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The effectiveness of microbial inoculants in fixing nitrogen

Soil biology can ‘fix’ and supply more nitrogen, and faster, than they are often given credit for.

The wheat field section on the right received an October application of AEA’s soil primer, which includes bacterial inoculants and stimulants. By March the following year, soil analysis reported an additional 80 units of N available for the crop.

To achieve these results, the soil must have adequate microbially active carbon, good gas exchange, and good moisture levels.

Soil microbial populations can regenerate quickly when given the right environment and support. Regenerating soil health can be accelerated to a few years, it is not a process that needs to take decades to achieve a significant turn around.

2020-05-28T07:05:35-05:00May 28th, 2020|Tags: , , , |

Keeping inoculants on the seed

If microbial inoculants are to be effective as seed treatments they need to remain attached to the seed until they arrive in the soil. Some products, such as mychorrizal fungi inoculant, can have a fairly large particle size, and does not stick to seed very well, particularly smooth seeds such as beans.

The last thing we want to see is accumulated inoculant at the bottom of the seed hopper when we get done planting.

When you apply seed treatments yourself, lightly spray a sugar-water solution onto the seed before the inoculant is applied. This serves to make the seed slightly sticky, and microbial powders remain strongly attached to the seed.

2020-04-11T15:39:36-05:00April 13th, 2020|Tags: , |

Considerations for spraying microbial applications

To produce the most effective response from applications that contain living microbes, we need to consider the path through the sprayer nozzle and the environment on the leaf surface or within the soil once the product is applied. 

It is best to have spray pressures below 55 psi to reduce or avoid sheer at the nozzle. Higher pressures can produce a sheer force with a markedly negative effect on living organisms in the solution. 

When applying products that are suspended in solution and with larger particle size, such as mycorrhizal fungi which can have a spore size up to 50 microns, use larger nozzle and screen sizes. We generally recommend a 50 mesh screen or even no screen in some cases. 

When applying products to the soil surface that will not be incorporated, add humic substances or dark-colored material such as molasses to the solution to protect organisms from UV. I suspect (but don’t know for certain) that this may be less necessary when applying to the leaf surface, since organisms which can survive on the leaf surface can likely handle UV exposure. 

Combine the inoculant with a biostimulant to develop a ‘synergistic stack’ of products that produces a much greater performance than either product by itself. These could be materials such as humic substances, seaweeds, food sources, prebiotics, enzymes, etc.

And by all means, avoid adding antimicrobials into the spray solution, at any concentration. This means you don’t use water that contains chlorine, chloramines, or anything with a similar antimicrobial purpose. Don’t add ionic or salt forms of boron, zinc, manganese, or copper. After all, in the right concentrations, each of these minerals are very effective antimicrobials. We need to consider not only the solution in the spray tank but also the concentration of the droplet when it begins drying on the leaf surface or soil surface. 

Field experience indicates it seems to be ok to add chelated or complexed forms of these minerals that aren’t immediately absorbed by the microbes in the solution, yet are quickly absorbed by the plant while the droplet is still liquid on the leaf surface.

2020-04-06T18:14:27-05:00April 7th, 2020|Tags: , , , |

When to use inoculants to regenerate soil

In our experience, when microbial inoculants are applied as part of a different nutrition management system, they have consistently been some of the most significant ROI applications, and produce dramatic changes in soil health. Yet, many growers buy ‘bugs in a jug’ and see little or no response. When this happens, it often because the applied inoculant was put into the wrong environment, was not supported with biostimulants, or fertilizer and pesticide applications were continued. Don’t expect to continue managing everything else the same, and a microbial inoculant will change soil biology. The biology became degraded in the first place because of management practices and product applications. If these remain the same, don’t expect biology to make a miraculous comeback.

From the Regenerative Agriculture Podcast with Michael McNeill:

John: When you have a degraded system like that—where there are suppressed yields and suppressed soil health, as you’re describing it—how do you go from depressed yields of 70 to 90 bushels per acre back up to 200, with aspirations of going back up to 250 bushels per acre? How do you achieve that?

Michael: Well, it’s a long, hard task. There aren’t any silver bullets. You have to figure out what was going wrong and stop doing that—that’s number one. Number two, you’re going to have to look at what it’s going to take to remediate the soil. Has the soil become really hard—hard like a road? I get penetrometer readings where it takes 500 pounds of downward pressure to penetrate the top two inches of the soil—that’s hard. That’s just like a gravel road. A crop will not grow in that.

When they tilling it, it’s breaking up into chunks. And then when it rains, it puddles and it just seals over. And so we get no oxygen into the soil. You have to incorporate some tillage, and then you have to start providing some food for the microbial life—which is almost non-existent. It’s not non-existent, because you can bring it back—that’s the good news. If you don’t let this thing go too long, you can bring it back.

Now whether we’re bringing all of it back or not, I don’t know. But once you get it started coming back, then you can look at inoculating with mycorrhizae and some of the things—the pseudomonads, the actinomycetes—that could be missing, and stimulate them. But first, you have to get oxygen into the soil, get the water working correctly, and get the food right. There’s no magic in inoculating the soil—if it’s loaded with poison, it will kill your inoculant. You have to fix that problem first before you try inoculating. You wouldn’t have to do an inoculation, but it does speed it up—you gain about a year, maybe two years, when you do that.

I see people thinking they’re buying a magic silver bullet by inoculating, but then they continue to do the things that caused their soil to die in the first place. And they’re not winning. They’re losing.

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