How can we grow truly nutrient dense fruit and vegetables?
Recently, I came across a study on the nutritional content of fruits and vegetables produced through modern agriculture in the U.S. The research showed that produce sold in supermarkets in 2010 had significantly lower nutrient levels compared to similar crops grown in 1975. For example, broccoli grown in 1975 contained 103mg of calcium, 1.1mg of iron, and 113mg of vitamin C. In contrast, broccoli grown in 2010 only had 47mg of calcium, 0.73mg of iron, and 89.2mg of vitamin C. That was already 15 years ago, and the issue of nutrient depletion has likely gotten much worse since then. I’m not sure if anyone in Vietnam has studied this yet, but I suspect it's already happening here too, as Vietnam is following the same path of modern agriculture that the U.S. started down 20 years ago.
What’s the cause?
While crop variety might be part of the reason, I believe plant nutrition is a much bigger factor. Fundamentally, if a plant isn’t supplied with all 17 essential nutrients it needs to grow, it won’t develop properly or produce the compounds it needs to fight off pests and diseases—leading to nutritionally deficient fruits and vegetables. Typically, vegetables sold in markets are only fertilized with NPK, while other minerals like calcium (Ca), sulfur (S), and zinc (Zn) are often overlooked. These nutrients are already present at low levels in Vietnamese soils. As a result, crops grown using industrial methods are more likely to be nutrient-deficient and more susceptible to pest attacks, leading farmers to rely on pesticides to maintain yields. In short, plants that receive a balanced supply of all 17 essential nutrients will be more nutrient-dense and healthier than those that don’t, and this nutritional quality directly affects the health of the people consuming them.
Organic matter isn’t the only solution
To be clear, we don’t use synthetic fertilizers or pesticides on our farm. When I grow crops, I focus a lot on increasing and maintaining soil organic matter, because it plays a big role in plant health and soil function. However, the main source of nutrients in soil comes from minerals, not organic matter (except for nitrogen). Of course, soil that’s extremely low in organic matter won’t be able to release minerals effectively—but soil that lacks minerals to begin with won’t become fertile just by adding more organic matter.
In Vietnam, organic/natural farms often struggle to grow nutrient-dense produce because mineral nutrients are frequently leached away by heavy rains. Moreover, the nature of Vietnamese soils is very different from the naturally fertile soils in temperate countries—like the loess soils in Northern Europe and North America, or volcanic soils (andosols) in Japan. These two are among the most mineral-rich soils in the world. Only certain regions in Vietnam, such as the Red River Delta and the Mekong Delta, are naturally fertile and nutrient-rich due to the constant deposition of alluvial silt. In contrast, most hilly and mountainous soils in Vietnam are mineral-poor and have been heavily leached over the years, leading to ferralitization (ferralitic soils have poor nutrient exchange capacity, high iron and aluminum content, and low pH). On soils like these (like ours), many methods designed for rich foreign soils simply don’t work when it comes to growing strong, nutrient-rich crops in Vietnam—unless your soil is naturally fertile and mineral-rich to begin with.
So what’s the solution?
Reading all of the above might feel discouraging, but I truly believe it’s possible to grow nutrient-dense vegetables and fruits in Vietnam using natural methods. The key is to understand your own soil and find specific solutions. If you find that your soil is low in minerals, just look for natural, sustainable, and locally available sources of minerals to supplement it. In fact, if you want to grow nutrient-rich crops using chemical methods, that’s still an option—but in my opinion, natural methods will better sustain soil and environmental health over the long term.
Here are some solutions for natural farming on poor soils:
Improve cation exchange capacity by increasing humus content and raising the pH of acidic soils
Create conditions for symbiotic microbes like AMF fungi to help release phosphorus (P) and potassium (K) from the soil
Apply indigenous microorganisms (IMO) to diversify the soil microbial ecosystem
Adjust the balance of base cations (Ca, Mg, K, Na) in the soil to roughly: 65–75% Ca, 10–15% Mg, 2–5% K, and 1–3% Na
Add high-quality manure (note: animals raised on mineral-deficient land will produce mineral-deficient manure!)
Provide nitrogen (N) from sources like fish amino acid, plant protein, manure, urine, or nitrogen-fixing microbes
Add phosphorus and calcium using fish bone meal
Add potassium from rice husk biochar, wood ash, banana compost, straw, or elephant grass
Add calcium from clam shells or agricultural lime (CaCO₃, not quicklime CaO)
If your soil is low in magnesium (Mg), use dolomitic lime. If Mg is sufficient, use normal lime. If your soil is low in Mg but already has enough Ca, use Epsom salt.
Add sulfur (S) and calcium from gypsum powder
Add trace minerals from seaweed meal
If your soil is low in sodium (Na) and not affected by salinity, add Na and trace minerals from sea salt
Note: Exact quantities depend on your specific soil. It’s best to conduct a soil test before applying these solutions, and make sure to do your research before getting started.
References:
Data on nutrient density from the USA:
https://bionutrient.net/.../docs/2011_Nutrient_Guide.pdf
Book on this topic:
https://www.amazon.com/Intelligent-Gardener.../dp/0865717184
