Evaluation of the effects of aerators on alfalfa stands

Final Report for ONE11-148

Project Type: Partnership
Funds awarded in 2011: $14,992.00
Projected End Date: 12/31/2013
Region: Northeast
State: Vermont
Project Leader:
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Project Information

Summary:

The primary purpose of this study was to evaluate the use of aerators on alfalfa hayland and distribute this information to farmers in the region.  While several studies have documented reduced nutrient runoff associated with the use of field aeration practices, there is limited information concerning the effects of soil aeration on alfalfa.  Aeration is often used in liquid manure systems prior to manure application to create vertical slots in the soil to allow manure to infiltrate into the soil for better nitrogen utilization and reduced runoff potential. However, it was unclear how aeration would affect alfalfa stands where taproots may be more susceptible to damage.  Alfalfa crops are of higher economic value in our region than hayland crops.

 Due to Tropical Storm Irene in 2011, and an unforeseen landowner conflict in 2012, complete data was collected on two of four farms for the duration of the study.  While data collected shows decreasing alfalfa crown counts on all of the plots, aerated and non-aerated, over the course of the study, there is not enough evidence to suggest that aeration or the additional pass of tractor and equipment over the field was the cause of the decline. The farms reported reduced yield in the fields that were outside the test area as well.  It is common for alfalfa yields to decrease over time.  The rate of this decline is affected by several factors including: management, disease, pests, improper fertilization and pH, varietal differences and weather.

 Overall, our results demonstrate that spring or post-first cut aeration has little to no effect on alfalfa/grass hayfields grown on light soils.

Introduction:

Farmers are struggling to stay in business with fluctuating milk prices, increasing fertilizer costs, increasing fuel costs, and increasing equipment costs. On top of that they also face increasing scrutiny from both the regulatory and private sectors surrounding their potential to pollute. This scrutiny arises from an increase in public awareness on water quality issues, primarily public beach closings due to toxic algae blooms in the northern sections of Lake Champlain and the pending TMDL for Lake Champlain.

 While it has been well-documented that timely manure incorporation through plowing, disking, or chiseling will reduce nutrient runoff, as well as increase nitrogen availability to crops, these methods of incorporation on hay land are not possible.  There has been some research documenting reduced nutrient runoff with the use of field aeration prior to liquid manure application; however, there is no readily available information or research results showing the effect that soil aeration has on alfalfa hayfields. 

 Alfalfa is a major hay crop in Vermont, which must be managed carefully for maximum yield and sustainability. Most farmers in the local region are hesitant to aerate alfalfa fields to decrease surface compaction and increase manure and water infiltration, due to the assumption that aeration will damage alfalfa crowns, resulting in decreasing production and stand life due to winter kill.

 The District owns two Gen-Til II aerators that it rents to local farmers, and promotes aeration as a tool to reduce compaction, increase crop yields and reduce potential runoff.  Aerators are attachments pulled by a tractor that have tines that pierce the soil creating a vertical slits for better water and nutrient infiltration and decreased surface compaction.  The tines resemble an upside down triangle.  At the tipping point between moving down through the soil then back up, the tine is designed to slightly twist which is thought to create a “shattering” effect in the soil which will decrease compaction.  The soil type determines how long the slits remain open.  

 In response to the lack of readily available information about aerating alfalfa, the District designed a study that would count alfalfa crowns in hayland plots that had been aerated and compare those results to the number of crowns in a control, or non-aerated plot.  The District initially set up plots on four area farms, though due to circumstances beyond their control, two of those farms had to drop out of the study before it began.  Suitable replacements were selected to replace those farms.

 The purpose of the project was not only to confirm how aeration will affect alfalfa stands where taproots may be more susceptible to damage, but to provide information and education to farmers in the area through one-on-one correspondence, peer-to-peer communication from the farms participating in the trials, brochures, and literature about the aeration and alfalfa relationship. 

Project Objectives:

The overarching objective of this project was to evaluate use of aerators on haylands containing at minimum 50% alfalfa over a three year period capturing spring alfalfa crown counts after two winters.

 Below are specific objectives and performance goals for the project:

  1. Evaluate the effects of aeration on alfalfa stands

  2. Conduct Cornell Soil Health Tests and Soil Tests (modified Morgan Phosphorus extractions) to measure the phosphorus levels and general health of the soil prior to the study and at the end of the study.

