Exam 12: Nutrient Cycles and Soil Fertility

Although slow release fertilizers take longer to have an effect, they are more economical than regular nitrogen fertilizers and so are favored by foresters and farmers.

Assume an A horizon depth of 15 cm. A well drained silt loam soil on an Iowa farm has 3.5% organic matter which is about 5% N. Estimate the kg/ha of nitrogen that this soil horizon will make available for plant use from soil organic matter in one year (without the addition of fertilizer).

Because of _______, soils developed in marine marshes can become extremely acid if drained for agriculture or used as topsoil.

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

Other things being equal, a soil with 30% clay of the ____ type would be expected to have the greatest phosphorus -fixing capacity.

On the average, agricultural soils in the US are currently being depleted of their nitrogen supply.

Nitrification requires the presence of a source of readily available carbon, such as manure.

Nitric acid deposited on forest soils with "acid rain" can increase the leaching of nutrient cations.

The terms "ammonium fixation" and "biological nitrogen fixation" refer to the same soil process.

Nitrogen is a component of which essential plant compounds?

Pesticides and other chemicals added to soils would be more likely to slow down nitrification than mineralization.

A deficiency of N typically ______ the maturity of annual plants.

Plant symptoms such as aborted fruits, dead terminal buds, and misshapen new leaves suggest a deficiency of which micronutrient?

Soluble organic N compounds are taken up by plants and are lost in leaching and runoff waters.

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

Which micronutrient element is found in the greatest quantity in most soils?

Most nitrogen leaching to groundwater is in the form of ammonium.

Ammonia losses from the shallow, algae-filled water of a non-tidal wetland are likely to be much greater at night than during the day.

Ammonium fixation would be expected to be greatest in soils containing a lot of______.

Unlike Rhizobium bacteria, Bradyrhizobium bacteria are effective at fixing N, regardless of the type of plants present.