Loamy soil is a mixture between sand, silt, and clay. It is rich in organic matter, and the properties of sand and clay combined allow it to hold air and water well.

Soil horizons labeled with brief descriptions:

The correct response is soil fertility. The amount of nutrients in the soil is a measurement of soil fertility. Soils with high nutrient content (especially with respect to nitrogen, phosphorous, and potassium) are considered fertile soils. Soils with low nutrient content are considered infertile soils. Soil porosity refers to the amount of air space between soil particles. Soil infiltration refers to its infiltration (absorption of water) capacity. Soil compressibility, as the name suggests, is the ability for a soil to be compressed. Soil strength involves the capacity of a soil to withstand sheer stress forces, which is influenced by many parameters including those mentioned above.

There is a sizable bank of nitrogen in the atmosphere that can be fixed by certain bacteria (and plants that harbor this bacteria in their roots), while phosphorus originates largely from bedrock and is released into the soil in limited quantities. Nitrogen can be fixed from a collective atmosphere that is three-quarters nitrogen, while phosphorus is more region-specific and can be harder to replace than nitrogen once it's depleted. Farms located in phosphorus-poor regions often have to rely on mined phosphates.

Phosphorus defficiency is a challenge to resolve because phosphorus stores are almost exclusively in bedrock and sediment, and there is only as much as the bedrock weathers over time. Manure is very rich in phosphorus, and since plants do not fix phosphorus directly into the soil, applying manure and then covering with mulch is the best option.

Sheet erosion occurs when either wind or widespread shallow water with a slow current degrades the soil in thin layers. A flooded and uneven field that is mostly bare soil will likely experience sheet erosion because the erosion is shallow and uniform. 

The correct response is waterlogging. In waterlogging, water covers plant roots and soils with water - preventing soils from absorbing oxygen from the air. If the water covers the soil surface for too long, plants begin to die because their roots can't absorb oxygen and/or carbon dioxide from the atmosphere in order to undergo respiration. Salinization involves the increase in salt content of soil. Sheet erosion is the process by which thin layers of soil are moved due to the force of rain drops and overland flow. Gully erosion involves the formation of gullies (small valleys) due to intensive erosion by water. Rill erosion involves water creating rills, small channels through which water flows.

The correct response is intensification. The term intensification refers to farmers working the fields more heavily and intensely. All the other responses are techniques used by farmers to conserve soil. 

A stable population is described as one in which birth rate equals to death rate, and the number of children is about equal to the number of reproducing adults.

By definition a population is all persons, plants, or animals inhabiting a specified area. A community is the interacting populations within an ecosystem. A gene pool is the total of all alleles of all genes in a population. The definition of an inhabitant is a person or animal that lives in or occupies a place. An organism is any living thing, plant, or animal.