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Mid-South soybeans: When is it profitable to irrigate?

Over 2.5 million acres of soybeans are irrigated in the Mid-South. The economic impact from irrigating soybeans is significant because yields resulting from proper irrigation generally are more than 20 bushels per acre greater than yields from nonirrigated acres.

Irrigation, like any input, must be profitable to justify its cost.

Information in the accompanying table provides estimated breakeven yields (excluding land, management, and overhead costs) when using surface irrigation with rollout vinyl pipe.

Estimated costs and returns were calculated by the Mississippi State Budget Generator using 2005 input prices, a diesel price of $2.23 per gallon, and projected yields of 62, 50, and 45 bushels per acre from irrigated April, May, and June plantings, respectively.

Major inputs/operations used to generate costs are as follows.

  1. All plantings use glyphosate-resistant varieties seeded into a stale seedbed in 20-inch-wide rows.

  2. All plantings receive a foliar fungicide at R3 to R5.

  3. All plantings are treated for stink bugs, and the June planting receives an insecticide treatment for worms.

  4. The April planting receives 7.5 inches per acre of irrigation water, whereas the May and June plantings receive 11 inches per acre.

The breakeven yield for April plantings with a projected yield of 62 bushels per acre ranges from 17.1 bushels per acre at a $5 per bushel price to 24.6 bushels per acre at a $6 per bushel price.

For May plantings, the projected yield of 50 bushels per acre is 4.2 to 11.8 bushels per acre greater than breakeven yields when price ranges from $5 to $6 per bushel.

For June plantings, the projected yield of 45 bushels per acre is estimated to be profitable at a price above $5.07 per bushel. Even at $6 per bushel, irrigated yields from June plantings are estimated to be only 7 bushels per acre above the breakeven yield.

Land costs, of course, must be considered in profit calculations. Estimated land cost is at least $80 per acre for irrigated soybean land.

Using $80 per acre for land cost, irrigated April plantings that yield 62 bushels per acre will be profitable at $4.92 per bushel or above. Irrigated May plantings that yield 50 bushels per acre will be profitable at $6.18 per bushel or above, and breakeven yield at $5.50 per bushel will be 56.2 bushels per acre. June plantings that are irrigated and yield 45 bushels per acre must receive $6.84 per bushel to be profitable, and breakeven yield will be 56 bushels per acre at $5.50 per bushel.

As these figures indicate, properly managed irrigation will not guarantee profit from a soybean enterprise when prices are in the range of $5 to $6 per bushel, yields are below 50 bushels per acre, and land cost is $80 per acre or above.

Profits will accrue from high yields achieved with early planting, starting irrigation on time, irrigating by schedule to prevent drought stress during reproductive development, and continuing irrigation until seed are fully developed.

Larry G. Heatherly is a retired USDA-ARS research agronomist and current crop consultant. e-mail

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