Soil health and water quality nexus in sustainable agroecosystems

Progress report for LNC20-439

Project Type: Research and Education
Funds awarded in 2020: $249,932.00
Projected End Date: 10/31/2023
Grant Recipient: THE OHIO STATE UNIVERSITY
Region: North Central
State: Ohio
Project Coordinator:
Dr. VINAYAK SHEDEKAR
THE OHIO STATE UNIVERSITY
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Project Information

Summary:

1.   PROJECT SUMMARY

This project explores co-benefits of long-term soil health practices (SHPs) and their potential impacts on water quality. Long-term, continuous, and integrated SHPs (e.g. no-till+crop rotation+cover crops) build healthy soils and are important element of sustainable agroecosystems. Few studies assess the effect of improved soil health on edge-of-field (EOF) water quality, i.e. nutrient and sediment loss. Those studies that have focused on both soil health and water quality have primarily considered the short-term effects of a single SHP. However, these studied systems are in fact “transitional” and measurement likely ceases before the systems become “mature” and manifest their full potential. Our preliminary studies piloted through past SARE-funded efforts suggest that fields with transitional (3 to 10 years) to mature (40+ years) SHPs not only exhibit unique soil health indicators, but also have unique water quality signatures compared to conventionally managed systems. Through this interdisciplinary and farmer-oriented project we will compare soil health and EOF water quality on paired-fields that have different histories of integrated SHPs, specifically (1) conventionally managed (2) transitional, and (3) mature SHP systems. We will work with farmer collaborators to assess soil health and monitor EOF water discharge, concentrations of sediment, soluble and total reactive nutrients in surface and subsurface drainage. Using soil health and crop yield data we will derive a ‘relative SHP-maturity index’ for each site. The paired-field design will aid in site-specific comparisons among the treatments while controlling for spatio-temporal and climatic factors. We will conduct inter-site comparisons of water quality impacts using correlation, multivariate regression, and principal component analyses. New information will be disseminated to stakeholders through farmer-led field days, conferences, news articles, peer reviewed publications/factsheets, and social media. The long-term funding option will enable us to (1) follow the sites through multiple crop rotations, and (2) track the 'transitional' sites as they become more mature, and over a range of climatic conditions. Such extensive dataset from the long-term project would validate and increase the confidence in findings. The learning outcome of the project will be an improved understanding of the relationship between soil health and EOF water quality in transitional and mature systems. The action outcome will be enhanced adoption of long-term SHPs by growers and promotion by educators who understand the environmental impacts/benefits of long-term soil health improvements. The project outputs and outcome will benefit agroecosystems, waters, and communities in Ohio as well as the North Central region.

Project Objectives:

2.   PROJECT OBJECTIVES/OUTCOMES

  • Objective-1: To assess soil health at conventional, transitional, and mature soil health practice (SHP) sites.
  • Objective-2: To monitor edge-of-field water quantity and quality at these sites.
  • Objective-3: To determine relationships between progressive soil health improvement and water quality at individual sites and across all sites.
  • Objective-4: To inform decision-makers about the soil health-agroecosystem-water quality nexus.

Learning outcome: improved understanding of the relationship between soil health and edge-of-field water quality in transitional and mature systems compared to conventional systems.

Action outcome: Clarifying the relationship between healthy soils and healthy waters will encourage broader adoption and incentivization of SHPs.

Introduction:

Healthy soils could potentially reduce agricultural nutrient losses by several mechanisms including more efficient nutrient- and water-use, improved water infiltration and water holding capacity, and reduced soil erosion (USDA-NRCS 2015). Conversely, nutrient loss risk could be increased by SHPs through increased concentration of nutrients, particularly in near-surface soil layers. Several studies have related soil health practice implementation to field scale nutrient losses, reporting inconsistent effects including increased P losses. There is a need for long-term research to determine how the water quality signature of SHP systems diverges over time from that of conventional systems. This project aims to fill this gap by connecting improvements over time (especially long-term) in soil health to the edge-of-field water quality impacts. 

Research

Hypothesis:

We anticipate testing the following hypotheses: 

(1) Soil health indicators under mature soil health practices are significantly different from those under transitional and no SHPs.

(2) Water quality signatures from fields under mature soil health practices are significantly different from those under transitional and no SHPs. 

Materials and methods:

We have adopted a collaborative, interdisciplinary, inter-agency approach and identified collaborators from within OSU and the USDA-ARS who have existing edge-of-field (EOF) monitoring infrastructure that can be leveraged to broaden the scope and impact of the proposed project.

We have established monitoring at three paired-field sites (6 individual fields) across Ohio (Figure-1). Each site consists of a mature SHP system compared to a transitional and/or conventional system. The paired-field approach helps minimize the uncertainty due to local factors as well as inter-annual variability. The sites are: (1) USDA-ARS site - MM (2 fields) comparing a conventional production system to a newly transitional system and will be monitored and maintained by the USDA-ARS as part of their EOF research network. There is no farmer collaborator since this is a demonstration farm in Seneca County. (2) OSU-PPP site - DM (2 fields) comparing a mature, long-term no-till +cover crops field with a neighboring conventionally managed field. The mature field is under 30-years of no-till and 15-years of cover crops.  and (3) Brandt site - DB (2 fields) comparing a mature field with a  a conventionally managed field. 

Site locations
Location map of research sites

Objective 1 - Assessing soil health 

Contributing areas at DM site
Example of soil sampling locations in paired fields

At each field site, we will determined sampling zones based on soil types, slopes, and yield histories. Standard 30 cm (12 in.) soil cores were taken in each zone with GPS-guided sampling procedure in year-1 (Fall 2020). The soil cores were then processed in laboratory, split into three depths (0-5 cm i.e. 2in., and 5-15 cm i.e. 2-6 in., and 15-30 cm, i.e. 6 to 12 in.), and sent to collaborating and external labs for soil health analysis. The list of analyses is as follows: 

Soil biological indicators: Haney test, Phospholipid fatty acid (PFLA), phosphatase enzyme activity.

