Decreased land use intensity improves surface soil quality on marginal lands

Authors: Li, Lidong; Jin, Virginia; Kettler, Timothy; Karlen, Douglas; NUNES, MÁRCIO - Orise Fellow; Lehman, R - Michael; Johnson, Jane; Mikha, Maysoon

Submitted to: Agrosystems, Geosciences & Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/27/2021
Publication Date: 12/1/2021
Citation: Li, L., Jin, V.L., Kettler, T.A., Karlen, D.L., Nunes, M., Lehman, R.M., Johnson, J.M., Mikha, M.M. 2021. Decreased land use intensity improves surface soil quality on marginal lands. Agrosystems, Geosciences & Environment. 4(4). Article e20226. https://doi.org/10.1002/agg2.20226.
DOI: https://doi.org/10.1002/agg2.20226

Interpretive Summary: Soil health is important for environmental sustainability and food security. Intensive land use can cause decreases in soil health, and conservation management can improve soil health. Our primary purpose was to understand how land use and conservation management affect soil health. The secondary purpose was to determine if soil health benefits were greater when conservation management was applied to very environmentally sensitive soils (steeper slopes) compared to less sensitive soils (lower slopes). We collected soils from 38 fields across 18 private farms in central Iowa (including yours) to compare soil properties within Conservation Reserve Program (CRP) with those in neighboring fields under business-as-usual (BAU) management. Our results show that conversion to CRP can enhance overall soil quality by increasing soil biological, physical, and chemical qualities, but CRP can decrease soil nutrient quality due to absence of fertilizer application. Increasing soil organic carbon (SOC) will serve to boost overall soil quality because SOC is interconnected to soil biological, physical, chemical, and nutrient qualities. Conversion to CRP may have stronger benefits for more environmentally sensitive soils (i.e., higher slope). Our research revealed the ecological benefits of CRP conversion in relation to soil quality and our methodology essentially targeted specific soil quality components that could be managed for, simplifying how management recommendations are made.

Technical Abstract: In agroecosystems, cropland expansion on marginal land is one of the major causes of land degradation. However, marginally productive cropland being converted to the Conservation Reserve Program (CRP) is expected to provide substantial benefits to ecosystem function and sustainability. Our study evaluated soil quality under different land use intensities (CRP, pasture, row crop) and CRP conversion histories (0-40 years) using the Soil Management Assessment Framework (SMAF). Soil quality was also compared on different landscape positions (higher and lower slopes) and soil depths (0-120 cm). Our results show that soil functioned at 84% and 78% of its theoretical capacity under CRP and row crop, respectively. Conversion to CRP can enhance overall soil quality by increasing soil biological, physical, and chemical qualities, but CRP can decrease soil nutrient quality due to absence of fertilizer application. Increasing soil organic carbon (SOC) will serve to boost overall soil quality because SOC is interconnected to soil biological, physical, chemical, and nutrient qualities. Conversion to CRP may have stronger benefits for more environmentally sensitive soils (i.e., higher slope) as demonstrated by structural equation modeling. Land use effect can be depth dependent, with more prominent effects in 0-5 cm than 5-15 cm depth. Our research revealed the ecological benefits of CRP conversion in relation to soil quality and our methodology essentially targeted specific soil quality components that could be managed for, simplifying how management recommendations are made.