Soil health recovery after grassland reestablishment on cropland: The effects of time and topographic position

Abstract

The Conservation Reserve Program (CRP) is a U.S. federal land conservation program that incentivizes grassland reestablishment on marginal lands. Although this program has many environmental benefits, two critical questions remain: does reestablishing grasslands via CRP also result in soil health recovery, and what parts of restored fields (i.e., topographic positions) recover the fastest? We hypothesized that soil health will recover over time after converting cropland to CRP grassland and that recovery will be greatest at higher topographic positions. To test this, we sampled 241 midwestern U.S. soils along a grassland chronosequence (0-40 yr, including native grasslands) and at four topographic positions (i.e., a chronotoposequence). Soils were measured for bulk density, maximum water holding capacity (MWHC), soil organic C (SOC), extractable inorganic N, potentially mineralizable C (PMC), and N. Native grasslands had superior soil health compared with cropland and most CRP soils, and even 40 yr since grassland reestablishment was not adequate for full soil health recovery. Topographic position strongly influenced soil health indicators and often masked any CRP effect, especially with MWHC and SOC. However, PMC (a measure of active C) responded most rapidly to CRP and consistently across the landscape and was 26-34% greater 19-40 yr after grassland reestablishment. Reestablishing grasslands through CRP can improve soil health, although topographic position regulates the recovery, with greatest improvements at shoulder slope positions. Patience is needed to observe changes in soil health, even in response to a drastic management change like conversion of cropland to CRP grassland.

Soil Nutrients and Carbon Dynamics in the Presence of Biochar-swine Manure Mixture Under Controlled Leaching Experiment Using a Midwestern USA Soil

“…Leachate was collected for a total of eight times (eight events) after the treatment application. Leachates were filtered through a 0.45 µm syringe filter and analyzed for nitrate-N (vanadium III, sulfanilamide and N-(1-naphthyl)-ethylenediamine dihydrochloride), ammonium-N (salicylate and ammonia cyanurate method), and dissolved reactive phosphorus (DRP; malachite green method; D'Angelo et al, 2001) using a Synergy HTX Multi-Mode microplate reader (BioTek Instruments, Inc.) colorimetric method (De et al, 2019;Doane & Horwáth, 2003). Figure 1.…”

“…The extractant was prepared by weighing approximately 5g soil in 200 mL Nalgene bottle, shaken with KCl at 1:5 ratio for 30 min, and then filtered through Whatman grade 1 filter paper. This extractant was used to measure KCl-extractable soil nitrate-N (vanadium III, sulfanilamide and N-(1naphthyl)-ethylenediamine dihydrochloride) and ammonium-N (salicylate and ammonia cyanurate method) (De et al, 2019;Doane & Horwáth, 2003). The Mehlich3 extractable elements were extracted by a modified method of Mehlich (1984) and analyzed by ICP-OES.…”

Soil Nutrients and Carbon Dynamics in the Presence of Biochar-swine Manure Mixture Under Controlled Leaching Experiment Using a Midwestern USA Soil

“…The leachate was collected overnight in labeled bottles, and the next morning the leachate was transferred to <0 °C until analysis. Leachate was collected for a total eight times (eight events) after the treatment application; leachates were filtered through a 0.45 µm syringe filter and analyzed for nitrate-N (vanadium III, sulfanilamide and N-(1-naphthyl)-ethylenediamine dihydrochloride), ammonium-N (salicylate and ammonia cyanurate method), and dissolved reactive phosphorus (DRP; malachite green method; D'Angelo et al, 2001) using a Synergy HTX Multi-Mode microplate reader (BioTek Instruments, Inc.) colorimetric method (De et al, 2019;Doane & Horwáth, 2003). Figure 1.…”

“…The extractant was prepared by weighing approximately 5g soil in 200 mL Nalgene bottle, shaken with KCl at 1:5 ratio for 30 min, and then filtered through Whatman grade 1 filter paper. This extractant was used to measure KCl extractable soil nitrate-N (vanadium III, sulfanilamide and N-(1naphthyl)-ethylenediamine dihydrochloride) and ammonium-N (salicylate and ammonia cyanurate method) by a Synergy HTX Multi-Mode microplate reader (BioTek Instruments, Inc.) colorimetric method (De et al, 2019;Doane & Horwáth, 2003). The Mehlich3 extractable elements were extracted by a modified method of Mehlich (1984) and analyzed by ICP-OES.…”

Does potentially mineralizable nitrogen predict maize yield in newly cropped soil?

“…Mahal et al (2018) illustrated this relationship in a meta-analysis of conservation practices and PMN for longer-term studies, so it is unsurprising the relationship holds for the transition year in contrast to our hypothesis. A combination of high spatial variability and large pre-existing levels of SOC may make it difficult to detect small changes in PMN accrual (De et al, 2020). The most likely explanation is that in the transition year the pool of mineralizable N, particularly in no-till management, is sufficiently large that additions through either leguminous cover crops or surface-applied manure are inconsequential.…”