This means that 89 percent of the cash sales in the state of Iowa were associated with just four commodities. The lack of diversity creates many problems. Certain weeds have either become major pests or adapted to the continuous row cropping. In addition to the pest problems, lack of diversity also can cause environmental problems. Chemical fertilizers are necessary to maintain yields and these can become sources of surface and groundwater pollution.
Soil erosion is still a major problem for the state.
Not only does it decrease the inherent productivity, it also serves as a means of transporting chemicals into the surface water. We also have witnessed a dramatic change in crop production techniques over the past few decades. These changes have created increased yields and output but they have not led to increased income for the farmers. Figure 1 shows the net farm income as a percent of the gross farm income. Notice that the line is trending downward.