Autoclaved citrate-extractable protein as a soil health indicator relates to soil properties and crop production

Authors: Sainju, Upendra; LIPTZIN, DANIEL - Soil Health Institute; Stevens, William - Bart

Submitted to: Nutrient Cycling in Agroecosystems
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/2/2022
Publication Date: 9/12/2022
Citation: Sainju, U.M., Liptzin, D., Stevens, W.B. 2022. Autoclaved citrate-extractable protein as a soil health indicator relates to soil properties and crop production. Nutrient Cycling in Agroecosystems. 124:315-333. https://doi.org/10.1007/s10705-022-10230-4.
DOI: https://doi.org/10.1007/s10705-022-10230-4

Interpretive Summary: Nitrogen is one of the most important nutrients required for plant growth and is applied in large amounts as fertilizer to many agricultural soils to ensure adequate soil fertility. Nitrogen is present in many different chemical forms in the soil as it cycles between various organic and inorganic forms. Given the essential role of nitrogen in plant growth and crop yield, one or more of these soil nitrogen fractions may have potential value as soil health indicators. Using soil collected from two long-term dryland field studies, ARS researchers in Sidney, MT collaborated with the Soil Health Institute to evaluate soil nitrogen fractions for their potential as soil health indicators based on how well they correlated with crop yield and 66 soil properties. They reported that potential nitrogen mineralization and autoclaved citrate-extractable protein were the soil nitrogen fractions most sensitive to management practices and related to most soil properties and long-term crop yields. Other soil nitrogen fractions showing less potential were soil total nitrogen, water-extractable nitrogen, ammonium-nitrogen, and nitrate-nitrogen. Although potential nitrogen mineralization was related to most soil properties and crop yield, it is not an ideal soil health indicator because the laboratory procedure for measuring it is time-consuming. On the other hand, autoclaved citrate-extractable protein may be the most suitable nitrogen-based indicator of soil health because it is easily and rapidly determined and is related to most soil properties and crop yield. One of the greatest challenges of improving soil health is the lack of simple and reliable assays of soil properties that are correlated with a productive soil ecosystem. This research provides evidence that autoclaved citrate-extractable protein may be a valuable indicator of soil health in semiarid dryland cropping systems.

Technical Abstract: Nitrogen is an important and most limiting nutrient for crop production, but its extensive evaluation as soil health indicator relating to soil properties and crop production has not been conducted. The objectives of this study were to examine the sensitivity of soil N fractions to management practices and their relationships to 66 soil physical, chemical, biological, and biochemical properties and mean crop yields in two long-term (14- and 36-yr-old) experiments under dryland cropping systems in the northern Great Plains, USA. Nitrogen fractions were soil total N (STN), potential N mineralization (PNM), water-extractable N (WEN), autoclaved citrate-extractable protein (ACEP), NH4-N, and NO3-N. Management practices were no-till and till crop rotations of spring wheat (Triticum aestivum L.), barley (Hordeum vulgare L.), pea (Pisum sativum L.), and fallow with and without N fertilization. Soil properties were analyzed from samples collected before farm operations in April 2019 and crop yields determined. Nitrogen fractions, except NH4-N and NO3-N, were greater with continuous cropping than crop-fallow. The principal component analysis (PCA) showed that PNM and ACEP were associated with most soil properties, followed by STN, WEN, NO3-N, and NH4-N. The PNM, ACEP, and STN were strongly related to mean crop yields across years in the longer than shorter duration experiment, but other N fractions were weakly related. Because of the sensitivity to management practices, stronger relationships to most soil properties and crop yields, and rapid measurement, ACEP may be used as a promising N indicator of soil health in dryland cropping systems in the semiarid region.