB 2018), the primary source of vegetable oil and a major protein source
Factor A consisted of three glyphosate formulations: isopropylamine salt (Roundup Original®), ammonium salt (Roundup WG®), and potassium salt (Zapp Qi®), factor B four application times: 0, 14, 28, 42 days after planting (DAP), and factor C two doses: the recommended dose of 720 grams of acid equivalent per hectare and twice that (1440 grams of acid equivalent per hectare)
The lowest yields were observed for application at 14 days after planting (DAP) in the BMX Ativa RR cultivar, and 28 DAP for BMX Apolo RR (Table 1)
Summary
Soybean (Glycine max (L.) Merrill) is the main commodity in Brazilian agribusiness (CONAB 2018), the primary source of vegetable oil and a major protein source. Given its importance, improving crop management techniques is vital to the global food supply (ZADINELLO et al, 2012) This includes weed management, which ensures crops achieve their full yield potential. Glyphosate is the main active ingredient used worldwide (GAUPP-BERGHAUSEN et al, 2015) This broad-spectrum herbicide is widely applied as a postemergence weed killer in glyphosate-resistant crops, with more than 150 commercial brands sold around the world in over 160 countries, registered for more than 100 crops (VELINI et al, 2009). It acts by inhibiting the biosynthesis of aromatic amino acids via the precursor enzyme EPSPs (5-enolpyruvylshikimate3-phosphate synthase), preventing shikimate transformation into chorismate (SENSEMAN, 2007)
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