Final Report for FS07-219

Treating Soil Compaction Using Woven Weed Fabric

Project Type: Farmer/Rancher
Funds awarded in 2007: $9,886.00
Projected End Date: 12/31/2009
Region: Southern
State: Texas
Principal Investigator:
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Project Information

Abstract:

PROJECT ACTIVITIES

Youth from the South Plains Food Bank, Inc., GRUB Project were including in all phases of the project. The youth are in junior high or high school and the farm is used to teach business skills, leadership skills, life skills and work skills to the youth.

Three plots each fifty feet by fifty feet were selected for the project. The first step was to use a cone penetrometer to determine the depth of the existing hardpan. It was determined that a hardpan existed at a depth of three to four inches throughout the selected plots. The surface under the fabric was hard and felt as if it had been packed with a roller. One plot that had been covered with a woven weed guard fabric for the past three years remained covered and undisturbed during the entire project. The central plot had been covered with weed guard fabric that was removed, compost was applied at the equivalent of sixteen tons per acre, it was chiseled, the tandem disk was used and the plot was recovered with the woven fabric. The woven fabric was removed from the north plot and discarded. Compost was applied, the plot was chiseled and the tandem disk was used. Drip tape with twelve inch spacing of emitters that provided one-fourth inch of water per hour was installed on all plots with one valve controlling all plots.

The plan involved siphoning one gallon of fish emulsion, one gallon of sea weed, and twenty gallons of humic acid into the irrigation system bi-weekly during the project. To provide information on how the use of humic acid affected the soil compaction three additional plots were brought into the project that were not supplied with humic for the period of the test. Two of these plots were covered and one was left uncovered. Tomatoes, Bell Peppers, and Onions were grown on one third of each plot with an irrigation cycle established that would provide two gallons of moisture per week during the growing season. Compaction tests to determine the hard pan were conducted at the end of tilling and monthly there after. The depth remained unchanged in the covered plot and remained at the four inch level for the first three months. The cone penetrometer would not penetrate the hardpan without damage to the instrument.

Immediately after tilling there was no hardpan on the central and north plots, however by the end of the second month a shallow hard pan had started to form on the central plot that had been recovered with the woven fabric after tilling. Initially it was at the eight inch level but after the fourth month had graduated upward to the six inch level. The north plot that remained uncovered started to develop a shallow hard pan at the eight inch level by the end of the third month. However it remained thin, less than a half inch thick, and could easily be penetrated with the cone probe.

Plant growth habit and root development was noted. In the plot that remained covered the plants were shorter, smaller stems, and the root development was shallow and limited to the area saturated by the drip irrigation. Very few root hairs were noted on the roots. The central plot that had been recovered had a healthier root development, the stem was larger, and the plants had a darker green color to both leaf and stems. The roots did not extend horizontally beyond the area saturated by the drip irrigation. Vertical development was less than five inches.

During the second year, 2008, the plastic was removed from the central plot with half of it being composted and cultivated as well as half of the uncovered plot. The weed fabric was returned and drip lines returned to the plots. The crops were rotated as best possible in the small area selected for the project with the same varieties being planted. The irrigation and nutrient cycle was the same as year one.

The plot that had not been uncovered remained hard as in the beginning. The central plot that had been uncovered with half the plot composted and cultivated showed a mark difference in the two halves. The surface area that had not been cultivated felt hard as if it had been packed down or a roller had been run over it. The other half was soft and the feet would settle into the covered soil when walking across it. Probe penetration indicated a hardpan existing at the six inch level on the uncultivated area and no hard pan on the cultivated area. Half of the uncovered plot was composted and cultivated. A shallow hardpan had formed at the eight inch level on the area not cultivated with no hardpan on the area cultivated.

During the second year the hardpan on the covered plot improved to a depth of six inches. Whether this was due to the continued use of humic acid or the larger than normal annual rainfall cannot be determined. However it remained to be approximately three inches thick and could not be penetrated with the cone probe in most areas. Even after a rain the surface was packed and hard. Root development was poor and limited to the area saturated during irrigation. Very few root hairs were noted and those roots that did form were small.

The surface on the central plot that had not been cultivated continued to become harder during the second year and as the year progressed the area that had been cultivated begin to harden. By the end of the year foot pressure would not indent the surface. The hard pan on the uncultivated area was up to the six inch depth with a thickness of two inches by the end of the second year. A hardpan reformed at the eight inch area in the area that was cultivated. Root and stem development was limited in the area not cultivated with root growth limited to eight to ten inches in length. In the cultivated area stems were larger and the root growth exceeded twelve inches on all plants inspected. Numerous root hairs were noted where the soil had been cultivate with almost no root hairs in the non cultivated area.

The surface of the uncovered plot was only affected by the thin crust formed by rain drops. The hardpan had reformed on the uncultivated portion of the plot and existed from six inches to eight inches. It could be penetrated with the probe. The probe would extend to its complete length in the cultivated portion of the uncovered plot.

