There is overwhelming evidence that replenishment of minerals to croplands has reached a critical point in history. Our foods are nearly empty of nutrients dependent on minerals for synthesis in food. The fields we have grown our foods in for 150 years are depleted of micro nutrient mineral elements. The rate of depletion from 1900 to 1940 is almost 85% and this is evidenced by the rate of mineral deficient diseases increasing in the population as minerals were removed from the soil.
Simply put, nutrient deficient fields are producing a product of low value. The research conducted at major Universities and government agencies offer compelling findings that indicate an overall mineral deficiency condition in the soil of the nation's croplands. In recent years a growing number of reports have appeared which conclude that today's foods are not as nutritious as those eaten in the past.
1936. United States Senate document 264 documented the issue of depleted soil borne micro nutrient trace minerals and concluded that a national crisis was looming in the near future with the outcome a dramatic increase in mineral deficiency disease. To quote from this study: "Countless human ills stem from the fact that impoverished soil of America no longer provides plant foods with the mineral elements essential to human nourishment and health!"
1997. The US Department of Agriculture confirmed this prediction with the graphic depiction of the reduction of soil borne micro nutrient trace minerals coincidental with the increase in mineral deficiency disease.
2008. The Society of Chemical Industry's (SCI) Journal of the Science of Food and Agriculture. It reported that there is no significant difference in nutrient value in organically grown food compared to non organically grown food.  Both methods produce remarkably low nutrient values deficient in critical minerals due to past over harvesting practices.
University of Texas. Donald Davis, a senior researcher at the University of Texas, performed research into the disappearing nutrients in food. He compared Agriculture Department figures on nutrient content for 43 common fruits and vegetables. Davis says historical data spanning 50 to 70 years show apparent declines of 5 percent to 40 percent or more in minerals, vitamins and proteins in vegetables.
Washington State University professor Stephen Jones and researcher Kevin Murphy. Research showed that today's modern wheat has less nutritional value concluding that grains have been developed for baking qualities that are related to protein, not related to iron and zinc and selenium and other essential vitamins and minerals. "You would have to eat twice as many slices of modern bread as you would of the older variety to get the same nutritional value."
2001. The Journal of Complimentary Medicine pointed out that US and UK Government statistics show a decline in trace minerals of up to 76% in fruit and vegetables over the period 1940 to 1991.
2003. News Canada reported that today's fruit and vegetables contain far fewer nutrients than they did 50 years ago. Potatoes, for example, had lost 100 % of vitamin A content, 57% of vitamin C and iron, and 28% of calcium. The report examined data from the US Department of Agriculture involving vegetable quality. Over the entire 20th century the average mineral content in cabbage, lettuce, spinach and tomatoes, declined from 400mg to less than 50mg.
2004. The Journal of the American College of Nutrition examined food composition changes from 1950 to 1999 recorded in the USDA food composition tables. Forty-three crops were examined showing statistically reliable declines for 6 nutrients. The declines were observed in protein, calcium, phosphorous, iron, riboflavin and ascorbic acid; 6% in the case of protein and 38% for riboflavin.
2008. The UK publication Food Magazine. Analysis of food quality changes in the UK over the period 1940-2002. In an analysis of milk: iron content had fallen 62%; magnesium was down 21%; copper content had disappeared completely. Parmesan cheese; 70% decrease in magnesium. The calcium and iron content of all the foods examined was reduced dramatically. Beef rump steak iron content fell 55%.
One thing is certain, mineral deficiency is a root cause of multiple medical conditions that are abated by mineral replenishment. It is likely that plant disease can also be reduced by mineral replenishment.