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 Caf�, 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