Final report for GNC19-292
What soil ecosystem services and economic benefits does 50 years of no-till provide in contrast to other tillage practices in Southern Illinois?
Adoption of no-till practices is slow among growers in Southern Illinois and surveys in Illinois and the Midwest indicate growers usually use tillage during the corn growing season and often no-till plant soybean. While benefits of continuous no-till are known, holistic efforts to look at soil quality indicators, environmental quality, and farm economics in Southern Illinois is lacking to further help with the adoption of no-till, especially during corn growing seasons. Utilizing a long-term tillage trial established in 1970, our goal is to answer multiple questions including (1) Does soil C sequestration saturate after 50-years of no-till?; (2) Does a no-till system after 50-years benefit air quality compared to a chisel disk system and what is the effect on nitrous oxide emissions?; (3) What soil health indicators explain crop yield?; (4) What factors explain soil aggregation and nitrous oxide emissions?; (5) Does no-till profitability, including ecosystem benefits, outweigh possible yield losses during wet and favorable growing seasons? The long-term study is a randomized complete block design with four replications. Treatments include (i) MP using moldboard plow to 15-20 cm; (ii) CD using spring disking followed by chisel-point cultivator to 15-20 cm; (iii) NT without disturbance to the soil, excluding a planter, for 50 years in 2019; and (iv) AT two-yr of NT followed by one-yr of MP. Sub-plot fertility treatments include: (i) no NPK; (ii) N only; and (iii) NPK application as broadcast. We will evaluate soil aggregate size distribution, aggregate stability, soil compaction, bulk density, microbial community, soil nematode communities, soil N availability, soil moisture, soil temperature, nitrous oxide emissions, and finally, carbon (C) fractions across depth. A comprehensive extension effort will be implemented including three fact sheets on soil health indicators, a YouTube video, one field day each year at Belleville Research Center at Southern Illinois University, and one presentation at a national conference. As a result of this project, we anticipate 40% of corn and soybean growers in Illinois will know about no-till benefits and consequences of tilling the soil after 2-yrs of no-till and 20% will adopt or show interest in further adopting continuous no-till. Our outreach activities with the help of the Illinois Farm Bureau will ensure an increased knowledge to growers, and adoption of continuous no-till among corn and soybean growers.
A two-year trial will be conducted with 4 replications to establish which tillage system provides the most soil ecosystem services, benefit air quality, and ensure farm profitability. Three agronomy factsheets and a journal article will be written, in addition to one YouTube video and two field days. Of all corn and soybean growers in Illinois, 40% will become aware of the benefits of no-till in comparison with other tillage systems. We will share the results in year-two through work and communication with consultants, extension educators and fellow farmers, as well as factsheets and a YouTube video. We will pre-survey growers to assess their perception of no-till system in both corn and soybean. We will post-survey growers in our field days and also conduct a follow up postcard survey (50 farmers) assessing intent to use project results to evaluate if the percentage of adopting a no-till system increased as a result of our outreach activities. We have initiated training an undergraduate student as a part of graduate student mentorship approach. The undergraduate student’s experience with the research will be documented in our website (https://asadeghpour.com/amir-sadeghpour/) and at local websites (https://thesouthern.com/news/local/siu/student-focuses-on-increasing-corn-production-while-making-life-easier/article_86417cb8-e2f1-588c-9ba7-096d6635564a.html).
In 1970, a long-term, randomized split-plot design consisting of a tillage by fertility trial field experiment was initiated at the Belleville Research Center in Belleville, IL. The soil type is a poorly-drained Bethalto silt-loam (fine-silty, mixed, superactive, mesic Udollic Endoaqualf). Tillage treatments (replicated four times) include: (i) using moldboard (MP) plow to 15-20 cm; (ii) reduced tillage using spring disking followed by chisel-point (CD) cultivator to 15-20 cm; and (iii) no tillage, (NT) without disturbance to the soil, excluding a planter, for 50 years in 2019; and (iv) alternative tillage (AT) two-yr of NT followed by one-yr of MP. Sub-plot fertility treatments include: (i) no NPK; (ii) N only; and (iii) NPK application as broadcast. Full treatment descriptions are presented in Kapusta et al. (1996) and Cook and Trlica (2016). For this study, due to financial limitations, we will focus on tillage treatments when they have received NPK as broadcast.
In spring 2018, prior to any tillage, soil samples (n=5) were taken from each plot (16 plots) with a shovel (0-15 cm) to evaluate soil aggregation and stability, aggregate associated C (total and active) and N. A well-explained protocol for aggregate size distribution and stability of wet aggregates as well as soil carbon fractions is found in lab manual “Nutrient Management Spear Program” at Cornell University (http://nmsp.cals.cornell.edu/publications/NMSPLabManual2017.pdf).
In 2018, corn was the year’s crop in rotation, therefore nitrous oxide emissions were measured 14 times during the corn growing season (for NT and RT only with and without NPK) using vented chambers as explained in Sadeghpour et al. (2018). At each sampling, soil moisture and temperature were measured, as explained in Sadeghpour et al. (2017). Nitrous oxide samples were analyzed using Gas Chromatography (GC) equipped with an automated sampler unit that is being shared with Dr. Sara Baer at SIU. In addition, nematode communities were extracted using Jenkins (1964) established protocol (triple elutriation and sugar floatation) from soil samples that were taken in the fall, after one year’s growing season influence on community structure and identified to genus using Bongers (1987). Corn was harvested in October 2018 and data including crop N uptake are available for sharing and calculating partial N balances.
In 2019, 16 experimental units were sampled up to 15 cm depth using a shovel method, sterilizing the shovel between blocks and wearing gloves as to not contaminate samples with human DNA, for phospholipid fatty acid (PLFA) analysis four times during the year: in early spring (pre-plant), 1 month after soybean planting, at soybean R1 growth-stage, and at the end of the growing season, to assess the temporal changes in microbial communities. Collected soil samples were shipped immediately as moist soil samples for PLFA analysis at Ward Lab in partnership with the Soil Health Institute. Soil PLFA patterns are commonly used to study microbial community structure (Frostegård et al., 2011). Each sampling time we will also took one soil sample per plot (n=4) to a 15 cm depth to assess changes in soil N availability. Nitrous oxide emissions were completed similar to 2018. We were also provided data on soil C fractions, aggregate stability, bulk density, infiltration, and compaction, which will also be provided through the Soil Health Institute (only sampling MP, CD, and NT). Soybean was be harvested in 2019 and grain samples will be sent to lab for nutrient analysis.
In spring 2020, soil samples prior to planting corn were taken using a probe truck to assess changes in soil C at different soil depths (0-15 cm; 15-30 cm; 30-60 cm; 60-90 cm) to compare with data previously published by Walia et al. (2017). Samples were separated in-field, dried, ground, and sent to Brookside Laboratory for analysis. This allowed us to assess whether NT is limiting in building C and if integration of other management practices would improve C sequestration.
PLFA sampling and analysis occurred prior to corn planting, 1 month after planting, at VT growth-stage, and at the end of the growing season to assess temporal changes in microbial communities. Similarly, at each sampling we soil sampled (0-15 cm) to assess soil N availability. We also monitored nitrous oxide emissions 15 times in 2020 and at each time, we measured soil moisture and temperature.
No-till increased large aggregates in size 1-2 mm (Fig. 1), whereas CD did so below 0.5 mm. No-till also increased aggregate associated C and N (Fig. 2) relative to all other treatments in small and large aggregate sizes, and additionally increased C, N and POXC (Fig. 3) relative to all other tillage treatments at the 5 cm depth. We concluded that NT provides a more stable soil system (Fig. 4) and was able to maintain or increase aggregate associated C, N and POXC given environmental stresses such as intense rainfall that could cause erosion, nutrient runoff, soil crusting, drought stress, etc.
Additionally, long-term NT practices increased SOC and POXC greatly at 0-5 cm soil depth and total soil C percentage in the top 15 cm (Fig. 5). At depths from 15-90 cm, 50 years of NT did not build total soil C. Therefore, additional practices to incorporate or deepen soil C could be beneficial (specific practices are discussed below).
