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John Reganold has been comparing organic and conventional agricultural systems since he noticed the drastic difference between them in a soil sample 25 years ago. He is an agro-ecologist who has always been interested in how land is used, and is the lead author of a study on the sustainability and nutritional benefits of organic farming, which was published in the journal PLoS ONE yesterday.

The demand for organic food continues to increase, and as we are huge fans of the benefits of organic produce here at HLife, we were thrilled to see such definitive information on a much-debated subject. While everyone knows that conventionally grown produce has more pesticide residue that the liver then has to discard, there wasn’t conclusive data regarding nutrition – until now. This study of strawberries grown on commercial farms is among the most comprehensive of its kind: A team of interdisciplinary researchers checked indicators like soil DNA, microbe diversity, fruit taste, antioxidant activity, and even appearance. Twenty-six strawberry fields were analyzed, and side-by-side comparisons found that the organic farms produced more flavorful and nutritious berries while leaving the soil healthier.

HLife chatted with Professor Reganold about the groundbreaking implications of this study, among which are the relationship between organic farming and better nutrition, a longer product shelf life, and quality soil.

Maryl Celiz: How was the study conducted?
John Reganold: Our research team was interested in looking at both the soil quality and also the strawberry quality, including the nutritional quality on real commercial farms. So it had to represent reality. The strawberry capital of the world is in Watsonville, California, so I made phone calls over a couple of weeks and visited Watsonville with growers to see if we could actually get these side-by-side comparisons of organic and conventional strawberry farms where the soils were the same, and where the strawberry varieties were the same and planted at the same time. I found out that we could do this in certain locations, and that’s very critical – that is one of the most important things about this study is the methodology: the varieties are the same, they are planted at the same time, and the fields from these farms are directly adjacent – they are probably about 20 meters apart – and we tried to get a sample, not right on the edge but fairly close, so the soils would not have a differing effect on the berries.

MC: The soil was the same but the difference was on the process of farming and the seeds?
JR: The seeds were the same – there were no genetically modified seeds on either side. We didn’t deal with any GM crops, the varieties are classically bred by either University of California, or, in the case of the Driscoll growers, they have their own breeders. Those seedlings are brought out and put in the ground in November and they grow through winter and in the middle of March you have strawberry production. Then they harvest every three or four days all the way until November, so it’s a seven month production. Strawberries go through cycles so you’re gonna have periods of time when there is high production, but it may be that the organic berries have a little bit of a different cycle than the conventionally grown berries. So, to make sure we took that into account, we sample all three seasons over two years. We samples in spring, summer, and fall and we did that across 26 farms – 13 organic and 13 conventional farms, they were in pairs – same variety, same soil.

MC: You found farms that produce both organic and conventional?
JR: Absolutely. In fact, Driscoll’s is probably the biggest strawberry producer, or one of the biggest in the world, and they grow both organic and conventional berries. Pacific Gold Farms, they were the other big company. The setting was really made possible by the cooperation of these two companies. When we were out in the fields, we didn’t pick the berries because that wouldn’t represent reality. We would make sure that the berries were picked on our study fields when the rest were normally picked by the pickers. And we would have them pick from the spots on the field that we wanted, and they would put them in the clam shells and take them to Driscoll’s. They were very cooperative – they have a big refrigeration system and they would cool the berries down and then the berries would be on their trucks all the way up to Washington state. They were on trucks that were coming to Washington state anyway, but when the berries got up to Spokane, which is near us, we would then take our research berries off the truck. Our berries would go right into the taste test and the other berries would go right into the store, so every part of the process represented reality.

MC: The only difference then was the actual farming process.
JR: That’s correct, and that’s all we wanted. We wanted to be able to say you have two different management systems. If you have these two management systems producing strawberries, what are the effects on the soil, and the soil DNA, the genetics – and what are the effects on the berries, meaning, their shelf life (how fast do they rot), their nutrition (vitamins, antioxidants), and taste? People often will say, “well, these particular berries taste better than these berries,” or, “organic berries taste better than conventional.” But that’s anecdotal. You really need to have scientific evidence for that. So we actually tested that. Our hypothesis was that organic strawberries produce healthier berries from healthier soils, because those are some of the reasons why people buy organic berries. We didn’t know that was the case, so we decided to check it out. So we had to make sure that the methodology was strong enough and done correctly so that we could test the hypothesis.

