Soil and soil-water relationships

W. Anderson Murfreesboro Master

Gardener Feb 20, 2009

From UTK Extension PublicationsPlanning the Vegetable Garden SP291-M

Soil Preparation for Vegetable Gardens

SP 291-C

Care of the Vegetable Garden SP 291-D

Organic Vegetable Gardening PB 1391

Definitions

• Natural medium composed of solids, liquids, and gases that occurs on land surfaces

• Supports plant and animal life

• Upper limit, lower limit, plant roots

• Does not cover all the Earth land surface

• It is not tracked in on the house carpet

Soil Components

• General rule, a soil is about one-half solids and one-half pores

• Water and air fills the pore space

• Soil air is lower in O2 and higher in CO2 than surface air– Plant roots– Biological organisms

Soil Components

• Solids– Soil texture, relative proportion sands, silts, clays

sized materials, separates• Sand 2.0 mm to .05 mm• Silts .05 mm to .002 mm• Clays less than .002 mm

– Clay soils, large surface area; small pores– Sandy soils, small surface area, large pores– Clay and Sand differ in ability to provide plants with

water, nutrients, aeration and physical support– Sands are drier, less fertile but better aerated & able

to support plants

Soil Texture

• Twelve textural classes• 3 clay textures, 3 clay loam textures, 3 loam

textures• 0 to 100 % sand, silt and clay by weight• Example: Clays, > 35% clay sized particles• Textural class Possible percentage

– Clay 20% sand, 20% silt, 60% clay– Clay loam 30% sand, 35% silt, 35% clay– Loam 40% sand, 40% silt, 20% clay

Soil Components

• Solids– Aggregate glue sand, silt and clay sized

particles together• Granular – glue organic matter and calcium• Destroy soil aggregates – adding sodium

– Density- mass per volume-pore space– Texture lbs/cu ft % pore space

• Loam 84 49• Clay loam 79 53• Clay 74 56

http://soils.usda.gov/education/resources/k_12/lessons/texture/

Soil Water Classification for Water Management

Think of a soil as a sponge lift the saturated sponge up does water drip.

• Saturation– Gravitational water - drainable

• Field Capacity [FC]– Maximum Plant available water

• Permanent wilting point [WP]– Plant unavailable water

• Air dry– Unavailable water

• Oven dry

Volumetric Soil Water Content Ranges

Textural class Θv @ FC Θv @ WP

Sand .07-.17 .02-.07

Loam .20-.30 .07-.17

Silt loam .22-.36 .09-.21

Clay .32-.40 .20-.24

Available Water = Θv @ FC - Θv @ WP

Θv * inches of soil = inches of water in soil

http://www.mt.nrcs.usda.gov/technical/ecs/agronomy/soilmoisture/clay.html

• Clay, Clay Loam, and Silty Clay Loam Soils

• Appearance of Clay, Clay Loam, and Silty Clay Loam Soils at Various Soil Moisture Conditions

• 75 to 100 percent available 0.6 to 0.0 inches per foot depleted

• Wet, forms a ball, uneven medium to heavy soil/water coating on fingers, ribbons easily between thumb and forefinger.

Irrigation

• Maximize production, vegetable require 1 to 2 ½ inches of water per week

• 1 inch of water over 100 square feet = 8.3 cubic feet or 520 lbs water

• Less water early in growing season• More when plants are larger and setting fruit• Apply water slowly• Don’t do frequent shallow watering. Why?

