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Managing airborne diseases with nutrition

It is possible for plants to become completely resistant to disease when we manage nutrition well. On the surface, this sounds like a bold statement. When you dig deeper to understand the enzyme interactions and infection pathways of different infectious organisms, it becomes clear how nutritional imbalance is a foundational cause that allows these organisms to express themselves and produce active infections.

In this discussion, I ask Don Huber how to develop disease resistance to airborne pathogens. To dig deeper into this subject, the best reference book available is Mineral Nutrition and Plant Disease. It is a very inexpensive book for the money it can save growers.

John: You and I have spoken before about the capacity of nutritionally sound plants to become resistant to soilborne pathogens and organisms residing in the soil. We haven’t spoken about airborne pathogens, such as bacterial and fungal pathogens. How can we develop plants that are resistant to those organisms?

Don: You’ll see the same thing there. Pathogens are looking at the plant and they’re attracted to it as a food source―a nutrient source.

Also, some of them actually require specific nutrients in order to cause disease. Several of the rusts, for instance, require an exogenous source of zinc on the leaf―an available source of zinc―before the spores will germinate and produce an infection. If you don’t have exudation of those minerals on the leaf, those pathogens are much less severe because they don’t have that specific nutrient resource.

Now, some of the pathogens can change that nutrient availability. A lot of bacterial pathogens―black rot and some of those organisms that produce siderophores, which are essentially chelators to increase the solubility and availability of iron—you’ll see that those siderophores are able to actually cause a depletion or a deficiency of available iron in the infection site for plant functions―for energy relationships―that iron is involved in.

It’s important to maintain the availability for the plants, in spite of the siderophore production by the pathogen. If we can block that siderophore production, we block the disease-causing mechanism for that particular pathogen―that particular organism―whether it’s black rot or rust.

John: How do you block the siderophore production?

Don: We do that with some of the antibiotics that we use for bacterial disease control―whether it’s in humans or animals or plants. A lot of those are blocking siderophore production by the pathogen. You see that with fire blight on apples and pears and with black rot pathogens―Erwinia and Pseudomonas and Xanthomonas―that produce those siderophores.

We also block them nutritionally by compensating for the plant and keeping the plant’s metabolism and defense reactions fully active, so that in spite of what the pathogen is doing, we keep enough active and available nutrients for the plant that this doesn’t have an effect. The pathogen’s reduction is compensated for so that it can’t compromise the resistance of the plant.

John: It’s my understanding that many bacterial and fungal pathogens require a specific amino acid, or perhaps a general amino acid and carbohydrate profile, to be within the plant. When we change the amino acid profile, it’s possible to change susceptibility or resistance to some of these organisms, and that is one of the mechanisms by which different varieties are resistant or susceptible. Is that a correct understanding? Can you explain that a little bit?

Don: Yes, in part. The early fungicides that we used for apple scab, for instance, didn’t have any direct effect on the fungus. Their effect was changing the amino acid profile in the plant so that asparagine was no longer available or released onto the leaf surface. So the pathogen never had the essential amino acid it required for establishment and infection.

We see that with a number of amino acids. Certain amino acids will increase disease severity. Others will be a very strong inhibition of it. One of the techniques that I developed early on in my career was aminopeptidase profiling, where we could actually identify microorganisms just by their amino acid profile. When we had very difficult organisms to culture, all we had to do was run the aminopeptidase profile on that particular organism. Just with adding three or four amino acids to a little bit of sugar and minerals, all of those organisms that we had considered obligate, or very fastidious organisms, could be grown in a simple, well-defined culture media.

I’ve done that for the rusts and the mildew pathogens, as well as for many of the human pathogens. Wilford Lee has five patents for human pathogens―just patenting the media for their culture in the laboratory. I don’t know of any organism we have followed that system on, that we haven’t been able to culture in the laboratory so that we can do other studies. It was one of the grant proposals that Bruce Hemming and I had submitted to the Florida Citrus Foundation so that we could start getting information on control of HLB―greening disease on citrus. They could never get funding to do that.

Specific amino acids can be very inhibitory. That’s one of the things for the rusts and the mildews. Most people who have been trying to develop media for those obligate organisms want to make sure they don’t leave something out. The problem is that they throw everything in the mix except the kitchen sink, and one or two amino acids work every bit as effectively for some of those obligate pathogens in stopping their growth as any of our fungicides. That’s a very sensitive relationship.

