The Use of Tree Mulch to Increase Native Grassland Pasture Fertility

The Use of Tree Mulch to Increase Native Grassland Pasture Fertility

Summary

“The Use of Tree Mulch to Increase Native Grassland Pasture Fertility” project activity began in May 2011 with site selection and the layout of the test plots. Once the test plot area was identified a soil sample representative of the test area was collected and sent in for analysis.

While waiting for the soil test analysis to be completed, a chipper-shredder was purchased so the trees could be chipped into small pieces for application onto the pasture test plots. Once the chipper-shredder was received, test plots identified for receiving the chips were dressed with a topcoat of the mulching material.

Fertilizers were added to the test plot area based upon the soil test report’s analysis. After fertilization, two test plots were inoculated with mycorrhizal fungi, with one of the inoculated plots seeded with legumes.

Objectives/Performance Targets

The test plot site was selected for its selection of native warm season grass and legumes, along with easy public access for project review. About one-half acre of native pasture was chosen and partitioned in the following manner as shown in Figure 1.

Each control plot is approximately 17 feet by 117 feet. A mulched plot is twice a control plot, measuring 34 feet by 117 feet. Each plot is prepared in the following manner.

Control Plot #1 – No cedar tree mulch added. See Figure 2 for photo.

Mulched Plot #1 – Light application of cedar tree mulch. See Figure 3 for photo.

Control Plot #2 – No cedar tree mulch added.

Mulched Plot #2 – Heavy application of cedar tree mulch.

Control Plot #3 – No cedar tree mulch added.

Mulched Plot #3 – Heavy application of cedar tree mulch with endo- and ectomycorrhizal fungi inoculation. See Figure 4 for photo.

Mulched Plot #4 – Heavy application of cedar tree mulch with fungi inoculation and seeded with legumes.

Cedar tree mulch is created with the assistance of a Wallenstein chipper that fits onto the 3-point of our John Deere 4010 tractor. The Wallenstein model number WLBX92S chipper can be seen here: http://www.embmfg.com/Forestry/Chippers/BXs-models.aspx#anc_BX92s.

In order for the soil to have good humus levels the soil must be biologically active. The production of humus comes from the degradation of organic matter by the soil organisms. In order for the soil organisms to efficiently create humus the soil minerals must be in the proper balance to be conducive for humus accumulation. Soil samples were gathered with a soil test probe, sampling the soil surface to a depth of eight inches. The soil test report for the test plot area shows an imbalance in the soil’s major macronutrients. The soil test report, analyzed by Midwest laboratories, is shown in Figure 5.

This soil type is considered a medium soil with a cation exchange capacity near 15. But looking at the “PERCENT BASE SATURATION” we see that the calcium (% CA) is 92.2 %; magnesium (% Mg) is 4.0 %; and potassium (% K) is 3.6 %. It’s desirable to have the percent calcium in the range of 60-70 percent; the percent magnesium in the range of 10-20 percent; and the percent potassium in the 3-5 percent range. Therefore, for this soil our calcium level is high and the magnesium level is low and we’d like to apply the appropriate fertilizers to push the soil closer to the desired level.

The pH of the test soil is 7.7, a slightly alkaline soil. When the soil nutrients are closer to the ideal proportions the pH will move lower becoming slightly acidic. We’d like a slightly acidic soil so more of the micronutrients can become available (if present) for plant growth. With the soil so heavily skewed with calcium it’s unlikely we can create a dramatic change in the soil pH, but we can nudge the soil in the right direction by adding some magnesium and sulfur.

It was decided in order to push the soil macronutrients in the desired direction we would add 100 pounds of magnesium oxide, 50 pounds of magnesium sulfate and 38 pounds of elemental sulfur to the test plot area. The fertilizer application was applied in September 2011. We entered a drought period starting the first part of July and didn’t receive significant moisture until late winter. With the lack of soil moisture at the time of the fertilizer application we decided to apply only half of the magnesium sulfate. The remaining 25 pounds of magnesium sulfate will be applied at green-up in the spring of 2012. Magnesium oxide and elemental sulfur need microbial action in order to become plant available. Magnesium oxide and elemental sulfur are not very water soluble. Magnesium sulfate (Epsom salt) is very water soluble, with magnesium an essential ingredient in chlorophyll production. We wanted the water soluble form of magnesium readily available when the plants would be taking up the mineral, so we’ve postponed some of the magnesium sulfate application. All of the magnesium oxide and sulfur products were applied with the magnesium sulfate.