  3. Collect information about manure nutrient levels and application rates, where appropriate to explain the results of the study.

  4. Conduct alfalfa crown counts on an annual basis to determine the effects of aeration on alfalfa crown vigor

  5. Provide information to farmers in the area about the effects of aerators on alfalfa hay land.

Cooperators

Click linked name(s) to expand
  • Steve Bromley
  • Cliff Cressy
  • Dr. Heather Darby
  • Matt Harvey
  • Cash Ruane

Research

Materials and methods:

Multiple on-farm, side-by-side, demonstration trials were a critical component of this project. These trials provided the opportunity for evaluating aeration effects on alfalfa stands, and provided a platform for sharing results with peers and partners.  Please refer to the attached map for farm locations within Rutland County.

Replicated side-by-side demonstration plots allowed for multiple experimental and control areas within the same field.  Each farm had three experimental and two control strips.  The minimum width of each test strip was determined by the aerator width (8’9” width).  Length of each test strip depended on field size and layout.  Plot locations were determined with farmer input and were marked with survey flags and soil paint.  Factors that were considered when locating test plots included: soil type, slope, ease of access, and past manure stacking sites, where applicable.

Test plots were not located along the edge of the fields.  The 3ft x 3ft sub-plots for alfalfa crown counts were randomly selected in every plot and marked by flags and soil paint.  The test plots were aerated each spring either before first cut or within a week after first cut.  Crown counts were collected from sub-plots in spring and fall.  Plots were observed throughout the summer.  Wooden stakes were driven into the corners of the test plots and sub-plots each fall after the last harvest for winter.  A location marker was also set outside the field as a back-up measurement incase the stakes were disturbed.

Test strip layout with the fields was as follows:

A1- Aerated:               20ft x 10ft

N1- Non-Aerated:       20ft x 10ft

A2- Aerated:               20ft x 10ft

N2- Non- Aerated       20ft x 10ft

A3- Aerated:               20ft x 10ft                                          

Before the grant was awarded, the Russo Farm had to drop out of the project due to management changes and the Clark Farm had to withdraw in May when a large tract of rental land was not renewed and the farm did not have access to land in alfalfa for the three years needed.  These farms were replaced by Clif-Dee Farm and Fern Hill Farm.  

Field Descriptions:

Harvey Farm:  Pure alfalfa stand seeded in spring 2010 with the appropriate herbicide control sprayed after emergence to control weeds.  One cut was taken late summer 2010. Previous crop was corn silage.

Clif-Dee Farm:  Alfalfa/Fescue stand seeded in spring 2010 and harvest late summer 2010.  Semi solid manure applied spring 2011 at a rate of 10 ton/acre.  Previous crop was a run out mixed cool grass stand with very little legume which was plowed after last cut.

Fern Hill Farm:  Established alfalfa field which had timothy inter-seeded in the summer of 2010. No manure applied.

K&C Ruane Farm:  Pure alfalfa stand seeded in 2010.  Previous crop was corn silage which was seeded down at the request of the land owner. 

District Agronomist, Jennifer Alexander, met individually with each farmer involved in the trial every spring to discuss the project details, results and observation and to gather farmer observations.  Cornell soil health tests and UVM soil nutrient tests were conducted in spring 2011 on three of the four participating farms to determine pre-trial soil conditions and nutrient levels of the fields. One farm did not consent to preliminary soil tests as his alfalfa was over 10” tall by May 15 and he did not walk anyone walking in the field “trampling my alfalfa”.

In spring 2013, end-of-study Cornell Soil Health Tests were collected in each plot on the remaining farms by the District Agronomist.  The District did not collect a separate UVM soil analysis sample as the Soil Health Tests contains soil analysis using the Modified Morgan’s extract. 

All crown counts and observation were made by the District agronomist or an intern trained by the District agronomist. 

Alfalfa Crown Counts and Aeration:

  • Spring 2011, initial crown counts were recorded on the four participating farms and test plots were aerated with the 8ft 9in Gen-Til II aerator with the tines set at 0 degrees for limited soil disturbance. Plots were observed throughout the summer with no noticeable decline noted.