After long-term maintenance of NT and CD, soil moisture and temperature only differed early in the growing season (~1.5 months after planting). Soil temperature was only lowered by 6% in the NT plots compared to the soil warming effects of CD. However, the soil volumetric water content (VWC%) was increased by 38% in the NT plots. Although these differences become insignificant later in the growing season, there is an advantage of early planting when using CD in overly wet conditions. Conversely, global warming trends are causing the common issue of extremes of both wet and dry, cold and hot. In these conditions NT having a higher VWC could be an advantage during sudden drought early in the season, or a disadvantage when early rains are too abundant.
Moreover, NT reduced both wet and oven dry bulk density by 8% compared to MP and CD on the surface, compaction at 10 cm was the lowest under the influence of a moldboard plow, with the greatest compaction under NT. This pattern continued at 20 cm, but at 30 cm NT was 30% less compacted. Our infiltration measurements were not affected by tillage. Therefore, even after 50 years without tilling, the physical benefits below the soil surface are limited and could be improved. To further build SOC and total C over depth, while reducing bulk density and improving infiltration, integrated management practices including over-wintering cover crops with extensive root systems such as annual rye grass (Lolium perenne L. spp. multiflorum) or winter cereal rye (Secale cereal L.) is needed (with caution for herbicide resistance problems). Our recommendation of building SOC over depth through overwintering cover crops is in agreement with previous recommendations from different climatic conditions: in Illinois under Aquic Argiudolls (Villamil et al., 2006), in Georgia under Orthic Luvisols (Sainju et al., 2002) and Rhodic Kandiudults (Sainju et al., 2003), and in central Italy under Typic Xerofluvents (Mazzoncini et al., 2011).
Over the course of three years (2018-2020) cumulative nitrous oxide gas emissions, a greenhouse gas that is 300x times more polluting per lb than carbon dioxide, were dramatically increased by fertilization and minutely increased by CD compared to NT. However, when those emissions were scaled with yield (g N2O-N Mg-1 grain yield), long-term no-till practices almost half the amount of nitrous oxide emissions compared to CD. Therefore, farmers can reduce their greenhouse gas emissions by maintaining NT rather than CD, despite fertility practices. Additionally, in N03-N and moisture (Fig. 6) were the main drivers of nitrous oxide emissions while the presence of gram negative bacteria and the Summed Maturity Index (ΣMI) were negatively related to emissions. Gram negative bacteria are known to be nitrogen fixing and in turn reduce emissions and a high summed MI (1-5) indicates a more stable soil system rather than a boom and bust soil system.
Year had a greater influence on N balances then tillage did. Although we had an idea that as root surface area increased with a reduction in compaction caused by tillage effect, yield and therefore N balances would increase nutrient availability, balances were unchanged statistically by long-term tillage in both soy and corn. Additionally, after 50 years of tillage effects, yield was unchanged from tillage to tillage.
Soil ammonium (NH4-N) was unchanged by tillage treatments. However, soil nitrate (NO3-N) under CD was increased by 360% in NT during one warm and wet sampling in August due to an increase in nitrification. Other than this change, it appears that NT and CD, after fertilization and planting, do not have an overall effect on N-release in the soil.
After forty-nine years of different tillage treatments, soil properties had also differed enough that nematode assemblages (total community analysis) had separated into distinct populations, but still remained statistically insignificant. Surprisingly, MP and NT had significantly higher nematode structure index (SI) than AT. This suggests that these tillage treatments, by the fall, had a food web state that was least affected by stress or disturbance. It appears as though the continuous maintenance of NT, aggregate stability and organic matter accumulation that is associated with NT was identified with a high SI; however, the yearly aeration of CT seems to have benefited the food web after an entire growing season to allow the stress effect of tillage to reduce (fall nematode soil sampling).
Phospholipid fatty acid analysis concluded that NT promoted gram positive bacteria. These bacteria are commonly encouraged by complexity of soil C and a higher level of microbial active carbon in the soil; thus, we can assume these attributes are occurring most in the NT treatment. Additionally, enzymatic activity was stimulated by NT, specifically arylsulfatase. This enzyme is commonly found in soils with consistent soil moisture and accounts for more than 50% of the total activity of soil microbial biomass.
