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.

Loss of nitrate‐nitrogen (NO ₃ ⁻ –N) from Midwestern U.S. agricultural fields can impair water quality and be an economic loss to farmers. Winter cover crops have shown promise as a remedy, but low adoption illustrates the need for alternatives. Here, we tested whether adding a carbon (C)‐rich soil amendment (i.e., crude glycerol, a biodiesel byproduct) can increase soil microbial biomass (MB) and promote N immobilisation under various conditions and then determined whether and when immobilised N would be released. We conducted a laboratory incubation with a full factorial combination of four glycerol rates (0, +117, +468 and +1872 mg C kg ⁻¹ soil), three supplemental NO ₃ ⁻ –N rates (0, +10 and +40 mg N kg ⁻¹ ) and two soils (Clarion clay loam and Sparta loamy sand). Soil inorganic N (NH ₄ ⁺ –N and NO ₃ ⁻ –N) and MB were measured at seven and three time points, respectively, across the 98 days incubation period. Across all treatments, glycerol increased MBN in both short term (7 days; 4%–1137% compared to no glycerol addition) and long term (98 days; 10%–169%) and decreased NO ₃ ⁻ –N with increasing rate of glycerol. Adding glycerol caused net N immobilisation of 21%–61% (+117 mg C kg ⁻¹ addition) and ~100% (+468 and +1872 mg C kg ⁻¹ addition) compared to the control. Some of that immobilised inorganic N was likely released through MB turnover, but timing and rate of release depended on the soil and added N rate. Adding 40 mg N kg ⁻¹ with no glycerol showed nearly twice the net N mineralisation rate than with the low or no applied N – providing evidence for soil N priming. Overall, glycerol has the potential for use as a soil amendment to increase MB and temporarily immobilise NO ₃ ⁻ –N and then make some of that N crop available through MB turnover. Highlights: Crude glycerol, a biodiesel by‐product, was evaluated as a soil amendment to reduce soil nitrate. Glycerol strongly increased soil microbial biomass and decreased nitrate under all conditions. N immobilisation was temporary, and N was mineralised at a lower glycerol rate. Glycerol rates, N rates and soil type affected N immobilisation‐mineralisation dynamics.

Maize (Zea mays L.) stover can be harvested for multiple uses or left in the field to sustain soil organic carbon (SOC), cycle essential plant nutrients, and protect soil health. This 13‐yr field study quantified effects of no (0 Mg ha^–1 yr^–1), low (1.0–1.4 Mg ha^–1 yr^–1), moderate (3.5–4.0 Mg ha^–1 yr^–1), or high rates (4.7–5.4 Mg ha^–1 yr^–1) of stover harvest from either continuous maize or maize–soybean [Glycine max (L.) Merr.] rotation on grain yield, plant nutrient concentrations, and multiple soil properties at two sites in Iowa. Stover harvest increased plant macro‐ and micro‐nutrient removal, but did not affect average grain yields of either crops. Soil inorganic carbon (IC), SOC, bulk density, pH, and cation exchange capacity (CEC) showed no significant differences due to stover harvest. Plant tissue and soil‐test nutrient concentration effects were also minor and site‐specific. Stover harvest significantly (p < .05) decreased exchangeable K and Ca concentrations by 8.3–23.8% and 0.3–22.5% but overall soil health indicator effects were minimal. Overall, based on crop yields, plant nutrient and soil‐test concentrations, soil health indicators, and carbon sequestration estimates, maize stover harvest can be sustainable provided: (a) grain yields consistently exceed 11 Mg ha^–1, (b) stover removal does not exceed 40% of the aboveground biomass (i.e., 3.5–4.0 Mg ha^–1 yr^–1), and (c) plant nutrients (especially K) are closely monitored.