  • Fall 2011, end of season crown counts were conducted and recorded on three participating farms and recorded. No yield information was collected from the farms due to the effects of Tropical Storm Irene on harvesting second and third cut.

  • Spring 2012, crown counts were conducted on three participating farms and recorded. No winter kill of alfalfa was noted within the test plot or the test fields. Aeration took place after first cut on two remaining farms with the 8ft 9in Gen-Til II aerator with the tines set at 0 degrees for limited soil disturbance.   It should be noted that the winter of 2011/2012 was a mild winter with little snow fall and warmer than normal temperatures. Spring 2012 was also an unseasonably warm spring with temperatures reaching over 80 degrees F during March and April (see attached weather data). Plots were observed throughout the summer with no visible decline in alfalfa viability noted. 

  • Fall 2012, crown counts were conducted on two participating farms and recorded. Both farm have stated that yields are declined in the fields overall.

  • Spring 2013, crown counts were conducted on two participating farms and recorded. No winter kill was observed in the test plots or the test fields.

The District Agronomist collected all soil samples used to determine the base-line nutrient levels of the test areas and to determine the general health of the soil prior to the study and then at the end of the study 

Cornell Soil Health Tests:

  • In May, 2011, Cornell Soil Health Tests were conducted and soil samples collected for UVM soil analysis were on 3 of the 4 farms. One farm did not want the District to dig the soil samples needed for the soil health test as the stand was over 10 inches tall by May 15 and he was concerned about crown damage and walking in the fields with tall alfalfa.

  • In May, 2013, Cornell Soil Health Tests were conducted in each test plot, aerated and non-aerated, on both farm and sent to Cornell University for analysis. It was determined that an additional UVM soil analysis was not needed as the Cornell Soil Health Test included a separate soil nutrient analysis using the Modified Morgan’s Extract.

Manure application was overseen by the District agronomist.  The two farms that applied manure had manure samples collected and sent for analysis.  The manure spreaders were weighed on state certified scales to determine application rates.  

  • K&C Ruane applied manure at a rate of 4.5 tons per acre in early April 2011. This provided 7.65 pounds of total nitrogen, 14.85 pounds of P2O5 and 27.9 pounds of K2O to the crop. While this manure application over applied nitrogen, it under applied phosphorus by 6 pounds and potassium by 212 pounds. The alfalfa and volunteer clover consistently showed signs of potassium deficiency

  • Clif-Dee Farm applied manure at a rate of 10 tons per acres in early April 2011. This provided 13.9 pounds of total nitrogen, 53 pounds of P2O5, and 78 pounds of K2O to the crop. This manure over applied nitrogen, and over applied phosphorous by 33 pounds and under applied potassium by 162 pounds. 

No farm applied any additional nutrients to the test fields during the test period.  The nutrient applied by both farm at the start of the trial was less than estimated crop removal rates according to UVM “Nutrient Recommendations for Field Crops in Vermont” per year.

Research results and discussion:

The research and data collection anticipated for this project did not go entirely according to plan.   Before the grant was awarded, two farms had to withdraw from the trials.  One farm had to drop out of the project due to management changes, and the other had to withdraw when a large tract of rental land was not renewed.  The District found suitable replacement farms before the study began.  The final farms entering the 2011 field season were: Clif-Dee Farm in Florence, Fern Hill Farm in Wallingford, K&C Ruane Farm in Clarendon, and the Harvey Farm in Florence. 

The field trials began relatively smoothly; however, on August 28-29, 2011, Tropical Storm Irene came roaring through the Green Mountains depositing between four and (at Least) seven inches of rain in Rutland County. Otter Creek overflowed its banks at near-record levels which resulted in sediment deposits ranging from four inches to two feet in the test field located at the Harvey Farm.  Needless to say, they withdrew from the trial. 

Clif-Dee Farm and the landowner of the field ended up parting ways in May, 2012 and the field was lost to the study.  At that time, the District attempted to assist the landowner in finding another farm that would manage the land so that the trial could continue but was unsuccessful.  The landowner finally found a farm that was willing to take first cut off in mid-July but the new farm was not interested in participating in the trial so this field was also withdrawn.

The final farms in the study were the K&C Ruane Farm, which participated fully throughout the study, and Fern Hill Farm, which has the full suite of crown count data, but penetrometer and soil health data only from 2013.

Crown Counts:

Table one, found in the supporting documentation for this section, lists the crown count data that was collected at each farm through the duration of the study.  K&C Ruane Farm and Fern Hill Farm had complete crown count dataset as outlined in the study methods.   The Cliff-Dee and Harvey Farm’s data sets were incomplete and therefore not analyzed in the final report. 

Crown Count Data

Five sets of crown count data were collected on the two farms that remained in the study.  The K&C Ruane Farm saw a mix of results in 2011 with plots A1 and N2 showing slight increased counts from spring to fall, plots N1 and A2 showing slight decreases, and A3 remaining the same.  In subsequent counts the only increases seen at the Ruane test plot were on plot N1 between spring and fall 2012 and between fall 2012 and spring 2013.  The rest of the plots experienced slight decreases in crown counts over the length of the study, with the overall comparison between spring 2011 and 2013 showing decreases in crown counts of 5-45%.

Table 2 shows the differences in alfalfa crown numbers at the K&C Ruane Farm between the initial 2011 spring count and the final 2013 spring count.

Fern Hill Farm plots A1, A2, and N2 showed slightly decreased counts from spring to fall 2011, while plots N1 and A3 remained the same.  The spring 2012 counts were relatively high, with three of the plots, N1, A2, and N2 showing 7-50% increases in alfalfa crown numbers.  Comparisons between spring of 2012, fall of 2012, and spring of 2013, however, showed mostly declining alfalfa crown numbers.  Each of the plots, except N2, showed slight decreases in crown counts over the length of the study, with the overall comparison between spring 2011 and 2013 for these plots showing decreases in crown counts of 7-27%.  The only plot with a measured increase in alfalfa crown numbers was plot N2 on Fern Hill Farm, with one additional crown counted in 2013.

Table 3 shows differences in alfalfa crown numbers at Fern Hill Farm between the initial 2011 spring count and the final 2013 spring count.

While the crown counts showed an overall declining trend over the course of the study, some of the decline may be due to the natural habits of the plants themselves.   According to Canevari and Putnam, University of California publication 8301, “the productivity of alfalfa fields typically declines over time due to the loss of plants and weakening of crowns from disease or other factors.  These factors include traffic injury, nematodes, insect damage, weed competition, winter injury, compaction of soils, saturation of soils, drought and heat stress, and rodents.  As stands decline weeds invade open areas and become more difficult to control (p. 1)   Declines were measured in all plots, except for one non-aerated plot.

Considering declines are seen in both aerated and non-aerated plots, the data does not conclusively point to aeration as being detrimental to alfalfa crown health. 

Cornell Soil Health Tests:

The District collected Cornell Soil Health Tests for the original three farms (Ruane, Cliff-D, Harvey) before the farmers conducted initial aeration in 2011.  After the final aeration in 2013, Soil Health Tests were run on soil samples from the two remaining farms, Fern Hill Farm and the K&C Ruane Farm.   The District collected soil samples from each of the plots (A1, A2, A3, N1, and N2) for post-trial Soil Health Analysis.  The following tables list the data from the Ruane SHA and the Fern Hill Farm SHA (Fern Hill Farm chose not to conduct initial SHA). 

Table 4 lists the Ruane Farm Soil Health Test analysis results for soil surface hardness, soil subsurface hardness, overall score and SHA quality category.

The Ruane Farm plots measured a 7.2 point difference in SHA overall scores between the averaged initial field test and non-aerated plots (48 points) as compared to the averaged scores for the aerated plots (55.2 points).

A comparison of Cornell soil health tests between the initial and final sampling on the K&C Ruane farm did show an increase in the overall health score.  This is probably due to increasing pH with the application of lime the fall before the trial began and alfalfa tap root growth relieving compaction.  We felt that no reliable conclusions could be drawn between the aerated plots and non-aerated plots at either Fren Hill or Ruane Farms. 

Table 5: lists the Fern Hill Farm Soil Health Test analysis results for soil surface hardness, soil subsurface hardness, overall score and SHA quality category.

The Fern Hill Farm plots measured a 5.3 point difference in SHA overall scores between the averaged non-aerated plots (54.3 points) as compared to the averaged scores for the aerated plots (59.6 points).

