Poor soils can mean less vitamins and minerals in our vegetables and fruits. A team of researchers from University of Texas, Austin compared USDA nutritional data from 1950 and 1999 for 43 different vegetables and fruits and found reduced amounts of protein, calcium, phosphorus, iron, riboflavin and vitamin C available in vegetables/fruits in 1999 (University of Texas, 2004). During this time, production agriculture focused on producing large, fast-growing, pest resistant crops rather than on growing nutritious crops. However, the decline also has something to do with how we farmed in 1950 versus 1999. In 1950, the average annual use of commercial fertilizer was around 20 million tons. By 2000, that amount was over 50 million tons. Through the years, farmers used less and less organic sources for fertility and improving soil.
Over time, the reliance on inorganic inputs decreased the amount of organic material (humus) in the soil. It reduced the natural input of nitrogen, the major plant nutrient, into the soil. To get plants to grow required more inorganic fertilizers creating an endless cycle of soil degradation.
There are often conflicting opinions on whether conventionally grown foods are more nutritious than organically grown foods. A study by researchers Reganold, Clancy and Benbrook in 2009 compared conventionally grown strawberries to organic strawberries. They found higher antioxidant activity and more vitamin C in organic berries. They then looked at the soil and found that the organic soils had more soil microorganisms and were healthier than conventional soils. Healthier, more diverse soils usually produce healthier plants, which can mean healthier food. Organic systems focus on building healthy soils.
What makes a soil “healthy”? Healthy soils are rich in organic matter and full of living creatures such as insects, earthworms and microorganisms (including bacteria and fungi) that make up the soil food web. These depend on the availability of air, water and nutrients in the soil to live. They then become the world’s best recyclers, breaking down organic matter to release nutrients for plant growth. Fewer living organisms in the soil means a soil is less fertile. Adding organic matter feeds the soil organisms increasing their numbers, which, in turn, increases soil fertility. Organic matter also improves the soil’s ability to hold water for plants to use.
If you want to maximize the nutritional value of fruits and vegetables you grow at home, build a healthy soil full of organic matter and living organisms.