Progress report for GNC20-313
In 2019, vast expanses of South Dakota were flooded. Many South Dakota producers are now left with the challenge of planting fields that were left fallow in 2019. Producers on the South Dakota Soil Health Coalition (SDSHC) Board state that they were able to access their no-till fields when neighboring conventional tillage fields were inaccessible. No-till management systems can protect our agricultural lands from flood, as well as drought, through increased soil organic matter and water holding capacity. Unfortunately, as severe weather events increase in frequency and decrease in predictability, many no-till acres risk being returned to tillage due to negative perceptions of increased management challenges and reduced yield.
Lake Area Technical Institute (LATI) in Watertown, South Dakota, operates a long-term, no-till demonstration farm north of their campus. The demonstration farm has been under no-till management for more than 20 years. Due to interest from area producers, strips of the farm have been returned to tillage in anticipation of yield gains. Initial plans by LATI for this experiment were to monitor yield only. Upon suggestion from South Dakota State University (SDSU) researchers and the SDSHC, baseline soil samples were collected prior to implementing the tillage treatments for comparison at the end of the three-year trial. However, there is high learning potential from collecting annual soil samples as is proposed here. For example, soil organic carbon changes may not be static from year to year and an opportunity exists to determine equilibrium rate constants using data from time zero, the baseline. The proposed SARE project would monitor changes in soil physical, chemical, and biological properties caused by tillage through aggregate stability, bulk density, soil chemical properties, and phospholipid fatty acid analysis (PLFA) annually for three years.
Learning outcomes include that area producers will witness the detrimental impacts of tillage on soil health parameters and insignificant increases in yield. Action outcomes include that area producers will use this information to determine if tillage is worth detrimental impacts on soil health parameters. Project summaries will be presented at two annual LATI producer field days, shared with SDSU Extension, the SDSHC, and with local Natural Resources Conservation Service (NRCS) offices. A publication will be submitted to a journal, such as Soil and Tillage Research, for peer-review.
03.27.2023: LATI has officially changed to Lake Area Techinical College (LATC)
Our hypothesis would include outcomes showing that, over the course of three years, there will not be significant yield increases in the tillage treatments compared to the no-till. However, significant improvements in soil physical, chemical, and biological properties in the no-till treatment compared to the tillage treatments will be observed. The primary learning outcome of this research will be utilization of quantitative data to inform producers on the negative effects of tillage on soil health properties. Coupling quantitative soil property data with yield and economic data, ample information will be available for area producers who are contemplating which management system would be best for their operation. Learning outcomes from this project will lead to the primary action item of producers opting to maintain their existing no-till systems, or convert to no-till management systems.
Lake Area Technical College (LATC), located near Watertown, SD, operates a long-term no-till demonstration farm that is under corn-soybean rotation. In 2019, two strips of tillage were implemented; one strip of "conventional tillage" (CT) and one of "minimum tillage" (MT). In total, there are three tillage treatments: CT, MT, and no-till (NT). The practices behind CT management include fall and spring tillage, while MT only consists of one pass. The exact tillage implements, implement depth, and intensity needs to be verified.
Tillage strips were implemented in a N-S direction on a gently sloping (2-6% slope) hill. Four replicates (blocks) per strip were sampled along a transect to encompass all landscape positions. Composite and bulk density samples were collected after harvest in 2020 and in 2021. Microbial samples and aggregate samples were collected in the spring due to adverse weather conditions preventing sampling in the fall.
At present, both 2020 and 2021 soil samples are in the queue to be analyzed for total carbon and total nitrogen by Isotope Ratio Mass Spectrometry (IRMS). Due to constraints caused by COVID research restrictions and lengthy repair times of the equipment, analysis has been delayed. Alternative avenues are being investigated to turn the samples around faster. Similarly, phospholipid fatty acid analysis has been delayed from COVID-related research restrictions, exacerbated demand for the equipment, and issues caused by moving our lab to a new building. All analyses of soil samples are behind schedule.
Samples have not been collected for the final year of the project yet due to a short window between harvest and when the weather prevented working in the field. I am working on arranging the paperwork to file for an extension so that there is enough time to collect samples this spring, analyze all project samples, and analyze the resulting data. Our IRMS machine had to be replaced last summer. Due to this and to other contraints on lab equipment by other projects, the current plan is to send all project samples (years 2020 to 2023) to Ward Labs in Kearney, NE. This will ensure that all samples are handled the same and that the methodologies used are consistent for each project year. Funds in the project budget are adequate for this approach.
Currently, the metrics that have been collected include soil samples, PLFA samples, aggregate samples, and yield data. Analysis has not been conducted due to the issues mentioned in the Materials and Methods section.
The roadmap for determining results include to compare annual changes in aggregate stability within each treatment from 2019 to present, as well as, compare differences in aggregate stability of CT and MT to the NT control. This will be conducted on the 2mm fraction utilizing wet-sieving. The same comparisons will be made when assessing changes in microbial community structure (i.e. does increased tillage reduce beneficial fungi and benefit bacteria). Using bulk density data and gravimetric carbon data, the carbon stocks of each treatment will be compared. Changes in aggregate stability, microbial communities, and soil carbon will be overlaid with yield to determine the impact of tillage on soil health and profitability.
03.27.2023: Aggregate samples were compromised when our lab space was moved to a different building. Therefore, aggregate stability will be assessed for the 2023 year only. Similar issues arose with PLFA samples as the -80 freezer had to be relocated and samples were lost.
Educational & Outreach Activities
To date, I have only attended one of the LATC field days at the demonstration farm. Due to COVID and my pregnancy, I did not attend the 2021 field day.
I will attend the 2022 LATC field day and provide an update on the data to the growers who attend. In addition to a short presentation, I will provide a summary sheet that succinctly provides information on findings thus far.
03.27.2023: LATC did not hold a field day at the demonstration farm this past summer.