Mitigating fertility effects of flooding with variable rate amendment

Mitigating fertility effects of flooding with variable rate amendment

Summary

Climate change predictions forecast more extreme and frequent precipitation events. This can lead to higher frequencies of and more prolonged floods. This research aims to assess the changes in soil fertility distribution patterns with the goal of providing nutrient management recommendations for flood-prone areas on a gradient. In partnership with the Intervale Community Farm, a field depression was identified on currently cultivated, flood-prone farm land. Soil samples were taken on five sampling dates, after snow-melt in 2012, autumn of 2012, after snow-melt in 2013, after the May/June rains in 2013, and in August of 2013. Elements iron, phosphorus, and potassium were analyzed for correlations with saturation. Soil fertility results of the remaining elements will be analyzed in the coming year.

A field-season, weekly WordPress blog¹ recorded field updates, analysis of results, and agricultural current events. Results were presented in a brochure entitled “Cover Crops to Cope with the Effects of Flooding on Soil Fertility” at a field day in NOFA’s fall workshop series. Results of the three element analysis were also presented at the 2013 International Annual Soil Science Society of America Conference. In January 2014, a presentation on this research will be given at the University of Maine’s Cooperative Extension’s In-Service Training for Agricultural Service Providers in Portsmouth, NH.

¹www.floodedsoils.wordpress.org

Objectives/Performance Targets

Work Under Objective I

Originally two farms agreed to partner with us on this project. However, due to the high flooding potential, one farmer unexpectedly chose not to cultivate that area. In effect, a replicate was lost with this decision. At the remaining site, soil samples were taken on five sampling dates (after snow-melt in 2012, autumn of 2012, after snow-melt in 2013, after the May/June rains in 2013, and in August of 2013) with 5 cm X 5 cm cores. Surveyor equipment was used to record the location of each soil sample.

The first set of samples was sent to Maine for analysis. In an effort to extend funds for more testing, the remaining soil fertility tests were carried out in UVM’s AETL lab with KCl extract on the Lachet for inorganic nitrogen, other soil fertility elements with ammonium acetate extract on the inductively coupled argon plasma mass spectrometer (ICP), and organic matter by loss on ignition. The August 2013 samples will be analyzed by the ICP in 2014. Active carbon was completed for the first set of samples and the remaining have yet to be analyzed. Electrical conductivity was taken on two sampling dates. Dates omitted are in October 2013 due to equipment malfunction and June 2013 due to time constraints. Measuring pH will be finished in 2014.

In the summer of 2012, height measurements of the squash crops were recorded for one row along the depression’s gradient on two sampling dates. Leaf samples were taken for tissue analysis. That data has yet to be analyzed.

Although some analysis has been conducted on correlation of iron, phosphorus, and potassium with sampling date ie level of saturation, more is needed. In 2014, data collected will be analyzed using JMP software for ANOVA and GS+ to correlate fertility data with elevation.

Work Under Objective II

Variable rate amendments were not applied because soil fertility analysis is not complete. The brochure, “Farmer’s Guide to Fertility Patterns in Flood Prone Fields” is not completed because further analysis is needed. However, a section of analysis was included in the handout “Cover Crops to Cope with the Effects of Flooding on Soil Fertility” along with information on general soil fertility loss and using cover crops as a remediating tool for soil damage caused by flooding.

This brochure was handed out to 15 participants during the field day by the same name. This field day was in conjunction with NOFA’s new fall workshop series and was advertised on their website.¹ Grants with this data were written to SARE Research and Education, Conservation Innovation Grants and AFRI-NIFA with fruitless results.

¹To see advertisement on NOFA webpage:

http://nofavt.org/events/cover-crops-cope-effects-flooding-soil-fertility

Workshop description

As the effects of this summers’ early season flooding lingers in the fields, come learn about strategies to mitigate the long term impacts of soil saturation. Lindsey Ruhl, Master’s Candidate in Plant and Soil Sciences at UVM, will take participants into the field to look her research sites and experimental cover crop plots in the Intervale. She will present on cover crops that have demonstrated ability to alleviate specific effects of soil degradation associated with flooding such as fertility loss, compaction, and mycorrhizae colonization. This event will be part field tour and part discussion- light refreshments and snacks will be provided.

Accomplishments/Milestones

May 2012: Case and Maden advise on suitable research areas. Soil sampling for fertility will be conducted early in May by Görres and Ruhl. An aliquot of each sample will be sent for soil testing, the remainder of the soil will be analyzed in the lab for organic matter, and active carbon (Ruhl). After these tasks are done, the fields will be surveyed and additional field tests such as electrical conductivity and moisture will be carried out by Görres and Ruhl. Farmers will receive fertility recommendations (from graduate student and PI) and plan their planting and fertilizer schedules accordingly. Farmers will apply nutrients.

