* not completed

. Which of the following statements regarding physical properties of soils is/are true? (Please select all that apply)

The bulk density of the soil can be calculated knowing the density of soil particles and the percentage of water in the soil correct incorrect

Soil permeability is affected by both the soil texture and its structure correct incorrect

Sandy soils tend to be nutrient-poor correct incorrect

A typical soil bulk density is in the range of 1.2 to 1.5 g mL^-1 correct incorrect

Structure of a soil is readily determined by a laboratory chemical analysis correct incorrect

* not completed

. The cations of 1.00 g of soil are extracted with 50 mL of an appropriate solution.  Concentrations (μg mL^-1) found were:  Ca²⁺  17.1, Mg²⁺ 5.5, K⁺ 3.3, H₃O⁺ 3.4. What is the cation exchange capacity (in cmol (+) kg^-1 soil)?

51.9 correct incorrect

7.8 correct incorrect

29.3 correct incorrect

4.6 correct incorrect

9.3 correct incorrect

* not completed

. Which of the following ways is/are able to neutralize acidity of soils? (Please select all that apply)

Through anion exchange reactions involving the clay minerals correct incorrect

Through reactions with aluminum hydrous oxides in the soil correct incorrect

Through reaction with hydroxide ion in the soil pore water correct incorrect

Through carbonate minerals in the soil correct incorrect

Through microbial respiration correct incorrect

* not completed

. In what way(s) can leaching of nitrogen compounds from soil be reduced? (Please select all that apply)

Through ensuring continuous crop cover correct incorrect

Through making it insoluble by the addition of limestone correct incorrect

Through retention of ammonium by additions of organic matter with high CEC correct incorrect

By precision nutrient additions correct incorrect

Through seasonally clearing dead/decaying organic matter by burning it in the field correct incorrect

* not completed

. Which of the following statements about soil physical properties is/are true?  (Please select all that apply)

Clay soils generally have a greater bulk density than sandy soils correct incorrect

Both texture and structure play a role in determining permeability of a soil correct incorrect

Low oxygen in soil water is often characteristic of soils with low permeability correct incorrect

For mineral soils particle density is greater than bulk density correct incorrect

Hardpans are observed at a depth of about 15 cm because this is the depth to which water percolates after a typical moderate rainfall correct incorrect

* not completed

. Which of the following statements about soil chemical properties is/are true? (Please select all that apply)

Partially decomposed organic matter contributes to good structural features of a soil correct incorrect

The C/O ratio in HM of terrestrial origin is typically different from that of aquatic origin correct incorrect

Elements incorporated within the mineral lattice are readily solubilized by rainfall of pH 5.7 correct incorrect

Temperate agricultural soils usually have a smaller organic matter content than tropical ones correct incorrect

Weathering affects the chemical nature of the mineral components of soil correct incorrect

* not completed

. Which of the following statements about soil properties is/are true? (Please select all that apply)

The two most important contributions to cation exchange capacity of a soil are from organic matter and clay minerals correct incorrect

Hydrous oxides of iron and aluminum are variable charge components of some soils correct incorrect

Phosphate retained by variable charged soils adds to the soil's cation exchange capacity correct incorrect

The most important metal cation on exchange sites of agricultural soils is usually sodium (Na⁺) correct incorrect

Base saturation is a measure of the amount of hydroxyl ion held on the exchange sites correct incorrect

* not completed

. Which of the following reactions involving soil nitrogen generate acidity? (Please select all that apply)

Denitrification of nitrate correct incorrect

Ammonification involving organic matter correct incorrect

Uptake of nitrate correct incorrect

Nitrification of ammonium correct incorrect

Ion exchange of ammonium from the soil solution with calcium on a clay mineral correct incorrect

* not completed

. Which of the following are processes associated with the soils indicated? (Please select all that apply)

The C horizon of most soils is relatively unaltered by chemical and biological processes above correct incorrect

An Ap surface horizon is a layer affected by ploughing correct incorrect

Vertisols are characterized by having a large content of 2:1 and other similar clay minerals correct incorrect

Alfisols have a large content of iron and aluminium hydrous oxides in the surface layer correct incorrect

The upper horizon of the mineral soil of a Spodosol becomes depleted in iron and aluminium correct incorrect

* not completed

. Acidity in soils can be neutralized by which of the following processes: (Please select all that apply)

Uptake of nitrate on plant roots correct incorrect

Dissolution of iron and aluminium hydrous oxides correct incorrect

The reduction of sulfate and reaction with iron hydrous oxide to form minerals like pyrite correct incorrect

Ion exchange causing uptake of hydronium ions on clay mineral exchange sites correct incorrect

The oxidation of ammonium ion that has been added as fertilizer correct incorrect