The importance and wealth of any state or country depend in great measure on its natural resources and the extent to which these resources are used. Some states are rich in mineral wealth, others in lumber or oil or water-power. All these Iowa lacks, yet she is not poor but fabulously rich in the most vital of all resources, the soil. Within her boundaries, north and south, east and west, lies one of the most concentrated of fertile areas of the northern hemisphere. Her climate, though one of extremes, is well suited to agriculture. Corn yields abundantly, and directly, or indirectly through livestock, is the source of much of her wealth. More than one-fifth of the corn raised in the United States is grown within the state of Iowa. The farm value of Iowa corn has for a number of years been in the neighborhood of 250 million dollars annually. This abundance of corn is due to the productivity of her soils, which in turn is largely an expression of their high organic matter content. Their continued productivity depends on proper management, and maintenance of this vital component of soil.

Modern civilization has exploited and wantonly dissipated many natural resources. Forests have been cleared and hillsides denuded, coal seams have been exhausted and the countryside despoiled. Our land is scarred by the wreckage of depleted resources. The soil has not escaped. Almost as serious as the visible ravages of erosion, however, is the invisible decline in fertility that may be caused by intensive cultivation, single-cropping and the absence of rotations that tend to replenish the supply of organic matter within the soil. The purpose of this bulletin is to review the role played by organic matter in soil fertility, to examine the causes of depletion of organic matter, and to consider the means by which maintenance can be accomplished.