Lentil Yield and Nitrogen Fixation Response to Inoculant and Fertilizer

Lentil production has grown dramatically in the northern Great Plains over the past 20 years. In Montana and North Dakota, planted acreage of lentil has increased from 67,000 in 2000 to 585,000 in 2022 (USDA-NASS, 2022. Lentil is capable of biological nitrogen (N) fixation, a process in which rhizobia bacteria in legume root nodules convert N gas into N that is available for plant uptake. This makes lentil an attractive option for producers wanting to decrease fertilizer N inputs in their operations. However, little is known about the effects of starter fertilizer or inoculant on lentil N fixation or yield. The objectives of this study were to (1) quantify lentil yield and N fixation responses to rhizobial inoculation with granular vs peat powder, seed-coat inoculant formulation, and (2) determine if potassium (K), sulfur (S), or foliar-applied micronutrients enhance lentil yield and N fixation.

Fertilizer Fact 81 is based on a 3-year, 7-site study (Montana and North Dakota) on the effects of potassium, sulfur, and inoculation on lentil yield and nitrogen fixation, led by Dr. Perry Miller (MSU Agronomist). The document can be found at https://landresources.montana.edu/fertilizerfacts/html/FF81.html Below are four fertilizer facts which were determined as a result of the study.

1. Inoculation and S fertilizer are two practices that can increase lentil yield and N fixation.

2. Lentil response to inoculation was not impacted by field lentil or pea crop history in this study, but other research suggests it can impact nodulation success. Inoculation is likely worth the cost

since nodulation failure risks an insufficient N supply.

3. Inoculant type did not affect amounts of N fixed, and neither granular nor peat powder inoculant consistently resulted in higher yields.

4. Lentil response to S fertilizer was inconsistent and not explained by soil sulfate-S levels, but some positive responses to relatively inexpensive S applications likely make S fertilizer cost-effective for many producers. Strip trials with ammonium sulfate or gypsum can assess potential for benefit.

Montana State University, U.S. Department of Agriculture and Montana Counties Cooperating. MSU Extension is an equal opportunity/affirmative action provider of educational outreach.