Also, he says, irrigated yields averaged 42 percent higher than non-irrigated yields.

“I met with an irrigation dealer, and we agreed on three typical scenarios where farmers might want to consider drip irrigation. Then, the dealer calculated how much it would cost to put a pivot in a situation and/or a drip in that situation.”

Example 1, he says, was a 114-acre center pivot, adding 62 acres of subsurface drip irrigation to non-irrigated areas.

“We’re running pipe from the well to those areas. In this case, the drip system is $103,000 for 62 acres, and that’s $1,656 per acre.

“Fixed costs on that system are $132. “Example 2 is a 48-acre field, and we put in a pivot that’ll cover 37 acres, in which case I’d leave 11 acres not irrigated. As an option, I could just forget the pivot and put subsurface drip on the entire 48 acres.

“On this system, the drip on the entire 48 acres would cost me $63,000 with fixed costs of $105 per acre, and the pivot would cost $52,000, but it would cover only 37 acres, leaving 11 acres non-irrigated and fixed costs of $102 per acre.

“For example 3, we have three small fields that are adjacent, and we’re putting subsurface drip on all three for a total of 38 acres. That would cost $56,000 with a total fixed cost of $118 per acre.”

Assumptions for the economic analysis, he explains, include a 450-pound yield difference between irrigated and non-irrigated cotton; no yield differences between center-pivot and subsurface drip; and no differences in fiber quality, although this may change in future research, says Shurley.

Pivot irrigation, he says, is 81 percent as efficient as drip, so a 1-inch requirement in pivot would be .81 inch in subsurface drip.

“In example 1, our net change in income — based on 85-cent cotton — would be about $182 per acre. In example 2, in a 48-acre field, the net change in income from having a pivot on 37 acres to having subsurface drip on all 48 acres was about $65 per acre. In example 3, the net change in income was about $139, and that’s compared to dryland cotton.”

In conclusion, Shurley says subsurface drip irrigation yields can be competitive with center-pivot irrigated yields.

“Secondly, every farm situation is different. If farmers are thinking about putting in a drip system, they need to look at their unique situation and see what the costs will be.

“Thirdly, economies of scale can be achieved, but every situation is different. Management is very important, knowing when to water, how much to water, and when to cut it off.

“Lastly, you have to be committed to GPS/autosteer — you need to know where your tape is and stay off of it. Also, you need a tillage system and row spacing that will work with drip irrigation.”

(For additional information on drip irrigation in the Southeast, see http://southeastfarmpress.com/equipment/alabama-research-looking-subsurface-drip-irrigation and http://southeastfarmpress.com/subsurface-drip-irrigation-new-approach-alabama).

phollis@farmpress.com