Soil acidity has become a problem for many dryland producers in Montana and elsewhere in the western U.S., impacting crop production and land sustainability. Without remediation, cereal grains, pulses, and other crops can no longer be grown in some areas. This problem can be traced to a rise in fertilizer N use and no-till cropping systems which have become the norm in major small grain-producing counties. Although the benefits of no-till are well recognized (erosion control, moisture conservation, greater soil organic matter, lower energy and labor costs), drawbacks include stratification and acidification of surface soil layers leading to aluminum and manganese toxicity. This project will be the first in Montana to address the emerging problem of soil acidification by engaging with growers in northern and central Montana who are currently experiencing lost production and reduced sustainability and are now experimenting with remediation strategies, including sugar beet lime applications, crop diversification, and intensification with cover crops. On-farm field-scale trials are being conducted to evaluate the efficacy of sugar beet lime applications. Also, replicated small-plot trials are planned for the 2018 and 2019 growing seasons to identify crop species and cultivars aluminum tolerance/susceptibility, and the impact of P fertilization on aluminum tolerance. Lab incubations studies are in progress to define the best protocols for estimating lime requirements. This project will identify practical management strategies for farmers in Montana to address the emerging soil acidity problem. Education and outreach activities include field day and workshop presentations, video, a soil acidification webpage, short summaries in grain grower newsletters and magazines, and an Extension Bulletin on acidification mitigation and prevention. Farmer surveys are planned to quantify the impact of this study on knowledge of the soil acidification process and soil acidity remediation. The potential significance of this project is tremendous as soil sampling data from Montana show a downward trend in pH, which unless addressed is likely to continue.
1). To develop and execute an on-farm soil acidity remediation and prevention program in central and northern Montana (April 2017-October 2019).
2). Identify soil buffer test methods that provide the best estimate of lime requirements for soils in central and northern Montana (July 2017- October 2019).
3). Identify canola, pea, barley, and wheat cultivars along with crop species grown in cover crop polycultures or cocktails that are best adapted to low pH environments (July 2017-April 2020).
4). Provide agricultural stakeholders with the research results they need to make informed decisions on acid soil mitigation and prevention with both direct engagement, through Field Days, workshops, one-on-one, and indirect contacts including press releases, webpage, radio interviews, and a video, and evaluate the impact of this outreach and engagement effort. Our goal is to reach >500 people directly and have another >5,000 indirect contacts (April 2018– April 2020).
Hypothesis 1 – Soil applications of sugarbeet lime will be effective at remediating acidity and preventing aluminum toxicity in crops.
Hypothesis 2 – Soil testing protocols using buffered solutions will be effective at quantifying lime requirements necessary to remediate acid affected soils in Montana.
Hypothesis 3 – Cultivars will vary in their acid tolerance allowing farmers to better select higher yielding cultivars on acid soils.
Hypothesis 4 – Our outreach and engagement strategy will improve economic outcomes for producers who have acid soils.
Objective 1 – On-farm soil acidity remediation and prevention program
We are conducting on-farm field scale strip trials with four sugar beet lime application rates at three locations in Chouteau County. Two of three farm locations are under a continuous crop management program (principally wheat) and one location under fallow-wheat rotation. The trials consist of eight lime strips and three treatments including an unlimed control, low (e.g., 2.24 Mg ha-1), moderate (e.g., 4.48 Mg ha-1) and high (e.g., 8.96 Mg ha-1) application rates (Figure 1). The high rate and unlimed control
Figure 1. Strip-trial lime plot map at Big Sandy and north of Geraldine farm sites. Plot plan at Fort Benton is similar accept strips are 450 meter-long and a 13.44 Mg ha-1 rate is used instead of the 2.24 Mg ha-1 rate. All strips are 18.3 meter wide. Soil cores are collected at geo-reference locations along a transect that runs parallel to the length of each strip (an example is provided for rep III).