A comparison of Cornell soil health tests between the initial and final sampling on the K&C Ruane farm did show an increase in the overall health score.  This is probably due to increasing pH with the application of lime the fall before the trial began and alfalfa tap root growth relieving compaction.  We felt that no reliable conclusions could be drawn between the aerated plots and non-aerated plots at either Fern Hill or Ruane Farms. 

Research conclusions:

While only half of the farms completed the full research, the consistent test results, and ongoing conversations with area farmers, led the District to recommend aeration of alfalfa on the lighter sandy, silt-sand, and sandy-loam-type soils where plant composition of the hayfield is less than 50% alfalfa.

Conversations with farmers at the UVM No-Till Conference gave additional insight on what issues other farms have experienced while aerating alfalfa, and most have been related to either wet field or tractor speed issues leading to stand damage.

Additional internet searches continue to find various forums discussing aerating alfalfa with most successful farms suggesting aerating either before or right after 1st or 3rd cut, as long as there is enough time for re-growth.  

An article in 2008 Greenbook, references a farm trial that aerated 91 acres of alfala/grass hayfield to incorporate turkey litter with no detrimental impacts to the alfalfa stand

The usual caveats when aerating hayland must be followed when aerating alfalfa: make certain soil conditions are not too soft, do not aerate at speeds exceeding 4mph and most of all, that the farmer must watch what the aerator is doing as they aerate the land. Different soil types and topography influence how the aerator performs.  

Tourtillout, J. 2008. Impacts of Aeration Incorporation of TUrkey Litter on the Yield and Quality of Alfalfa Production in Northern Minnesota, MN Department of Agriculture, Sustainable Ag ad IPM Program, SARE 2007 project, North Central Region.

Participation Summary

Education & Outreach Activities and Participation Summary

Participation Summary

Education/outreach description:

One of the goals of the project was to provide information to farmers in the area about the effects of aerators on alfalfa hay land. Listed below are the ways that the project coordinator reached out to the community:

  • The District published results in the December 2013 email newsletter published by the UVM Champlain Crop Soil Team located in Middlebury. This newsletter is emailed to 620 people including farmers, industry representatives, extension personnel, and government personnel located throughout Vermont.

  • The District published results in the UVM Crop Soil Team newsletter which is mailed to 425 recipients.

  • The District purchased display space at the UVM No-Till Conference held February 19-20, 2014 at the Sheridan Hotel in Burlington VT which was staffed by District Agronomist Jennifer Alexander. The conference was attended by 80 farmers, 23 industry representative, 16 UVM extension personnel and 23 government representatives.

  • Project and results were discussed at the 2012 Annual Vermont Association of Conservation Districts annual meeting attended by District staff, Supervisors and partners

  • Project and results were discussed at various District Board meetings

  • In addition to those listed above, District Agronomist, Jennifer Alexander, also discussed the project results with two industry personnel, six UVM extension personnel, four NRCS staff, and eight District personnel in VT and NY and 30 farmers.

Project Outcomes

Project outcomes:

While applying manure on pure seeded alfalfa fields is not a common practice due to potential crown injury, leaf burn, and weed seed potential, it is common on mixed alfalfa/grass stands.

What this study has done is shown that aeration of mixed alfalfa/grass stands that are no greater than 50% alfalfa can be aerated either in early spring when growth is just starting or within 7 days of first cut without impacting the stand.  For those farms that apply liquid or slurry manure, manure can be applied using an aeration system and be eligible for cost share through the Vermont Agency of Agricultures Farm Agronomic Practices program of up to $25/acre. 

Farmer Adoption

While adoption of aerator use on lighter soils has been relatively slow due to a perceived lack of impact, this practice is being implemented on farms in other areas of the state.  While at the No-Till conference in February, 2014, District Agronomist, Jennifer Alexander, discussed the project with attending farmers and found that several were aerating their grass/alfalfa hayfields and had not experienced any detriment to alfalfa health.

Assessment of Project Approach and Areas of Further Study:

Areas needing additional study

With the Harvey Farm having their test field severely damaged by silt deposition from Tropical Irene, the study lost the one farm that had a pure seeded alfalfa stand. Further study on the effects of aeration on alfalfa should be conducted on higher alfalfa density fields and also in alfalfa planted on heavy clay soils

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.