FAQs About Inoculants & Biologicals

Frequently Asked Questions

At XiteBio Technologies Inc. we have gotten a lot of questions over the years about inoculants and ag-biologicals. We have done our best to answer them on this page. Do you have a question you don’t see here? Please contact us and we will do our best to answer it for you.

N-fixing inoculants

N-fixing inoculants basics

What is an Inoculant?

Inoculants contain live rhizobia bacteria that are needed to form root nodules on legume plants. These root nodules fix atmospheric nitrogen and transfer nitrogen to the plant, in return the plant supplies energy to the bacteria. This symbiotic nitrogen fixation is an essential process for good legume production.

Are multiple strains of Rhizobium better than single strains of Rhizobium?

Having multiple bacterial strains in your inoculant may be better in some situations, but it is more important to have at least one strain that is active, healthy and effective. Multiple strains of bacteria do not always fix nitrogen as effectively as a single, optimal strain. XiteBio® SoyRhizo® and PulseRhizo® are formulated with bacteria that are selected to provide optimal nodulation and nitrogen fixation potential.

When is dual inoculation a good idea?

In general, dual inoculation is the application of both a liquid inoculant on-seed and a liquid or granular inoculant in-furrow. Dual inoculation increases the rhizobia population in virgin and new legume acres and is a recommended best practice for virgin legume acres. Dual inoculation has been shown to have a greater effect on soybean crops with the development of new varieties and increasing new acres in Western Canada (3).

Should I inoculate if my soil has high nitrogen levels?

It depends; if soil nitrogen levels are high, plants will use this source first, before fixing their own. Soil nitrogen levels above 35 lbs/ac generally reduce nodule formation and nitrogen fixation (10).

How do I know if my inoculant is working?

Approximately 4-6 weeks after planting, carefully dig out a plant with the roots and surrounding soil. Gently wash or break away the soil to reveal the nodules adhered to the roots of the plant. Slice them open and they should be pink in colour, indicating that the process of nitrogen-fixation is being carried out by the rhizobia.

Do I need to inoculate my soybeans every year?

Soybean inoculation is a simple and easy way to increase soybean yields, and XiteBio® SoyRhizo® has shown a consistent yield increase of an average of 2.5 bushels per acre.  It only takes 1/3 to 1/2 bushel per acre yield increase to offset the cost of inoculation, making yearly inoculation a feasible way to ensure nitrogen fixation is always at its maximum. Inoculation is also cheaper than applying N fertilizer. It takes 4.8 lbs of N to grow one bushel of soybeans on average (9), which is far more costly than inoculating seeds with rhizobia.

Types of inoculants

What are the different kinds of inoculants?

Legume inoculants are generally available in liquid, powdered, and granular formulations. Selection of the best formulation depends on the type of legume crop and agronomic practices.

Do I need different inoculants for different crops?

Yes, although all inoculants contain live rhizobia, different crops require different rhizobia. For instance, soybeans need Bradyrhizobium japonicum bacteria to form nodules, while peas need Rhizobium leguminosarum bacteria. While different legumes often need different species of rhizobia to form nodules, there are some exceptions, e.g., peas, lentils, and faba beans associate with the same species of rhizobia


Where do I look for nodules?

With seed treatment inoculant application, nodules are more prevalent at the crown and with in-furrow inoculant application, nodules are more prevalent on the lateral roots.

Why are some nodules not pink inside?

Young nodules, not yet fixing nitrogen, are white or greyish inside. When they are pinkish to red, active nitrogen fixation is taking place and these should be the most abundant during the middle of the growing season. Nodules no longer fixing nitrogen turn green/grey and can be shed from the roots (1).

My legumes don’t have any nodules, is there anything that can be done?

In the event of a light green, slow-growing crop with no nodules some options may be available. These include reseeding the crop, if it is still early enough in the season, with the correct rhizobia at higher concentrations (1). Studies have shown that the application of 60-70 lbs N/ac between the R1 and R2 stages can improve plant growth (4), though this will inhibit further nodule development and nitrogen fixation. Thus, the economics of such a decision are difficult to evaluate (5).

How can I ensure good nodulation when planting soybeans on virgin ground?

Higher rates of inoculant may be beneficial in fields with little or no history, or virgin soil, of any particular legume crop. It is a recommended best practice to apply both on-seed and in-furrow inoculant on virgin ground.

I used an inoculant, but the plants have no nodules, what may be the cause?