Soil chemical indicators: pH, electrical conductivity, soil organic matter, total organic carbon, total- and organic nitrogen, active carbon (POX-C), plant available N-P-K, base saturation, cation exchange capacity, ACE protein.

Soil physical indicators: Bulk density, aggregate stability using wet sieving,

Objective 2 - Monitoring edge-of-field water quantity & quality

A total of 4 (at Brandt site and PPP site) of the 6 fields were installed with new monitoring equipment. The remaining 2 fields (USDA-ARS site) are already instrumented. In general, the surface runoff and subsurface (tile) drainage monitoring was set up as follows: An H-flume with wing walls captures surface runoff and allows for flow measurement. The outlet of sub-surface (tile) drainage system is retrofitted with a Thelmar V-notch for flow measurement. Automated water sampling equipment (Isco 6712 water sampler, Isco Signature bubbler flow meter, and Isco 350 Area/Velocity sensor) is installed to collect water samples and measure discharge. The equipment is housed in an insulated box and powered by on-site solar panels and battery. A propane water heater enables cold-weather sampling. Precipitation is measured using an on-site tipping bucket raingauge and/or automated weather station. 

Note that with the help of our shared resources, we were able to include "surface runoff monitoring" at all three paired sites. This was an improvement over the originally proposed research plan, that focused only on subsurface drainage losses.

Paired Fields at Brandt Site Edge-of-field water quality monitoring Soil Sampling

Water Quality analysis

The automated water samplers collect 2-day composites at 6-hr time intervals during baseflow conditions and 1-hr composites at 15-minute interval during high flow conditions. We visit each site every 2 weeks for sample collection and system maintenance. The water samples from the USDA-ARS site are then analyzed in the  USDA-ARS analytical laboratory using methods described in Williams et al. (2015). Samples from the Brandt and PPP sites are returned to OSU water quality laboratory and analyzed for concentrations of sediment (as needed), ammonium (NH4-N), nitrate (NO3-N), total Kjeldahl nitrogen (TKN), total N, DRP, and total P using methods similar to the USDA-ARS laboratory.

 

Research results and discussion:

Soil Health Analysis - Preliminary Results: 

Although, we have not received all the soil health data from the first year sampling, the preliminary analysis based on partially received data suggest a logical trend of soil health enhancement from soils under no SHPs (conventional fields) to those under transitional SHPs and mature SHPs. We also compare some of these results with soils from nearby woods. See figures below for preliminary results of soil organic matter, water stable aggregates and enzyme activity observed at the Brandt site. 

Soil Health - Soil Organic Matter Soil health - water stable aggregates Soil Health - Enzyme Activity

Edge-of-field water quantity and quality  - Preliminary Results:

We were able to summarize water quantity and quality data collected at two of the three paired sites for calendar year 2021. The preliminary results are presented in the following figures with brief description in figure captions. 

Results
Although, the Long-term SHP field (green line) generated huge amount of total tile flow (41,472 ft3) compared to the conventional field (red line), when normalized on "per-acre" basis, the tile flow accounted for only 0.17 in from the long-term soil health field, compared to 0.3 in. from the conventional field.
Results
Similar to tile flow, the surface runoff from long-term SHP field (green line) was much less than that from the conventional field (red line).
Results
For the calendar year 2021, the total discharge (i.e. tile + surface) from fields under long-term soil health practices was less than that from the fields under no SHPs and conventional tillage practices. Note that one of the long-term SHP fields - the DM field did not generate any surface runoff.
Results
Although, the concentrations of dissolved reactive phosphorus (DRP) were greater at one of the long-term SHP fields, the total loss of DRP through tile+surface discharges was much less from long-term SHP fields than that from the fields under no SHPs.
Results
Although, the concentrations of total phosphorus (TP) were greater at one of the long-term SHP fields, the total loss of TP through tile+surface discharges was much less from long-term SHP fields than that from the fields under no SHPs.
Results
The nitrate concentrations as well as loads were much lower from fields under long-term SHPs compared to those from fields under no SHPs.

 

Research conclusions:

Preliminary findings suggest that compared to “No SH” long-term soil health systems…

  1. Generate less volume of water discharge through both tile and surface pathways
  2. Had lower DRP and TP losses per acre, despite greater DRP and TP concentrations in surface runoff
  3. Had lower concentrations and losses of Nitrate per acre

For conclusive evidence long-term monitoring is crucial at these sites.

Participation Summary
4 Farmers participating in research

Education

Educational approach:

This being the first year of the project, we did not conduct any major education and outreach, except for the following: 

  • Vinayak Shedekar and Nathan Stoltzfus presented an overview of project and monitoring set up during the virtual Soil Health Field Day conducted at the Brandt Site in collaboration with the Ohio No-Till Council. (April 7, 2021). See minutes 57 to 71 of https://www.facebook.com/OhioNoTill/videos/1410154932672947/ 

Project Activities

Water quality research update on Brandt Farm

Educational & Outreach Activities

3 On-farm demonstrations
1 Webinars / talks / presentations
1 Workshop field days

Participation Summary:

150 Farmers
25 Ag professionals participated
Education/outreach description:

Virtual Soil Health Field Day at Walnut Creek Seeds (Brandt Site) by the Ohio No-Till Council 

Recording available at: https://www.facebook.com/OhioNoTill/videos/1410154932672947/

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.