Part 3 - Planting The Seeds

In order to look deeper into the requirements necessary for good plant growth, the preferred environmental conditions for the prairie grasses have been outlined in the proceding table. In order to understand these concepts further each column of the table is explained here.

Species Name:

Common names are used for the ease of reference.

Annual Precipitation:

Amount of yearly rain necessary to support a healthy grass community. Rain water replenishes the soil column and facilitates nutrient absorption from the soil into the plant roots.

Soil Texture:

When discussing soil, most concepts are expressed as a measurement within the soil 'column'. A soil column is what you would get if you dug straight down and you can see a vertical cut of the soil. This exposes the different mineral layers and the texture within the soil. Soil texture is a major factor in determining how much water is available for plant growth. Water is held in the spaces between the soil particles called pores. Coarse sandy soils, with little or no clay or silt (Figure 3.2), will hold little to no moisture available for plants, the grains are larger, and so the pore spaces are simply too big to hold water (Figure 3.1). However, this soil texture does have very efficient drainage, which is necessary for some plants. Fine soils have a large portion of clay, with little or no sand or silt (Figure 3.2). These soils have very small and tight pores which hold the water too tightly for plants to access.

Soil Separate	Particle Diameter
Sand (Coarse)	2.0 - 0.05 mm
Silt (Medium)	0.05 mm - 0.002 mm
Clay (Fine)	< 0.002 mm

Preferred Environmental Conditions

Soil Drainage:
Soil drainage is strongly related to soil texture. Fine clay soils have small pores and so water has a hard time flowing through the spaces, and so are poorly drained. Coarse sandy soils have large pores in comparison, the water can flow through quickly, and so they are well drained. Drainage is important to plants so that the water available to the plants does not stagnate, as roots respire, and literally drown if left in water-logged soil. Nutrient availability becomes replenished as the water moves down through the soil column; nutrients dissolve in this water, which then get transported to different depths, different root segments, and/or straight to the water table below.

Water table depths refer not to the depth of the water below the surface, but to the depth that the water table has itself. This is important because of it s relation to the depth of the tap root.

Soil pH:
The pH of a soil is a measure of the concentration of H~ ions in the soil column. It is important to note that the pH scale is a logarithmic scale, and so every single unit change represents a 10 fold change in the H~ concentration. 1± ions play a large role in the availability of nutrients, toxicity, and the activity of soil organisms (Figure 3.3).

Essential Fertility:

This condition relates to the concentration of essential nutrients in the soil, mainly nitrogen, phosphorous, and potassium.

Salt Tolerance:

When the soil containing a relatively large concentration of dissolved sodium is brought into contact with a plant cell, water will pass by osmosis from the cell into the more concentrated sodium solution in the soil. The cell then collapses and the plant dies. Salt concentrations are measured through conductivity testing (the ability of the soil to conduct electricity) and are expressed as millimhos per cm. Conductivity is a good indication of salt concentration because the more dissolved sodium ions that are present in the soil, the easier it is for the soil to conduct electricity.

Flood Tolerance:

Too much water in the soil can wash the top soil out exposing the rhizomes, can quickly leach the nutrients out of the soil, and can submerge the basal growth cells from available oxygen, all causing trauma to the plants. As with drainage, if roots are left in water-logged soil they will not get the gases they need and will suffocate.