Assessing Nitrogen Limitation in Inoculated Soybean in Southern Brazil

AMBROSINI, VÍTOR GABRIEL; VIEIRA FONTOURA, SANDRA MARA; PAULO DE MORAES, RENATO; CARCIOCHI, WALTER; CIAMPITTI, IGNACIO A.; BAYER, CIMÉLIO

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AMER SOC AGRONOMY

Año: 2019 vol. 2

Overcoming potential N limitation in soybean [Glycine max (L.) Merr.] is a critical factor for sustaining plant nutrient demand and improving productivity. Following this rationale, a set of studies were executed in southern Brazil with the goals of quantifying yield response to early season fertilizer N rates (up to 40 kg ha−1), ?starter N fertilization,? and to understand if soybean seed yields are limited by N (testing a non-limiting N scenario) when grown in soils with medium to high organic matter content. The main key outcomes of this research were: (i) starter N fertilization did not increase yields compared with non-fertilized soybean, potentially highlighting the absence of an early season N limitation; and (ii) N limitation was observed when soybean yields were compared with non-limiting N scenario and it tended to be greater in low compared with medium-high yield levels, potentially connected with co-limitations on both N sources (N2 fixation and mineralization) to satisfy soybean N demand. Producing soybean in a sustainable manner implies focus on production practices to conserve and, potentially, to increase soil organic matter on a long-term basis. Furthermore, it requires enhancing the biological N2 fixation process for satisfying the large plant N demand for achieving high soybean yields. Future research should be focused on understanding factors governing biological N2 fixation and N mineralization processes in soybean grown in soils with medium-high organic matter content.