Corn planting after soybean harvest boosts oilseed yields, study finds
Soybean harvest in Mato Grosso; a study showed that fertilizer costs decrease when soybean cultivation is followed by the planting of other crops
Rodolfo Perdigão/Secom-MT
Farmers who grow soybeans followed by corn in the same crop year achieve higher soybean yields, greater financial returns, and greater climate resilience than those who rely solely on soybean monocropping, according to a study by Agroicone, Unicamp, and Fundação Mato Grosso.
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According to the authors, the research confirms what many farmers had already observed. What was still lacking, however, was a scientific basis demonstrating the gains regardless of weather conditions in a given crop year.
“This dataset shows that sequential cropping systems fundamentally improve the agronomic and economic performance of tropical agroecosystems compared with continuous monocropping,” said Luciane Chiodi Bachion, the study’s lead researcher and a partner at Agroicone.
The experiment covered 15 consecutive crop years, from 2008/09 through 2022/23, in Itiquira, Mato Grosso, in tropical soil and a climate with a dry season from June to August. Five soybean production systems were grown side by side in four experimental blocks, with the treatments repeated each season: two monocropping systems, no-till and conventional, and three crop-sequencing systems, in which soybeans were followed by corn, brachiaria, or millet. The same amount of fertilizer was applied to soybeans in all systems.
The study found that the highest yields came from the crop-sequencing systems. Over the 15 crop years, soybeans followed by corn averaged 65.89 60-kilogram bags per hectare, while the soybean-brachiaria sequence averaged 66.47 bags. Monocropping systems produced lower averages: 52.15 bags per hectare under no-till and 54.36 bags per hectare under conventional tillage.
“In addition to the higher average, the sequential systems also fluctuated less from year to year over the 15 crop seasons. That stability helps protect farmers from weather variations between seasons,” said Sofia Arantes, a researcher at Agroicone.
The gap between monocropping and sequential systems widened precisely during the driest years, in the 2014/15 and 2020/21 crop seasons. In those years, soybean yields under monocropping fell below 20 bags per hectare in some experimental blocks, while sequential systems maintained yields close to 50 bags.
The highest yield in the entire period analyzed also came from a sequential system: 91.74 bags per hectare in the soybean-corn system in the 2018/19 crop season.
The same amount of fertilizer was applied across all five systems, which researchers said isolates the effect of crop sequencing on costs. Fertilizer accounts for 40% of soybean production costs, making it a significant component of farmers’ expenses.
From the 2009/10 through 2022/23 crop seasons, systems alternating soybeans with brachiaria and corn had the lowest average fertilizer costs among all systems, at $9.25 per bag and $9.28 per bag, respectively. By comparison, the average fertilizer cost for soybeans under no-till monocropping was $10.22 per bag, while the cost under conventional tillage was $10.07 per bag. The average cost peaked at $16.26 per bag for soybeans under conventional tillage in the 2014/15 crop season.
According to Bachion, soil management provided by cover crops improved water and nutrient-use efficiency and increased soybean yields in the sequential systems. “Even with the same amount of fertilizer applied, diversified systems have a lower cost per unit of soybeans produced and generate higher economic returns. The combination of these factors explains how diversified systems achieve lower costs even when receiving the same amount of fertilizer during the soybean phase,” she added.
Profitability was also higher in the sequential systems. The best result among the five systems came from the soybean-corn rotation, with peaks above $30 per bag in the 2011/12, 2020/21 and 2021/22 crop seasons.
According to the researchers, income increases because of higher soybean yields as well as additional revenue from the second corn crop. In addition, growing corn spreads fixed costs for machinery, labor, and land financing across the two crops.
The study also highlights several soil benefits from planting corn after soybeans, including increased organic matter, improved water infiltration, stimulation of beneficial microorganisms, and disruption of pest and disease cycles associated with monocropping.
“These benefits are cumulative and may explain why sequential systems maintained higher and more stable yields throughout the 15-year experiment,” said Luís Guilherme Furlan de Abreu, a researcher at Unicamp.
