Exam 14: Soil Phosphorus and Potassium

For an unfertilized temperate region forested soil with a large amount of interlayer fixed potassium,but a low amount of readily available potassium,the level of readily available potassium is expected to be higher in early spring than in late fall.

Unlike the use of nitrogen fertilizer on forests,the use of potassium fertilizer can be expected to increase the trees' resistance to diseases and/or pests.

Deep rooted vegetation such as forest trees can increase the available potassium content of surface soil horizons even though no potassium is added to the soil profile.

Loss of P to groundwater is likely to be most significant for which type of soil?

The total phosphorus lost from various watersheds is most closely correlated with _____.

Although only about 2 to 5 percent of the total P in most surface soils is in organic form,this form supplies nearly all the P taken up by plants.

In most soils,mineralization of soil organic matter is an important source of plant available ____.

In various parts of the world,soil phosphorus is associated with which of the following environmental problems?

In a soil with a very low potential buffering capacity,the most efficient approach to using potassium fertilizer would be to apply frequent small doses rather than a single large dose.

In acid soils the principal chemical form of phosphorus available for plant uptake is ____.

Mycorrhizae improve the nutrition of many plants by ______.

The fixation of large amounts of potassium from applied fertilizer would reduce the cation exchange capacity of a soil.

The amount of P lost from agricultural soils by the process(s)of _____ is generally considerably greater than the corresponding losses of potassium.

The amount of K lost in subsurface drainage waters from humid region forested watersheds is generally far greater than the amount of P lost in this manner.

During the last several decades,modern agriculture in the industrialized countries has tended to deplete cropland soils of their supply of available P.

In a soil at pH 5.0,most of the inorganic P is likely to be in the form of _______.

Non-point source losses of which element are considered to be a serious water pollution problem because the resulting high concentration of the element in stream water is toxic to most fish.

For optimum growth of herbaceous plants such as cassava,corn,and lettuce,a concentration of at least 1.0 mg/L P should be dissolved in the soil solution.

Luxury consumption of potassium most often occurs in coniferous forests growing on low potassium soils where the ecosystem can least afford it.