Understanding production and conservation tradeoffs of vertical tillage practices

Progress report for GNE21-263

Project Type: Graduate Student
Funds awarded in 2021: $14,124.00
Projected End Date: 07/31/2023
Grant Recipient: Penn State University
Region: Northeast
State: Pennsylvania
Graduate Student:
Faculty Advisor:
Dr. John Wallace
Penn State University
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Project Information

Project Objectives:

On-farm strip trials will be utilized to contrast no tillage with vertical tillage conducted once in the spring to manage corn residue after no-till corn grain production in transition to no-till, full-season soybean production.  Our overall objective is to characterize and communicate production and conservation tradeoffs associated with vertical tillage practices using a multi-criteria assessment.  Specific objectives include:

Objective 1. Evaluate vertical tillage effects on surface residue cover [i.e., soil erosion potential].

Hypothesis 1. We expect to measure greater than 60% surface residue cover in the no-till treatments and less than 60% surface residue cover in the vertical tillage treatments.

Objective 2. Evaluate vertical tillage effects on weed management outcomes by measuring (a) pre-plant winter annual weed control, (b) summer annual weed emergence timing [i.e., false-seedbed potential], and (c) soil-applied residual herbicide efficacy.

Hypotheses 2. Relative to no-tillage, vertical tillage will (a) reduce density of established winter annual weed species, (b) increase recruitment of early-emerging summer annual weed species due to stimulation of disturbance-related germination cues, and (c) increase soil-applied residual herbicide efficacy due to reduced herbicide interception and adsorption by crop residues.  We anticipate the magnitude of vertical tillage effects on weed control will vary considerably across locations but be partially explained by the difference in surface residue incorporation within each location.

Objective 3. Evaluate vertical tillage effects on crop performance metrics, including (a) crop emergence, and (b) crop yield.

Hypotheses 3. Relative to no-tillage, vertical tillage treatments will result in (a) more uniform soybean plant emergence and early season vigor and (b) higher crop yields.

Objective 4. Evaluate vertical tillage effects on selective nutrient management factors, including (a) pH stratification, and (b) P stratification [i.e., nutrient loss potential] across the soil profile [0-5 cm, 5-10 cm, 10-15 cm, and 15-20 cm depths].

Hypotheses 4. Relative to no-tillage, soil within vertical tillage treatments will be characterized by (a) higher pH and (b) lower soil test P levels at shallower soil depths.

Objective 5. Evaluate vertical tillage effects on short-term soil health indicators, including (a) soil organic C stratification, (b) soil penetration resistance [i.e., compaction alleviation], and (c) soil bulk density.

Hypotheses 5. Relative to no-tillage, vertical tillage will result in (a) decreased soil organic C stratification due to greater soil mixing with crop residue; (b) higher soil penetration resistance below the operating depth of the vertical tillage tools, and (c) lower soil bulk density at shallower soil depths.

Introduction:

The purpose of this project is to assess the effects of vertical tillage on crop production and soil conservation goals in long-term, no-till cropping systems within southeastern Pennsylvania. Adoption of vertical tillage is increasing in the Northeast to address residue management and planting challenges in long-term, no-till cropping systems, yet little is known about the impact of this practice on soil conservation, soil health, pest management and crop productivity. Consequently, our proposed research will contribute to sustainability goals of no-till grain crop systems in the Northeast by providing a science-based, decision-making framework for farmers to assess the impact of vertical tillage on soil conservation, water quality, crop productivity, and net farm income.  We propose to study vertical tillage impacts on these sustainability goals with use of coordinated on-farm trials, which will facilitate co-learning opportunities among growers, extension personnel, agronomic consultants, and ag retailers within Pennsylvania.

No-till crop production aims to minimize soil disturbance while maintaining at least 60% surface residue cover (Residue and Tillage Management, 2016).  This conservation practice, coupled with high corn yields, can result in accumulation of substantial crop residue on the soil surface.  A need to effectively manage previous crop residue prior to planting a subsequent crop has led to the adoption of minimum (or ‘vertical’) tillage.  Vertical tillage is primarily a residue management practice characterized by cutting, sizing and incorporation of crop residue within the top 5-10 cm of soil. 

Grower adoption of vertical tillage has steadily increased in the last 10 years, especially in southeastern Pennsylvania where increasing corn grain yields result in corresponding increases in corn residue (Adler et al., 2015).  Vertical tillage can improve crop stand establishment without having to significantly alter planting equipment to negotiate crop residues, thus off-setting planter upgrade and maintenance costs.  Performing vertical tillage also negates the need for additional replacement or after-market modification of existing harvesting equipment designed to size and distribute residue more efficiently.  Growers also use vertical tillage to hasten soil drying and warming in wet spring seasons, potentially facilitating earlier or more timely crop establishment.