In the adjoining plots that were covered and where no humic acid was used the hard pan remained at the three to four inch level. Root development was limited to approximately four inches in depth and the six inch horizontal width of the area saturated during irrigation.

Final root examination, compaction tests, and harvest data could not be collected due to flood damage. September 11, 2008 the farm received more than eight inches of rain in a twelve hour period. This resulted in a lake north of the farm spilling out of its banks and flooding the area. By the morning of September 12th the SARE plots were covered with five feet of water.

Another change that had a big effect on the outcome of the project was the taking in of three adjoining plots that humic acid was not applied to. The hard pan on these plots remained unchanged on these plots. This change was made to allow siphoning of humic into the irrigation system rather than trying to spray it onto the crops. With separate control valves we could limit the area covered with humic.

RESULTS

The two years of research definitely proved that two things are taking place when we use the woven weed guard fabric for extended periods of time. A hard pan begins to form under the surface and with each year it becomes thicker as it moves toward the surface. In addition the surface area becomes packed shortly after cultivation even in areas where there is no foot or mechanical traffic. This packing is intensified by hard rains and high winds. By the end of the project the plot with the undisturbed weed fabric had been covered for five years. The soil had to be wet to penetrate it with a hand trial. The youth could not work it when the soil was dry.

Using the woven weed guard as a plastic mulch was very effective for weed control however to use it one would have a need to take up the plastic annually, compost, cultivate and recover the area with it. The labor required would not be cost effective.

The use of humic acid appeared to help in eliminating the hardpan, however the length of the test was not sufficient to make a positive determination. The positive information gathered justifies further use of humic and to continue this study.

In addition to the flood during the second year a blight attacked the tomatoes and peppers. Tentative DNA results indicate that the Psyllid has now found its way into West Texas thus causing the blight. Working with Dr. Ron French, Texas AgriLife Plant Pathologist and Dr. Russ Wallace, Texas AgriLife Vegetable Specialist further test will be run during the 2009 and future growing seasons. These test results will be shared with local growers as well national growers

FUTURE WORK

If I were repeating the project I would take in a larger area to allow for three to four reps of each trail. Smaller plots with more reps would help justify the data collected. I would move the project to higher ground to limit the possibility of flooding although this would not have helped September 11, 2008. I plan to continue the study of soil compaction on the entire farm. More sticky traps will be placed into the field to collect insect samples and to monitor insect pressure. I plan to incorporate a minimum of fifty yards of compost (approximately 100,000 pounds) into the soil annually to study how the addition of compost affects hardpan development. We will also begin using the 1 mil polyurethane mulch for weed control and to reduce surface water evaporation and study its affect on hardpan development.

ADOPTION

All woven weed guard fabric (7680 feet) has been removed from the field. This year the 1 mil plastic mulch will be used on most growing areas. Working with Dr. Russ Wallace, Texas AgriLife Vegetable Specialist I will begin trials using some biodegradable mulches and high tunnel growing during the 2009 growing season. The desire is to transition to a biodegradable mulch in the near future to further reduce labor costs. A program of monitoring soil compaction will be implemented and followed. The study on the use of humic acid to increase microbial activity and the results will continue.

OUTREACH

The results of this project was shared with local growers during two open houses each year, 2007 and 2008. It was also discussed with interested growers at the Southern SAWG conference during 2007 and 2008. A field day is scheduled for June 13 that will include growers from all states on the Ogalalla. A presentation will be made at the 2009 West Texas Vegetable Growers Conference. Book of photographs is available at the farm to share with those visiting the farm.

The GRUB project serves an average of 100 youth annually. Of these ten to twelve or hired to work the farm during the summer months. The youth were taught to use the cone probe, to examine root and stem development, to examine surface hard panning, and to visually inspect the vegetables growing in the test plots as well as the balance of the farm. During the open house the youth conduct tours of visiting adults and explained to them their part in the research that we conducted.

SUMMARY

My goal was to study soil compaction while using a woven weed guard fabric. The study consisted of areas where the fabric had been down for three or more years and had not been disturbed. In other areas the fabric was removed, the area composted and cultivated, and the fabric replaced. In the third area the fabric was removed, the area composted and cultivated, and the soil left uncovered. Drip irrigation, humic acid, sea weed, and fish emulsion were used for irrigation and nutrient supply. Humic was eliminated from adjoining plots to allow determination of the affect humic acid had on increasing microbial action to the point of eliminating hard panning. The study reveals that formation of hardpans is greatly increased when using the woven fabric unless it is taken up and the soil cultivated annually. In addition a compaction of soil at the surface occurs when the woven fabric is used. The longer the fabric remains in place the tighter the soil is compacted at the surface. The limited time of the trial did not result in positive information on the effects of humic acid. This test will continue. The study proved beyond a doubt that a surface and subsurface compaction of the soil increases with the use of a woven weed guard fabric to the point that it limits vegetable plant growth and yield. Surface compaction even in no traffic areas was much greater than anticipated. These trials opened the door for additional research in weed and moisture control while growing vegetables.

Research

Participation Summary
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.