Strips are replicated three times in a randomized complete block design. The low and moderate rate strips are applied as single strips. The individual strips have a long (e.g., 0.50 mile) and narrow (e.g. 60 feet) configuration to incorporate natural variances in terrain and/or background soil pH that are anticipated, across individual field sites. The sugarbeet lime applications were completed this past fall (Oct 2017) in cooperation with participating farmers. The Stoltzfus wet-lime spreader of Marcus Roddy, our producer advisor representative, was used to perform the lime application (see video below).
Prior to application of the lime, soil cores (0-20 cm) were collected at precise geo-referenced locations (< 1 m resolution) along a transact running through the middle of each strip. Eight geo-referenced locations were identified at Big Sandy and Geraldine farms, and six location at the Fort Benton farm. Five cores were collected around all geo-referenced location and then composited by depth increment (0-5, 5-10, 10-15, and 15-20 cm). The resulting soil samples were sieved (< 2 mm) and analyzed for pH (1:1 water) this past fall. In 2018, these samples will be analyzed for 1 M KCl (or NH4Cl) extractable Al and exchangeable bases. Soil cores will be collected and processed similarly at these same geo-referenced locations approximately 1-yr (2018) and 2-yr (~2019) post-lime applications to quantify the impact of lime practices on soil properties over time. Longer term legacy effects (e.g. 3-5 years) of the lime applications can be achieved by soil sampling beyond this proposal time-lime.
Future activities (2018-2019)
Early-season biomass (prior to drought onset), and/or mature biomass yield measurements will be collected from small areas around the georeferenced soil cores in 2018 and 2019. ANOVA and regression analysis will be used to analyze data-sets to establish the impact of remediation practices on soil properties, soil aluminum vs. pH relationships, and pH thresholds below which crop growth is affected. Grain yield measurements will be contrasted among the remediation strips from combine records/maps developed by the cooperating growers. The cost of lime applications, net return benefit from soil acidity remediation will be used to provide a partial budget analysis which focuses on only those costs and revenue items that change because of the adoption of a new practice.
Large differences in plant growth may be observed at one, or more, of our strip trial locations. If these conditions occur we will coordinate unmanned drone flights (led by Dr. Scott Powell, LRES Assistant Professor Environmental Spatial Analysis) for aerial photography of the lime strips. The imagery created will be used to complement extension/education publications planned for this study under Objective 4. In addition, we wish to explore the possibility that aerial imagery (visible and near-infrared reflectance indexed as NDVI) of plant growth differences can be used to direct future soil sampling efforts of acid affected fields. We view this as a long-term goal that will extend beyond the timeline of this proposal. However, we feel this is important as our initial survey of fields affected by soil acidity revealed large soil pH gradients that will require a systematic approach to better define the boundaries where crop growth is affected, and to optimize soil sampling and lime applications using site-specific information.
Previous research from Great Plains has shown that boosting P fertilizer rates, particularly as band applications with, or near the seed, provides a short-term approach for mitigating developing soil acidity problems. Therefore, we will conduct on-farm small plot replicated trials at two locations to evaluate the impact of P fertilizer management on crop tolerance to acidity. These trials will be integrated with our cultivar-crop species trials discussed under Objective 3, and will include two lime management levels and four P rates (0, 20, 40, and 80 kg P2O5 ha-1). Grain yield, protein, and quality data will be collected from all plots, as well as early-season biomass samples. Treatments will be compared using ANOVA, and individual comparisons will be based on Fisher’s least significant difference (LSD). We find this approach to be a very producer adoptable practice in Montana where isolated areas of soil acidity exist within fields (a common occurrence). Additionally, producers regularly apply P fertilizer with their seed; and can easily vary their P fertilizer rates on-the-go with air seeders now in use.