Background and aims Farmers are increasingly interested in regenerating soil health after centuries of soil-degrading practices. However, the most effective soil health regenerating practices (SHRP) and underlying mechanisms that regenerate soil health remain unclear. Our objectives were to determine: (i) how agriculture management, hillslope position, and their interactions affect soil health and root characteristics, and (ii) if there is a relationship between management-induced root characteristics and observed improvements in soil health. Methods Soil and plant root samples were collected from 0 to 120-cm from three management practices: conventional maize-soybean rotation (Row Crop), cattle-grazed pasture (Pasture), and restored grassland (Grassland). Soil health indicators (SHIs) that are responsive to management differences: soil organic carbon, potentially mineralizable carbon, permanganate oxidizable carbon, beta-glucosidase activity, total nitrogen, and autoclaved citrate extractable protein were measured, along with root mass, root mean diameter (RMD), and root length density (RLD). Results Overall SHIs for Pasture and Grassland increased by an average of 54% and 41%, respectively, when compared to Row Crop. Pasture and Grassland management also had twice the root mass as the Row Crop systems. Pasture had the greatest proportion of very fine roots (< 0.2 mm RMD), while Row Crop had the lowest proportion. Individual biological SHIs showed the best negative correlation with RMD and were positively correlated with RLD. Conclusion Soil health regenerating practices that increase total root mass, and fine root mass in particular (i.e., Pasture and Grassland), can lead to vast improvements in soil health regardless of hillslope position.

Plant and animal agriculture is a part of a larger system where the environment, soil, water, and nutrient management interact. Biochar (a pyrolyzed biomass) has been shown to affect the single components of this complex system positively. Biochar is a soil amendment, which has been documented for its benefits as a soil enhancer particularly to increase soil carbon, improve soil fertility, and better nutrient retention. These effects have been documented in the literature. Still, there is a need for a broader examination of these single components and effects that aims at the complementarity and synergy attainable with biochar and the animal and crop-production system. Thus, we report a comprehensive dataset documenting the interactions of biochar with manure, soil, and plants. We evaluated three biochars mixed with manure alongside both manure and soil controls for improvement in soil quality, reduction in nutrient movement, and increase in plant nutrient availability. We explain the experiments and the dataset that contains the physicochemical properties of each biochar–manure mixture, the physicochemical properties of soil amended with each biochar–manure mixture, and the biomass and nutrient information of plants grown in biochar–manure mixture-amended soil. This dataset is useful for continued research examining both the short- and long-term effects of biochar–manure mixtures on both plant and soil systems. In addition, these data will be beneficial to extend the findings to field settings for practical and realized gains.

Biochar application to the soil can improve soil quality and nutrient leaching loss. Recent studies have reported that surficial application of biochar to stored swine manure can reduce emissions of odorous compounds and reduce the volatilization loss of ammonia. Our working hypothesis was that the biochar-treated manure application to the soil would decrease nutrient leaching from manure and increase plant-available nutrients. The study objectives were to evaluate the impact of biochar-treated swine manure on soil total C, N, and other major and minor nutrients. Three biochars (i) neutral pH red-oak (RO), (ii) highly alkaline autothermal corn (Zea mays) stover (HAP), and (iii) mild acidic Fe-treated autothermal corn stover (HAPE) were incubated with swine manure for a month. The biochar-manure mixture was applied in triplicate to soil columns with application rate determined by the P2O5-P content in manure or manure-biochar mixtures after the incubation. The ammonium (NH4+), nitrate (NO3-), and reactive P concentrations in soil column leachates were recorded for eight leaching events. Soil properties and plant-available nutrients were compared between treatments and control manure & soil. Manure-(HAP&HAPE) biochar treatments significantly increased soil organic matter (OM) and increased soil total C, N, and improved soil bulk density. Concentrations of KCl-extractable NH4+ and NO3- significantly increased in HAPE column leachates during this 4-week study and in the soil after the experiment. A significant reduction in soil Mehlich3 Cu was also observed for the manure-HAPE mixture compared with the control. Overall, the manure-biochar incubation enabled biochar to sorb nutrients from manure, and the subsequent manure-biochar mixture application to soil improved soil quality and plant nutrient availability in comparison to conventional manure application to soil. This proof-of-the-concept study suggests that biochars could be used to solve both environmental and agronomic challenges and further improve the sustainability of animal and crop production agriculture.