Sunday, July 21, 2024
HomeGrazing ManagementWater Makes Grass Grow!

Water Makes Grass Grow!

That is a theme I frequently use in my grazing management presentations around the country. I often say I have learned more about grazing management by working the last dozen years in the extremes of irrigated and desert environments of Idaho than I did in 23 years of the high natural rainfall environment of Missouri.

We had a situation develop this summer on the pivots here at Circle Pi-Patterson that really brought the lesson home. The three pairs of pre- and post-grazing pasture pictures are from the same paddock, just at different distances from the pivot center.

To set the stage. We were having poor water flow on the upper pivot (150 acre) for some unidentified reason. Remember these are gravity flow water pressure, no pumping. Historically the lower pivot (300 acres) has run at about 80 psi & puts out tremendous amount of water. We shut the lower pivot valve to half-open. Water pressure should have been adequate. The output ‘looked’ good.

After a month of hot weather from mid-July to Mid-August, it was time to move the cattle onto the higher side of the lower pivot and I got a shock when we were grazing there. I had missed doing one of my biweekly pasture inventories and hadn’t been out to that part of the pasture for a month.

The pictures and graph tell the rest of the story.

This is between towers 7-8. Grass is green, lush & 18-20 inches tall. Cattle will be here for 24 hours at 75,000 lb stock density.
Jim Gerrish Between Towers 7and8
After grazing we have an acceptable 3-5″ residual.
Jim Gerrish PostGrazingTowers7and8

This is between towers 9-10. Grass is only 6-7″ tall and dried out.

Jim Gerrish Dried Grass Towers 9ans10
Post grazing residual is only about 2-3″. Very little green leaf left at all. This will be slow recovery.
Jim Gerrish Post Graze Towers 9 and 10
Between towers 12-13 (2000 ft from the pivot center, pointed uphill, on thinner soil) the grass is about 6 inches.
Jim Gerrish twoers 13

Post-grazing residual is under 2″ & no green leaf at all. Remember, this is the same paddock with the same herd of cattle for the same length of time. All we are looking at is inadequate water flow as we get farther away from the pivot center.

Jim Gerrish POst Graze Tower 13
Here is the water distribution measured on July 11-12. We put a rain gauge every 50-60 ft moving away from the pivot center. I love grazing my pivots, but worn nozzles & inadequate water flow leave us with horrible distribution pattern. The green line is our target application rate of 3/4″ of water every 3 days. Blue bars are the actual measurement & the red line is the linear regression trendline. The trendline pretty well perfectly predicts the photo series. Adequate water at towers 7-8, then a steady decline out to the end of the pivot.
Jim Gerrish Water Graph
Here is the punchline to the photo set. The graph below shows the water flow measured after we fixed the problem on the upper pivot and turned the water back to full-on for the lower pivot. Same lousy distribution pattern, but adequate water quantity all the way to the outer end.
Jim Gerrish Improved water distribution
Water grows grass.



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Jim Gerrish
Jim Gerrish
Jim Gerrish is the author of "Management-Intensive Grazing: The Grassroots of Grass Farming" and "Kick the Hay Habit: A Practical Guide to Year-around Grazing" and is a popular speaker at conferences around the world. His company, American GrazingLands Services LLC is dedicated to improving the health and sustainable productivity of grazing lands around the world through the use of Management-intensive Grazing practices. They work with small farms, large ranches, government agencies and NGO's to promote economically and environmentally sustainable grazing operations and believe healthy farms and ranches are the basis of healthy communities and healthy consumers. Visit their website to find out more about their consulting services and grazing management tools, including electric fencing, stock water systems, forage seed, and other management tools.


  1. Jim: I assume you have gotten your nozzle package fixed for the proper pressure and flow rate for each pivot. You didn’t mention this. Do you use pressure regulators? If so, closing the valve down may have reduced pressures below the minimum for regulators to even work, and nozzles (even if new) will not work as designed. If you are not using pressure regulators, that is one option you could look into so you don’t have to close the valve down. Glad to provide a little pro bono advice if you are interested.

    You pictures do show an amazing difference in pasture growth.

    Richard Sparks

    • The system had pressure regulators on the drops. Because our water is unfiltered direct from the creek, we get a lot of scouring through the regulators & nozzles. Ir was time they needed to be changed. It is in the budget for next year & will happen in the Spring.

      • OK. Good deal. Check your pressures, even if you put new regulators and nozzles on. You must maintain 5 psi above pressure regulator PSI. I had one this year that was 40 psi at 900 gpm. When the flow decreased to 700 gpm the pressure went below the minimum for regulators. They ceased to work, and pressure dropped clear down to 14 psi.

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