Objective 2 – Buffer test and lime requirements
The primary goal of this objective will be to identify soil chemical buffer tests among a number of published protocols that provide the best estimate of lime-requirement for acid-affected soils of central and northern Montana. This objective will be achieved by collection of surface soil samples (0-10 cm) from a minimum of ten agricultural fields/locations from central and northern Montana, and including the field sites where our strip lime applications trials are run under Objective 1.The soils will be dried and processed for 1) a laboratory incubation with calcium carbonate to determine the theoretical lime requirement necessary to achieve a targeted soil pH (e.g. pH 5.5, 6.0, or 6.5); and 2) analysis of lime requirements utilizing five established soil buffer protocols including the Shoemaker McLean and Pratt (SMP) test (Shoemaker et al., 1961), Adams and Evans test (Adams and Evans, 1962), Woodruff 6 test (Gavlak et al., 2005, modified Mehlich test (Hoskins, 2008), and Sikora test (Sikora 2006). Agricultural fields targeted for sample collection will have soil pH <5.2, and will represent different soil series (defined from USDA-NRCS soil surveys) that are common to Montana and representative of soils under crop production. The laboratory incubation with calcium carbonate will be performed over several months (e.g. 90 days) using at least five levels of calcium carbon ranging from 0 to 11.2 Mg ha-1 (= 5 tons per acre). Regression analysis will be used to determine the theoretical lime requirement for each soil to achieve a target pH value (e.g. pH 5.5, 6.0, and 6.5). A predicted lime requirement to achieve a pH of 6.0 will be estimated from each of the five soil buffer protocols. Regression and correlation analysis will then be used to compare predicted lime requirements with theoretical lime requirements. This analysis will enable us to identify the best soil chemical buffer test for our region and any correction factors that can be applied to soil buffer test calculations to improve their performance. The efficacy of chemical buffer tests will also be evaluated by contrasting predicted lime requirements with observations at field sites (large demonstration trials and replicated small-plot trials – Objective 1 and 3) where liming material applications (sugar beet lime or limestone) have been made.
Objective 3 – Canola, pea, barley, and wheat cultivars trials screening for pH tolerance /susceptibility (Dr. Carr will lead in cooperation with Dr. Engel and two participating producers).
We will identify canola, pea, barley and spring wheat (including several durum entries) cultivars adapted to Montana’s dryland agriculture for susceptibility and resistance to low pH and/or aluminum toxicity. Our approach here will be to embed replicated small plot trials inside of fields that have been identified as having production related problems due to soil acidity. Two locations will be identified with pH ≤5.2 on private farms in central Montana. The study will run for two growing seasons (2018 and 2019) and will consist of a minimum of ten entries per crop species and two pH management levels (-lime, +lime). Treatments will be replicated four times in a strip-split-plot design with pH management as main-plots, crop species as sub-plots and cultivar selection as sub-sub-plots. The four individual crop species will be seeded in separate areas. Individual plots (1.5 x 6.2 m) will be seeded with a small-plot cone seeder. The lime material used will be a fine-grind agricultural limestone (i.e. dolomitic limestone, 99.2% passing through a #100 sieve). This material was purchased this past-fall, hauled to our field sites in sacks (Figure 2), and spread to the +lime strips at 11.2 Mg ha-1. using the Stoltzfus wet-lime applicator (Figure 3) and with the participation of our cooperating farmers.
Figure 2. Fine-grind and reactive agricultural limestone was transported to our field sites in 1-Ton (short) sacks.
Figure 3. Lime application with the Stoltzfus wet-lime applicator. Lime material was incorporated with the surface soil shortly after application.
Crop density, reproductive dates, above-ground biomass, and grain/seed yield data will be collected from all plots. An evaluation of nodulation success by pea entries will be made during the early season as this parameter is known to be sensitive to low pH. Ten plants will be excavated from each plot (11.4 m2) and transported in cold storage to labs at the MSU-Central Agric. Research Center. Roots will be washed and nodule density (i.e. number of nodules per plant) and mass of nodules will be recorded. Barley, canola, and wheat roots will be scored for aluminum toxicity on-site by inspection of five plants. Mid-season, above-ground plant biomass will be determined by hand-harvesting plants from a 0.5 m2 area within each plot, and drying (50 ⁰C) to constant weight, Grain/seed yield will be determined by combining seed from within each plot (~7-8 m2) and reported on a constant moisture basis (e.g.12% for wheat). Grain quality (test weight, 250-kernel weight, and kernel plumpness for barley), protein (barley, wheat, and pea) and oilseed concentration (canola) will be determined from subsamples of combine harvest.
Objective 4 – Outreach to agricultural stakeholders, including evaluation
We will provide agricultural stakeholders with the research results they need to make informed decisions on acid soil mitigation and prevention by direct engagement at Field Days, workshops, one-on-one contact, and through indirect contacts achieved through press releases, webpage, radio interviews, and video production. Our goal will be to achieve >500 direct people contacts and >5,000 indirect contacts. To achieve our outreach goals, we will partner with the Choteau Conservation District, NRCS, Choteau County Extension (Tyler Lane Extension Agent), and the Montana Salinity Control Association (Jane Holzer Program Director) to maximize turn-out at project sponsored field days. Field days will be planned in 2018 and 2019 at our Research and or strip-trial locations (Objective 1 and 3). Dr. Jones will personally invite Extension Agents from neighboring counties, and as chair of the Rocky Mountain Certified Crop Adviser program will invite CCAs from Choteau County and surrounding counties to these Field Days. In late fall or early winter of 2019/20, we will lead a workshop in Choteau County summarizing the results of our study, and again invite producers (through local contacts) and ag professionals. Most importantly, at Field Days and at this workshop, we will ask the farmer-collaborators to discuss their observations given that farmer-farmer education is often the most impactful.
We also will write one press release per year, be interviewed on the Northern Ag Network in 2018 and 2019, develop a soil acidification webpage (in 2018), produce a Montguide on soil acidification, mitigation, and prevention (in 2019), write an article in the Montana Conservationist (in 2019), and produce a video (with help from MSU Film School) to be uploaded to YouTube on soil acidification, including mitigation strategies (in 2019 or 2020). Dr. Jones will request time at the Montana Grain Growers Association and the Montana AgriBusiness Association annual meetings to present findings from our studies (in 2019 and 2020). In addition, Dr. Jones will send emails to MSU agricultural extension agents, NRCS personnel, and RM CCAs annually on project results, and will share results of this study with colleagues in the western region at the Western Nutrient Management Conference in 2019.
Each field day and workshop will be evaluated using the WSARE-approved Research and Education Outreach Survey with the added question: “What would have made this program more useful to you?” We will use the survey results from the first Field Day and first workshop to adjust our outreach approach for future efforts. To assess project impact, we will conduct a survey in January 2020 through the USPS of ~1/3 of Choteau County producers (selected randomly from FSA lists). In this survey, it will be critical to ask if the farmer had experienced soil acidification on his/her fields and had heard about the project, to assist with survey result analysis. Dr. Jones has considerable experience with surveys; for example, he led a state-wide randomized survey in 2015 from a previously funded cover crop WSARE study (501 surveys; 40% response) and assisted with two county-focused surveys for a USDA-National Integrated Water Quality Program study in 2012 and 2015 (280 – 400 surveys each; ~55% response rate). He received his training in survey approach and analysis from rural sociologist, Douglas Jackson -Smith (at that time with USU). The major goals of the survey will be to determine 1) if producer knowledge and understanding of the acidification process and mitigation options have improved, and 2) if producer practices have changed or are more likely to change because of this study.
Research activities are still in progress. A brief summary of activities, progress and highlights is provided for each Objective below.
Under Objective 1
Lime strip trials were established in October 2017 at three farms in Chouteau County with the application of sugar beet lime that was transported to the field sites from the Western Sugar Cooperative in Billings. In fall 2018, we collected soil samples at all field locations to determine the impact of beet lime applications on soil pH. At two of the three locations (N. Geraldine and Fort Benton), the cooperating farmer incorporated beet lime with tillage after its application. For these locations, sugar beet lime raised soil pH (0-10 cm) over a 1-year time window according to the curvilinear relationship of Figure 4. The relationships demonstrated beet lime is effective at ameliorating soil acidity and validating Hypothesis 1. However, the cost of acidity amelioration provides an example of “bad news and good news” story-line. The “bad news” is that the initial cost input to correct soil pH is substantial. For example, raising soil pH by 1.2 units at N. Geraldine or 1.4 units at Fort Benton to a target soil pH of 6.0 requires approximately 7 MT ha-1 of sugar beet lime (30% moisture). This application equates to a $270 ha-1 (or $105 ac-1) investment for transport of the lime material to the field from Billings. In addition, there are additional costs associated with field application and tillage for incorporation. The “good news” is that soil pH amelioration may last many years, e.g. >15 years, if our current models of soil pH change with cumulative fertilizer N inputs are accurate for our climate/region. Sugar beet lime applications were not incorporated at one of the three locations, i.e. Big Sandy by the cooperating farmer. The soil pH vs. depth profile measurements collected at this location in fall 2018 revealed little effect from the lime applications on soil pH. These results confirmed our belief that incorporation of liming material is essential to realize soil remediation of acidic pH.
