Varieties Section 6 Soybean Soybean acreage has increased rapidly over the last 15 years, from approximately 60,000 to 300,000 acres. Soybean basically is a cash crop, but the acreage being used as a farm-grown protein source is increasing yearly. Determinant types stop vegetative growth once reproductive development starts. Indeterminate types, on the other hand, continue vegetative growth after reproductive growth begins. The determinant character is found in varieties grown south of Pennsylvania.
Varieties grown in Pennsylvania show the indeterminate character.
As is true for other grain crops, soybean growth and development are influenced by temperature. Soybean, however, is very sensitive to photoperiod, or day length, and does not move from vegetative to reproductive growth until a critical day length is met. This requirement restricts a variety's adaptability to a band about 150 miles north and south of its origin. Since Pennsylvania falls within the same latitudes as the major growing areas of the midwest, our growers have access to the same varieties. Figure 6-2 shows suggested maturity groups for each county in Pennsylvania.