It’s not a matter of making sure you have everything there―it’s making sure that some of those natural products and metabolites aren’t present to support the virulence mechanism of the pathogen. We see that with Fusarium and with a lot of the other pathogens―that nitrogen metabolism is very critical for them. One of the reasons you see shading controlling greening disease is that with shading you block photorespiration that provides those nitrogen intermediates for the pathogen.

2020-10-02T06:08:39-05:00October 2nd, 2020|Tags: , , , |

Insect and disease attraction to plants with reducing sugars

How is it possible for a high Brix plant to be resistant to insects and not provide them with an abundant food source when insects are attracted to sugars? The key insight is that plants contain different concentrations of different carbohydrates at various levels of plant health. The goal for optimal plant health is to have all photosynthates and soluble sugars such as glucose and fructose converted to non-reducing sugars in each 24-hour photoperiod. This means a healthy plant will have a high Brix concentration and very low levels of reducing sugars.

From the podcast interview with Don Huber.

John: Are there any negative health consequences of plants having high levels of fructose and glucose?

Don: Yes and no, depending on what other stresses there are present. If you have a deficiency of manganese, for instance, it can’t store the reducing sugars―glucose and fructose―that are being produced through photosynthesis. It can’t store them as sucrose, and so they become very attractive reducing sugars, and they become very attractive to insect pests and to a number of plant pathogens.

Manganese is a critical factor for that sucrose-phosphate synthase enzyme that converts glucose and fructose into sucrose for storage. If you’re deficient in manganese, you’ll have high reducing sugars―glucose and fructose. As insects like aphids fly over these plants, they can detect that high reducing sugar, and for them, it’s a red flag saying, “Hey, come in for dinner!” But if those sugars are converted to sucrose and stored there, you don’t see that attraction.

Reducing sugars come out of the root system―they’re the root exudates that are attracting Pythium and Phytophthora and Aphanomyces and those other oomycete pathogens―root-rotting pathogens.

Later:

John: Don, you described how the carbohydrate profile can attract aphids. Are there other insects that can be attracted by the carbohydrate profile?

Don: A lot of them are. I don’t know that all of them are, but many recognize the difference between the reducing sugars, and they don’t seem to be attracted to the non-reducing sugars nearly as much. You’ll see that association. When we get the minerals balanced for the plant, you’ll see all of those problems start to disappear or be very minor.

P.S. I appeared as a guest on The Modern Acre podcast in this episode.

Economic impact of cover crops and compost in orchard systems

From the podcast interview with Mike Omeg. A longer read, and very much worth the researched perspective.

John: Can you tell us about some of the things you tried that perhaps didn’t work so well, and then what you eventually ended up doing?

Mike: There are a lot of things I tried that didn’t work out well. We all like to talk about the successes, but oftentimes we can learn a great deal from failures. It was a mixed bag―like anything that is worthwhile, this was a complex project.

We started learning how we could enhance our soils and things we could do to boost our plants. One of the challenges that we had was how to scale that up―how to go from techniques that worked in, say, a small market garden―where the grower is selling directly to consumers and maybe only working part time―and scaling that up to the size of operation we have, which is 350 acres of fruit and 1,800 tons of fruit produced every year.

We started out with things that we thought would be simple and easy. One of those was putting compost on all acres that we have under management. We set a timeframe, because we couldn’t apply compost on all of those acres. What we found was that the logistical expense of moving thousands and thousands of yards of compost was huge. We had to go to the Portland metropolitan area, which is about 80 miles away, to get the volume of compost we needed. Getting that compost here, paying for the trucking, paying for an area where you can load that much material, buying or renting equipment that was out of our norm―bucket loaders and that sort of thing―became a real challenge for us. It was a really massive operation. It was a lot of diesel and a lot of steel, and that is not where I wanted to go with bio-intensive management of my farm.

I think that the compost did work for us. But if I were to do it again, I would have taken that capital that I invested in the compost and put it into other materials that we produce here on the farm or from other techniques. I think we could have probably had an equal or better return on our investment with a lot less giant equipment rolling up and down the roads and our orchard rows.

John: If you were to do it over again, where would you prioritize? Where would you focus, based on what you’ve observed?

Mike: I think that if I were to start at day zero again, in this process, I would focus a majority of my energy on mulches. What we learned over time was that the primary benefit we received from the compost was getting the soil underneath the tree covered with an organic material.

It didn’t matter as much what material was on top of the soil. We put pine chips on top of our soils. We put straw on top of our soils―wheat straw and grass-seed straw. What I found over time was that the compost was of course contributing nutrients. I love compost―but in my flower pots, not on an orchard scale.

