Soybean nutrient frustrations: Doing more with less or less with more
2021
- Department of Plant, Soil and Microbial Sciences, Michigan State
Project Media
Increases in soybean (Glycine max L. Merr.) biomass production have some practitioners questioning
whether reduced interplant competition from below recommended seeding rates may provide opportunities
for greater response to early and mid-season nutrient applications. Additionally when soil test
nutrient concentrations are above critical, soybean producers often question whether alternative in-season
nutrient management strategies may improve yield and profitability. Below recommended seeding rates
can reduce input costs without decreasing soybean grain yield while simultaneously increasing biomass
production, nutrient uptake, and yield per plant. However, non-irrigated nutrient management strategies
may not directly transfer to irrigated production and vice versa. Multiple field studies conducted over the
last several years evaluated soybean grain yield, dry matter accumulation, nutrient uptake and partitioning,
and net economic return as affected by seeding rate and in-season nutrient applications under both
irrigated and non-irrigated environments. Seeding rates included 60,000, 120,000, and 180,000 seeds A-1.
Fertilizer strategies consisted of: no fertilizer, 150 lb. MESZ (12-40-0-10S-1Zn) A-1 applied two inches to
the side and two inches below the seed (2×2) at planting, 15 gal. liquid K2O (0-0-28) A-1 applied using a
Y-drop applicator at growth stage V6, 16 gal. 10-34-0 A-1 applied using a Y-drop applicator at growth
stage R1, and a combination of the MESZ, liquid K2O, and 10-34-0 fertilizer applications. Results from
the 2020 growing season indicate fertilizer applications should not accommodate for alterations in
seeding rate, and that nutrient application beyond what is recommended in accordance with soil test
concentrations may not increase grain yield or profitability regardless of environment (i.e. irrigated or
non-irrigated). Although fertilizer application (especially starter fertilizer in a 2×2) may increase early
season biomass production and likely nutrient uptake, accelerated crop growth rate and the ability of
soybean to compensate for inter-plant competition could diminish early season differences. Among the
tested seeding rates, 120,000 seeds A-1 increased grain yield at the non-irrigated site. However under
irrigated conditions, seeding rate did not impact grain yield. Economic return was not impacted at the
irrigated or non-irrigated site due to high seed cost offsetting greater grain yield.