Mitigating and preventing flood-related soil quality degradation using cover crop blends
Single cover crops are often used to reduce erosion, maintain water quality, manage pests and diseases, cultivate good tilth, and in general improve soil quality. However, flooding causes a variety of soil fertility problems that are commonly called post-flood syndrome. These include compaction, loss of mycorrhizal infectivity, phosphorus deficiencies, and reduced infiltration rates. To address this suite of problems in pasture soils, NRCS has proposed cover crop cocktails. I am trialling different cover crops to assess whether cover crop cocktails can alleviate post–flood deficiencies in organic vegetable production systems: Will a single cover crop or blend work better in redressing multiple mechanisms of soil quality degradation caused by flooding? This project aims to assess the ability of winter rye, forage radish, hairy vetch, lupine alone and in a blend to rejuvenate soils after a flood. I will combine physical, chemical and biological indicators to evaluate success of the cover crop. I will present the new information at the NOFA Winter meeting and invite farmers to a field day at the Intervale Center.
1) Demonstrate the ability of cover crops to mitigate fertility and soil health problems associated with flooding.
• Conduct soil tests before and after flooding.
Accomplished: No. Soil samples were taken prior to planting cover crops from each plot in each of the three experimental blocks for soil fertility testing. Further soil tests will be taken in the Spring and Fall of 2013.
• Conduct June nitrate test.
Accomplished: No. This process will be done in June 2013.
• Measure soil physical test before and after flooding (infiltration rates, bulk density, and organic matter content).
Accomplished: No. These tests will be taken in the Spring and Fall of 2013.
2) Show impact of yield when using different cover crop varieties and blends.
• Conduct indicator crop nutrient analysis to demonstrate effect of cover crop on crop quality.
Accomplished: No. This will be done in June of 2013.
• Measure salable yield of indicator crop.
Accomplished: No. This will be done in June 2013.
3) Assess biomass of cover crops.
• Take a random 1X1 foot sample of each cover crop stand, separating weeds, drying and weighing weed and cover crop.
Accomplished: No. Emergence of weeds was measured in November 2012. Weed and cover crop biomass will be measured in April 2013.
4) Disseminate information on the value of cover crops on flood prone lands.
• Produce a brochure recommending practices.
Accomplished: No. This will be created in the summer of 2013.
• Hold a field day with a target of reaching 20 farmers and 5 extension personnel.
Accomplished: No. This will be completed in the Summer of 2013.
• Present our results, at the Northeast Organic Farming Association’s summer conference. Accomplished: No. I will present at a workshop on cover crops at NOFA’s winter conference in 2013.
Field plots at sites 1, 2 and 3 were planted on September 20th, 21st and 29th, 2012, respectively. At each site four replicate plots of lupine, forage radish, winter rye, hairy vetch, a mix of all four cover crops, and fallow were arranged in a random block design. Arrays of Watermark soil moisture sensors (7 moisture blocks and 1 temperature sensor) were installed at Site 1 in October 2012. These data are being logged every 2 hours. On October 25, after seed bed preparation and sowing, I measured soil strength at five locations per plot using a cone penetrometer to establish a pre-flood baseline for compaction.
I found that I got better responses from farmers when I sought them out to meet in person. Had I realized this earlier, I would have been able to coordinate the planting dates earlier and thus produced a more mature cover crop stand.
In NESARE Graduate Grant “Mitigating and Preventing Flood-Related Soil Quality Degradation Using Cover Crop Blends,” objective one states “Demonstrate the ability of cover crops to mitigate fertility and soil health problems associated with flooding.” Before planting the cover crops, three 6” Oakfield punch auger cores were taken from each plot. The samples taken from each block were combined and submitted to UVM’s AETL for base line soil fertility analysis. Four samples per site were submitted for a total of 12 samples. In October, I took 5 random penetrometer readings per plot at each site for a total of 360 readings. In addition, I took 1 infiltrometer reading per plot at each site for a total of 72 infiltrometer readings.
• There will be further samples submitted to UVM’s AETL for fertility measurements and I will measure organic matter by loss of ignition in the spring and bulk density in the fall and spring of 2013. In June, a nitrate test will be completed.
• I will take further penetrometer readings in the spring and fall of 2013.
• I will take further infiltrometer readings in the spring and fall of 2013.
During the month of November, I started a pilot weed suppression study. A circle with a 9” diameter was used as a parameter to count weeds and germination of the cover crops. Three counts were taken per plot.
• Two more weed counts will be taken to complete the weed suppression study. One before the cover crops are tilled in and another before harvest of indicator crop.
Objective two states, “Show impact of yield when using different cover crop varieties and blends.”
• Planting of the indicator crop is scheduled for May 2012 after typical spring flooding has receded.
Objective three states, “Assess biomass of cover crops.”
• The crop biomass will be collected in the spring of 2013 for analysis.
Objective four states, “Disseminate information on the value of cover crops on flood prone lands.” I have maintained a weekly blog, Flooded Soils, from September 2012 to November 2012 at http://floodedsoils.wordpress.com. I also was a speaker for UVM’s Department of Plant and Soil Science seminar series and covered the topics of how floods affect soils and how the aforementioned cover crops can remediate those issues.
• I am scheduled to present at an intensive course during NOFA’s 2013 winter conference and join a panel discussion about agricultural issues farmers face in the Northeast.
• I will resume weekly blog posts starting in May 2013 and ending in September 2013.
• I will produce a brochure of recommended cover crop practices in the summer of 2013. A field day will be conducted in the summer of 2013 to share the research findings and show field plots.
Impacts and Contributions/Outcomes
I have been able to share my knowledge with my peers at UVM by speaking at the Department of Plant and Soil Science seminar series. I have also posted the details of my experiment, certain soil processes, flood damage facts, and cover crop effects on soils on my WordPress blog, Flooded Soils, http://floodedsoils.wordpress.com. According to statistics of my blog, FloodedSoils, has had 321 views from 23 countries. The popularity of my posts is as follows: 1) 211 homepage views; 2) 18 views on post “Potassium Cycle Part I,” and 3) 18 views on post “Potassium Cycle Part II.” The number of views of Potassium Cycle Part I and Part II signify that there are some repeat followers indicating an interest in the topics and quality of my posts.
Nationally, farmers are faced with increasing difficulties due to marginalized land and climate change. Cover crop remediations for flood-damaged soils is a novel concept and would benefit from additional study. In addition to these challenges, the location of my sites in Burlington, Vermont has the additional hardship of a shorter growing season than much of the U.S. The farming community I am working with indicates that they would embrace using cover crop blends if proven to be effective soil quality stabilizers. This past year has set-up the conditions for demonstrating the ability of cover crops to remediate flood damage. If proven successful, farmers could adopt this alternative agriculture management practice nationally to improve soil quality sustainably and remain or become independent of reliance on fertilizers and other amendments.
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