The material we were applying wasn’t great compost. It wasn’t a super powerful compost with those humic components that we needed. It was really serving as a mulch. It protected the soil from the sun and from irrigation―the physical damage that irrigation causes.

In our orchard systems, we maintain a permanent side alleyway in between the tree rows. For generations, our family has been mowing that alleyway―like many other growers―and leaving the clippings sitting in the alleyway. What I arrived at was that if we could move that grass that we cut and windrow it right in the tree row, and cover the soil in the tree row, we could accomplish similar results to the compost with a fraction of the land, labor, and capital investment of the compost with practice we were already doing―mowing our alleyway rows.

If I were to pick one thing that we landed on that improved upon the compost, it would be to mow and blow. During the growing season we throw our grass clippings right onto the tree row. With cherries and other tree fruits, pruning is a very, very important process. We do it during the winter, during a dormant period of the orchard, and we generate a huge amount of carbon in the form of cut branches that we stack in the alleyway. And just like the grass, we used to mow that down and just leave it there.

But with mow-and-blow, we’re able to shred those prunings and move that carbon source over into the tree row. That’s a technique that really pushed us forward―getting the soil covered. I think that it allowed us to then put some very focused and very fine-tuned applications of nutrients and biological stimulants onto the soil―onto that mulch―and get a very rapid response, without the big earth-moving equipment that the compost required.

A valuable compost in our system is a very intentionally made, refined compost that can go on at a fraction of the amount that we applied when we used to buy thousands and thousands of yards of municipal compost. Instead, what we started doing was making a very small amount here on our farm―a nutrient-focused compost that incorporates nutrients we know we need. We put that material on in small amounts and get a lot more bang for our buck, because that compost is really a nutrient input instead of a mulch.

John: You’ve identified mow-and-blow as being foundational to building a soil cover within the tree row. What are the possibilities of using cover crops and producing even more biomass for that mow-and-blow operation, in addition to the grass that you’re growing?

Mike: We have begun to utilize cover crops in our alleyways. We maintain an alleyway between the trees that we can drive up and down. You need to have some kind of crop that’s growing there to hold the soil in place so that it doesn’t erode―to keep your orchard from turning into a dust bowl. We don’t want to have thousands of small dirt roads going up and down our alleyways, because that creates a giant dust plume that is bad for everybody, especially the soil and our trees.

We have maintained sod―a perennial ryegrass with creeping red fescue. There are orchardgrass sods. Many growers have their own favorites. That sod does its job―it holds the soil in place and keeps the dust down. But it does not contribute a whole lot to the trees. After we landed on the mow-and-blow technique, we started blowing what we already had in the alleyways over into the tree line. But I began to wonder if that was the best way to do it.

We eventually began to explore cover crops in order to generate more biomass in the alleyway and to transfer that biomass using our mowers over into the tree row to act as a mulch. We started cover cropping on fallow fields that were waiting to be planted. We would maintain cover crops there, and we had various mixes of plant species that we utilized. We just took the plants that worked in our fallow fields and started putting them in the alleyways.

We had some successes and some failures with that, because a big, open field with no trees growing above it is a very different environment for sun-loving cover crops than the shade of an orchard canopy in an alleyway. We have found a series of plants that we really like to put into our alleyways that generate a lot of biomass during the dormant season―basically from fall until spring. We don’t have a lot of equipment passing over our alleyways during that time, so the cover crops have an opportunity to grow.

Then in the spring, before we start our orchard management activities, when the alleyways are quite busy with equipment, we take that cover crop that grew over the winter and that generated a lot of biomass and we blow it into the tree row, and it generates a good start to our growing season for the cherries when the soil is starting to warm up. It gets this very nice coating of a diverse-species mix of mulch on top of it.

John: Mike, when you grow these cover crops during the winter months, doesn’t it have the effect of then choking out the sod? How do you manage that? Do you still have a sod for the following year?

Mike: We maintain two crops in our alleyways each year. We have an overwintering cover crop, and then we plant a fast-growing temporary sod. I don’t know if it would be proper to call the cover crop that grows during the warm season in our rows a true sod, but we maintain a green crop there. But it’s not grown as a cover crop because it’s very difficult to generate a whole lot of biomass when you have so many equipment passes going up and down the rows from May through August.

