08Jan/18
Trophic levels of the soil food web

Soil quality impacts of agricultural and municipal biosolids applications

Background

Soil health management refers to the preservation and improvement in soil physical, chemical, and biological properties to maximize the productive capacity of soil. Cover crops and reduced tillage are promoted for improving soil health; however, soil amendments such as application of livestock manure and municipal biosolids have received less attention as a soil health improvement practice. A literature review, funded by the North Central Region Water Network and the Soil Health Institute, was conducted to summarize and discuss results of studies reporting chemical, physical, and biological soil properties from application of livestock manure, animal by-products (i.e. compost), and municipal biosolids and to identify further research needs.

Current State of the Science and Understanding

The effects of manure and municipal biosolids on soil physical and chemical properties are well documented in scientific literature (and previously in this blog). When applied at agronomic rates, these amendments:

  1. increase soil organic carbon,
  2. increase soil cation exchange capacity,
  3. provide beneficial micronutrients for crops,
  4. decrease soil bulk density,
  5. improve soil resistance to compaction,
  6. increase soil aggregate stability,
  7. increases water retention and plant available water, and
  8. increase water infiltration, which reduces risks for runoff and erosion.
Trophic levels of the soil food web

Figure 1. Trophic levels of the soil food web (Source: nrcs.usda.gov)

The effects of these amendments on soil biological properties have not been, however, well researched, likely due to cost and time constraints for these measurements. Three main soil biology measures are microbial abundance, diversity, and activity, with abundance being the most commonly reported. These reveal the types (diversity), quantity (abundance), and roles (activity) of soil microbes. Overall, manure and biosolid applications increase the abundance of bacteria, fungi, and earthworms but does not affect abundance of higher order soil microarthropods (i.e. shredders and predators) (figure 1). Increased microbial activity (e.g. respiration and mineralization), an indicator of nutrient cycling, increases with organic amendments; however, faunal diversity does not appear to be positively impacted compared to inorganic fertilizer.

Challenges and Research Needs

Most published research reporting on the impacts of manure or biosolids on soil properties, crop production, and water quality is based on studies involving annual application of the amendment. If annual application rates exceed crop nutrient requirements, risks of leaching, runoff, and accumulation of nutrients (e.g. N, P, K, salts and heavy metals) increase. While few studies have investigated the residual effects of manure or biosolids, improved infiltration and decreased runoff and erosion have been demonstrated to have enduring effects in the years immediately following the last manure application.

Future research endeavors should:

  1. incorporate quantification of soil biological metrics to improve understanding of manure and biosolids effects on ecosystem services such as nutrient cycling;
  2. investigate short- and long-term effects of a single manure or biosolids application to support identifying the optimal frequency of application for soil health and

provide discussion clearly relating research findings to management decisions relevant to agricultural crop producers.

Authors: Linda Schott and Amy Schmidt, University of Nebraska-Lincoln

Reviewer: Humberto Blanco, University of Nebraska-Lincoln

01Dec/17
Value of beef open lot manure assuming crop benefits from potassium supplementation and 5% increase in yield. Estimated manure value is $28/ton.

What is the Economic Value of Manure?

Manure has value.  That value may result from improvements in soil quality, increases in yield, and replacement of commercial nutrient required for crop production.   Previous articles on manure’s value have focused on its soil health,  environmental benefits, and tools for estimating manure’s value. This article will focus on the economic benefits of manure. Continue reading

01Nov/17
Photo of rainfall simulation study

Setbacks Reduce the Concentration of Manure Constituents in Runoff

What setback distance is required to reduce the concentration of manure constituents in runoff to background values? John E. Gilley, Aaron J. Sindelar, and Bryan L. Woodbury, researchers with the USDA-Agricultural Research Service, examined the effects of setback distance on concentrations of selected constituents in runoff following land application of beef cattle manure to a site in Southeast Nebraska (Figure 1).  Continue reading

03Oct/17
photo of sand recovery system in Iowa

Can application of sand laden manure impact soil texture?

What does soil texture have to do with manure? Sand bedding has become a popular choice at many dairies due to the cow comfort and health benefits it offers. A question raised at manure application time is how does sand in the manure impact the health of my soils? While using sand laden manure as a fertilizer source does add sand to the soil, the change is small and would take about 100 years for a silt loam soil to see a change in soil texture. Continue reading

01Sep/17

The Soil Health Institute and the Water-Soil Health Connection

The Soil Health Institute (SHI) was created in 2015 to “Safeguard and enhance the vitality and productivity of soil through scientific research and advancement.” As the independent, non-profit organization charged with coordinating and supporting soil stewardship and advancing soil health, the SHI is focused on fundamental, translational, and applied research and ensuring its adoption. Enhancing soil health allows us to improve water quality, increase drought resilience, reduce greenhouse gas emissions, improve farm economies, provide pollinator habitat, and better positions us to feed the nine billion people expected by 2050. Continue reading

01Aug/17
A recently added aggregate of livestock manure (left) versus a heavy soil aggregate of poor structure on the right.

Soil Organic Matter and Its Benefits

Soils of Northern Great Plains are relatively young (11000 to 14000 years old) and have some of the highest organic matter levels (4 to 7%) of all mineral soils in the United States (Overstreet and DeJong-Huges, 2009). However, continuous cropping, poor management practices and loss of topsoil have adversely affected the soil organic matter levels. Continue reading

03Jul/17
soil with earth worm

Manure Impact on Soil Aggregation

If manure increases formation of larger (macro) and more stable soil aggregates, several benefits may result for fields fertilized by manure compared to commercial fertilizer including:

  • Reduced runoff and soil erosion;
  • Increased water infiltration into the soil possibly leading to greater drought tolerance; and
  • Partial offsetting of higher soil P levels resulting from manure application and limiting P loss to local surface water.

Continue reading

01May/17

Manure and Soil Health Presentations Bring Experts, Give Voice to Wondering Minds

Farmers and ranchers are becoming increasingly aware of the importance of soil quality/health to the productivity and sustainability of their agricultural system. Research and field observations have demonstrated that carefully managed manure applications can contribute to improved soil quality with limited environmental and social risks. However, a comprehensive assemblage of outputs and conclusions from research studies, field trials, soil labs databases, and other sources has never been developed. Continue reading

19Apr/17

Should farmers strive for more organic matter mineralization or stabilization?

Tunsisa Hurisso and Steve Culman, School of Environment and Natural Resources, Ohio State University

In short, the answer is usually both.

Soil organic matter is a mixture consisting of various compounds (e.g. simple sugars, cellulose, proteins, etc.) derived primarily from plants and microbes. It represents 1-6% by mass of agricultural soils, but plays a disproportionate role in soil function. Organic matter in soils acts like a sponge, holding nutrients (sequestration or stabilization) that become available to plants when organic matter is broken down (mineralization) by the collective action of the soil food web (mainly by bacteria and fungi). In addition to nutrients, organic matter also enhances the soil’s water holding capacity, making farmlands more resilient to periods of drought. In contrast, when organic matter is depleted due to repeated plowing and/or removal of crop residues from the field, the ability of a soil to hold water and nutrients will be greatly diminished. Therefore, growers should strive for both organic matter stabilization and mineralization processes to ensure short-term crop productivity and to build long-term soil resilience.

Continue reading