One farmer unexpectedly decided not to cultivate the agreed upon area. This decision was not communicated in a timely manner to the researchers in order to make any possible adjustments like identifying another depression on the farm to study. The Intervale Community Farm applied 30 lbs of nitrogen in the form of peanut meal in the summer of 2012.

May 2012 – April 2013: Statistical analysis will be conducted (Ruhl, Görres)

Some analysis has been completed, namely elevation, element, and sampling date correlations for iron, potassium, phosphorus. Some inconsistencies with data collection make analysis difficult. For example, the Watermark Sensor with one sensor that records temperature and seven sensors that record saturation six inches underground, were not present or working properly throughout the entire duration of the study. In other words, some dates have temperature and soil moisture tension data to correlate with soil fertility and others do not. Precipitation data has been used as a proxy for saturation.  

Furthermore, different types of crops were present and at different stages of growth which can alter length of saturation. If there are more roots present, infiltration rate may increase and water uptake may increase resulting in a reduced length of saturation. Decomposition may also minimize the effect of elevation and length of saturation on fertility distribution patterns by adding or reducing an amount substantial enough to have a leveling effect on the amount of available nutrients. Tilling and other cultivation practices mixed soil and may have had a homogenizing effect on soil fertility patterns.

Furthermore, the first sampling date had 60 samples and was analyzed at a lab outside of UVM. The other sets of soil samples had 30 soil samples per sampling date and were analyzed in UVM’s AETL lab by Ruhl. The method of analysis between labs uses a soil standard to test for comparable results. Both labs are consistent with measurements. However, having more samples allows for a greater potential of finding more correlations. As a result, it appears that the first sampling date has a higher rate of correlation with elevation, sampling date, and element when in fact this could be more of a reflection of the inequality in sample size.

At the current level of analysis, there is too much variability during time of sampling to say with certainty that nutrient distribution does or does not correspond to marginal elevation differences. More analysis is needed with ANOVA and using co-krigging GS+ software.

June 2012: Farmers will plant their crops.

The Intervale Community Farm transplanted squash by the end of May 2012. Originally, this land was to be left fallow. However, in the October of 2012, rye was planted as a cover crop.

June 2012 – October 2012: Case, Maden, Gorres and Ruhl will assess crop health using visual cues for nutrient deficiencies. Yield of crop in plots will be assessed.

Plants were visually assessed for health. One row of squash plants was measured for height at two sampling dates and leaf tissue was taken of analysis. Analysis of this data is pending. Yield was not assessed due to incompatible farmer and researcher schedules during harvest time.

October 2012: Soil sampling and testing to assess residual nutrients after harvest (Gorres and Ruhl). See May 2012 for more detail.

Thirty soil samples were taken in October, locations recorded with surveyor equipment, and analyzed for nutrients.

October 2012 – April 2013: Görres and Ruhl will write grants to NIFA-AFRI, CIG and SARE to continue this work.

            Grants to the aforementioned institutions were written with fruitless results.

May 2012 – April 2013: Gorres and Ruhl will write Farmer’s Guide to Fertility Patterns in Flood Prone Fields

This brochure has not been created yet and will be made after data analysis is complete. Some results have been shared in the Cover Crops to Cope with Effects of Flooding on Soil Fertility brochure.

April 2013: Soil sampling and testing to assess carry over after harvest (Görres, Ruhl). See May 2012 for more detail.

Thirty soil samples were taken in April, locations recorded with surveyor equipment, and analyzed in UVM’s AETL for nutrients.

April 2013: Field day at an Intervale farm or the Intervale Center (Gorres, Ruhl, Case, Maden).

The field day was held in September of 2013. Fifteen participants attended including farmers and university personnel. This field day was a part of NOFA’s fall workshop series and also included information from NESARE Graduate Grant, Mitigating and Preventing Flood-Related Soil Quality Degradation Using Cover Crop Blends.

June 2013:

Thirty soil samples were taken in June, locations recorded with surveyor equipment, and analyzed for nutrients.

August 2013:

Thirty soil samples were taken in August, locations recorded with surveyor equipment. Soil analysis is still needed.

October 2013:

Data was presented in a talk at UVM’s Plant and Soil Science Department Seminar Series.

November 2013:

A poster was submitted to the 2013 International Annual Soil Science Society of America Conference in Tampa, Florida.

Impacts and Contributions/Outcomes

Preliminary data has been shared at outreach events. When data analysis is complete, an informational brochure will be created with practical recommendations from observed soil fertility distribution patterns. On the basis of graduate student Lindsey Ruhl’s SARE blog she has been invited to speak at two outreach conferences on climate change and cover crops.

Collaborators: