Soil acidity management of long-term no-till fields in Montana to prevent crop failure

View the project final report

Commodities

• Agronomic: barley, canola, peas (field, cowpeas), wheat

Practices

• Crop Production: cover crops, cropping systems, fertilizers, no-till, nutrient management, lime applications
• Farm Business Management: budgets/cost and returns
• Production Systems: dryland farming
• Soil Management: soil analysis, soil quality/health
• Sustainable Communities: local and regional food systems

Soil acidity has recently 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 because of the detrimental effects of low pH on crop growth, aluminum (Al) toxicity, and rhizobia-pulse crop interactions. In Montana, the problem has been traced to fertilizer N use, which has grown 3-fold since the mid-1980s.  Also, the popularity of no-till cropping systems has to lead to stratification of soil pH in the profile with the most acidic layers now appearing near the surface.  We established this project to address the emerging problem of soil acidification by examining on-farm remediation with sugar beet (sb) lime, soil buffer tests for estimating lime requirements, soil phosphorus (P) fertility for mitigating Al toxicity, and soil acidity adaptation through the identification of cultivar tolerant crop selections.  Our on-farm sb lime rate trials demonstrated this product was efficient for soil pH remediation of two acidic (pH 4.6 and 4.8) clay loam soils provided it was incorporated with tillage.  We observed benefits to lentil (Lens culinaris) and yellow pea (Pisum sativum) pulse crops because of improved nodulation by Rhizobia bacteria. Yellow pea seed yield was also greater for sb lime (30.0 bu/ac) than no lime (23.2 bu/ac). We identified an application rate of 2.5 tons of sb lime (wet weight) was necessary to remediate the two acidic clay loam soils to a target pH 6.0.  A partial economic analysis of lime application costs indicated that remediating acid soils may require a $100/ac investment.  Although this represents a considerable cost input, the costs were modest when viewed over a long-term time horizon, as a single lime remediation application should last 15-20 years (based on other studies).  Fertilizer trials revealed that seed-placed P (0-45-0) applied at high rates (i.e., 60 lb P₂O₅/ac) mitigated Al toxicity effects in durum wheat (Triticum durum) and increased grain yield from 23.3 bu/ac without P to 45.5 bu/ac with P; a similar increase as from lime. Management practices that utilized seed-placed fertilizer-P would be most applicable where a farmer is renting land under a short-term lease agreement and does not want to commit to a lime remediation program that requires a considerable cost input.  We identified one soil buffer test, the modified Mehlich protocol that shows promise for estimating lime requirements for acidic soils in Montana. We evaluated up to nine cultivars of spring wheat (Triticum aestivum L.), barley (Hordeum vulgare) , canola (Brassica napus) and field pea (Pisum sativum) in low-pH soils and identified acid-tolerant lines within each crop. We conducted a vigorous extension and outreach program to farmers, ag-consultants, extension personnel and ag-scientists in the region that included three Montana Fertilizer Fact Sheets, eight press articles or newsletters, 39 presentations/webinars, three workshop field days, six on-farm demonstrations, one television production on Montana Aglive, and 1 Youtube video production. Our outreach activities were all targeted at agricultural sustainability (present and future).  The cumulative number of attendees at our presentation/webinars was 1585.  We estimated our direct contact hours at 1187, in-direct contact hours at >10,000, and conservatively that in the near-term 272 farmers plan to change their management practices because of our study based on survey responses and this number is likely to grow as we continue disseminating results from our study.

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: to reach >500 people directly and have another >5,000 indirect contacts (April 2018– April 2020).