Addressing Micronutrient and pH Variability in Grid Sampled Soils
Farmers on the Delmarva Peninsula have long used grid soil sampling to guide variable-rate applications of lime, phosphorus, and potassium. These maps are great for managing macronutrients, but what about micronutrients like manganese (Mn), iron (Fe), and zinc (Zn)? These elements are essential for plant growth, yet their availability can vary widely across a field—especially Mn, which is highly sensitive to soil pH and often our most limiting micronutrient on Delmarva.

On the Atlantic Coastal Plain, our soils are often acidic and highly weathered, requiring lime to maintain proper pH. However, these same soils can vary greatly in native Mn content. As a result, variable-rate liming strategies could potentially address Mn deficiencies along with soil acidity—helping balance both pH and micronutrient availability across the field.

Jarrod Miller, Extension Agronomist, University of Delaware

Precision nitrogen (N) management through the use sensors has been used to improve nitrogen use efficiency (NUE) for field crops by estimating corn needs during early growth stages (Aula et al., 2020; Cao et al., 2017) Indices have been developed using specific wavelengths of light, such as the normalized difference vegetation index (NDVI) to estimate plant biomass and correlate it to N needs (Holland et al., 2012; Raun et al., 2005a; Dellinger et al., 2008). The use of NDVI has allowed for reductions in N application have been performed without reducing crop yield (Barker and Sawyer, 2012; Aula et al., 2020).