Exam: Section 8 - Assessing field problems and solutions

1. Describe the soil characteristics of a saline soil that can be seen in the field.

Answer:

White crusts on soil surface.
Plants stunted, appearing to be drought stressed even though soil is moist.
Uneven plant height and soil moisture in the field.

2. Define: (1) EC, (2) amendment, and (3) leaching.

Answer: See Glossary

3. Results of a soil sample analysis come back with an ECe of 2.2 and an ESP of 8. (1) How would this soil be classified? (2) What problems would a farmer expect to encounter when irrigating this soil?

Answers:

(1) Saline-sodic
(2) Drainage and infiltration problems; runoff with heavy irrigations; uneven crops; problems with salt-sensitive crops

4. Using Table 7.2 on crop salt tolerance levels, what yields would you expect for beans? for barley? for carrots?

Answer:

Beans - About 75% of normal harvest
Barley - Normal harvest
Carrots - 75% of normal harvest/d

5. How would you identify a waterlogged soil in the field?

Answer:

Gray soils with black or red mottles
Water-saturated soil, standing water in holes 30- 80 cm deep

6. Draw bed shapes and plant locations that would control salinity problems with furrow irrigation.

Answer:

If a farmer wanted to apply 1 ton/ha of pure gypsum to reclaim soils with sodium problems, and only lime sulfur was available, how much lime sulfur would he or she have to apply? How much sulfur would he or she apply in the process?

Answer: Given:

Equivalent

1 Ton of Pure Gypsum
1 Ton of Sulfur

Lime Sulfur 0.78 4.17

a. 78% x 1 ton gypsum = 1 ton lime sulfur
1 ton gypsum = 1.28 tons lime sulfur

b. Applying 1.28 tons lime sulfur x 4.17 = 5.35 tons sulfur