Soils 456 Notes Chapter 5

1. Spacing

Triangular and Square

S= spacing between sprinklers

L= spacing between rows of sprinklers mounted on the lateral lines

For triangular spacing sprinklers are spaced equal distances from each other and L= S* 0.866

Values of Ks for different spacing. 

s< ks* Dt   where Dt is diameter of through


The boundary of a lawn is 110 ft.  Maximum spacing is 30 ft. based on wind speed and Dt. 

                                                                                    Spacing 110/ 4=27.5 ft. 



2. Precipitation rate

P=q/Ar  P= 96.3 q/A 

Where P= in/hr
            q= gal/min
            A= ft^2

Example 5.2 in book. 

3. Application Uniformity

Christiansen's Coefficient of Uniformity

CU = 100 (1-D/M)

D = (1/n) Xi-M

M = (1/n) Xi

Where: CU = Christiansen's Coefficient of Uniformity (%)

D = Average Absolute Deviation From the Mean

M = Mean Application

Xi = Individual Application Amounts

n = Number of Individual Application Amounts

Statistical Uniformity= Standard deviation/ mean *100

Value should be higher than 80% and 90% is better.

4. The total water applied to the field must satisfy the water needs of the crop in all or part of the field and must satisfy the leaching requirement. The definition of irrigation application efficiency is the Et / Water Applied  and can be calculated for one irrigation or the season. See Dr. Lamm paper for a complete discussion