There continues to be interest in utilizing mineral fertilizers to promote greater grain yields and support seed quality. Recent occurrences of spring weather variability combined with what has become cool, wet Michigan spring planting conditions may provide opportunities to influence early-season dry matter and nutrient accumulation by reducing the lag-phase of soybean growth and account for potential delays in biological N fixation contributions to the plant. Earlier planting dates may offer additional opportunities for Michigan soybean growers to capitalize on a longer growing season and maximize investment in nutrient application strategies.

Cool soil temperatures will often restrict root growth, inhibit soil microbial activity, and impede nutrient mineralization. Thus earlier soybean planting dates may be subject to more sub-optimal growing days and display differential responses to nutrient application as compared to an optimal planting date under warmer soil conditions. Investigating this aspect as part of a larger management regime will generate useful nutrient application data for those growers pursuing earlier planting dates.

Avoiding reductions to seed quality and ensuring grain yield of current higher-yielding varieties may be two reasons 44%, 43%, and 69% of Michigan soybean acres are fertilized with either N, P, or K, respectively. With the variable spring seasons the state of Michigan has endured recently, growers need to develop the “start-right capacity” of the soybean plant early in the growing season to capitalize on mid-season climate conditions. Comparing similar nutrient application strategies across irrigated and non-irrigated systems and multiple planting dates will provide vital management information for Michigan soybean growers moving forward.

Objective 1. Determine the impacts of wet vs dry 2x2 starter, pre-plant N, and in-season N on soybean biomass accumulation, growth and development, mineral nutrition content, N-fixation, grain yield and seed quality. Our working hypothesis is that irrigated environments may provide the necessary yield potential to capitalize on more intensive nutrient management strategies.

Objective 2. Determine the effects of soybean planting date to multiple nutrient application strategies at different soil moisture levels. Our working hypothesis is that starter fertilizer and in-season N may account for slower early-season growth or the inability to provide enough N to the seed under greater yield potentials.

Objective 3. Determine the impact of fertilizer (or biological product) application timings on soybean grain yield, biomass production, and tissue concentrations. Our working hypothesis is that in-season nutrient applications close to peak uptake periods may provide greater nutrient availability at near-critical soil nutrient concentrations

The long-term goal of this research is to enhance the efficiency of soybean producers’ nutrient applications to the crop and simultaneously improve both the production and profitability of Michigan agriculture. These projects will also serve as a tool for soybean producers’ to utilize when making nutrient investment decisions.