We were never able to find a warm season crop that we could plant and grow as a cover crop that would generate a lot of biomass. We just have too many different-sized pieces of equipment. By the time you take all those tire tracks and draw them out going down the alleyway, we really only end up with about 24 inches, right in the very center of the alley, where anything has an opportunity to grow. And keep in mind that it can’t grow that tall because the crown of the plant is constantly getting batted down by equipment passing over the top of it.

John: What you’re describing, if I’m understanding it correctly, is that you actually plant two crops―you plant what you’re considering a cover crop in the fall to produce biomass during the winter months, and then you’re planting a soil cover, or a ground cover, in the spring. Is that right?

Mike: Yes, that’s exactly what we do.

John: Can you tell us a little bit about the cover crops that you ended up selecting, particularly for winter cover? What was the rationale for those?

Mike: It was really difficult, because when I began my research, I quickly found that there was a giant laundry list of species that are available to us as growers. Keep in mind that our focus has been on what works―if it will sprout and grow and accomplish our goals.

It was very difficult to find anybody in orchards who was doing what we were. There was nobody I knew of that I could call and talk to and have an in-depth conversation about what species they were planting. There were people that were planting cover crops in fallow fields, but there wasn’t anyone who was planting them in the alleyway.

So, I took the species that grew the best in the fallow fields and tried them in the alleyways. I found that not every species did well; in fact, most species didn’t do well. But the species that we landed on, that did do a good job in the alleyways, really do a good job.

The mix we like in our alleyways is a mix of annual rye―all the row crop growers are maybe cringing when I say that, but it’s not a problem for us in our perennial system―with triticale, and then a mustard species, a hybrid forage kale, and a tillage radish. Those species work really well for us.

You might notice that I didn’t name a legume in that mix. That’s because we had difficulty finding a legume that would work in this application. We tried lots and lots of different ones, but we were never able to find one that worked for us. When we were evaluating legumes in our fallow fields and in our alleyways, voles and gophers would become a real issue for us. They were very attracted to the legumes. I avoided those because we didn’t find one that worked well, and the vole and gopher problem they generated was a big deal to us.

John: When you say that you didn’t find a legume that worked well for you, what were the parameters and characteristics you were looking for? Was it just because of slippery slopes? What were the constraints on the legumes, other than the gophers and the voles?

Mike: We evaluated a lot of different clover species. We found that they just didn’t establish well for us, consistently. When we talk about having a return on our investment, we need to have every seed that goes into that mix work―it needs to earn us a return. We just did not have consistent stands of clovers become established.

We did find that vetch could work for us. It would establish and it would grow, and it would be a benefit. But here’s the catch: it’s just not very well behaved at staying in the alleyway. It would take advantage of that nice open space underneath the tree, where it didn’t have competition from its companions in the alleyway. It would grow into the tree row, which would be fine until it would encounter a micro-sprinkler. We irrigate almost all of our acres by drip or micro-sprinkler irrigation. When that vetch vine would encounter the micro-sprinkler, it would whip up around it, and it would make the micro-sprinkler ineffective because it would cover the sprinkler. Because I couldn’t make vetch behave, I was forced to eliminate it from our mix.

John: Have you considered growing any cover crops in the tree row? Is that a possibility?

Mike: That’s something I would love to have happen for us. It seems so incredibly simple to say. Why can’t we just grow something in the tree row? Yet it is incredibly, incredibly complicated to find something that works.

I have tried countless species and countless mixes to grow underneath our trees in the tree row, and I am yet to find one that works really well. I’m sure people are wondering, “My gosh, what do you mean? Just look at all those species that you could plant.” But it is very difficult to find a plant that stays low enough to not interfere with our micro-sprinkler irrigation and that can grow well.

There are areas of the tree row that are in full, blazing sun all day, and yet that species also needs to be able to grow right up to the trunk of the tree, which may be in full shade for almost the entire duration of the day. Most importantly, it has to compete with weeds that grow in a tree row―weeds that we unfortunately can’t allow to be there because of the micro-sprinkler irrigation.

John: And it has to survive being buried underneath the mow-and-blow mulch and still emerge and remain short while doing all those things.

Mike: Yes, and handle foot traffic. There’s not a lot of foot traffic in the tree row except during harvest. Then, several hundred people enter a small block, and those people have to trample around the tree to get the fruit picked. That tramples a lot of cover crops.