Various studies show that there are a variety of reasons why nodules may fail to form following inoculation. These include:
– Low soil pH (<5.5) (2)
– High soil pH (≥8) (4)
– Presence of root diseases (6)
– Cool soil temperatures (5,7)
– Presence of high background levels of N (4)
– N applied beyond any starter N application (2, 4)
– Saline soils (6, 8)
– Soil compaction can prevent air from getting into soil where bacteria can fix nitrogen from it.
– Soil flooding and excess soil moisture.
– Nutrient deficiency or toxicity, including phosphorous, potassium, iron, molybdenum, manganese, calcium, and zinc (6)
– Failure to follow all label directions, including proper storage conditions, application directions, length of time between inoculation & treating and planting (4,6), and awareness of seed treatment/pesticide combination compatibility (8)

Soil testing and native rhizobia

Is there a way to test Rhizobium levels in my soil?

It is possible to test the levels of a Rhizobium species in a soil sample, but it is not possible to tell whether or not these bacteria will be effective at nodule formation or nitrogen fixation.

Is it possible to determine the amount of native Rhizobium in soil versus Rhizobium introduced by inoculation?

It is not possible to differentiate between native vs introduced Rhizobium in soil.

Can soil acidity kill rhizobia?

Yes, rhizobia can die rapidly in soil pH below 5.5 (2).

My field has been flooded for more than 3 days, do I need to inoculate?

Yes, anaerobic conditions stress the rhizobia populations and reduce their numbers. Inoculation adds fresh and healthy rhizobia.

Application specifications

Are higher levels of Colony Forming Units (CFU) of Rhizobium per gram/per seed better than lower CFUs per gram/seed?

A higher CFU level is not always better. Having too high CFU will lead to competition for space and nutrient resources in your inoculant or on-seed by bacteria. If bacteria are competing for resources with each other, nodulation will be negatively affected and nitrogen fixation will suffer as a result. An inoculant that provides the optimum number of healthy & active bacteria while preventing resource competition is best.

How do I apply my inoculant in-furrow?

In-furrow application should be performed by applying inoculant into the seed trench on top of the seed, after furrows have been seeded, and should be immediately covered with soil. Inoculant should not be applied to soil surface.

Can I apply an inoculant in-season after seeing a lack of nodulation in my crop?

No, inoculants must be applied before or during seeding to allow nodulation.

After applying inoculant on-seed, can my treated seed go in a freezer?

No, this will kill the bacteria in your inoculant. Proper storage conditions for inoculants remain the same even after application onto seed.

After applying inoculant on-seed, can my treated seed be left outside/ in sunlight?

No, wind, UV rays, and exposure to the elements will harm the bacteria in your inoculant. Proper storage conditions for inoculants remain the same even after application onto seed.

Can I use polymers with XiteBio® inoculants or biologicals?

XiteBio® inoculants and biologicals have a non-sticky formulation that makes polymers unnecessary. Because of this, polymers are not recommended for use with XiteBio® products.

Can I use chlorinated water when tank-mixing inoculants?

Yes, you can use chlorinated water when applying XiteBio® SoyRhizo® and PulseRhizo® so long as the water is fit for human consumption. A good reminder: If it’s drinkable, it’s mixable!

Is XiteBio® OptiPlus® compatible with fertilizers?

Yes, it is compatible with some tank-mix fertilizers. Click Here to see a full list of compatible products.


What does on-seed window mean?

On-seed window refers to the period of time after application of your inoculant within which the treated seed must be planted in soil. The on-seed window of XiteBio® SoyRhizo® is up to 90 days and the on-seed window for XiteBio® PulseRhizo® is up to 7 days. After application onto seed, the same storage directions still apply to these inoculants until the seed is planted i.e. do not freeze, do not leave in direct sunlight, etc.

P-solubilizing inoculants

P-solubilizing inoculants basics

What is XiteBio® Yield+?

XiteBio® Yield+ is a ready to use liquid biological for oilseeds, cereals, legumes & tuber crops that promotes soil nutrient availability and plant health. It is a naturally occurring Plant Growth Promoting Rhizobacteria (PGPR) and the active ingredient is a unique patented strain of Bacillus firmus.

How does XiteBio® Yield+ work?

XiteBio® Yield+ introduces optimum numbers of a patented PGPR (Plant Growth Promoting Rhizobacteria) into the soil. This PGPR is a vigorous colonizer of plant roots with three distinct modes of action:

– Solubilizes soil-bound phosphorous, making it available for uptake by plants.

