Irrigation heart of dairy water-use efficiency

The ability to irrigate is a key factor in dairy feasibility, according to a Texas AgriLife Extension Service specialist.

Speaking during Southwest Dairy Days held recently on the Spandet Dairy north of Hart, Nich Kenny, AgriLife Extension irrigation specialist in Amarillo, said the irrigation system and the water it brings to the region's cropping systems are what allow feasibility, especially on the magnitude of what dairy and feedlot operations require.

The featured dairy included a center pivot sprinkler system with multiple wells attached, which Kenny said is typical of irrigation in the region.

"This is how we pump most of the water in the West Texas area, especially in the High Plains, through internal combustion engines with a 90-degree gearhead, or electrical motors, and a pump that goes down into the Ogallala Aquifer and extracts that water out to deliver it to the crops," Kenny said.

He said a dairy-specific irrigation system has two real needs.

The first is to provide crops as feedstock for the dairy. Crops involved in a dairy forage system include different types of sorghums, from grain to forage sorghums; corns, from grain corn to forage or green-chop silage corn; and wheat, triticale and, in some cases, alfalfa.

"In some other dairy sectors, alfalfa would be a more predominant crop where more water is available," Kenny said.

"But here where we are pumping out of the Ogallala Aquifer, water is a limited resource and we try to use crops that are going to get us more forage for less water applied," he said. "So a lot of the alfalfa that comes into these dairies is sourced from outside of this area or even outside of the state."

Kenny said the crop-water demands vary for all those crops. They range anywhere from 24 inches of water per season up to nearly 40 inches of water per season.

"In this area we get about 18 inches of rainfall, and we can accumulate that in the soil in the offseason or during the season," he said.

The difference between what is received in rainfall and the crop requirement is generally made up with irrigation. "For example, the wheat crops are going to have an irrigation requirement of 10-acre inches across the entire crop to get a suitable crop that can be taken to harvest," he said.

"The corn will go up to 24 inches and the alfalfa, near 30 inches of irrigation in this area. The sorghum falls between the corn and the wheat, somewhere between 16 and 18 inches to get a fully matured crop to harvest."

The other equally important use of the irrigation system is for responsible disposal of runoff water.

"Dairies use a lot of water in the process of producing that milk," he said. "They use water for wash; they use water for other processes and therefore have a lot of runoff water that has to be disposed of responsibly.

"This is one of the ways they dispose of it properly, by going back through the irrigation system and applying it across the field," Kenny said.

He said that produces some great benefits in that it allows the nutrients of runoff water or effluent water to be used on the crop and it disposes of it responsibly. But it also creates some challenges too.

"With any effluent, especially dairy or livestock effluent, you have a lot of solids in that water that have to be dealt with," he said.

While the water undergoes a tertiary treatment to separate the solids and liquids, it still has some particles that end up in the sprinkler, Kenny said.

"If you walk down the sprinkler and see the water coming out, it would have a little tint to it, either brown from the wash water or even a little bit of a green tint symbolizing the manure that's in that water," he said.

One problem that creates is plugging, Kenny said. The irrigation system is pressurized with small orifices to control water flow, and with those small orifices comes the potential to plug up emitters.

"So there are some challenges with getting rid of the effluent responsibly, but in most cases this is allowing the dairies to deal with their waste problems -- using an irrigation system," he said.

"One of the advantages for the pivot system is you don't really have to create a whole lot of pressure to operate the irrigation system once you get the water up to the ground," he said.

Kenny said most pumps in the West Texas area are driven by natural gas engines or electric engines. Some use diesel engines, but most of the time the natural gas engines and the electric motors provide the most economical method for crop irrigation.

The energy consumed in lifting and pressurizing water in this area is the only real cost to that water, he said, because this is a right-to-capture groundwater state.

"If you can lift the water from the aquifer to the surface, you own that water," Kenny said.

While that has created political pressure in terms of dealing with the declining water situation, Kenny said it is also "one of the reasons you see this dairy using water in multiple points, for drinkers and wash and then finally land-applied, to get back into the system of responsible use of that water."

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