BOOSTING SOYBEAN YIELDS REQUIRES ATTENTION TO LOCAL CONDITIONS
As members of the High Yield Team embark on another year’s quest to better soybean yields throughout the US, it is helpful to be reminded of the diversity of soybean production in the country. Because there are differences in soils and climate among the disparate regions of the country, producers in each region manage and produce a soybean crop differently. Therefore, it is logical that no one system of production will fit every environment, and perceived remedies to fix problems will not be applicable to every region.
There are three distinct soybean-producing regions in the United States: the midwest, the midsouth, and the southeast. The midwest is characterized by rolling terrain with deep soils, consistent summer rain, and moderate temperatures. The midsouth has both alluvial and upland soils, and summer drought with high temperatures. The southeast has sandy soils, summer drought and high temperatures, and possible inundating rainfall from sporadic summer hurricanes.
Harvested acreage and yield, along with percentage of acres planted by May 1, percentage of acres doublecropped, and percentage of acres irrigated are presented in the accompanying table for selected states within each region. All values were compiled from data presented in National Agricultural Statistics Service publications. All values are five-year averages except the percentage irrigated acres, which are taken from the 2002 Census of Agriculture.
Virtually all of the soybeans in the shown midwestern states are grown in dryland systems. Soybeans in the midsouthern states (except Tennessee) have a significant portion that is irrigated. The southeastern states have virtually no irrigated soybeans, but a significant percentage of their soybeans are doublecropped. Summer weather patterns in the midwest are favorable for dryland production, whereas weather patterns in the other two regions generally are not.
Five-year average acreage, yield (bushels per acre), percentage of acres planted by May 1, and percentage of acres doublecropped, and 2002 percentage irrigated acreage.
% planted May 1
*Average yield for each region calculated by dividing 2002-2006 total production by total harvested acres.
Virginia is arbitrarily included as a southeastern state because of the similarity of its climate and soils to the other states along the Atlantic Coast.
Missouri (6% planted by May 1, 4,986,000 harvested acres, and 36.7 bushels per acre average yield) and Kentucky (6% planted by May 1, 1,288,000 harvested acres, and 41.5 bushels per acre average yield) are not included in the table because portions of their acreage can be arbitrarily assigned to both the midwest and the midsouth. A significant portion of the soybean acreage in southeast Missouri is irrigated. About 30% of Kentucky’s acreage is doublecropped.
Kansas (5% planted by May 1, 2,732,000 harvested acres, and 31.5 bushels per acre average yield) and Nebraska (3% planted by May 1, 4,700,000 harvested acres, and 45.2 bushels per acre average yield) are not included in the midwest data because they have significant irrigated acreage.
The three regions have three distinct yield levels. The midwest average yield of 44.0 bushels per acre exceeds the midsouth average yield of 35.6 bushels per acre, which exceeds the southeast average yield of 29.0 bushels per acre. The yield data indicate that production limitations and conditions are more restrictive to soybean yield potential in the midsouth and southeast.
The midsouth (excluding Tennessee) has little doublecropped acreage and a high percentage planted by May 1, whereas the opposite holds for several states along the Atlantic coast. Interestingly, Indiana and Ohio, which are located at midwest latitudes, have 11% and 14% of their soybeans planted before May 1.
Recent price increases for corn, soybeans, and wheat likely will change the acreage allotments among crops in the coming years. However, these shifts in acreage probably will not affect the yield differences among the regions. Those will only be changed by the development and adoption of improved production and management practices and inputs in the lower-yielding regions.