The goal of modern farming is to produce the maximum amount of food at the lowest cost, in order to be competitive in a free market.
It's probably true that much food grown in soil that gradually becomes depleted in micronutrients, trace elements, and beneficial soil microbes, as a result of regular tilling of the land, removal of biomass with each harvesting of the crop, and regular application of pesticides, and so on, contains smaller percentages of the nutrients essential for human health.
There have been a number of studies which suggest that the fruit and vegetables our grandfathers, or great grandfathers ate, had a much higher nutritional content than the food most of us eat today. However, the science is not very reliable because the testing procedures many decades ago were not as accurate as modern testing procedures (a bit like comparing past climates or past weather events with today's climate), and the variation of nutrient content in the same species of plant can vary enormously depending on so many factors, such as location, quality of soil, pH of the soil, application of which fertilizers and in what quantities, and so on.
The fertilizers which are most effective in increasing plant growth are Nitrogen, Potassium and Phosphorous. Applying these fertilizers to produce maximum growth, which farmers tend to do, can result in a 'dilution' effect with respect to the uptake of other minerals which are less essential for the plants' growth and are present in smaller quantities in the soil.
Carbon dioxide can also be considered a fertilizer which increases plant growth and also results in a dilution effect with respect to the uptake of certain micronutrients which might not exist in the soil in sufficient quantities for the percentages in the plant to remain as high as they would with slower growth.
However, generally, the quantity of these micronutrients and trace elements in the food crop is still higher, in absolute terms. In other words, if a doubling of CO2 results in a 30% increase in crop biomass, the increase in elements such as zinc, iron and copper might be only 20%, but still greater in terms of absolute quantity than in the crop grown without the increase in CO2.
A solution to this problem is
not to reduce atmospheric CO2,
nor to reduce the application of fertilizers so that crop growth is less, but to increase the application of the scarce minerals and trace elements such as magnesium, sulfur, boron, iron, manganese, zinc, copper, molybdenum, nickel, selenium, and so on, if they are found to be lacking.
Another solution, which some farmers have already adopted, is to change farming techniques, avoid tilling the soil, which disrupts the natural biodiversity of the soil, and leave the residue of the previous crop in the soil, allowing it to gradually decompose and provide nutrients for the next crop.
No-till farming can also sequester carbon in the soil, so climate change alarmists should be overjoyed with this technique.
"Climate change benefits
The benefits in reducing farming's global warming footprint are immense. Fuel costs saved by running the tractor less, one estimate suggests, no-till can reduce fuel usage by as much as 80 percent. In addition to the reduced carbon emissions from mechanical equipment used in no-till farming, there are several other benefits to the environment. No-till farming, often when paired with crop covering (a technique in which a crop is planted for the express purpose of soil health), reduces carbon emissions through greater sequestration of carbon dioxide by the soil. Over half of the potential carbon sequestration from farmlands comes from conservation tillage.
Carbon dioxide isn’t the only greenhouse gas reduced by no-till, the release of nitrous oxide, a very dangerous greenhouse gas, is also reduced through no-till. As more nitrogen is immobilized in the soil there is a reduced need for the application of nitrogen rich manure."https://geneticliteracyproject.org/2016/06/02/no-till-agriculture-offers-vast-sustainability-benefits-so-why-do-organic-farmers-reject-it/
