Why invest in tissue sampling when soil sampling is cheaper, easy to perform along a grid and the basis of variable rate applications?
Soil samples tell you the concentration of nutrients in the soil. However, nutrient “concentration” is not the equivalent of nutrient “availability.” What is in the soil may not be available to your plant. Why not?
Compact, cold or wet soils may limit root growth. Dry soils or chemical interactions may reduce nutrient solubility. Insect damage to roots and leaves can limit uptake and transport. Negatively charged anions in the soil with the exception of phosphorous can move out of the root zone especially in soybeans with excessive rain event. Critical anions in the soil include sulfur and boron. Boron can be addressed easily with foliar materials. We can adjust sulfur somewhat with foliar but most focus should be on soil applications.
Agronomists also like to look at specific ratios of selected nutrients in plants. Specifically, we like to compare levels of nitrogen to sulfur as the corn plant uses N+S at a specific ratio of 10:1 at the cellular level and we like to see the N:K ratio at a 1.4/1.6:1 level.
Agronomists use term “bioavailability” to describe the actual nutrient availability to living plants. The only way to quantify this is to measure the plant itself through tissue sampling.
Sunrise Cooperative uses local laboratories to provide real time results from tissue samples. Results are often implemented in time to combine foliar feeding with post herbicide and /or fungicide applications. Results are presented in a customized report that describes the availability and significance of each nutrient and if/how our basic foliar products should be augmented with additional nutrients.