Abstract
Abstract: The objective of this work was to evaluate the effect of raised seedbeds associated with irrigation on the yield of soybean (Glycine max) rotated with rice (Oryza sativa) in lowland conditions in Southern Brazil. Field experiments were conducted in two crop seasons (2014/2015 and 2015/2016), with two planting systems (raised seedbed and flat planting) and two irrigation managements (irrigated and nonirrigated). Water use, biological nitrogen fixation, and yield were evaluated. The water used for raised seedbeds was 14% (151 m3 ha-1) and 27% (163 m3 ha-1) lower than that for flat planting in the first and second crop seasons, respectively. Irrigation increased nodule number per plant, nodule dry weight, and biological nitrogen fixation. The average grain yield of the raised seedbed system was 10% (529 kg ha-1) and 9% (362 kg ha-1) higher than that of flat planting in 2014/2015 and 2015/2016, respectively. Irrigation improved yield by 5% (203 kg ha-1) and 7% (265 kg ha-1) in each crop year. The use of raised seedbeds associated with irrigation improves the yield of soybean grown in rotation with rice in lowland in Southern Brazil.
Highlights
The cultivation of soybean [Glycine max (L.) Merr.] in rotation with rice (Oryza sativa L.) is rapidly increasing in Southern Brazil
According to surveys conducted by Instituto Rio Grandense do Arroz (IRGA, 2018), the soybean area rotated with rice increased from 11,000 ha in the 2009/2010 crop season to 280,000 ha in 2017/2018
Raised seedbeds increased by 25% the number of established plants, in comparison with flat planting at 20 days after crop emergence
Summary
The cultivation of soybean [Glycine max (L.) Merr.] in rotation with rice (Oryza sativa L.) is rapidly increasing in Southern Brazil. The stagnated yields in Brazil have been attributed to the traditional practice of growing soybean in flat-planted systems on Planossolos Háplicos, i.e., Albaqualfs, soils of lowland areas, common for rice production. The management practices particular to rice production have led to the formation of a traffic-induced hardpan 15 to 20 cm below the soil surface (Sartori et al, 2016) This increases both waterlogging in early soybean development and water stress later during reproduction, with concomitant effects on important physiological process such as photosynthesis and nitrogen fixation (Lanza et al, 2013; King et al, 2014).
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