Blog #2 (Practice for Soil and Agriculture Exam)

Scenario: You will be going to the garden this week to add compost to the soil. In late November, that soil will be bursting with crops ready for harvest. Imagine taking a cubic foot section of the soil and plants on the surface and inspecting from the visible down to the atomic level.
-What organisms would you find and what would they be doing?
-How would they be interacting with one another?
-What do you think the mineral context of the soil would look like?
-What would the benefits be of such soil composition?
-What are its limitations?

Some organisms you would find in the soil would be soil microbes, earthworms, vertebrates and invertebrates and many more that are too small too see. These microscopic organisms include bacteria, fungi, protozoa, and nematodes, which there are a couple of thousand in good soil. The common denominator of all soil is that every organism needs energy to survive and therefore each of these organisms found in soil would most likely be looking for ways to get energy. For most of these organisms, except a few bacteria, their way of getting the energy they need to sustain life is by eating something containing carbon. Carbon may come from waste products produced by other organisms, organic material supplied by plants, or the bodies of other organisms so there might be some organisms eating one another in order to get carbon. The most important thing of all soil life is obtaining carbon to fuel metabolism. It is an eat-and-be-eaten world in and on soil. 

If you were looking at a cubic foot of soil you would most likely be able to notice the rhizosphere, which is the area of interaction between the surface of a plant root and the area surrounding it. The rhizosphere is filled by bacteria and other microorganisms as well as soil debri. It contains a constantly changing mix of soil organisms, including bacteria, fungi, nematodes, protozoa, and even larger organisms. All this life competes for the exudates , a substance that oozes out from plant pores, in the rhizosphere, or its water or mineral content. The rhizosphere is the site of root-nutrient absorption. Bigger microbes, like nematodes and protozoa, eat the bacteria and fungi, which are at the bottom of the soil food web, and anything they don't need is excreted as waste, which plant roots are able to absorb as nutrients. Soil bacteria and fungi are like small bags of fertilizer as they retain in their bodies nitrogen and other nutrients they gain from root exudates and other organic matter. The mineral content in this soil would be composed of clay, silt, and sand, which should all be balanced so that there is not too much of one or the other because then that would affect the plant roots. For example, if the soil had way too much sand then the water would just go through and the roots wouldn't have enough time to get water and if the soil had way too much clay then no water would get through at all. Soil with good structure tends to encourage water to penetrate deeply rather than run off so it greatly decreases erosion. Soil life provides the nutrients needed for plant life, and plants initiate and fuel the cycle by producing exudates.