I have not yet found the plant that accomplishes everything. There are things that grow beautifully underneath young trees―trees that don’t have a big canopy and aren’t in production. But as soon as those trees get up and start to shade―as soon as we start having pruning activity―we would trample those cover crops down. The mow-and-blow brings a whole new dynamic because there’s nothing I have found that will not interfere with the micro sprinklers and that can take that mulch getting put on top

I’m open to any ideas. There are a couple of species that do okay. But to plant hundreds of acres of them is impossible. They may be a tuber, or they may be a bulb, or we may need to start them as a small potted plant. That’s practical under a few trees or in a backyard scenario, or maybe a smaller orchard. But when you talk about hundreds or thousands of acres, you could be talking about millions of plants, and you can’t find a horticultural nursery that could produce them for you economically. It’s a real challenge.

I found some species that I thought were great. But after we got a foot of snow on the ground, the gophers also thought they were great, and they were gone come spring.

John: It’s an interesting set of challenging conditions. Can you tell us a little bit about some of the species that you experimented with that were tubers or potted plants?

Mike: I can. Three of them did a good job, but we just weren’t able to scale them effectively. One of them was ajuga―Ajuga reptans. We planted not the variegated types or anything―the fancy ones―just the wild type. The second plant is moneywort―Lysimachia nummularia. It worked quite well. Again, it was just something that was impossible for us to scale. And then the third species is a non-hybrid comfrey―Symphytum officinale var. patens―that we found worked very nicely. 

2020-09-15T06:05:52-05:00September 15th, 2020|Tags: , , , , |

Reversing bacterial canker on cherries

Bacterial canker is considered an untreatable infection in stone fruit and cherries.  When the infections become severe enough, the block of trees may be pushed out and replanted for a fresh start.

Our experience indicates it is possible to reverse bacterial canker infections. We can’t point to a specific nutritional profile or disease suppressive soil microbial populations as having produced the resistance. We used soil mineral analysis and plant sap analysis and fine-tuned soil amendments, fertilizers, and foliar applications based on the results. Bacterial canker disappeared from trees that had previously been infected to the point of being destined to be pushed out the following year. Today, these trees are a productive block five years after the initial applications were made.

Lynn Long and I discussed this specific cherry block in our conversation on the podcast here.

John: We’ve worked together on some orchards where we’ve seen some interesting things concerning bacterial canker. At one farm that we at Advancing Eco Agriculture have worked on, the incidence of bacterial canker has been greatly reduced―I think to the point where now, after several years, we can say that it seems to have been eliminated on a couple of blocks. Many growers have asked what we did and what products we used.

And the answer, as Lynn has pointed out so well, is that we don’t know. We worked with nutrition products, we worked with biological products, and we tried to manage that ecosystem. As the ecosystem changed, bacterial canker pressure changed. We can’t point to one thing and say that we did one thing that made a difference. I agree with you that there seems to be the potential to shift that disease in particular, and perhaps others as well. This would be really exceptional.

Lynn: Bacterial canker is a disease that is pretty relentless once it gets into the tree. Occasionally, you’ll find that the canker will dry up and will not progress any further, but much more typically, once it’s established, it will continue to grow and expand and will eventually kill part of the tree, or all of it.

When this grower approached me, he mentioned that he was having some severe infection with bacterial canker. There’s really no effective chemical that you can apply on that tree that is going to stop an infection once it’s started. You can help prevent infections by using some products. One particular product would be copper, but even that’s not all that effective.

When I saw this orchard, there were infection strikes all over the trees. It really did not bode well for the future of that block. But then the grower started to do some of the things we’ve been talking about―using compost and mulching and using some of the AEA products. As I’ve mentioned before, we can’t point a finger to any scientific data that says this turned it around. All we have are observations.

After the first year, the grower came back to me and said that those cankers had dried up. This was in the summertime, and these cankers do go dormant in the summertime. I thought, “Let’s see what they look like in the fall and then in the spring, and we’ll make a better assessment then.” The next spring came around, and the next summer, and the cankers had stopped. For two or three years I went back to that block and continued to look at it, and I saw no more advance of that disease. The oozing that comes about as a result of that disease―from the sap coming out of the tree―had totally stopped. The infections had dried up. It was pretty remarkable. It was quite atypical of what we would have expected for a commercial cherry orchard that was so badly infected. 

P.S. Several weeks ago I wrote about our observations preventing and managing spider mites predations with nutrition, which we have been quite successful with. Today at 4 PM EDT AEA is hosting a webinar where we will describe the plant nutritional profile that allows spider mites to be present, and how you can shift away from this profile. If spider mites are a challenge for your crops, you won’t want to miss it. You can sign up here.

