USDA LTAR Common Experiment measurement: Concentration of phosphorus, potassium, and sulfur in aboveground biomass

Authors: Kovar, John; Fortuna, Ann Marie

Submitted to: Protocols.io
Publication Type: Research Notes
Publication Acceptance Date: 8/2/2024
Publication Date: 8/8/2024
Citation: Kovar, J.L., Fortuna, A. 2024. USDA LTAR Common Experiment measurement: Concentration of phosphorus, potassium, and sulfur in aboveground biomass. Protocols.io. https://doi.org/10.17504/protocols.io.14egn6bnql5d/v1.
DOI: https://doi.org/10.17504/protocols.io.14egn6bnql5d/v1

Interpretive Summary: Knowing the amounts of nutrients removed in harvested biomass (grain, forage, etc.) is the first step in calculating fertilizer required. A detailed method of best practices for collecting and handling biomass samples is critically important to ensure high quality analysis of nutrient content. High quality analysis includes measurement of nutrients such as phosphorus, potassium, and sulfur. High quality analysis also includes quality assurance/quality control procedures that must be followed by the laboratory performing the analysis. This protocol will provide consistent sample collection and handling, analyses, and quality assurance/quality control procedures throughout all LTAR research network sites.

Technical Abstract: An adequate supply of plant nutrients is an important part of sustainable crop production and the overall health of a crop. Knowing the amount of each nutrient removed in the harvested biomass (grain, forage, etc.) is the first step in calculating plant nutrients required. Without replacing the removed nutrients, soil fertility declines over time, leading to a loss of yield potential. Phosphorus (P) is a primary macronutrient, with total P concentration in crops generally varying from 0.1 to 0.5%. Phosphorus can be found in roots, stems, and leaves, but most P is in seeds and fruit. It is a component of phytin, a major storage form of P in seeds and tubers. Potassium (K) is a primary macronutrient stored in the stems and foliage of aboveground biomass. Seeds contain only small amounts of K. Potassium is mobile in plant tissues and can easily leach. Therefore, estimates of plant biomass removed and remaining in the field are valuable for determining soil K fertility. Sulfur (S) is a secondary macronutrient in seeds and plant tissues. Nodule formation in legume crops requires S. Research has shown that S fertilization may improve nitrogen (N)-use effciency in many crops by increasing N uptake. To measure P, K, and S concentrations in biomass first digest the material. The nutrient concentrations in the digestate can then be determined using inductively coupled plasma-optical emission spectrometry (ICP-OES).