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The Rise of Irrigated Soybeans in Arkansas

Irrigation in Arkansas cropland has increased due to expansion of irrigated soybean area.

Brad Watkins, Professor

August 16, 2023

3 Min Read
Irrigated soybeans
Every county in eastern Arkansas has experienced an increase in irrigated soybean area, but counties bordering the Mississippi River have experienced the greatest expansion. Brent Murphree

Arkansas has experienced a significant expansion in irrigated cropland since the beginning of the 1980s. From Census year 1982 to Census year 2017, irrigated harvested cropland acres grew from 2.022 million acres to 4.848 million acres, respectively, representing an increase of +2.826 million acres (USDA, NASS, 2023a).

The majority of this increase in irrigated cropland acres (approximately 75% of the increase) was due to the expansion of irrigated soybean area. 

Figure 1 presents Arkansas soybean harvested acres split into all acres, non-irrigated acres, and irrigated acres for the years 1979 – 2018. All soybean harvested acres (non-irrigated + irrigated) dropped from a record level of 5.15 million acres in 1979 to 3.20 million acres in 1988 and thereafter remained relatively level for the state at 3.21 million acres.

Non-irrigated acres dropped steeply from 4.80 million acres in 1979 to 0.51 million acres in 2018, while irrigated acres expanded from 0.35 million acres in 1979 to 2.71 million acres in 2018.

Converting acres

It is obvious that most expansion in irrigated soybean acres was the result of converting non-irrigated acres to irrigated acres.

Every county in eastern Arkansas experienced an increase in irrigated soybean area during this time, but counties experiencing the greatest expansion were those bordering the Mississippi River, where ample water from lateral river recharge of the underground aquifer allowed for greater transition of non-irrigated area to irrigated area.

A major factor for the upward trend in irrigated soybean acres in Arkansas is the increased world demand for soybeans, particularly in China.

Increased world demand for soybeans has increased the value of soybeans relative to other crops grown in the state, such as rice and cotton. However, a more fundamental and straightforward reason for expanded irrigated acres is more consistent yields under irrigation relative to non-irrigation.

Figure 2 presents detrended soybean yields for Arkansas non-irrigated soybeans versus irrigated soybeans from 1979–2018. Yields have been detrended to remove the influence of technological advancement over time.

Greater yields

Yields were 12.6 bushels per acre greater on average under irrigation compared to non-irrigation. Also, variation around the irrigated soybean mean, which represents yield variation due to weather, is considerably narrower relative to variation around the non-irrigated soybean mean. Thus irrigation makes soybean yields more stable relative to yields under non-irrigation. 

The phenomenon of expanded irrigated soybean area was not isolated to Arkansas alone. Other locations in the Mid-South also experienced significant irrigated soybean area expansion during the same timeframe.

Changes in both irrigated acres and irrigated soybean acres from Census year 1982 to Census year 2017 are presented for locations in the Mid-South.

All Mid-South locations in Table 1 receive most irrigation water from the Mississippi River Valley alluvial aquifer. Irrigated soybeans account for approximately 69% of increased irrigated area expansion in this region.

Arkansas experienced the largest expansion in soybean area (75% of increased irrigated area) but all locations experienced significant expansion as well.

Preliminary evidence indicates that irrigated soybean acres may be leveling off in many parts of Arkansas, particularly in counties farther removed from the Mississippi River, where groundwater is more limiting. However, expansion in irrigated acres appears to continue in counties bordering the Mississippi River.

A closer evaluation needs to be conducted to verify these preliminary findings.

Source: Southern Ag Today

About the Author(s)

Brad Watkins

Professor, University of Arkansas System Division of Agriculture

Dr. Watkins is a native of Northwest Arkansas and grew up on a small hillside cattle farm in the Ozark Mountains. He received his B.S. degree in Agricultural Business (1988) and his M.S. degree in Agricultural Economics (1990) at the University of Arkansas. In 1994, he received his Ph. D. degree in Agricultural Economics at Oklahoma State University. He then took a postdoctoral economist position in the USDA Agricultural Research Service (ARS) at Beltsville, Maryland and was employed with the ARS until 1999. While in the ARS, Dr. Watkins conducted economic research in the areas of sustainable agriculture, precision farming, and technology adoption. From 2000 through 2001, Dr. Watkins lived in San Antonio, Texas and was employed as an industry analyst with the firm Frost & Sullivan, where he conducted market research and wrote syndicated reports about the U.S. food industry and other various markets.

Dr. Watkins has been a member of the Department of Agricultural Economics and Agribusiness at the University of Arkansas since 2002. He is stationed at the University of Arkansas System Division of Agriculture, Rice Research and Extension Center in Stuttgart, Arkansas. He has a 75 percent research appointment and a 25 percent Extension appointment. The primary focus of his research program is identification of production systems and management practices leading to reduction in production inputs and greater profitability in rice production. His Extension program is devoted to dissemination of economic information related to alternative cropping systems, management practices, and/or technologies that promote the long-term economic and environmental sustainability of rice production in Arkansas. He also works on other economic problems important to Arkansas, such as economic evaluation of alternative government programs in Arkansas row crops, quantification of economic losses to Arkansas agriculture resulting from extreme weather events, and economic analysis of cattle and stocker grazing systems. A strong component of his program is interaction with scientists from other disciplines.

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