Figure 4. Soil pH change or differential between fall 2017 and fall 2018 for 0-10 cm depth as affected by sugar beet lime rates at two farms (Fort Benton and N. Geraldine). Initial pH at Fort Benton and N. Geraldine in fall 2017 is 4.57 and 4.78, respectively.
In 2018, we observed visually obvious differences in growth of lentil at our sugar beet lime strip-trial near Fort Benton. Lentil top growth was greener, and biomass was greater in areas receiving lime compared to the non-limed area (Figure 5). Also, an aerial drone flight on June 24 revealed the +lime strips were visible from the air, though differences in growth between adjacent lime and non-lime areas were not apparent along the entire field transect (Figure 6). The benefits to lentil growth, biomass and coloration were believed to reflect greater rhizobium activity that translated to improved nitrogen nutrition. Unfortunately, these early season growth differences did not translate to greater seed yield at harvest.
Figure 5. Visual differences in lentil growth were apparent from the sugar beet lime applications at Fort Benton with the green strips receiving lime vs. the chlorotic, non-limed areas. Spring soil pH (0-10 cm depth) was 4.7 in the non-limed strips and 5.9 in the lime (9 MT ha-1) strips. The photograph was taken June 14, 2018.
Figure 6. Aerial drone imagery of the lentil field on June 24, 2018, revealed darker magenta coloration in strips receiving sugar beet lime relative to strips without lime.
In 2018, we observed a very large response to P fertilization in durum at our field location on the Highwood Bench. Growth benefits from P fertilizer were very evident early in the growing season (Figure 7). Grain yield response to P fertilizer was affected by Ag-lime (presence vs. absence (significant lime – P interaction). In the absence of lime, grain yield improved approximately 1500 kg ha-1 with seed-placed P fertilizer. Conversely, when soil acidity was mitigated with Ag-lime, durum was unresponsive to P fertilizer (Figure 7). Aluminum toxicity symptoms were very apparent in durum plants early in the season in the absence of lime (soil pH 4.4). The toxicity effects from Al were mitigated with the addition of seed-placed P and which was reflected in early-season biomass measurements. Conversely, Al toxicity symptoms were not present in the areas that received Ag-lime. The interaction of soil pH and P fertilizer observed in this study has been reported previously in other Great Plains States. The response to P fertilizer is not associated with a nutrition benefit as it occurs in soils that test very high in available P, and which was the case at this location (i.e. soil P test = 50 ppm). Rather, the mechanism results from a reduction in Al+3 concentration because of Al-P precipitation in the plant roots or rhizosphere. The fertilizer strategy of placing P with the seed to mitigate Al toxicity in crops should be viewed as a short-term approach to manage acidic soils as soil pH is not remediated. In Montana, this strategy might best be suited for a situation where a farmer is renting land under a short-term lease agreement
Figure 7. Seed-placed P (right) resulted in more vegetative growth and higher durum yields than non-fertilized P areas (left) at our field site on the Highwood Bench. Soil pH was 4.4 in these plots that did not receive Ag-lime.
Figure 8. Durum grain yield on the Highwood Bench was improved with P fertilizer under acid soil conditions (-lime), but was not affected by P where soil acidity was mitigated with lime applications. Olsen soil P level = 50 ppm (very high).
