Iowa soybean production history

Another soybean harvest is completed and the yields were above expectations of many producers. Table 1 shows the average annual number of soybean-harvested acres by the decade since 1924 when USDA recorded the first Iowa soybean production. The table includes data for each year since 1990. During the years before the 1950s soybean was grown extensively as a forage crop, but those acres are not included in the table because they were not harvested for grain.

In Iowa, soybean production expanded rapidly from 1924 through the 1940s due to the expansion of soybean oil extraction facilities in the area. Total production increased 10-fold between the 1920s and the 1930s, and again during the 1940s. During the 1950s, soybean acreage expanded steadily and doubled in harvested area between 1952 and 1958. During the 1970s the average annual harvested area was 6.8 million acres. Expansion of production area continues until the present time when 11 million acres was harvested in 2001 for a record area under production. Fluctuations in area of production vary depending on weather, commodity price, and government programs.

Yields ranged from 20 to 26 bushels per acre during the 1950s. Total production nearly doubled each decade in the 1950s, 1960s, and 1970s, and in Iowa the production has remained above 400 million bushels since 1994. However, the record total soybean production occurred in 1998 when nearly 500 million bushels was produced. The most recent weather-related events that reduced total soybean production were excess moisture in 1993 and drought conditions in 1988. However, the weather in 1994 was very favorable to soybean production and the record of 50.5 bushels per acre was recorded.

Soybean yields per acre also have continued to increase since those early years of soybean production in Iowa. Yield average per decade (Table 1) indicates that the yields increased from 14 bushels per acre in the 1920s to 43 bushels per acre in the 1990s, a threefold increase. Yields have made steady progress due to improved varieties and better management by the producers. Continued yield improvement can be expected in the future as new pest-resistant varieties are released and management is fine-tuned.

Table 2 includes average annual soybean harvested acreage, yield, and the rank for each crop-reporting district in Iowa from 1990 to 2001. Harvested acreage varies by more than threefold from the south central to the northwestern districts. The northwestern district has the highest acreage of soybean, followed by the west central and central districts. The northwestern district has produced the most acres of soybean every year since 1990, and more acres were produced in 2001 than any other year for all districts. In northeastern Iowa, the harvested soybean area has more than doubled between 1990 and the present. All other districts have increased their acreage since 1990, but to a lesser degree than the northeastern district.

Yields vary from year to year primarily due to weather and other conditions causing stress, such as insects, diseases, nematodes, and weed pressure. East central Iowa ranks as the highest yielding district during the past 12 years with an average yield of 46.6 bushels per acre. Northeastern and central Iowa districts are close behind with yields of 45.7 and 45.1 bushels per acre, respectively. For seven of the past 12 years the east central district has produced the highest annual soybean yield averages in the state. In 1994, 1997, and 1998 the yields in the east central district were more than 50 bushels per acre, and the highest recorded average yield was 53.6 bushels per acre in 1998. The central Iowa district produced the highest average yield during four of the past 12 years. Yields were lowest in the south central and southwestern Iowa districts. During five of the past 12 years the lowest district yield averages have come from the south central district. The north central district has produced the lowest yields during three of the past 12 years.

Table 1. Iowa average annual soybean-harvested acreage, yield, and total production from 1924 to 2001.

Year Harvested acres

(x 1,000,000)
Average yield

(bu/acre)
Production

(x 1,000,000 bushels)
Results by decade
1924-1929 0.02 14.3 0.3
1930-1939 0.2 16.8 3.8
1940-1949 1.5 19.9 30.7
1950-1959 2.2 23.5 51.9
1960-1969 4.3 28.8 126.0
1970-1979 6.8 33.8 231.6
1980-1989 8.2 37.4 306.8
1990-1999 9.2 43.4 401.4
Individual year results
1990 7.9 41.5 327.8
1991 8.6 40.5 349.5
1992 8.2 44.0 350.5
1993 8.3 31.0 257.3
1994 8.8 50.5 442.9
1995 9.3 44.0 407.4
1996 9.4 44.0 415.8
1997 10.4 46.0 478.4
1998 10.4 48.0 496.8
1999 10.8 44.5 478.4
2000 10.7 43.5 464.6
2001* 11.0 44.0 481.8
* November 2001 estimate.

Source: Iowa Agricultural Statistics.

Table 2. Average annual soybean-harvested acreage, yield, and rank for all districts in Iowa from 1990 to 2001.

District Harvest acres

(x 1000)
Rank Average

yield

(bu/acre)
Rank
Northwest 1603 1 44.2 4
North central 1386 4 42.4 6
Northeast 701 8 45.7 2
West central 1481 2 42.4 6
Central 1479 3 45.1 3
East central 798 6 46.6 1
Southwest 860 5 40.7 8
South central 455 9 38.5 9
Southeast 705 7 43.2 5
State average 1052 43.4

Source: Iowa Agricultural Statistics.

This article originally appeared on page 4 of the IC-488 (1) -- January 21, 2002 issue.

Updated 01/20/2002 - 1:00pm