2020-07-15T21:46:34-05:00July 16th, 2020|Tags: , , , |

Larry Phelan biological buffering

The objective of regenerative farming systems is to develop soils with a robust microbial community which can supply all of a crops nutritional requirements without the need for added fertilizers. The pathway to getting there is to harness the photosynthetic engine every day of the year possible and cycle as large a volume of carbon as possible as a food source for soil biology.

While on this pathway, one of the most valuable things we can do is, in Michael McNeill’s words “stop poisoning your soil!”

One very significant way many farmers poison their soil and inhibit their microbial community is with nitrogen fertilizer applications. The less carbon that is in the soil, the less biological buffering the soil has, the more pronounced the damage from nitrogen applications is to the soil microbial community. In a previous post I described how to buffer nitrogen applications so as to not have this damaging effect.

In this conversation, Larry Phelan desrcibes the capacity of soil organisms to absorb the excessive nitrogen that is so often applied, and then release it later in the crops development cycle.

John: What you’re describing, in essence, if I’m understanding you correctly, is the capacity of biology in the soil to absorb large amounts of nutrients that are applied and to contain those nutrients within their cells and then release them over a period of time. Is that what you’re describing?

Larry: Yes. So, even in this artificial situation that we created—where we put inorganic fertilizer into a soil that had an organic history—even in that situation, that organic soil from that organic farm had enough carbon lying around that those microbes could actually use that inorganic form of nitrogen, in combination with the carbon that was there, and then bring that into that microbial community. As they then die off and you have other organisms that are feeding on those microbes, they then allow for the mineralization of some of these nitrogenous compounds, and then it becomes available to the plant.

To follow up on this, we studied the dynamics of nitrogen across the growing season in these organic and conventional corn fields. Just as we would have expected, when you look at a conventional system, where in the spring the farmer is putting down relatively high levels of soluble fertilizer and really not much carbon, other than maybe some plant residue, you see huge fluctuations in terms of the availability of that nitrogen. So, of course, before fertilization, nitrogen levels are very low, so the farmer applies the fertilizer. Now they shoot way up, well above what the plant can use, and then over the course of the growing season that nitrogen declines.

But if you look at that same pattern in an organic system, what we found was that the levels of soluble nitrogen in the soil solution generally were lower overall, and they also didn’t vary much during the course of the year. That plant was getting this constant supply of nitrogen throughout the growing season. What we found when we compared these farms was that, overall, there was no difference in terms of the production at the end of the year between the organic and the conventional farms.

2020-06-25T09:24:20-05:00July 8th, 2020|Tags: , , |

Feeding plants to provide digestible nutrients for the following crop

The growers we work with who regenerate soil the most rapidly, and produce the most profitable crops, care for the cover crops as closely as their cash crops. Cover crops are planted with inoculants and nutritional support, and foliar fed. When you calculate the increased efficiency of a cover crop at 60% of it’s photosynthetic capacity as compared to 20%, and realize that it is sequestering three times more carbon in each 24 hour photoperiod, you quickly realize there is no other management practice which can build soil organic matter levels as inexpensively as harnessing the photosynthetic engine of a crop.

These crops can stimulate biology and build a large reserve of plant available nutrients that completely displaces the need for any soil applied fertilizers for following crops.

Here are some thoughts from my discussion with Gary Zimmer on this topic.

John: We’ve been talking about nitrogen management, and a few moments ago you were describing humic substances. One of the pieces that you and I spoke about in our prior conversation was the idea of delivering nutrients much more efficiently and much more effectively using carbon-based fertilizers. I think this ties in directly to our nitrogen management conversation, because what we’re really talking about is the need to have a balanced carbon-to-nitrogen ratio in the soil profile, and to hold that and to stabilize it and to keep it plant available. How does that concept of carbon-stabilizing nutrients transfer to other nutrients, in addition to nitrogen? And how do you utilize that?

