Mechanical approaches to perennial weed suppression in organically established no-till cover crops

Mechanical approaches to perennial weed suppression in organically established no-till cover crops

Summary

This project proposes to use a yeoman’s plow with large and adjustable swept undercut bars fitted with a heavy coulter to test two main approaches. The first approach is to set the undercut bar just below the top sod root layer to further weaken or kill the sod before organic no-till drilling of spring and winter covercrops, and later no till planting of corn, sunflowers, or soybeans. The second approach is to set the coulter to make one slice through the rolled mulch layer and undercut perennial weeds just below the mulch while leaving the mulch layer largely in place. This project will trial several dates, sod and mulch conditions and different depths and plow/cultivator setups.

The results of the trial are mixed and still being analyzed with quantitative data from two years of trials in Corn plots in comparison with conventional tillage, no-till, and strip till methods.  

Initial observations indicate that there are some conditions where the technique may be effective in the pre-planting strip till type treatment, and that undermulch “sweeps” could be effective with some changes to the equipment design and tractor setup to improve accuracy durring cultivation.   Recomended changes and associated 3D sketchup drawings will be provided as part of the final report.  The proposed improved tool design, which is closer to a sweep plow design, will also be posted to www.farmhack.net as part of ongoing project dissemination. 

Objectives/Performance Targets

The objectives and operational performance targets of this trial as laid out in the proposal were as follows:
Stage 1) Planning and procurement of appropriate varieties and amendments
Stage 2) Plot layout, planting and treatments
Stage 3) Observation and data collection
Stage 4) Analysis reporting and outreach

Stage one and stage two proceeded well for the objective of sod preparation with some delay in plot layout due to substantial rain in late May. Initial first stage trials in the preparation of sod with the yeoman’s plow started on June 9th 2012 at site 1 and continued on the 11th on site two and then ultimately on an alternate site 3 on the 14th of June. 

In 2013 a randmoized complete block design trial was designed and planted at UNH’s Kingman research farm.  Yield data from strip till, yeoman’s undercut passes, convential tillage and conventional no-till plantings will be compared.  Overhead aerial imagery was taken after planting, mid season and prior to harvest in October.  

• sod treatment
• sod treatment2
• grass kill from undercutting
• grass kill from undercutting
• Closeup of undercutting rye mulch
• thin rye mulch left in place after undercut pass
• Closeup of undercutting vetch mulch
• organic no-till sunflowers coming though killed vetch
• the undercut bars fit to the yeoman’s plow
• undercutting heavy sod
• undercutting a lighter sod
• heavy grass pressure through rolled mulch
• strip till as a comparative treatment
• organic no-till sunflower coming through rolled winter rye

Accomplishments/Milestones

In 2012 the first site was attempted on June 9th in a rocky Hollis Charlton soil dominated by timothy and orchard grass and some red clover. Depth control and draft requirements were effectively adjusted. Technique for implement steering and control was also documented. Accurate guidance though adjustments to tractor steering was one of the great challenges in following previous rows in a plot or staying within a row during cultivation during the second stage trials in July.

The second first stage site was primarily timothy and orchard grass in a Buxton sandy loam with a heavy three inch sod mat that resisted cutting and had lots of horizontal rooting that bound together tightly. The third site was the most effective and compatible with the technique. It was a sandier well drained soil and primarily an alfalfa clover mixed plant population. This was the one plot that yielded data. The four replications on June 14th included conventional tillage, yeoman’s tillage with and without undercut bars, and an unverferth ripper stripper, and a no-tillage. All treatments were seeded with silage corn (biomass data attached in table format)  No yield data was collected on the sunflower treatments due to heavy deer damange on all the plots. 

Photo documentation of setup and immediate effects in various sod and mulch conditions will provided the basis for an annotated handbook on approaches to undercutting roots for strip tillage and under mulch cultivation which will be published on www.farmhack.net

in 2013 the yeoman’s setup with undercut bars was incorporated into a larger field trial at Kingman Reasearch Farm.   Corn and biomass data from those plots are currently being tabulated and will be included in the final report.  Aerial images of the plots will also be used to analize the effect of the treatments. The images were taken by a low cost unmanned aerial system based on free open source technology.  The airframe was a stock Bixler2, with a Cannon A2200 12Megapixel camera mounted in the nose running a CHDK(cannon hacker development kit) intervelometer at ISO 800 and fixed focus at infinity.   To complete the analysis the images will be stitched together for a higher resolution image of the entire plots and the images will be compared with the on-the ground data collected. 

The most significant accomplishment to date is a much greater understanding in the classification and description of the conditions of the cover and root community that is being affected by the type of technique used in this project. For example, an established sod that is primarily shallow rooted and has a highly matted structure is not as good candidate for applying this technique as a stand that is largely deeper rooted and less matted and composed primarily of legumes like clover and alfalfa.

• aerial 2013 prior to harvest 1
• aerial 2013 prior to harvest- prior to stitching
• aerial 2013 prior to harvest- prior to stitching
• aerial 2013 after planting
• aerial 2013 mid season treatments
• aerial 2013 prior to harvest- prior to stitching
• aerial 2013 prior to harvest- prior to stitching

Impacts and Contributions/Outcomes

The impact of these trials has already positively affected approaches to reduced tillage and maintenance of cover and future crop planning on the land managed by the farm. Even before the statistical analysis is done, the importance of soil health and of describing the physical root structure beyond species composition has become very clear. Based on observations from this trial our farm will continue to work towards a higher legume mix with a less matted sod and more species with deeper roots that are more vulnerable to undercutting and not as matted in the first few inches. This type of sod stand fits with a more regular rotation with grains oil seeds and high legume forage and grazing rotations. Another possible outcome is the development of a purpose built implement that is closer to a dryland sweep plow to reduce the draft requirement. Additional anticipated outcome of this work are as follows:

-development of a guide to setup and operation of a yeoman’s plow with undercut bars in various conditions (including moisture level, species composition, time of year, and root structure and above ground growth description)  This guide will be in the form of a farmhack.net tool wiki post. 
-recommended improvements to the equipment to improve effectiveness in various conditions and to improve steerability, and reduce power requirements
-development of a descriptive vocabulary and approach to describe the above and below ground conditions of the soil and plant community, both living and dead, to classify conditions where the technique has been tried. This will be critical to determine when and in what condition undercutting may be effective

The aerial imagery used to document the different treatment effects is also a significant contribution to provide a low cost method for analysis of field trials, which may have implications beyond the scope of this individual project.  

Collaborators: