NEWARK, Del. - “The next time your irrigation system is operating, climb into a rain suit and take a look at what the water’s doing, once it hits the ground,” advises University of Delaware extension agricultural engineer Tom Williams. “It’s the only way to tell whether you’re irrigating properly.” the speed with which an irrigation system applies water to the soil is the application rate in inches per hour. This must be balanced with the soil’s infiltration or intake rate (its ability to absorb water). When the application rate exceeds the intake rate, runoff occurs unless the field is perfectly level. Runoff causes uneven water distribution as well as erosion, Williams says. With runoff, fer tilizers and chemicals applied through the irrigation system aren’t uniformly distributed. And erosion moves topsoil-along with nutrients-to other parts of the field, or off of it entirely, thus reducing potential yield. “Center pivots can have the highest application rates of any of the mechanically moved irrigation systems,” the engineer says. “The longer the lateral pipeline and the higher the crop’s water requirement, the higher the ap plication rate required. This rate also varies along the lateral, with rates increasing from the pivot to the end gun. On a 1,320 foot system, the last 177 feet have to cover the same area as the first 660. This means the water has to be applied faster at the end of a pivot system than at the beginning.” On all irrigation systems, the application rate depends on the BARN SPRAY** & I BRUSH PAINTING | Try our new concept in I Penetration & Adhesion z Being Self Employed Enables Me To Take The Time * To Properly Apply My Barn Paint & Sealer At Prices i Below Suggested Retail Cost. Average Barn Costs I $750. The Farmers in Lane. Co. Are Lucky Because ; Of The Amount Of Competition In Barn Painting. | Call Us For Free Estimates | PHARES S. HURST I ) RDI - Box 503 Z Narvon, PA 17555 I BRUNING PAINT 215-445-6186 BEAT THE HEAT With Drip-Cool or Spray-Cool Systems • DRIPPERS For Farrowing & Gestation Stalls • MISTERS For Finishing & Gestation Pens • SPRINKLERS Saving One Pig Or Sow Pays For The System! n & U-? , mL , c=zlr_ S~ Y DRIPPER SPRINKLER Balance Water Application/Intake Rates When Irrigating sprinkler or spray package. Once the nozzles are selected, the peak application rate is fixed. The only way to change it is to change the nozzles. Changing the travel speed of the system only changes the total amount of water applied, not the application rate, Williams says. “The further a sprinkler throws water, the lower the application rate on center pivot and linear move systems,” he adds. “It takes a lot of pressure and pumping energy to get those large wetted diameters. Most farmers have opted for low-pressure systems to reduce pumping costs, and ap plication' rates have increased accordingly.” For instance, a high pressure center pivot system might have a peak application rate of 0.7 inches per hour, whereas the same system with a low-pressure 180 degree nozzle package could have a peak rate of 8 inches per hour-more than 11 times higher. “Obviously, there’s a tradeoff between reduced pressure and potential runoff,” the engineer says. “Dr. Robert D. vonßemuth at the University of Tennessee has studied this problem. He’s con cluded that it’s probably cheaper to use a low-pressure system and increase pumping time to offset the resulting runoff. In his study, low-pressure spray booms on the center pivots had the least pum ping costs of the systems he compared, because they had the least runoff of the low-pressure systems. However, vonßernuth did not compare cost differences between systems.” Droplet size also affects soil intake rates. Large droplets striking bare soil expend a lot of All Solid State Controls MISTER energy on impact, dislodging soil particles and causing surface sealing and compaction, which in turn reduce infiltration. The larger the droplets and the heavier the soil, the worse the problem. High pressure and small nozzles give smaller droplets and higher intake rates. That’s why it’s important to use high pressures on big gun sprinklers to get the proper stream breakup, William says. Many factors determine soil intake rates, and this makes it hard to establish general guidelines for matching ap plication and intake rates. Soil texture is the biggest factor in fluencing intake, he says. Coarse textured sandy soils will absorb water much faster than fine textured silty soils. The higher the sand content, the higher the intake rate; the higher the silt content, the lower the rate. For instance, a sandy soil may take in 2 inches or more of water per hour, compared to only Vi inch or less, on a silt loam. Intake rate also depends on the initial moisture content of the soil. A dry soil will absorb water very rapidly at first, and then level off to a lower rate as it becomes wetter. This means potential runoff can be reduced by applying less water more often. For the same reason, Williams says to apply as little water as possible when chemigating. Other factors which affect water intake rate are soil structure, aggregate stability, organic matter content, the tillage method used and soil cover. In turn, all of these are influenced by soil and crop management practices. A covered soil (that is, a well mulched soil) can have twice the intake rate of bare soil. “The only way you can know whether your irrigation system is applying water as effectively as possible is to observe it m operation,” Williams concludes. Carroll County 4-H and i—mmm.FFA Fair mmmmm Truck and Tractor Pull August 3 f 1986 Time 10:30 A.M. Rain Date - Aug. 10,1986 Place: Westminster Ag Center Westminster, MD Admission $6.00 Senior Citizens $4.00 7-12 Years Old $4.00 6 And Under With Guardian Free / if /> SOLID STATE CONTROLS STARTING AT $199.00 All Necessaiy Fittings In Stock “So climb into that rain suit and go farm. If runoff is a concern, take a look. Note the application keeping the ground covered with rate, surface ponding, soil texture no-tillage under irrigation will and cover when deciding what usually help reduce this problem.” adiu«trr>pntc atp hp