5 minute read
The Soil Connection
The Vegetable Systems Trial digs into how food production methods affect nutritional content.
THE RAPIDLY DECLINING nutritional value of food over the last 70 to 80 years has been well documented, and the topic still requires long-term, controlled research studies before experts can draw an informed conclusion about the nutrient density of modern crops. This is why Gladis Zinati, PhD, director of Rodale Institute’s Vegetable Systems Trial, and her team are studying how different growing systems and management strategies affect the nutrient density of vegetables they produce. The early results of this long-running study indicate that both humans and soil health benefit from regenerative organic practices.
Study Guide
Vegetable Systems Trial. Established in 2016 on 3 acres at the Rodale Institute main campus, it is a side-by-side comparison of organic and conventional farming practices for vegetable growing. The research generates data about the nutrient levels in the harvested crops while at the same time measuring changes in the soil health. These soil health measurements include carbon levels and indicators of the soil’s ability to trap and hold atmospheric carbon, which is a critical factor in mitigating climate change.
The crops. The trial focuses on five major vegetables: potatoes, snap beans, winter squash, sweet corn, and lettuce. The various edible parts of plants, including tubers, seeds, fruits, and leaves, are represented in these crops.
Fertility resources. In the organic system, two cover crops—hairy vetch with cereal rye—along with compost and other organic amendments furnish the nutrients the vegetables need to grow. Cereal rye is also planted as a cover crop in the conventional system, but it is burned down with the herbicide glyphosate prior to the planting of the vegetable crops, which is the standard practice among commercial growers. The conventional vegetable crops get their nutrients primarily from synthetic sources of nitrogen and potassium applied to the soil.
Weed management. Many farmers rely on mechanical cultivation of the soil, or tilling, to control weeds. Frequent tilling has been shown to impair the soil’s overall health, degrading its abil- ity to hold on to carbon. In this study, the researchers are comparing the use of cover crops, combined with either intensive- or reduced-tillage practices, to manage weeds in both conventional and organic plots. Conventional growers typically replace tilling with herbicides to eliminate weeds. In the reduced tillage organic rows, terminated cover crops form a dense, natural mulch that blocks weeds and then gradually decomposes into valuable organic matter for the soil.
First Look
This study is designed to evaluate the long-term impact of regenerative organic food production methods versus conventional practices; however, it has already yielded a few fascinating findings.
Protein power. The total protein levels in organic sweet corn and potatoes are significantly greater than those in the conventional crops. The protein content in the organic and conventional vegetables parallels that in the soil in both systems,
Zinati says, indicating that increasing healthy nutrients in the soil may result in more nutritious food.
Less sugar. The sugar level in the conventionally grown butternut squash is significantly greater than in the organically grown vegetables. What’s more, the sugar content in the conventional squash continues to rise after harvest, increasing by 50 percent in storage. More sugar adds calories without adding essential nutrients, making these vegetables less nutrient dense and potentially less healthy for people who need to manage their blood sugar levels.
Potent micronutrients. Polyphenols are minute compounds in food that act as antioxidants, disposing of damaging molecules in our bodies. The butternut squash grown organically has tested with greater levels of total phenols than the conventionally grown crop.
Carbon capture. The organic management system has shown a 30 percent increase in soil carbon compared to the level in the conventional plots. Reducing tillage in the organic system has also proved to increase the carbon level in the top 4 inches of the soil, while intensive tillage has depleted soil carbon.
WHAT’S NEXT
The power of this trial lies in the accumulation of data gathered over a long period of time and with a large sample size. The results will offer insights into trends and document the lasting effects of different farming practices. As the research continues, Zinati says, her team will be “exploring the role of microorganisms, including fungi, bacteria, and viruses, in enhancing soil health and nutrient density in vegetables.” By dedicating time and resources to this study, Rodale Institute is paving the way for a deeper understanding of how to cultivate the healthiest food, ultimately benefiting all of humanity.
Learn more about the Vegetable Systems Trial at RodaleInstitute.org/vst.
Know This
“Nutrient density” is a term used by dietitians and other experts to assess food for its concentration of vitamins and minerals relative to the number of calories. The healthiest foods are nutrient dense because they are high in essential nutrients and low in calories. Many people today struggle with “hidden hunger” because they’re consuming enough calories but insufficient amounts of the vital nutrients necessary for good health.