When the soil is out-of-balance, such as seen in our test plot area, the micronutrients can be tied up and not readily available to the plants. The soil test report shows the phosphorus levels to be very low with P1 at 5 parts per million (ppm) and P2 at 15 ppm. I’d like to see the P2 level closer to 50 ppm or higher but at this time we’re going to hold back with an application of phosphorus and give the soil time to adsorb the applications of magnesium and sulfur. A reduction of the soil pH may make phosphorus and other micronutrients more available. If this year’s (2012) soil test reports shows insufficient nutrients we will consider adding some phosphorus.

The whole point of the study is to increase the soil’s fertility so better forages can be produced to grow healthy cattle, using resources locally available. One way to measure success is by measuring an increase in soil carbon. Shown in Figure 6 is the soil test report from Midwest Laboratories showing the total soil organic carbon to be at 1.76%. An increase in soil carbon (humus) will have a couple of beneficial aspects. An increase in soil humus will increase the water storage capacity of the soil, making the plants more drought tolerant. And more soil humus will increase the soil’s cation exchange capacity, the soil will be able to hold more cation and anion nutrients.

Three days prior to the application of the elemental sulfur, Mulched Plots #3 and #4 were inoculated with mycorrhizal fungi purchased from Fungi Perfecti. The mycorrhizal product used can be found at this web address: (http://www.fungiperfecti.com/mycogrow/index.html). The MycoGrow™ Soluble mixture contains endo- and ectomycorrhizal fungi along with beneficial bacteria needed to have a biologically active soil. As noted above, a drought condition started in early July, with only 52/100 of moisture occurring during the month of September in three separate rains. Because of this situation only half of the mycorrhizzal product was applied to Mulched Plots #3 and #4 in late September. The remaining half of the product will be applied this spring when there is sufficient rain to move the fungal spores into the soil profile. Since the Mulched Plots are small, the mycorrhizal product was applied by hand with the aid of a garden sprinkler can. A lick tub was filled with well water (no chlorination) and one-half pound of the HMSO1P MycoGrow™ Soluble product was added to the water then stirred gently. The water mixture was then applied across the two test plots with a garden sprinkler can.

In late September a quarter pound of Alice White Clover/Crimson Clover mixture was broadcast across Test Plot #4. The clover was added to encourage nitrogen production for consumption by the soil life. The Alice White Clover is a perennial while the Crimson Clover is an annual this far north. It is hoped after the first year of growth the Crimson Clover will freeze out. When the Crimson Clover freezes then dies, the nitrogen in the clover’s roots will become available for consumption by the surrounding soil life. Once the Crimson Clover is finished, subsequent nitrogen will be injected into the soil by the perennial Alice White Clover.

• Figure 1 – Test Plots
• Control Test Plot – No Mulch
• Test Plot – Light Mulch Application
• Test Plot – Heavy Mulch Application
• Organic Soil Carbon – Initial
• Soil Test Report – Initial

Accomplishments/Milestones

At this time no project results are available showing an increase in soil humus. In June 2012 soil samples will be extracted from each test plot and sent in for mineral and carbon analysis. Soil humus creation is a slow process. With a series of annual soil test reports we hope to see a general increase in the soil carbon content. A few years of data will be needed in order to have statistically relevant results.

Impacts and Contributions/Outcomes

This coming year we will be soil sampling the test plots, finish fertilizing with the magnesium sulfate, apply the remaining mycorrhizal inoculant on Mulched Plots #3 and #4, and create roadside posters to inform the public of the SARE activity taking place.

Once the pasture growth has increased appropriately, the test plot pasture will be grazed with cattle. We expect to graze the test plots twice during the growing season. The grazing plan will be conducted according to research presented by Dr. Manske of NDSU Dickinson Research Extension Center. Dr. Manske’s information can be found here: http://www.grazinghandbook.com/.

Simply stated, Dr. Manske’s research shows that grazing cattle can be used to facilitate nitrogen pumping within the soil. The warm season perennial grass plants will feed the soil microbes with carbohydrates in the root exudates. In exchange, the soil microbes will provide nitrates to the plants for plant growth. The key soil organisms needed for this nitrogen exchange to function are the mycorrhizal fungi.

Collaborators: