Plants & Human Affairs - Introduction

Plants & Human Affairs (BIOL106) - Stephen G. Saupe, Ph.D.; Biology Department, College of St. Benedict/St. John's University, Collegeville, MN 56321; ssaupe@csbsju.edu; http://www.employees.csbsju.edu/ssaupe

Soil/Growth Medium
(also see Powerpoint in Public Folder)

I. Soil

A. Composition

organics (derived from organisms; partly decayed plant and animal, fecal material, roots)
inorganics (not derived from organisms; minerals; rocks)
living organisms (bacteria, fungi, nematodes, protozoans, worms, mycorrhizae)
gasses (carbon dioxide, oxygen, ethylene)
water

II. Function/Requirements

A. Anchor plant – substrate for root attachment, support (hydroponics – must provide support)

B. Aeration for roots – for cellular respiration in mitochondria, requires oxygen to produce ATP (cell’s energy). Soil – pore space; Hydroponics – bubble or aerate solutions, running;

C. Moisture – function of soil structure and texture

Texture: properties of particles of different size: sand > silt > clay
Structure: soil particles aggregate in clumps or remain individual grains; clumps better cuz allows for greater pore space = more air and water; clumps develop from freeze/thaw cycles or dry/wet cycles or activites of soil organisms

D. Fine-textured soil – lot of clay

avoid destroying structure causes forms large clumps, dry as large hard clods
slow to warm/cool
holds lots of water, minerals
good for main season crops

E. Coarse-textured (sand)

large pores, good aeration
poor water holding capacity
warm quickly, good root and bulb crops

F. Soil and water.
In lab we looked a the following: saturated, field capacity, capillary water, wilting percentage (click here for the growth medium lab)

II. Plant Food

A. Required Nutrients

C H O P K N S Ca Fe Cl Zn Mo B Cu Mn Mg
mnemonic device: C Hopkins Café, Closing mob coming with machine guns

B. CHO – required in large amounts; C taken up through pores in leaf (stoma) as carbon dioxide and used in photosynthesis to make carbohydrates. O - uptake with C in carbon dioxide, also taken up as water via roots; H - primary uptake via roots

C. Macronutrients: N P K Ca Mg S

D. Micronutrients – Fe, Cl, Zn, Mo B Cu, Mn

E. Fertilizers provide the macro & micronutrients, especially macro

F. Labeling - fertilizers labels with percent N, P, & K

G. Forms

liquid –dilute prior
soluble salts – dissolve in water

H. Organic vs. Inorganic fertilizer

organics – contain carbon, from living source (manure, fish emulsion, gelatin)
inorganic – no carbon, from mineral source

I. Slow release – pellet, release nutrient over time

III. Fertilizer Cost Comparisons (not covered, not on exam)
Nitrogen most important element – because it is required in the greatest amount (1-4%) Since it is a major consideration, calculate cost. Click here for details.

IV. Fertilizer Dilution Rate (not covered, not on exam)

growers typically apply 100 – 200 mg N/liter
click here for details on how to calculate the concentration of nitrogen in a fertilizer.

V. pH (not covered, not on exam)

VI. Electrical Conductivity (not covered, not on exam)

monitors soluble salts
EC readings
millimho’s
refers to amount of CA, Mg,, Na, Cl
fertilizers increase
measure of amount of fertilizer and other in root zone
0 – 1.5 mmho/cm acceptable for irrigation water