LHAP 302B-61-40681 (FA25) - Landscape Irrigation/Course/Water Requirements/Water Storage Capacities in Soil Lecture.pptx
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At field capacity all the small pores are filled with water.
It is extremely important that you become familiar with identifying textural classes to perform water storage capacities in field situations.
Important;
One liter of water spread evenly over a waterproof surface 1 m2 will give a depth of 1 mm.
Calculating Water Storage Capacities of Soils
Calculating Water Storage Capacities of Soils
Important;
One liter of water spread evenly over a waterproof surface 1 m2 will give a depth of 1 mm.
1 Liter of Water
1 mm H2O
1 m2
Table 1.0. Water Storage Capacities of Soils
Textural Class
Total Storage Capacity
Macropore
Space (%)
Plant Available Moisture
(%)
(mm H20/cm soil)
(%)
(mm H20/cm soil)
Coarse Sand
24.4
2.44
17.7
6.7
0.67
Coarse Sandy Loam
24.5
2.45
15.8
8.7
0.87
Sand
32.3
3.22
29.0
13.3
1.32
Loamy Sand
37
3.70
26.9
10.1
1.01
Loamy Fine Sand
32.6
3.26
27.2
5.4
0.54
Sandy Loam
30.9
3.09
18.6
12.3
1.23
Fine Sandy Loam
36.6
3.66
23.5
13.1
1.31
Very Fine Sandy Loam
32.7
3.27
21.0
11.7
1.17
Loam
30.0
3.00
14.4
15.6
1.56
Silty Loam
31.3
3.12
11.4
19.9
1.99
Sandy Clay Loam
25.3
2.53
13.4
11.9
1.19
Clay Loam
25.7
2.57
13.0
12.7
1.27
Silty Clay Loam
23.3
2.33
8.4
14.9
1.49
Sandy Clay
19.4
1.94
11.6
7.8
0.78
Silty Clay
21.4
2.14
9.1
12.3
1.23
Clay
18.8
1.87
7.3
11.5
1.15
Sample Calculation;
A 1250 m2 nursery has a topsoil layer of loam with a depth of
24.5 cm. How much available water will be held in this soil at field capacity?
Perform the following steps to solve the problem;
Step #1; Identify the depth of soil and textural class.
Step #2; Locate the appropriate soil texture in Table 1.0 and identify the available water held at field capacity for that textural class.
Step #3; AW = Soil Depth x Coefficient from Table #1
Calculating Water Storage Capacities of Soils
Calculating Water Storage Capacities of Soils
Sample Calculation;
A 1250 m2 nursery has a topsoil layer of loam with a depth of
24.56 cm. How much available water will be held in this soil at field capacity?
Answer;
AW = depth of soil x coef. (from Table 1.0) Table 1.0 Loam - 1.56 mm H2O / cm of soil depth = 24.56 24.56 cm soil x 1.56 mm H2O
AW = 38.22 mm H2O
Calculating Water Storage Capacities of Soils
Note:
Soil depth always has to be in cm before plugging it into the equation.
Calculating Water Storage Capacities of Soils
Sample Calculation;
A field production facility that is 650 m2 has a Silty loam root zone that is 7.5 inches in depth. How much available water will be held in this soil at field capacity?
Calculating Water Storage Capacities of Soils
Sample Calculation;
A field production facility that is 650 m2 has a Silty loam root zone that is
7.5 inches in depth. How much available water will be held in this soil at field capacity?
Answer;
Convert Inches of soil to cm of soil.by;
7.5 inches of soil x 2.54 cm = 19.05 cm of soil AW = depth of soil x coef. (from Table 1.0) Table 1.0 Silty Loam - 1.99 mm H2O / cm of soil AW = 19.05 cm of soil x 1.99 mm H2O
AW = 37.91 mm H2O
Calculating Water Storage Capacities of Soils
Sample Calculation;
How many liters of water will you have to apply to bring the following landscape from PWP to field capacity?
A field production facility landscape that is 650 m2 and has a Silty loam root zone that is 7.5 inches in depth.
Calculating Water Storage Capacities of Soils
Sample Calculation;
How many liters of water will you have to apply to bring the following landscape from PWP to field capacity? A field production facility landscape that is 650 m2 and has a Silty loam root zone that is 7.5 inches in depth.
Answer;
Convert Inches of soil to cm of soil.by;
7.5 inches of soil x 2.54 cm = 19.05 cm of soil AW = depth of soil x coef. (from Table 1.0) Table 1.0 Silty Loam - 1.99 mm H2O / cm of soil AW = 19.05 cm of soil x 1.99 mm H2O
AW = 37.91 mm H2O
Calculating Water Storage Capacities of Soils
Sample Calculation;
How many liters of water will you have to apply to bring the following landscape from PWP to field capacity. A residential landscape that is 650 m2 and has a
Silty loam root zone that is 7.5 inches in depth.
Answer Continued;
1 litre of H2O spread over 1 m2 is 1 mm deep Therefore;
37.91 mm deep of H2O over 1 m2 = 37.91 L H2O
37.91 L H2O / m2 x 650 m2 of soil = 24641.5 liters of H2O