MC: So taking the hypothesis one step further, since your findings support your hypothesis, would you add that these healthier berries from healthier soils support healthier people because of the benefits that you found?
JR: One thing about strawberries is that they are one of the higher foods in antioxidants and vitamin C, so our study found that with the organic berries tended to have significantly more dry weight. So, if you have more dry weight, that means you have “more strawberry” in the strawberry, which means you’re getting more strawberry when you eat an organic strawberry. We also found that organic berries have more antioxidants, more phenolics, and more vitamin C – all very important for the health of humans. And, organic berries – we didn’t test this, but we know this from other studies that have been done – have much lower residues or no residue of pesticides on the berries, so, in that sense, it’s healthier. If people are concerned about eating pesticides or if they want more vitamin C, it would be better to eat the organic berries.

MC: What did you find about taste?
JR: When we did the taste tests on the berries – these were blind taste tests done with untrained panelists, ranging all the way from 20 years old to folks in their 60s. They would go into a little tasting cubicle and it’s all professionally done, there’s even a red light on so they can’t see the color of the strawberry because that could affect their judgment. They have no idea they’re comparing organic and conventional berries – that would bias them. They just know they taste two berries, and they have to rank them, score them, and we evaluate the scores. We looked at the sweetness and the overall flavor and the firmness of the strawberry. Then the red light goes off and they can see the strawberry and they have to evaluate color. With two of the varieties there was no difference – but with one of the varieties, the organic berry was sweeter, more flavorful, it was even preferred aesthetically, it had better color to the tasters. There are very few taste tests done comparing organic to conventional foods, so, that was quite a finding right there.

MC: How significant was the antioxidant difference?
JR: About 10%. The organic had about 10% more total antioxidant activity than the conventional berries, and the numbers were similar for vitamin C and phenolics.

MC: What did you find about the health of the soil?
JR: When we looked at the soil, there are traditional properties that one can look at, chemical and biological, that give you and indication of soil health or soil quality, and we looked at about 31 properties. And if you were to say, summarize that, there were about 12-14 differences of the 31 properties. And it was with some of the major properties, like the amount of organic matter in the soil, the amount of nitrogen, or the amount of microbial activity in the soil. All those factors, every one, were higher in the organic. Then we took soil samples and inspect the DNA from the soil. You might say, “well, what do you mean DNA?” Soils are living – they have microorganisms in them, both soils that are farmed conventionally and organically. You can go in and kind of get a shot of what the gene pool is like in these systems. We know from doing this enough that certain organisms, or genes that we can see, carry out some important processes in the soil, such as nitrogen fixation or pesticide degradation. When we looked at what we call the signal intensity coming off the organic soils versus the conventional, the signal intensity was greater in all 11 of these processes, meaning, the gene pool, the microbial activity was greater in the organic in every case. There was also more diversity. We can basically say that the organically farmed soils were not only healthier and higher quality, but they were also more genetically diverse, and likely more resilient to stress that might come upon that soil system. Those were pretty significant findings too. We really got to look at soil as well as the berries themselves.

MC: How does the organic process differ from the conventional process?
JR: Both of these management systems are intense. They grow strawberries on mounds that they have to build with special equipment. They plant the strawberries and the mounds on both systems are covered with plastic tarp, which basically knocks out weeds, and it is interesting because the use of this tarp basically excluded the need for herbicide in both systems. The big difference is though, before they put on that tarp usually all the conventional growers use methyl bromide to fumigate the soil, which is basically a brief sterilization of the soil. A lot of the microbes come back, but during that time it helps cut down disease. The organic can’t do that because certification processes don’t like it. Other differences were that the conventional growers could use an arsenal of synthetic pesticides. The organic growers don’t have that, they can’t use synthetic pesticides, however, they can use organically certified pesticides but they are much more limiting. For example, sulfur, which is a more natural pesticide. Organic growers do use pesticides, it’s just that they have to be certified and they’re usually natural. Another thing is that the number of pesticides used is relatively small in the organic systems but in the conventional systems it’s relatively high. And then the conventional growers can also use synthetic fertilizers, but the organic not. So the organic had to use organically certified fertilizers, and they used compost. Now the interesting things is that both systems used compost – the conventional growers used compost to bring back some of the microbes lost during fumigation more quickly. But the organic used twice as much. I think that was one of the main reasons we found so much of a difference in soil quality – and probably not having the methyl bromide might have helped too. But that’s the difference: It comes down to pesticides and fertilizers. The harvesting and irrigation is similar.