An external policy factor partially responsible for increasing vertical tillage was an income tax credit that growers could obtain when purchasing “Low-Disturbance Residue Management Equipment,” which included popular vertical tillage tools, through the Resource Enhancement and Protection (REAP) Program sponsored by the Pennsylvania State Conservation Commission (REAP Program Guidelines, 2019).  From 2007-2019, this tax credit incentivized growers to purchase vertical tillage tools to manage residue in no-till cropping systems.  However, a recent 2019 policy change removed the tax credit for vertical tillage tools due to grower use of increasingly more aggressive vertical tillage tools that produce soil disturbance levels that appear to no longer meet policy thresholds for soil conservation.

Our proposed research is designed to improve grower and policy decision-making related to the role of vertical tillage in conservation agriculture by utilizing a multi-criteria assessment to characterize production and conservation tradeoffs of this practice on farms in southeastern Pennsylvania, which are located within the sensitive Chesapeake Bay watershed.

Cooperators

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  • Dr. Charlie White (Researcher)
  • Dr. Sjoerd Duiker (Researcher)
  • Dr. Paul Esker (Researcher)
  • Jeffrey Graybill (Educator)

Research

Materials and methods:

We propose to conduct on-farm field trials that compare no-till and vertical tillage treatments on nine farms across Lancaster County (n=6) and Chester County (n=3) in southeastern Pennsylvania in 2021 and replicate on-farm field trials in 2022.  These cooperating farms consist mostly of cash grain operations raising no-till corn (Zea mays L.), soybeans (Glycine max L.), winter wheat (Triticum aestivum L.), and winter barley (Hordeum vulgare L.).  Well-drained silt loam soils coupled with frequent manure applications (and occasional applications of spent mushroom substrate) contribute to relatively fertile and historically high-yielding environments on all cooperating farms.  Many of the farms utilize no-till and cover cropping practices.

Experimental Design

On-farm strip trials comparing no-till and vertical tillage will be conducted using a nested treatment structure due to variability in tillage legacy and equipment type across farms.  We will use tillage management legacy as a grouping factor with two levels: 1) fields where long-term no-till has been practiced for approximately 10 years or more and where vertical tillage will be introduced (n=10); and 2) fields where vertical tillage has occurred annually for the previous six to eight years (n=10).  In total, ten tillage treatment comparisons will be conducted at locations with each tillage management legacy (with or without a history of vertical tillage), resulting in 20 pairwise tillage treatment comparisons and 40 experimental units.  At each cooperating farm, strip trials will be placed in either multiple fields or unique locations within large acreage fields that contain variability in soil conditions and/or typography. These trials will occur in fields being rotated from no-till corn grain to no-till, full-season soybeans.  In these fields, the corn stubble has remained unharvested and undisturbed over the winter.  Tillage treatments will be employed in the spring prior to planting in paired and randomly located field-length strips that include a no-till (NT) control strip and a vertical tillage (VT) strip.

Field Operations

Farmer cooperators will employ vertical tillage using owned or rented implements at an average working depth of 5 cm to manage no-till corn residue in the early spring (April) prior to establishing no-till, full-season soybeans.  The vertical tillage tools will be compliant with standards for “Low-Disturbance Residue Management Equipment” as defined by the Pennsylvania Resource Enhancement and Protection (REAP) Program Guidelines for fiscal year 2019 (REAP Program Guidelines, 2019).  These guidelines stipulate that qualifying equipment should be set as follows: (1) disc blade angle must not exceed five degrees, (2) disc blades must have no concavity, (3) working depth of equipment must not exceed four inches and (4) minimum surface residue cover must not fall below 60% throughout the year (REAP Program Guidelines, 2019).  Three types of common vertical tillage implements used on cooperating farms include a Salford Independent series tool (Salford Group, Inc., Salford, ON, Canada), a Great Plains Turbo-Till (Great Plains Manufacturing, Inc., Salina, KS), and a Kuhn-Krause Excelerator (Kuhn North America, Inc., Brodhead, WI).

Each cooperating farm will implement standard fertility, seed protection, and crop protection programs for no-till, full-season soybeans.  A burndown and pre-emerge herbicide program will be implemented on each farm and herbicide product selection will be determined by the cooperator or their custom pesticide applicator.  Additionally, all cooperators plan to apply a post-emerge soybean herbicide product(s).  Harvest data will be collected using either a yield monitor or by using a weigh wagon or truck scale.  Strip width will be based on the size of available harvesting equipment so one or two combine passes can be completed within tillage treatment strips.

Data Collection and Data Analysis

1. Soil conservation metric:  The proportion of surface residue cover will be determined after vertical tillage treatments are implemented (April) using the line-transect method following the USDA-NRCS standard surface residue cover assessment protocol (Estimating crop residue cover, 1984).

2. Weed management metrics:  We will measure winter annual weed abundance in the early spring (April) after tillage treatments are employed and just prior to soybean planting to evaluate the potential for vertical tillage to be employed as a pre-plant weed control tool.  We will also measure summer annual weed abundance at the early spring (April) sampling point to assess vertical tillage effects on recruitment of early-emerging summer annual weed species, which may facilitate the use of false-seedbed tactics in no-till systems.  To assess weed abundance, we will utilize a belt-transect sampling approach.  Three 15 m transects will be established in unique field positions (toe slope, foot slope, backslope) within each strip and co-located between paired strips (i.e., 3 paired transects; 6 transects per paired strip location).  The location of these three paired transects will be marked using geo-referencing software (i.e., QGIS) and these locations will be used for data collection later in the trial.  Within each transect, the presence or absence of weeds located within 15 cm on each side of the transect will be recorded every 15 cm lengthwise.  Presence data will be expressed as a proportion of the total number of observations per transect (n=100) as an estimate of weed abundance.  We will assess weed abundance in early summer (June) prior to a POST herbicide application using the same sample methodology to assess recruitment patterns of summer annual weeds and residual herbicide efficacy between no-till and vertical tillage strips.