Gary: I think this goes back to digestibility. In order to have the biology do its work and break it down, you need trace minerals. How do we make them available?  Some of them, like molybdenum, are pretty small additions. How do we take that addition in very small amounts and make sure it’s active and plant available? By burning up carbon, those nutrients get lost. That’s the whole thing with carbon. Let’s say I just put some of this stuff out there and grew a plant and then managed the digestibility of that plant. I’m now going to be more time released, and I’m going to be distributed better.  A farmer asked me the other day if he should put trace minerals on his cover crop. A cover crop is not a cover. It’s not covering anything―it’s actually a crop that you’re using to distribute minerals for the next crop, and you need to manage it accordingly. Managing the carbon ratio comes in line in terms of digestibility. If I’m too low on carbon or nitrogen, it’s going to take a long time to break down. I can set myself up for disease and insects, and I don’t get availability of my minerals.  I’m a dairy nutritionist. That’s how I got introduced to some of these things forty years ago―to create better feed for cows. When we started, I spent nine years at the university balancing rations based on a set of numbers. If you have more digestible feed and the mineral levels in your feed are higher, that highly digestible feed might have 95 percent of its minerals available to the cow. The stuff you buy in bags might only be 40 percent available.  When we started balancing rations for cows―and I think it’s the same thing with soils― once we started using highly mineralized, digestible feeds, we could actually cheat on numbers and cut down what we applied by at least 25 percent. We could back off those ration numbers with a lot of success once they started mixing minerals into highly digestible feeds.  In the soil it would work the same way. That’s why it takes several years to really get this going. For us as organic farmers, during that two years in transition from conventional to organic, we remineralized and grew cover crops to build up our soil. Once it was organic it was far from perfect, but we started getting a higher nutrient exchange. It’s all based on first getting out there and building carbon-biological cycles with plants and biology.

John: Essentially, Gary, what you’re describing is that farmers should grow their cover crops as a ration for soil biology―similar to growing a ration for rumen biology. In saying that, do you believe that farmers should manage their cover crops as carefully and as well as they do their actual crops?

Gary: Yes, I think those cover crops are my reserve to hold and release the kind of minerals that I want to release.  The other day a guy asked if he could just spray homogenized trace minerals onto his cover crop. I don’t know whether they get absorbed or where they go; I think that’s certainly not a bad idea. Then asked if he could use a cheaper source of those minerals, and I said that they still have to be able to get into the plant. I’m not sure how that would really work. But it starts with the process. The last thing I want them to do is spend money on something and have it just be another stone added to the big pile of stuff that we already have in our soil.

John: We have observed that our most successful growers―those who have regenerated soil health the most rapidly and who have achieved the greatest crop responses―manage their cover crops as carefully as they do their crops. They use foliar sprays and will put on fertilizers; they will manage those crops as well as they do the crops that they’re actually harvesting.

Gary: I’m 100 percent in agreement with that. I was just at some farms that had some really poor stands of alfalfa, and their cover crops were half a stand. They said that they weren’t getting much success. But they didn’t really have a very good cover crop or a very good alfalfa stand to work back into the ground to feed the soil―obviously they’re not going to get all the benefits.  I think you’re absolutely right. I think that’s a huge ticket to using cover crops. As a dairy farm, we only leave our alfalfa in one or two years. We like to take that beautiful, lush stand of alfalfa grasses and let it get up to that highly digestible stage and work it back into the soil. And people say, “Oh my gosh―I could be feeding that to my cows!” But I say that I am feeding it―to my soil livestock. They need to be just as well fed as our cows.

2020-06-25T08:53:52-05:00July 7th, 2020|Tags: , , , |

The degree of protein synthesis determines insect susceptibility

Plant absorption of ammonium instead of nitrate influences the degree of insect susceptibility. Excessive nitrogen in any form results in excessive soluble amino acids within the plant that enhances insect development and population growth.

From the podcast interview with Larry Phelan.

John: I’d also like to understand the insect attraction piece a bit better. You mentioned that when you have this surge of nitrogen supply on the non-organic farms from the nutrient application period, you have an increased attraction because you have a nutrient-rich food source. Why can insects not utilize plants that don’t contain high levels of amino acids as a food source? They would also contain some level of amino acids, wouldn’t they?

Larry: Yes, all plants are going to have some levels of free amino acids, and they can also digest protein—let’s keep that in mind too. But it’s going to take energy for that insect to digest that protein.

Furthermore, a lot of plants have defenses that involve the inhibition of enzymes that break down protein in the insect. These are called proteinase inhibitors. And in terms of what we call inducible defenses, this is one of the responses of many plants to insect attack. They start the production of these proteinase inhibitors in order to reduce the insect’s ability to digest that protein. It basically knocks out those proteinases in the insect. The insect doesn’t necessarily starve, but it slows its development way down.

Well, in that situation, if you’ve also given that plant these high levels of nitrogen and it’s accumulating these free amino acids, that now short-circuits that plant defense system. So, in other words, the insect doesn’t need those proteinases as much because it’s getting these free amino acids that it doesn’t have to break down.

