Impacts of cropping system diversification on soil phosphorus fractions and enzyme-mediated p cycling

Authors: CRESPO, CECILIA - Oak Ridge Institute For Science And Education (ORISE); Berkey, James; Kovar, John; O'Brien, Peter; HUANG, WENJUAN - Iowa State University; LIEBMAN, MATT - Iowa State University; MCDANIEL, MARSHALL - Iowa State University

Submitted to: Nutrient Cycling in Agroecosystems
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/12/2025
Publication Date: 11/27/2025
Citation: Crespo, C., Berkey, J.R., Kovar, J.L., O'Brien, P.L., Huang, W., Liebman, M., McDaniel, M.D. 2025. Impacts of cropping system diversification on soil phosphorus fractions and enzyme-mediated p cycling. Nutrient Cycling in Agroecosystems. https://doi.org/10.1007/s10705-025-10450-4.
DOI: https://doi.org/10.1007/s10705-025-10450-4

Interpretive Summary: Throughout the world, there is increasing interest in efficient use of phosphorus (P) fertilizer, yet the movement and transformation of P in cropping systems with extended crop rotations and livestock integration is poorly understood. Therefore, we set up an experiment in central Iowa to evaluate the impact of two diversified cropping systems on P compared with the conventional corn-soybean rotation using commercial P fertilizer. The two diversified cropping systems are: corn-soybean-small grain rotation including red clover fertilized with composted cattle manure, and corn-soybean-small grain rotation with alfalfa and alfalfa hay also fertilized using cattle manure. Results showed that less plant-available P forms showed short-term increases of up to 60% in the diversified systems. Soil P enzyme activity, in contrast, was influenced by management practices. Also, extended crop rotations with small grains, forage legumes, and composted manure improved soil P enzyme activity by more than 60%. Overall, our results suggest that diversification improves short-term P cycling and availability in cropping systems. The results of this work improve our understanding of P cycling in diverse cropping systems and contribute useful information to producers in the midwestern U.S.

Technical Abstract: Diversification of crop rotations provides several benefits for agroecosystems, yet the effects of extended crop rotations and livestock integration on soil phosphorus (P) dynamics are not well understood. We examined the short- and long-term impacts of three cropping systems: a maize (Zea mays L.)-soybean (Glycine max (L.) Merr.) rotation with synthetic fertilizer (2 years), a maize-soybean-small grain rotation with red clover (Trifolium pratense L.) with composted cattle manure as a fertilizer source (3 years), and a maize-soybean-small grain rotation with alfalfa (Medicago sativa L.) and alfalfa hay (4 years), also using composted manure. We compared soil P fractions and phosphatase activity among the three systems and across crop phases. While soil test P and labile P fractions were consistent across treatments, moderately labile and non-labile P pools showed short-term increases of up to 60% in diversified rotations. Phosphatase activity, in contrast, was influenced by management practices both short- and long-term. Extended crop rotations with small grains, forage legumes, and composted manure improved acid monophosphatase activity by more than 60%, indicating that diversified systems can enhance enzymatic activity linked to P cycling, beyond changes in P fractions. Overall, our findings suggest that diversification improves short-term P cycling and availability in cropping systems. In addition, the absence of significant long-term increases in Mehlich 3-extractable P in the diversified systems suggests that the crops capture more P compared to a conventional maize-soybean system and thus, have potential to reduce the environmental risk associated with P losses.