– Produces phytohormones to encourage earlier initiation of root hairs and helps to develop the root system.

– Produces siderophores that chelate iron and increase uptake by plants, making the plant more competitive.

These characteristics work together throughout the growing season to help maximize plant growth and cope better with stress conditions.

Where does P-solubilization take place?

P-solubilizing microbes operate in the rhizosphere. The rhizosphere is also known as the root zone defined as the area within 4mm (1/8 inch) around plant roots.

Why should I use PGPR?

PGPR enhance crop performance throughout the season through several modes of action, including phosphorous solubilization and phytohormone release. PGPR bacteria like those found in XiteBio® Yield+ can enhance your soil fertility program with little to no extra steps, which can result in better early season phosphate availability, healthier plants and better yields.

How is XiteBio® Yield+ different from conventional inoculants?

Conventional inoculants contain nitrogen-fixing bacteria (Rhizobium) that create root nodules and form a symbiotic relationship with the plant. XiteBio® Yield+ biologicals contain Plant Growth Promoting Rhizobacteria (PGPR) that are attracted to and colonize the root surface. The PGPR stimulate plant development by solubilizing phosphorus and boosting overall plant growth and yield.

Application specifications

How do I apply XiteBio® Yield+?

XiteBio® Yield+ is a liquid biological applied early post emergence at the 0-6 leaf stage with the first post-emergent herbicide application. Alternatively, XiteBio® Yield+ can be applied in-furrow. Always read and follow label recommendations.

Can XiteBio® Yield+ be applied on-seed prior to planting?

XiteBio® Yield+ is currently formulated to be applied in-furrow or early post-emergence. Yield+ cannot be applied on-seed, however future developments may allow for additional application methods.

Can I apply XiteBio® Yield+ as part of the tank-mix with herbicides?

Yes, XiteBio® Yield+ is tank-mixable and compatible with select post-emergent herbicides including Glyphosate, Roundup®, Liberty® and select Clearfield® technology herbicides. Please consult XiteBio® compatibility charts for specific tank-mix compatibility information before application. Click the following links for compatibility information on XiteBio® Yield+ for Canola, Corn, Wheat & Barley, and Legumes.

Can I apply XiteBio® Yield+ with my pre-seed glyphosate burn off?

XiteBio® Yield+ is not recommended for application with a pre-seed glyphosate burn off. The active ingredient needs to be either placed in-furrow in close proximity to the seed or applied early post emergence after germination.

How does the biological get to the roots if it is sprayed on the crop?

The target is the soil surface rather than the crop itself. The PGPR bacteria in the biological are able to swim through the macro and micro pores within the soil. They are attracted to the roots by compounds exuded by the crop roots and sloughed off root tissues.

Is the application rate the same for early post emergent application and in-furrow application?

The application rate of XiteBio® Yield+ is the same whether applied in the furrow or early post-emergent (250 ml per acre). The bacteria in XiteBio® Yield+ colonizes the plant rhizosphere, and is nourished by the root exudates and sloughed off tissues of plant roots. When applying early post-emergent, the bacteria will move down into the soil and seek out plant roots to colonize. When applying in-furrow, bacteria will have to survive until germination before they can begin to establish themselves in a plant’s rhizosphere. Having extra bacteria applied in both situations will guarantee a sufficient number of bacteria make it to your plant roots for colonization. Because of this, there is no significant difference in rates between both methods of application

Will the application of an in-furrow phosphorus starter fertilizer impact the effectiveness of XiteBio® Yield+ active ingredient?

Performance may vary from field to field depending on the level of plant-available phosphorous (P). If total soil P is high but it is not in a form available to plants, then XiteBio® Yield+ will solubilize the phosphate from these compounds and make it available for plant uptake. If soil P is high and in a form available to plants (such as in manure application) then XiteBio® Yield+ will not be as effective, as the plant already has access to P it can uptake. Phosphorus solubilisation is only one of the multiple modes of action of XiteBio® Yield+ products. XiteBio® Yield+ also increases root mass which impacts uptake of nutrients (water, oxygen, etc.) and assists the plant to better cope with stress conditions.

Will manure application or soils with high organic matter affect the performance of the product?

Application of manure may reduce the effectiveness of XiteBio® Yield+ and we recommend it not be used on soils that have received a recent application of manure. Soils with high organic matter (i.e. 14%) may also see reduced effects.