3. Crop performance metrics:  Crop emergence will be assessed by measuring the emerged plant population when soybean plants reach the Cotyledons Expanded (VC) growth stage.  A 5.3 m long transect (equivalent to 17.5 ft or 1/1,000th of an acre) will be established in each strip at each previously georeferenced location.  Emerged soybean plants will be counted along this transect and the final plant stand calculated.  Timing and uniformity of soybean emergence may be influenced by warming soil temperatures or evenly distributed crop residue due to vertical tillage.  Crop yield will be measured using a yield monitor on the combine or by measuring crop mass harvested from each strip using a weigh wagon or truck scale.  By measuring crop yield at harvest, we evaluate a tangible and direct result of changing a field management practice. Grower interest in adopting or continuing to practice vertical tillage may grow or diminish based largely on yield results.

4. Nutrient management metrics:  Soil samples will be taken in late fall (October) after soybean harvest is completed to assess nutrient management and soil health metrics (see below).  Within each strip, three soil samples will be randomly collected around each georeferenced field position (n =3) used previously for the surface residue cover, weed abundance, and crop emergence metrics.  Soil cores will be stratified by sampling depth (0-3, 3-8, 8-15 cm) and then composited.  Soil pH stratification will be assessed using the buffer pH method conducted by the Penn State Agricultural Analytical Services Laboratory (AASL).  Soil P stratification will also be assessed by sampling depth.  Soil test P will be measured using a Mehlich 3 soil extractant based soil test conducted by the Penn State AASL.

5. Soil health metrics:  Soil sampling for soil health metrics will be conducted during the same sampling event and methodology as the nutrient management metrics (above).  Soil organic C will be measured by sampling each strip around georeferenced locations at 0-3, 3-8, and 8-15 cm depths.  Samples will be sent to the Penn State AASL for analysis.  We will also measure active carbon (permanganate oxidizable carbon - POXC) by sampling around the same georeferenced points and oxidizing the active C fraction of soil organic matter with a weak solution of potassium permanganate (KMnO4).  A hand-held colorimeter will be used, along with standard concentrations of POXC, to determine the sample specific values of POXC in mg C/kg soil (Weil, et al., 2003).  Field penetrometer readings will be taken in each strip around georeferenced points to measure soil penetration resistance at 2.5 cm depth increments to a maximum depth of 20 cm.

Statistical Analysis:  For each response variable described above, we will estimate the mean effect size of vertical tillage using linear mixed models by considering tillage treatment, tillage legacy and their interaction as a fixed effect and year, farm (nested within year), and field (nested within farm and year) as random effects.  Mean effect size for each production and conservation metric will be reported together to visualize management tradeoffs using our multi-criteria assessment framework.

Participation Summary
9 Farmers participating in research

Education & Outreach Activities and Participation Summary

3 Consultations
2 Webinars / talks / presentations
1 Workshop field days

Participation Summary:

45 Farmers
10 Number of agricultural educator or service providers reached through education and outreach activities
Education/outreach description:

Outreach activities engaged in to date include:

Summer Soil Health Field Day facilitated by Pennsylvania No-Till Alliance, July 2021, Lancaster County, PA

-Presentation on project design and initial results of vertical tillage study followed by panel discussion on benefits/tradeoffs associated with vertical tillage

Summer Soil Health Field Day facilitated by Pennsylvania No-Till Alliance, July 2021, Butler County, PA

-Presentation on project design and initial results of vertical tillage study followed by panel discussion on benefits/tradeoffs associated with vertical tillage

Soybean Grower Meeting facilitated by Pennsylvania On-Farm Network, Lebanon County, PA

-Breakfast meeting with Penn State faculty, Penn State extension educators, and local crop growers discussing pertinent issues in soybean production including vertical tillage practices; shared project design and initial project results

Initial outreach objectives still in progress:

Results from this project will be shared by graduate student Andrew Lefever with growers and agricultural professionals in Pennsylvania and the Northeast using multiple extension-outreach platforms accessible through cooperation with extension-research scientists who will serve as mentors for the project and are members of the Penn State Extension Agronomy team. Written outreach products will include (1) a Penn State Field Crop News newsletter article, (2) a Pennsylvania On-Farm Network newsletter article, and (3) a Lancaster Farming newspaper article.  A summary of our findings will also be presented at multiple in-person events, including: (1) a Penn State summer field day hosted at the Southeastern Agricultural Research and Extension Center (i.e., Farming for Success), and (2) a Penn State Soils and Crops Conference.

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.