PIVOT PRODUCTS

 

We’d never criticize mother nature, but sometimes “rain-like” irrigation is not the best for soil integrity.

 

 

Soil textures react differently to droplet size and velocity (intensity) and it’s important to understand how a “wet / rest” cycle can be very beneficial to a field. Rotating streams over a wide pattern have proven to be the best possible way to treat most soils.

 

Without sprinkler performance that can apply water at an application rate that more closely matches the infiltration rate of the soil, the efficiency gained with drops and money saved with low pressure, is soon lost to runoff. The rate at which a center pivot applies water increases with the higher flow demands required at the outer portion of a center pivot. By increasing the wetted throw distance of the sprinkler, the rate at which water is applied can be reduced to match the soil’s infiltration rate. Look at a typical infiltration curve below with superimposed application rates for center pivot sprinklers. It is obvious that the Rotator, which provides the widest throw distance on drop tubes, comes the closest to matching infiltration rates of the soil. The best condition for infiltration is to keep the soil surface open and apply water using a wide application width.

 

Understanding
Application Rates

Average application rate (AAR) is the rate of water application over the wetted area. It is an average value assuming uniformity within the wetted area. Pivot average application rates increase with the higher flow demands required at the outer portion of a center pivot. Comparably, in analyzing different sprinkler options, superior throw distance yields lower average application rates.

Instantaneous application rate (IAR) is also an important element of sprinkler performance especially for silt type soils that are prone to compaction. Instantaneous application rate (IAR) is the peak intensity of water application at a point. IAR and droplet kinetic energy are important variables in maintaining good soil intake rate throughout the season. Pivot sprinklers that produce high instantaneous application rates with high velocity, large droplets are detrimental to some soil types causing surface damage by sealing off the soil pore space at the surface. The rate of instantaneous application for a fixed stream type sprinkler can be more than ten times the average if measured at the instant the stream hits the soil. The problem comes when some surface damage occurs, sealing off the soil pore space at the surface. The best condition for infiltration is to keep the soil surface open, and apply water using a wide application width.