Can I apply XiteBio® Yield+ in any field condition?

The target for the XiteBio® Yield+ active ingredient is the ground and it will move through the soil to the plant root zone. Any excess ground cover (straw, plant growth) may prevent the active ingredient from reaching the soil and may reduce effectiveness of the application. Further investigations are under way to understand the effects of excess ground cover and currently we suggest the product should be applied in field conditions of 25% ground cover or less and no later than the 6 leaf stage (two open trifoliates stage for soybeans).

I would like to use your product but have excessive ground cover because of trash from the previous crop. What are my options?

XiteBio® has an in-furrow application registered for use where the product can be applied in the seed furrow with select liquid fertilizers or in water. This is an effective alternative application method in higher trash-covered soils.


Can XiteBio® OptiPlus® increase my soil phosphate levels?

The PGPR component of XiteBio® OptiPlus® colonizes plant roots and increases plant available phosphates. Applied P fertilizers generally have an efficiency of less than 50%, with most applied P becoming bound by soil particles, creating phosphate compounds or deposits that plants cannot uptake. Phosphate solubilizing bacteria found in XiteBio® OptiPlus® break the bonds between phosphates and soil particles that bind to them and create plant-available forms of phosphate, increasing the efficiency of your applied P fertilizer. These bacteria also solubilize fixed phosphates naturally found in your soil, and can increase your soil P even without fertilizer application.


Jar test

DISCLAIMER: The above is provided for information only and based on the references cited below. Always check with your local agronomist to confirm appropriate measures for specific crops & each unique situation in the field, and specific recommendations for local growing conditions.


(1) Lindeman WC, Glover CR. 2015. Nitrogen Fixation by legumes. Guide A-129, Revised June 2015. New Mexico State University, USA. Available on-line at http://aces.nmsu.edu/pubs/_a/A129. Accessed 6 Aug 2015.
(2) Bjederbeck VO, Bjorge HA, Brandt SA, Henry JL, Hultgreen GE, Kielly GA, Slindard AE. 2005. Soil improvements with legumes. Ed: BJ Green, VO Bjederbeck. Government of Saskatchewan. Available on-line at: http://www.agriculture.gov.sk.ca/Default.aspx? DN=4b50acd7-fb26-49a9-a31c-829f38598d7e. Accessed 18 Aug 2015.
(3) Quarry Seed. 2014. Inoculant and seed treatment trial. 2014 Oakville, MB Summary Report. Quarry Seed, Stonewall MB.
(4) Staton M. 2014. Identifying and responding to soybean inoculation failures. Michigan State University. Published 4 Feb 2014. Available online at: http://msue.anr.msu.edu/news/identifying_and_responding_to_soybean _inoculation_failures. Accessed 24 July 2015.
(5) Conley S. 2015. Non-nodulating soybean questions. Agri-View Briefs. Published 23 July 2015. Available online at: http:// www.agriview.com/briefs/crop/non-nodulating-soybean-questions/article_9b2f79e6-dd9d-5277-b414-4e80a63fd84f.html. Accessed 24 July 2015.
(6) Epp M. 2015. Why nodulation fails. Grainews. Published 26 March 2015. Available online at: http://www.grainews.ca/2015/03/26/why-nodulation-fails/. Accessed 24 July 2015.
(7) Bohner H. 2014. Cold temperatures hamper soybean nodulation. Ontario Ministry of Agriculture, Food and Rural Affairs. Published 2 Sept 2014. Available online at: http://www.omafra.gov.on.ca/english/crops/field/news/croptalk/2014/ct-0914a4.htm. Accessed 24 July 2015.
(8) Panwar JDS, Laxmi V. 2005. Biological Nitrogen Fixation in Pulses and Cereals. In: Developments in Physiology, Biochemistry and Molecular Biology of Plants Volume 1. Eds.: B Base, A Hemantaranjan. New India Publishing Agency, New Delhi, India. pp.125-158.
(9) Cafaro La Menza N, Monzon JP, Specht JE, Grassini P. 2017 Is soybean yield limited by nitrogen supply? Field Crops Res. 213, 204-212.
(10) https://www.saskatchewan.ca/business/agriculture-natural-resources-and-industry/agribusiness-farmers-and-ranchers/crops-and-irrigation/soils-fertility-and-nutrients/inoculation-of-pulse-crops

Submit your information to schedule a consultation with an XiteBio sales agronomist.

[wpforms id="27465"]