Overall, NT had the greatest positive effect on physical, chemical, and biological characteristics in the soil over the long term. Tillage, even periodically like in AT, appears to retard the development of positive effects seen by reducing tillage intensity in NT. Alternate tillage (2-yr of NT followed by a MP) offered some improvements in aggregation size and stability compared to continuous MP, but did not significantly increase yield compared to NT. Therefore, practicing NT and periodically deep-tilling, when it is deemed necessary by the producer, can be as detrimental to soil physical properties as yearly reduced tillage, but not biological. Added benefits of NT also include a large reduction in greenhouse gas emissions and reduction of farm time and labor in addition to soil biological health from even CD. However, the differences in soil physical, chemical, and biological properties do not necessarily translate to higher corn yield in any given year due to variability in soil moisture and temperature early in the growing season. Thus, we can conclude that if farmers would like to continuously NT there will be more soil and ecological benefits than economical drawbacks.
Educational & Outreach Activities
We created three factsheets in conjunction with a factsheet writing course Dr. Amir Sadeghpour teaches at SIUC. Each student was assigned a topic and under the direct guidance and editing of Amanda Weidhuner and Dr. Sadeghpour, those factsheets were elevated to a level ready to be made available to the public. Our three factsheets included aggregation, soil carbon, and soil nematodes. Our focus on these aspects were deliberate to make more abstract concepts of soil health accessible to the average farmer.
We also published a journal article in Soil & Tillage Research on the long-term tillage effects of aggregation fractions and carbon and nitrogen storage within those fractions. The efforts of bringing this article into fruition were brought about by an undergraduate in a research program offered by SIUC. She was trained in research, data collection, statistics, and journal publication under the direct education of Amanda Weidhuner. We are proud to say that this student went above and beyond the knowledge of her peers.
Finally, we also created a "how-to" YouTube video on field sampling for earthworms made available online. We chose to publish how we successfully collected earthworm samples in our research field because earthworm sampling is accessible to both researchers and farmers, has direct benefits to soil health, and has many different protocols. This video is linked on our lab website and also available on YouTube.
Although we anticipated on giving two educational talks at SIUC's annual Field Day, we were only able to accomplish one of those demonstrations due to Covid-19. During our first Field Day (2019) we educated local farmers about long-term implications of reduced, periodic, intensive, and no-tillage. Additionally, we surveyed our farmers who physically came to the Field Day about each of their farming practices and education about tillage practices We had planned to distribute a follow-up survey on our education efforts of the farmers who returned to the 2020 field day. Instead, we plan on conducting a follow-up survey during the 2021 Field Day and completing our study.
Our economic analysis was made simple. We analysed 3 years of yield data and found no significant differences between long-term tillage and no-tillage. To be sure, we then analyzed historical records and found that yield increases were only made when corn or soybean varieties were updated, and in very early years of no-till establishment, with no differences in tillage systems. Therefore, due to the natural cost reduction of no-till (reduced farm labor and equipment), no-till is the most economic option.
Environmentally, no-till is the clear option. As mentioned in the results, no-till produced nearly half of the nitrous oxide emissions (a potent greenhouse gas) than did using a chisel disk. Over many years of practice, the amount of reduced air pollution adds up quickly! Additionally, soil microbiology is improved with a lack of tillage. We found that frequent disturbance created a "boom-and-bust" ecology, which is linked to a greater amount of greenhouse gas emissions.
According to our preliminary survey, 76% of surveyed farmers would choose a 10 bu/ac increase of corn grain yield if it required tillage. This survey was taken directly after learning about the soil and water quality benefits of no-till. Because farm-profit is the number-one value, conservation incentivization must economically equal early-years' loss in no-till adoption.
We have learned that over the long-term, no-till has some tremendous benefits including a large reduction in greenhouse gas emissions, reduced labor and cost, and biological, chemical, and physical benefits that can only be achieved with time. However, we have also learned of its own limitations. Most benefits are limited to the top 15 cm of the soil. In order to continue to improve soil management and sustainability, to build our soils for the future generations, additional management practices must be incorporated. This may include more innovative rotations of cash crops, cover crops, or ground covers. Simply not-tilling our soil is not enough to maintain sustainability.