MC: How much of a difference was there in shelf life?
JR: We basically took the strawberries and set them on the counter and did what we called the rotting test. You can, basically, watch them rot over a series of days. Most growers and stores that buy strawberries want them to have a long shelf life, maybe five days and not rot. We actually thought that the conventional berries would rot more slowly because they had this array of pesticides. But what happened was the opposite: The organic berries rotted significantly more slowly. So, after a five or six day period, you could have 25% more good organic berries than conventional, on average over the varieties. That’s a plus when you’re selling berries because you want the berries to be able to last longer. And be fresher. To me, that was a surprise.

MC: Any guess as to why that happened?
JR: We don’t really know. If you would have asked me before the study, “ok, which soils are gonna be healthier?” I would’ve probably said the organic. But if you would’ve said about the rotting test, I would’ve said that the conventional is gonna rot more slowly, which is why it was so amazing to me that it was the opposite.

MC: With so many benefits – nutritional, soil health, shelf life – to the organic system, what would be the advantage of farming conventionally?
JR: The advantage for a grower is yield. You get higher yields in general. The industry data from these two companies for these two years showed that the conventional strawberries were producing 25% more yield. Now, at the same time, organic berries were more than making up for that in price premium. The price that a grower can get for an organic berry will more than make up for that 25% yield difference. A grower may get about 40% more for growing an organic berry. Another advantage to conventional farming is that it’s easier to grow conventionally – you have an arsenal of pesticides to use which the organic farmer can’t use, and because there are more conventional farmers, there is more information out there to help you farm conventionally. Organic farming is more intensive and there is less information out there on how to do it.

MC: Did you measure pesticide residue?
JR: We didn’t look at pesticide residues because there’s already information out there on that. The Environmental Working Group has information on pesticide residue, and strawberries are usually in the top 5, they’re certainly in the dirty dozen. The three main reasons people buy organic are because they think it’s healthier, it tastes better, and they think it’s better for the environment. Now, we already know there are more pesticide residues on conventional strawberries. But where the jury is out is on the nutritional differences between the organic and conventional, so we wanted to look at the antioxidants, the vitamin C and the phenolics. Then there’s very little information on taste, so we ran some taste tests. And then as far as better for the environment, I’ve looked at other farming systems where we’ve looked at the effects of organic/conventional farming on, say, soil erosion. And while soil erosion wasn’t part of the study, what is better for the environment is what is better for the soil. People think that organic growers are doing a better job with the soil and we thought, if that’s the case, let’s look at these 31 soil properties and see if that is the case. And let’s look at the DNA, and from those two things, we should get an indication of soil health.

MC: Can you define what sustainability means from a soil studies perspective?
JR: Sustainability is kind of a Utopian concept. What it says is, if we meet sustainability guidelines, or if a particular farm is to be sustainable, it needs to be economically sustainable, environmentally sustainable, and socially sustainable. Then within those three there are all kinds of variables. How do you measure that? You have to test the farm. You can have a farm that is not profitable – that is not sustainable. Or a farm that is causing erosion or polluting a lake – that’s not sustainable. So, when we do studies, we look at different sustainability indicators. For example, soil quality, crop yield, crop quality – if it’s a strawberry, more vitamin C. The farm also has to make money. It has to be good for the environment. But it also has to be socially just – the people working there should get fair wages, benefits, and it should be good for the community. When you look at all of these things you say, wow, that’s a tough business to be in – and it is. But if you look at those variables in general, and you look at the studies that have been done, in general, organic systems are more sustainable than conventional systems.