USA
March 10, 2014
Source: Cargill
“What form of inoculant should I use on my farm?”
This is one of the most common questions I answer about inoculants. There are a number of factors to consider when selecting the best inoculant for your situation. My tips should help you decide which of the three most common forms — liquid, peat-based or granular — is right for you when growing pulses and soybeans.
First, consider what crop you are going to plant and, in turn, what strain of rhizobia bacteria is needed to form that all-important symbiotic relationship between plant and bacteria, which converts nitrogen gas to ammonia in the plant’s nodules. Other significant factors that will influence your selection and, ultimately, the inoculant’s success on your farm, are the equipment available to you, inoculant cost, planting window and environment.
Granulars
Granulars are often considered high-end inoculants. If you’re planting pulses for the first time (into virgin soil), I usually recommend them if they are suitable. The granular formulation helps protect rhizobia in their environments (remember, rhizobia are living organisms). Under challenging conditions, such as drier or wetter years, the rhizobia count remains higher when compared with other forms because of this protection.
If we were going into a drier spring this year, for example, I would consider recommending a granular form first because they are hardier in tougher environments and offer more bang for your buck. However, granulars can be pricier than peats or liquids and the cost may scare you off from the get-go.
Another major factor is your equipment. You must have enough tanks in your cart to hold the granular inoculant.
With granulars, there is no need to worry about seed treatment compatibility, and you have a longer planting window when compared with liquids and peats. Remember to put only enough granular inoculant in your tank for the day because when left overnight granulars can bridge as a result of moisture from precipitation or humidity. Bridging can also happen if you fill your tank too full. Follow label rates, which is based on row spacing. Don’t go below label rates because those are the minimum amounts required for proper nodulation.
Peats
Peat-based products are another good choice for planting pulses in virgin soil. And with a price point somewhere in between granulars and liquids, it won’t break the bank. Peat-based products offer more protection to rhizobia from the environment and more seed safety in terms of seed treatments than liquids, but always check seed treatment compatibility when using peat inoculants. The planting window is from six to 48 hours, but this range narrows when the seed treatment is applied.
Liquids
For the budget-conscious, liquids are usually cheaper than granulars or peat-based products. The planting window can range from 24 hours to four days. However, when inoculating soybeans that window can be widened to 120 days by adding an extender, and in some cases the extender is already packaged in.
In fact, as part of a double inoculation system, liquids are a standout for soybeans: the liquid is right there with the seed in addition to a granular applied in-furrow, providing the soybeans with ample inoculant to form nodules in soils with limited or no natural rhizobia.
When using liquid inoculants, it is vital to follow label recommendations with respect to seed treatments. Rhizobia could be damaged if the seed treatment and inoculant are incompatible. Finally, inoculate only what you can seed within four to six hours.
Inoculation Know-How
Whether you’re putting down granular, peat-based or liquid inoculant this spring, following these general guidelines will ensure success:
- Make sure to choose the right inoculant for the crop (i.e. Rhizobium leguminosarum for peas and lentils, Mesorhizobium ciceri for chickpea and Bradyrhizobium japonicum for soybeans).
- Remember, you are working with a living organism. Avoid storing rhizobia bacteria in extreme heat or cold, and keep it out of direct sunlight, as these conditions could kill the rhizobia before they reach the field.
- Watch the nitrogen levels in your soil. Nitrogen above 35 pounds per acre can cause lazy nodules, while levels above 55 lb/ac can cause a large reduction in nodules or result in no nodulation at all — they’ll take nitrogen from the soil before forming nodules with the rhizobia, as the symbiotic relationship does cost them energy.
- Book your inoculant early, and before you get started make sure you have enough on-farm. Availability of certain inoculants can be tight as companies only produce so much per season.
No matter what form you choose, getting that inoculant down for nodule formation in the spring is crucial — a legume can fix up to 80 per cent of its nitrogen requirements. That’s a lot cheaper than applying nitrogen fertilizer.
What types of inoculants do you use on your farm? I’d love to hear from you. Or contact a Cargill expert today for more information on choosing the best form for your situation.
Species
