This study was conducted across five cattle ranches located throughout New Mexico.
At each ranch, we identified 18 headcuts (with the exception of the ranch in Mora, where we identified only 9 headcuts). In fall/winter of 2021, rock rundown structures were built and we marked a 5 m x 5 m plot immediately upslope of the structure. We collected baseline measurements for infiltration rate and aggregate stability in the plots and measured the cross-sectional area of the channel below the headcut (see below). We then randomly assigned the plots to a treatment combination in a full factorial design: organic amendment (three levels: compost, mulch, or control [no amendment added]) and native seed addition (two levels: 2.5 lbs of locally found native seeds applied across the plot by hand), or control [no seed applied]) with three replicates per treatment combination.
Organic amendments were applied to a 0.64 cm depth using wheelbarrows, rakes, and shovels. Wood mulch was purchased from Soilutions in Albuquerque, NM. Premium Compost was also purchased from Soilutions and used at the Mora, Santa Fe, and Eddy county ranches. Compost purchased from a local hog farm that composts waste and wood chips in windrows was used for the two ranches in Rio Arriba County.
Several responses were measured in 2021 (baseline) and all measured after one year in 2022. Infiltration rate was measured with a single ring infiltrometer (15 cm diameter) in a randomly selected interspace in the plot. 444 mL of water was added and the time for infiltration was recorded, then the process was repeated with a second 444 ml. Aggregate stability was measured on six haphazardly-collected surface samples within the plot using methods from Herrick et al. (2001). We measured the channel cross sectional area using a portable erosion/accretion metering device described in Kornecki et al. (2008).
We assessed aboveground biomass within our study plots by collecting aboveground biomass using a randomly placed 45 cm x 45 cm PVC square to clip all plants to ground level after one year. Material was placed in paper bags, dried at 60 C for 3 days, oxidized material was removed with forceps to capture material that was likely to have been alive in the previous 1 year, and weighed to 0.01 g. Vegetative cover and species richness and diversity were captured using the line intercept method on a 5 m diagonal transect in the plot above each rock structure. We identified dominant plants that intersected the transect every 5 cm or categorized the point as bare ground or litter. Litter included fine and coarse herbaceous and woody debris and dung. Soil carbon was measured after one year by taking one soil core in each study plot (2 cm diameter, 10 cm depth) and soil samples were sent to Ward Laboratories (https://www.wardlab.com/) where soil organic carbon levels were analyzed using the combustion method.
References:
J.E Herrick, W.G Whitford, A.G de Soyza, J.W Van Zee, K.M Havstad, C.A Seybold, M Walton (2001) Field soil aggregate stability kit for soil quality and rangeland health evaluations, CATENA, 44(1), 27-35, https://doi.org/10.1016/S0341-8162(00)00173-9.
T. S. Kornecki, J. L. Fouss, S. A. Prior (2008) A portable device to measure soil erosion/deposition in quarter-drains. Soil Use and Management 24(4), 401-408, https://doi.org/10.1111/j.1475-2743.2008.00181.x.