Plant essential nutrients such as boron (B), copper (Cu), iron (Fe), manganese (Mn), and Zinc (Zn) are used by crops in small amounts and are categorized as micronutrients. Deficiencies can have large impacts on crop yield and quality, however, because they perform vital physiological functions. Inherent soil properties and annual variability in growing conditions affect the availability of micronutrients, making their availability to crops more difficult to predict than phosphorus (P) or potassium (K). For this reason, method of analysis and interpretation of soil and plant analysis for micronutrients strongly affects our ability to guide micronutrient fertilization.

Soil and plant analysis are the foundation of fertilization guideline philosophies and decisions on the farm. For a soil (or plant) analysis test to be useful for production agriculture, soil fertility scientists agree it must:

• Accurately determine the nutrient status
• Clearly indicate the degree of deficiency or excess
• Can be calibrated to provide basis for fertilization recommendations
• Reliable and reproducible laboratory throughput

Micronutrient fertilization decisions, similar to macronutrients of phosphorus (P) and potassium (K), rely on soil tests to identify if fertilization is needed and many times relies on plant analysis to identify in-field deficiencies. However, current Wisconsin approved soil micronutrient test methods are not backed by well-documented research from this century informing critical concentrations.

This project aims to evaluate nutrient use efficiency when manure is applied using a real-time nutrient sensor. Specific objectives include:

1. Provide messaging and materials for stakeholders on performance data, systems impact, limitations, system integration, and economic impacts to evaluate selection and integration of real-time manure nutrient sensors.
2. Evaluate manure applied, nutrient use efficiency, crop yields, soil nutrients, and supplemental N mapping when manure is applied based on P using a real-time NIRS nutrient prediction technology verses conventional manure sampling and application

Our hypotheses are that: (i) manure applications that are closer to the time of corn planting will have greater N availabilities compared to applications applied further away and (ii) cover crops will reduce N availability of manure regardless of application time.

Funding Level: $106,019

To explore nitrogen management practices that are profitable and sustainable for growing seed potatoes, improve competitiveness of the Wisconsin seed potato industry, and contribute towards a healthy environment.

• Objective 1: Investigate the logistics of split-nitrogen applications (between planting, hilling and tuber bulking) to potato plants in silt loam soils in the Antigo Flats region;
• Objective 2: Identify the optimal split N application timing and amount (dose) for growing common seed potato varieties with good yield and quality in Wisconsin.

We hypothesize that small grains receiving manure at phosphorus requirement levels will respond positively to nitrogen from chemical fertilizer, both maximizing forage production, nutritive value, and minimizing environmental risks associated to excessive phosphorus application. We also hypothesize that nutrient management strategies will affect inorganic nitrogen concentration in the soil, which indicates nitrogen amount that will be available for subsequent crops.

The overarching objective of this study is to provide nutrient management recommendations for small grains used as forage. Specific objectives are:

• Tailor chemical fertilizer application recommendations for small grains receiving manure in
• Evaluate how different nutrient management and planting date strategies affect forage dry matter production and nutritive value.
• Estimate the effect of nutrient management on soil inorganic
• Estimate soil phosphorus saturation rate of soil receiving manure applications based on Mehlich-3 extractable phosphorus, aluminum, and iron.

Ongoing research has recently correlated three new soil P tests (Mehlich-3 ICP, Mehlich-3 colorimetric, and Olsen) and two new soil K tests (Mehlich-3 and ammonium acetate) to identify critical soil-test concentration ranges for corn and soybean (Jones et al., 2022). This is the first soil-test correlation work for P and K of Wisconsin crops in over three decades and agrees with updated critical concentrations in states like Iowa (Mallarino et al., 2023). However, field correlation is the first of two steps to provide updated fertilization guidelines for Wisconsin.

These new (to Wisconsin) soil tests must be calibrated to identify fertilizer P and K rates that will (1) maximize crop yield, (2) build low soil tests to optimum levels, (3) maintain optimum soil test levels, and (4) estimate crop removal for profitable decisions when soil tests are high.

Funding Level: $122,608