Under Objective 2
We collected soil samples for the lime-requirement incubation study were in fall 2017. A description is provided in Table 1. Results of our 90-day lime incubation experiment are provided in Figure 9. The measured lime requirement to correct or change each soil to a target pH of 6.0 or 6.5 was then estimated from the curves in this figure. The final stage of this objective involves running five established soil testing protocols for estimating lime requirement using buffered solutions. The buffer lime requirement test to achieve a target pH (e.g. soil pH 6 or 6.5) is then compared to the measured lime requirement from the incubation. This work is currently in progress. However, to date, we have not identified a soil buffer test that estimates lime requirement with greater reliability than soil pH measure in a 2:1 water to soil extract.
Table 1. Series name, location, and pH of soils (1-11) collected for the coming lime-requirement incubation study.
Figure 9. Soil pH after a 90-day lab incubation as affected by lime for 10 of 11 soils collected under Objective 2.
Under Objective 3
We conducted Aglime (+,-) x cultivar selection trials of four crop species (pea, canola, spring wheat, and barley) at two farms in 2018 (N. Geraldine and Highwood Bench) to determine potential benefits to lime applications and to identify selections with tolerance to soil acidity. Yield results are summarized in Tables 2 and 3 for the two locations. Visual benefits to crop growth were evident in barley and canola at the N. Geraldine location. However, only barley showed a small yield increase with Aglime (+Aglime = 3103 kg ha-1 vs. – Aglime = 2651 kg ha-1) at harvest. At the Highwood Bench farm, early and mid-season differences in growth from lime applications were visually evident in barley, pea, and spring wheat with greater biomass occurring in areas receiving lime. However, the greater top growth likely created more drought-stress at grain-fill resulting in smaller mature kernel sizes and compromised yield. This phenomenon was particularly evident in barley, which actually showed a significantly lower yield with Aglime vs. the control, no limed areas.
Under Objective 4
Outreach activities are summarized in the Education and Outreach section. Briefly, our activities have included 15 oral presentations including talks to Montana Agbusiness people, growers, fertilizer dealers, private consultants, and scientists. Also, we have presented our research project on Montana AgLive. Our research has also been reported in newsletters and popular press, including Montana Grain News and The Prairie Star.
To be determined.
Education and outreach activities include field day and workshop presentations, video, a soil acidification webpage, short summaries in grain grower newsletters and magazines, and an Extension Bulletin on acidification mitigation and prevention. On-farm field scale research and demonstration trials are planned at four farms in Chouteau County and will serve as a backdrop for field day presentations and discussions. Workshops are planned during the fall or winter and will provide a forum for updating the ag-community on research results generated by this project as well current research information from the Pacific Northwest. This information will also be presented in grain grower newsletter and magazines. Videos, webpages, and extension bulletins on acidification mitigation and prevention will provide a long-term legacy effect of this project.
Educational & Outreach Activities
Table 4. Oral presentations since March 2017 (project inception) including the web. 603 direct contact hours.
Upcoming presentations – Northern Agricultural Research Center Advisory Committee and growers, Havre MT- Feb 14; Alberta Soil Science Workshop in Calgary – Feb 19-21; MonDak field day in Sidney, Montana – March 7, Western Nutrient Management Conference, Reno, NV – March 7; Dr. Jones has six presentations planned from Feb 21 to 28 in different counties of Montana.
Fact Sheet – Soil acidification: An emerging problem in Montana. http://landresources.montana.edu/fertilizerfacts/documents/FF78SoilAcidifIntro.pdf
Published press articles, newsletters
Montana Grain News – Soil Acidity: Emerging Issue That Requires Scouting – May 2018 (see insert below)
The Prairie Star – Management solutions to low pH soils and yield loss – June 8, 2018
The Prairie Star – Yellowing leaves, club roots, yield loss may be low soil pH – June 8, 2018
Montana NRCS – https://www.nrcs.usda.gov/wps/portal/nrcs/mt/newsroom/features/soil+acidification+a+growing+concern+for+montana+farmers/
Indirect contact hours – are estimated to exceed 3000 hours via publications and news media including MT AgLive
- To be determined.
To be determined.