Page 104 - Calculating Agriculture Cover 20191124 STUDENT - A

9-16 Land, Soils and Fertilizers CH 9]

Evaluating soil types using the Textural Triangle. A simple method of calculating these
percents is to take a soil sample, put it in a glass jar, add water and shake vigorously. The soil
particles will separate and resettle in the jar based on the particle weight, the heaviest first to the
lightest. This can be measured and a relative percentage of each to the whole can be established to
identify the soil type. Where the percentage lines intersect will identify the soil type.

Example 1: A soil sample is found to consist of 30% sand, 35% silt and 35% clay.
Using the Textural Triangle, identify the soil type. Refer to Figure 9.13.
Water
Solution: Locate on the side of Figure 9.13 30% of Sand and mark a straight line.
Organic Matter Locate on the side of figure 9.13 Silt 35% and draw a straight line. Locate
Clay 35% on the Clay side of the Figure 9.13 and draw a straight line. Where
these three lines converge will be in the soil type: Clay Loam
Silt
Example 2: A soil sample is found to consist of 40% sand, 40% silt and 20% clay.
Using the Textural Triangle, identify the soil type.
Sand
Solution: Locate on the corresponding sand, silt and clay the percentages indicate in
this problem, 40%, 40% and 20%. Draw straight lines and where they
Soil Sample separates in Water
intersect will identify a soil type: Loam

Table 9.1. Various soil textures weights and water content.

Water Content
At Field Wilting
Capacity Point Area of Soil
Lbs./Acre In. in In. in Particles in
Kind of Plow Layer Plow Plow One Acre
Soil (7 in.) % Layer % Layer Plow Layer

Sand 2,625,000 8 0.70 4 0.34 500 acres
Sandy loam 2,415,000 16 1.50 10 0.80 5,000 acres
Silt loam 2,100,000 30 2.24 15 1.00 50,000 acres
Clay 2,100,000 45 3.60 25 2.20 25,000 acres
Peat 525,000 180 3.60 100 2.10 —

Using the data in Table 9.1 Solve the following problems.

Example 1: Erosion of 5 inches of Sandy loam from an acre of soil removes how many pounds
when the plow layer is 7 inches?

Solution: Given: Sandy Loam weighs 2,415,000 lbs/ac in the 7 inches of the plow layer

Solve for only 5 inches.
5 Sa L#
—— = —————
7 2,415,000 #

2,415,000 # 5 Sa L# 2,415,000 #
———— x —— = ————— x —————
1 7 2,415,000 # 1

2,415,000 # 5 Sa L# 2,415,000 #
———— x —— = ——— x —————
1 7 1 2,415,000 #

2,415,000 # 5 Sa L# 1
———— x —— = ——— x ——
1 7 1 1

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