Herb Young, Squeeze Citrus LLC
Thomasville, Georgia
The decline in nutritional value of food produced with industrial agriculture is becoming alarming. This loss of nutrient density can be linked to three primary causes which are fundamentals of large-scale industrial agriculture: tillage, synthetic fertilizers and pesticides. Elimination of all three practices in my organic regenerative citrus grove proved that nutrient density can be restored.
TILLAGE:
Tillage significantly affects soil structure, composition, and soil microbiome. Every tillage practice impacts the soil microbiome and has subsequent effects on the nutrient density of crops. Research demonstrates that intensive tillage practices can lead to a decline in microbial diversity and biomass (González et al., 2016). Tillage disrupts soil aggregates, exposing microorganisms to harsh environmental conditions and reducing their populations. A study by Powlson et al. (2014) indicated that reduced tillage systems, such as no-till farming, preserve soil structure and enhance microbial diversity, leading to improved soil health.
Furthermore, tillage can affect specific microbial groups that play vital roles in nutrient cycling. For example, a meta-analysis by Ochoa et al. (2020) found that no-till practices significantly increased populations of beneficial bacteria and fungi, which are essential for nitrogen fixation and organic matter decomposition. This microbial diversity is crucial for maintaining soil fertility and nutrient availability.
SYNTHETIC FERTILIZER:
Several studies have indicated that conventionally grown plants with high NPK inputs have lower concentrations of vitamins and minerals compared to organically grown counterparts:
- “Dilution effect" occurs when rapid growth caused by high fertilization leads to a decrease in nutrient concentration within plant tissues. (Jarrell and Beverly, 1981).
- Reduced Antioxidants: There is evidence of a decrease in antioxidant levels in plants grown with synthetic fertilizers, as rapid growth can sometimes bypass the natural synthesis of these compounds (Benbrook, 2012).
- Synthetic fertilizers have been shown to cause an imbalance in microbial activity and microbiome species which alters mineral uptake in the plant. (Bhattacharyya et al. 2009).
- Lower Mineral Content: Research has shown that conventionally grown fruits and vegetables may contain lower levels of essential minerals like magnesium, iron, and zinc (Davis, 2009; Marles, 2017, Leifert, 2007).
- High levels of NPK can cause imbalances in the uptake of other essential micronutrients (e.g., iron, zinc, magnesium), leading to nutrient-deficient plants.
Mitigation:
- Organic Farming: Utilizing organic fertilizers and compost can promote balanced growth and potentially higher nutrient content. (Leifert et al. 2015)
- Soil Health: Ensuring soil is rich in organic matter and diverse in microorganisms enables plants naturally access a wider range of nutrients. (Jansa et al. 2006)
While synthetic fertilizers can indeed enhance plant growth, there's compelling evidence that this can come at the expense of nutritional density.
PESTICIDES:
The application of synthetic pesticides can significantly alter soil microbial communities, leading to consequences for both soil health and crop nutrition. Research indicates that pesticides can reduce microbial diversity and disrupt beneficial microbial functions (Garbeva et al., 2011). A study by Zhang et al. (2020) demonstrated that frequent pesticide applications led to a significant decline in key microbial populations, such as mycorrhizal fungi and nitrogen-fixing bacteria, which are essential for nutrient availability.
As soil microbiome health declines, so too does the nutrient density of crops. A study by Lu et al. (2021) found that crops grown in pesticide-treated soils exhibited lower concentrations of essential elements, including zinc, iron, and magnesium, compared to those grown in organic systems with healthier microbial communities. The altered microbial interactions hinder nutrient solubilization and uptake, leading to less nutrient-dense food products.
SQUEEZE CITRUS VALIDATION RESEARCH
Since initiation of the grove in April 2021, 10 varieties of citrus have been grown regeneratively and organically. Squeeze Citrus organic regenerative practices included:
- No tillage of any kind since the initial chisel plow to break any residual hard pan.
- Cover crops: 10 species planted spring and fall trunk-to-trunk
- Certified Organic fertility program
- Nutrition includes fish hydrolysate, kelp, molasses-based products, humic and fulvic acids in addition to organic P, K, Mg, Mn, Cu, Fe, Zn, B, Si.
- No fungicide or bactericide use (no diseases present).
- Organic insecticide program to control Citrus Leafminer and Cottony Cushion Scale (Neem, Thyme, Chitosan, Spinosad and Beauveria bassiana endophyte.)
- Intensive beneficial bacterial inoculations, multiple times per year, foliar and soil.
- Algal inoculations to stimulate soil microbes.
- Mycorrhizal fungi inoculations that are symbiotic link between the trees and microbes.