John: Got it. That was a piece that I had always not fully understood. I’ve heard it described that insects don’t have the capacity to digest complete proteins and that they’re dependent on soluble amino acids as a food source. And that never quite made sense to me. It made sense from a theoretical perspective, but it didn’t make sense to me that plants might have no amino acids versus one plant having very high levels of amino acids.

Larry: Yeah, it’s a matter of degree. And even proteins vary in terms of their digestibility for insects too. And, of course, insects evolve enzymes that are going to be most effective in digesting the proteins they’re likely to encounter, depending on what host plant they feed on. 

Farmers need constant learning

Experience, knowledge equity is the most valuable equity young people can have. From Sarah Singla:

if you want to be a farmer, you will have to go to school. In the past we used to say that you should go to school—otherwise you will have to stay on the farm. But today, if you want to be farmer, you must go to school

John: Sarah, you have developed a very interesting perspective in a farming operation. What are some of the memorable moments and the highlights that have led you to make different decisions?

Sarah: I travel a lot. I’ve visited the US, New Zealand, Australia, and some of the parts of Europe, Brazil, Argentina, etc., and I have met very insightful people.

And what I’ve seen is that some farmers are very efficient. They don’t have any tractors or big machinery. First of all, they think. They understand how nature works; they often want to mimic nature. So what I would say to people is to go and learn, learn, learn. In Brazil, they say that efficiency is directly linked to the knowledge you have. The more knowledge you have, the more efficient you will be, and the more profitable you will be. And I truly believe that.

The more knowledge you have, the more profitable you will be on your farm, because the agriculture of tomorrow will be directly linked to knowledge. Farming is the most difficult job in the world, because being a farmer is walking with nature. We have to produce food, we have to respect the environment; we have to have knowledge in agronomy, in husbandry, in mechanics, in accounting.

This means that in the future, if you want to be a farmer, you will have to go to school. In the past we used to say that you should go to school—otherwise you will have to stay on the farm. But today, if you want to be farmer, you must go to school—you must go study. I see that all around the world.

2020-05-05T05:17:03-05:00May 14th, 2020|Tags: , |

How the form of nitrogen influences insect feeding

The form of nitrogen influences not only the pathogenicity of soil borne fungal diseases, but also susceptibility to insects.

From the podcast interview with Larry Phelan.

John: As you were looking at these plant-insect dynamics in the field and developing your hypothesis of biological buffering, what was something that surprised you?

Larry: The one thing that was particularly exciting to us was when we took the next step and tested this idea of mineral balance resulting from this biological buffering of organic matter. We started growing plants hydroponically so that we could vary the proportions of different nutrients. The hypothesis we were testing was actually that when the plant was in good mineral balance, you would get both good growth and resistance to insect attack. And then as the plant moved out of balance nutritionally, you would see plant growth go down and insect performance actually go up. And then, ultimately, as the plant was way out of balance nutritionally, we expected the plant to not grow very well and the insects not to do very well either because of the poor host plant.

We tested this with a number of different combinations of nutrients, and the one that was most dramatic—that actually supported this prediction—was looking at soybeans in which we varied the ratios of ammonia to nitrate in the plant. We provided it all the nutrients that it needed in constant levels for all the plants. What we were testing was different ratios between these two different forms of nitrogen. And what we found was that as we increased the amount of ammonia up to about 30 percent, we saw the best plant growth. That ratio of 30 percent ammonia and 70 percent nitrate is where we got the best plant growth.

And then, when we looked at insects, we plucked the leaves off of these plants and then fed them to insects to see how the insects grew. The particular insect we were working with was the Mexican bean beetle. When we fed these leaves to the Mexican bean beetle, we saw just the opposite response. In other words, where the plant was out of bounds nutritionally and not growing very well, that’s where the insects grew the largest and that’s where we saw the best survivorship. But as we moved towards that 30 percent ammonia level, where the plants were growing their biggest, insect survivorship dropped from about 90 percent down to about 30 or 40 percent.

It was a very dramatic effect—even more dramatic than what we were expecting. When we followed up on this and measured the levels of free amino acids in these plants, it was consistent with the prediction. In other words, those plants that were not growing as well, that were out of balance in terms of this ratio, had much higher levels of free amino acids relative to that 30 percent ammonia plant.

2020-05-05T05:16:18-05:00May 12th, 2020|Tags: , , , , , |
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