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- Title
Sowing date affects soybean biological nitrogen fixation.
- Authors
Barat‐Carnino, Mercedes; Santachiara, Gabriel A.; Borras, Lucas; Rotundo, Jose L.
- Abstract
In many temperate soybean [Glycine max (L.) Merr.] production systems sowing date expands for several months. Early sowing dates commonly show maximum yields, but their consequences for crop N uptake and biological nitrogen fixation (BNF) are unknown. Our objective was to evaluate the role of sowing date, a major management variable defining soybean yield, on BNF. We hypothesized BNF is maximum at intermediate sowings because BNF is limited by low soil temperatures at early sowing dates and by high soil nitrate concentrations at later sowings. Four genotypes (maturity groups [MGs] IV and V) were tested over a 16‐wk sowing date period, and a N fertilizer treatment at sowing was added in all sowing date by genotype combinations (0 and 100 kg N ha–1). The N fertilization treatment helped to test sowing date effects independently of soil N availability. Seed yield and total N uptake were affected by sowing date and genotype, but not by the N treatment. Both seed yield and total N uptake followed similar quadratic responses, but MG V genotypes maximized yield and N uptake at the earliest sowing while MG IV cultivars maximized both traits at intermediate sowings. However, delaying sowing date always decreased the proportion of total aboveground N that came from BNF (average decline 0.22% d–1). Nitrogen fertilization reduced BNF by 15% across sowing dates and genotypes, with no yield effect. The linear decline in BNF with delayed sowing dates, instead of an optimum response, supports the concept that soil nitrates are the main driver of soybean BNF in this production system. Core Ideas: Later sowings showed lower yields because of lower N uptake.Percentage biological nitrogen fixation was negatively correlated with sowing date (average decline −0.22% d−1).Sowing soil temperatures around 11°C did not reduce biological nitrogen fixation.Nitrogen fertilization reduced biological nitrogen fixation by 15% across sowing dates and genotypes.Results support that sowing date effects over biological nitrogen fixation are more related to soil N than to soil temperatures.
- Subjects
NITROGEN fixation; SOYBEAN; SOWING; SEED yield; SOIL temperature
- Publication
Crop Science, 2022, Vol 62, Issue 6, p2428
- ISSN
0011-183X
- Publication type
Article
- DOI
10.1002/csc2.20812