- Compost applications around trees and compost tea drenches
To directly compare the level of our nutrient density to conventionally grown fruit, Page Mandarins and Pink Frost Grapefruit were located in the nearest commercial conventional groves. Both conventional groves used standard citrus production practices consisting of granular synthetic fertilizer (2-4 times/year), insecticides for mites, scale and leaf miner, fungicides for greasy spot and melanose, bactericide for citrus scab. The ground in these groves is maintained weed and grass free year round in a 12’ wide band in the tree row by using primarily glyphosate herbicide applied 3-4X per year.
Fruit was picked from Squeeze Citrus and the competitive groves on the same day and juiced that day. The juice was frozen and stored. Samples were shipped overnight frozen to Eurofins lab in Raleigh, NC for analysis. Eurofins is a USDA Certified lab. Each sample consisted of 16 fruit from five or more trees.
Results for Regenerative samples for the two citrus varieties were averaged and results for the Conventional varieties were averaged to give two replications of the data. Nutrient levels for the conventional fruit were lower and used as a baseline in the following graphic with the nutrient level from the regeneratively grown fruit expressed as a multiple of the conventional.
Three of the flavonoids evaluated were absent in both varieties of the Conventionally grown fruit but present in one or both of the Regeneratively grown fruit samples.
Concentration (ppm)
CONVENTIONAL REGENERATIVE
Mandarin Grapefruit Mandarin Grapefruit
- Tangeretin 0 0 29 0.97
- Nobiletin 0 0 59 3.02
- Neohesperidin 0 0 0 89
- Didymin 8 4.59 0 8.36
- Vitamin C mg/g 760 330 347 349
The lab explained that the modest and inconsistent levels of Vitamin C are caused by UV breakdown which occurs within hours of juicing.
Flavonoid concentrations for seven of the eight measurements taken were higher for the fruit produced regeneratively (graph expressed in ppm).
The carotenoids and flavonoids evaluated by Eurofins Lab have multiple health implications.
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CONCLUSION:
In three growing seasons, I was able to show that regenerative and organic growing practices could result in production of citrus with nutrient levels far in excess of those in fruit grown with conventional production practices. I attribute the increases in nutrient density to establishment of a healthy soil microbiome. Conventional agriculture production practices greatly impact the Soil Microbiome and as a result the crop’s Nutrient Density.
REFERENCES
Bhattacharyya, S., Roy, R. K., & others. (2009). Impact of long-term organic and mineral fertilization on bulk density and soil porosity as related to the microbial biomass and water-stable aggregates. European Journal of Soil Biology, 45(3), 309-315. https://doi.org/10.1016/j.ejsobi.2009.03.003
Benbrook, C. M. (2012). Impacts of genetically engineered crops on pesticide use in the U.S. -- the first sixteen years. Environmental Sciences Europe, 24, 24. https://doi.org/10.1186/2190-4715-24-24
Davis, D. R. (2009). Declining Fruit and Vegetable Nutrient Composition: What Is the Evidence? HortScience, 44(1), 15-19. https://doi.org/10.21273/HORTSCI.44.1.15
Garbeva, P., van Veen, J. A., & van Elsas, J. D. (2011). Microbial diversity in soil: the role of the soil environment. Microbial Ecology, 62(1), 1-16. https://doi.org/10.1007/s00248-011-9945-2 (https://doi.org/10.1007/s00248-011-9945-2)
González, J. M., et al. (2016). "Effects of tillage on soil microbial communities." Soil Biology and Biochemistry, 102, 1-11. https://doi.org/10.1016/j.soilbio.2016.07.003 (https://doi.org/10.1016/j.soilbio.2016.07.003)
Jansa, J., van Veen, J. A., & Kowalchuk, G. A. (2006). Soil Health and Sustainability: Managing the biotic component of soil quality. Applied Soil Ecology, 33(2), 327-331. https://doi.org/10.1016/j.apsoil.2006.09.009
Jarrell, W. M., & Beverly, R. D. (1981). The dilution effect in plant nutrition studies. Advances in Agronomy, 34, 197-224. https://doi.org/10.1016/S0065-2113(08)60887-1
Leifert, C., Niggli, U., & others. (2007). Effects of Mineral Versus Organic Fertilization on Nutritional Quality of Fruits in a Long-Term Field Trial. Journal of the Science of Food and Agriculture, 87(6), 1228-1236. https://doi.org/10.1002/jsfa.2824
Leifert, C., Cummins, N. D., Roberts, E. C., & Bullock, P. C. (2015). Effects of organic versus conventional farming systems on food quality and safety outcomes: a systematic review. Environmental Health Perspectives, 123(12), 1407-1415. https://doi.org/10.1289/ehp.1409528
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