Three control plots along with four test plots have been constructed to monitor a change in soil carbon caused by the application of Eastern Redcedar chips to native grassland pasture. Soil carbon data has been collected. Once three years of data have been collected, statistical analysis will be conducted on the data to determine the trend in soil carbon levels.
The Oak View Park (a.k.a. Oak View Beef) ranch has an abundance of Eastern Redcedar trees at various stages of growth. Instead of continuing the practice of burning piles of cut cedar trees, we speculated that some good could come from the utilization of chipped cedar trees.
The soils on this ranch consist mainly of various types of sand (we’re located on the eastern edge of the Nebraska sandhills region) with an aerobic zone appearing to extend up to three feet deep (the depth to which a fence post will rot). Historically, many of the land parcels on the ranch suitable for farming (prior to cedar tree infestation) have been tilled, with active tillage ending in the late 1950s. Once we took ownership of the ranch initial soil tests indicated that the soils have less than 1% humus, are deficient in calcium and lack sufficient phosphorus levels. The soils have been mined out with traditional farming methods. Ironically, subsoil testing down three-to-four feet deep shows excess quantities of calcium and phosphorus, registering 3691 ppm calcium and 126 ppm phosphorus. This lack of upper soil fertility manifests itself with Big Bluestem, Switchgrass and Indian Grass commonly growing as bunch grasses with no seed heads. Exposed bare ground is common among the plants. A cross-section of the soil in the barren spaces lacks a well-defined A-horizon.
Bare ground heats up considerably faster than soil protected with a layer of thatch. A thatch layer also helps conserve soil moisture by protecting the soil from desiccation. The longer a soil can be kept cool with adequate moisture the longer the microbial life can remain active. It’s the soil’s microbial life that recycles the minerals in the soil and creates humus (soil carbon).
An increase in humus has the capability to store more moisture. More humus also increases the soil’s cation (CEC) and anion (AEC) exchange capacities. The higher the CEC/AEC the more nutrients the soil can hold and eventually make available to the plants, thus an increase in soil fertility. Of course, if the nutrients are not present in the soil, the nutrients will need to be added by some other means to fill the AEC/AEC reservoir.
The objective of this project is to increase the soil carbon levels in grassland pasture by using the residue from chipped Eastern Redcedar trees to cover the topsoil.
Soil carbon was measured at the beginning of the project, then measured again two years later for comparison. It is expected to take several years of carbon measurements to see a statistical impact upon the soil carbon levels.
The initial soil carbon level sample was collected from all test plots. This sample established the year 2011 baseline. Separate soil samples were collected in year 2013 from the Control, Mulch 1, Mulch 2, Mulch 3 and Mulch 4 test plots. Each subsequent year will test soil carbon levels in each test plot to determine the change in soil carbon levels.
You can find the differences among test plots by reading the project proposal. In summary, the three Control plots have no cedar chips added; Mulch 1 has a light application of cedar chips; Mulch 2 has a heavy application of cedar chips; Mulch 3 has a heavy application of cedar chips along with an innoculation of endo- and ectomycorrhizal fungi; and Mulch 4 has a heavy application of cedar chips with fungi innoculation and seeded with a legume.
An increase in soil carbon has not yet been verified. It’s still too early in the project to see a significant change in soil carbon. If successful, we expect to see the soil carbon increase. With an increase in soil carbon we expect to see an increase in the soil’s exchange capacity and ability to hold water (more drought tolerance).
Educational & Outreach Activities
At this time only a road side poster has been created to identify the SARE research plots to the public. With more time and the accumulation of more data we plan to share the information as noted in the original SARE proposal, through the county extension newsletter and natural resource district’s (NRD) newsletter/web site.