NATIONAL UNIVERSITY OF COLOMBIA

AGRICULTURAL ENGINEERING
Workshop 1
2020

A sample of moist soil has a mass of 1000 g and a volume of 640 cm.3. When drying in a
oven at 105 °C for 24 hours, its dry mass was 800 g. Calculate the bulk density, the volume of soil.
dry, total porosity, if the real density is 2.60 g/cm3.

2. Discuss the concepts of field capacity and permanent wilting point:

a. from a soil physics perspective;

b. from a water risk perspective ('usable moisture');
c. from the perspective of plant water relations.

A soil sample with 40% porosity has a total volume of 120 cm.3and a content of
humidity of 0.3 cm3/cm3If the density of the solid phase is 2.5 g/cm3What is the apparent density?

A wet soil has a moisture content of 0.15 g/g. If 200 g of dry soil is needed to
an experiment How many grams of wet soil are needed?

A natural lump of wet soil has a volume of 150 cm3a wet weight of 240 g and a space
occupied by air of 0.15 cm3/cm3If the particle density is 2.65 g/cm3Calculate:
a. Bulk density based on dry weight.
b. Moisture content based on weight.
d. Total porosity

6. In which of the specified soils will the bulk density be greater, and from an agricultural standpoint,
management or recommendation can be given for each of them.

Soil A B C
% Arena 52 48 32
% Limo 25 25 25
Clay 12 24 38
% M.O 1 3 5

7. There is a soil sample with a wet mass of 6 kilograms, with a moisture content of 16%.
Based on mass. It is requested to find the mass of dry soil and the mass of water.

Data:
Wet mass: 6 kg
16%
Dry soil mass:
Water mass:
8.A soil has a moisture content (θ) of 20% in its first 15 cm of depth;
how muchThe water sheet would need to be infiltrated into the soil to raise the humidity to 32%.

The usable water from a soil (Wcc–W pmp) is 16% (based on mass), when the capacity of
the corresponding field is 0.4. If irrigation is done when the depletion of usable water is
51%, what is the soil moisture when irrigation is done.

10. 68 grams of soil were mixed with 50 grams of an organic material. The initial moisture content of the soil was
10% for the inorganic material and 30% for the organic material (based on mass). What would be the possible moisture content of the mixture?

Soil mass: 68 g
Organic Matter: 50 g
Initial Soil Moisture: 10% = 6.8 g
Humidity of organic matter: 30% = 15 g

11. A moist soil has a water content of 0.15 g/g. If 200 g of dry soil is needed to
an experiment How many grams of moist soil are needed? Result: 230 g of soil
damp.

Water content: 0.15 g/g

Dry Soil: 200g
Wet Soil: ?

12. A soil has a porosity of 0.45 cm3/cm3. If the soil moisture content is 0.20.
g/g and the average particle density is 2.6 g/cm3. Calculate the cm of water in a
depth of 30 cm of soil.

13. A natural clod of moist soil has a volume of 150 cm3, a wet weight of 240 g and a
space occupied by air of 0.15 cm3/cm3. If the particle density is 2.65 g/cm3. Calculate:
Apparent density
Total porosity (%)

14. A sandy-loam soil has a gravimetric moisture content of 15.3% at field capacity and of
6.5% at the wilting point. The bulk density is 1.60 tm/m3Calculate the volume of
water easily available on a surface of one hectare and at a depth of 60 cm.

15. Calculate the net irrigation dose knowing that the gravimetric moisture at field capacity and in
the wilting point is, respectively, 25% and 14%. The bulk density of the soil
the soil moisture is 1.36, the depth of the soil explored by the roots is 0.60 m and the fraction of
the depletion of available water is 0.68.
16. With the data from the previous exercise, calculate the interval between irrigations knowing the needs.
daily net is 5 mm of water height.

A soil sample was taken at a depth of 15 cm that weighed 350 g, then it was dried in a
oven at 105°C for 24 hours and its weight was 280 g. If the apparent density of said soil is
1.3 g/cm3, calculate: a) The volume of water that the soil sample had in the field. b) The
gravitational content of water that the soil sample had in the field. c) The content
volumetric water content that the soil sample had in the field. d) The water height that they have
first 30 cm of depth of that soil.

18. A soil has an apparent density of 1250kg/m3the porosity is 35.10%. What is its
real density? How much will 2 trucks of 13m weigh?3from this soil?

19. Soil samples are contained in cylinders (open at both ends) of 105 cm3.
Taking advantage of a pressure cooker set, the samples are subjected to different stresses and
when equilibrium is established the volumes of water drained from the samples at the different
tensions are presented in the following table:

THS (cm) 100 205 350 460 596 800 1300 1825 3000
V (cm3) 37 35 33.5 33.0 32.5 32 31.5 30.8 29.5

a. Build a moisture retention characteristic curve for that soil assuming a moisture
a saturation of 40% based on volume. Work with pf units to represent the THS.

b. Identify the areas corresponding to gravitational water, usable water, and non-available water.

There are 2 tensiometers with mercury manometers located at different depths in the profile of the
Soil A=30cm, B=60cm. Both tensiometers read 18.8 cm of mercury. What is the potential?
total water in A and B? Where is the water moving? (Assume the ground level as the level of
reference).

21. There is a field with loamy soil, whose infiltration rate is defined by i = 23
t -0.52where i represents the infiltration rate in cm/h and t the opportunity time or time of
water contact with the soil, in min. The crop that will be installed has a root depth
It is 90 cm and needs a water sheet of 7.2 cm to meet its water requirements. Calculate the
infiltration time or water-soil contact time (min)?

22. Calculate the hydraulic conductivity of the soil in m/day and its classification in the following test
field:

Well diameter: 0.10 m

Well depth: 1.80 m
Depth of the water table: 2.62 m
The NF readings with reference to the ground surface were:

t (seg) h (m) t (seg) h (m)

0 0.12 180 0.33
30 0.16 210 0.35
60 0.20 240 0.37
90 0.24 270 0.39
120 0.27 300 0.41
150 0.30 330 0.42