Shallow root growth you want deep roots

Irrigation (2)

• Irrigate early to reduce incident and spread of disease

• Cultivate prior to overhead irrigation to increase water infiltration

• Trickle irrigation, reduce water use by up to 50 times– Reduces weed growth, weed problems, soil

compaction– Expensive

Irrigation (3)

• Irrigation system– Back flow preventer must be connected to

water source– Screen or disk filter– 10 to 12 psi pressure regulator– Trickle tape– Pressure gauge

Irrigation (4)

• Soaker hose – non engineered– Cheap– Not uniform water distribution

• Trickle system can be purchased at garden centers for $100 to $200

Time Irrigation Properly

• Water late in day – increase diseases

• Trickle, drip, furrow – conserve water, avoid foliage diseases

• Sprinkler irrigation – best done early morning – apply 1 to 1 ½ inches of water – wait several days before repeating

• Less frequent irrigation – less foliage and root diseases

Use Mulches

• Reduce some pest pressures but increase others

• Reduce moisture stress

• Reduce weed pressure

Maintaining or Increasing Soil Organic Matter

• Improves structure

• Holds water

• Increase microbe activity

• Stored and releases nutrients

• Plants and animals (organic matter) decay to more stable organic matter called humus

• Balance between lost and added

Maintaining or Increasing Soil Organic Matter (2)

• Sandy soils – less Soil organic matter

• Clayey soils – more soil organic matter

• More soil mixing – less soil organic matter

• Tennessee – warm moist climate – favors decomposition

Using Crop Residues

• Residue source of organic matter

• Left or composted

• If left – may increase insect, disease and weed problems

• Turning under – breaks down faster – releases some nutrients

• Fewer insect, disease and weed seed survive

Using Lime and Organic Fertilizers

• Increase Soil pH– Ground limestone– How much? Soil test– Calcite, dolomite– Basic slag– Wood ashes – don’t dump in one spot

Adding Nutrients - Manure

• Manure– N, P, K– Poultry manure highest in N, P, and K– Spread on garden before planting

• 250-500 lbs large animal manure per 1000 square feet

• 100 to 200 lbs poultry manure per 1000 square feet

– Irish potato and sweet potato develop scab and canker if manure is used

Adding Nutrients – non-manure

• Fertilizer %N %P2O5 %K2O

• Blood meal 8-15 0-3 ---

• Bone meal 2-4 12-28 ---

• Granite dust --- --- 3.5

• Greensand --- 1-1.5 5-6

• Wood ashes --- 1-2 3-7

• Guano .5-12 4-8 1-3

Questions

• What is soil?

• Why manage water? How can a soils field capacity be used to manage irrigation?

• Why should fertilizer be used? Can fertilizer improve a plants water use efficiency?

Water

• Precious resource

• Lost water means lost dollars

• What is water use efficiency?

• Defined as equal to units of crop production from each available unit of water

• Example: bushels of grain per inch of water

• A long term fertility experiment has been conduct in Illinois. The experiment is called the Morrow Plots. The plots are on the National Historic Registry.

The Morrow Plots to gauge WUE

• Plots received only lime, manure, rock phosphate or bone meal from 1904 to 1955

• 1955 a portion of some plot received lime, and commercial fertilizer annually

• Fertilized continuous corn used precipitation more efficiently

• Better management and improved varieties have also increased crop yield

The Morrow Plots can gauge WUE

• Yields of both fertilized and unfertilized corn are increasing.

from 1955-1984

Fertilized Not Fertilized

130-150 bu/acre 40-50 bu/acre

The Morrow Plots can gauge WUE

• Dry weather and poor fertility can reduce WUE. Proper fertilization that builds high fertility can help the crop overcome drought stress.

from 1955-1984

Fertilized Not Fertilized

3.3 bu/inch of water 1bu/inch if water

Question

• If plants are fed the proper amounts of N, P2O5 & K2O will these plants:– Produce more dry matter/acre: T or F

– Remove more CO2 from atmosphere: T or F

– Will decrease the amount of water percolation through the soil and regolith:T or F

– Will increase the amount of chemicals percolation through the soil and regolith to the ground water:

T or F– Will utilize water less efficiently: T or F

What a soil need to grow: 150 bu/ac of corn

• Ingredient pounds per acre supplied• Water 6 to 8 million 30 to 36 inches of rain• Oxygen 10,200• Carbon 7800 C or carbon in 6 tons of coal• 28,500 CO2• N 310 675 lbs urea• P 52 115 lbs TSP• K 205 340 lbs KCl• Ca 58 150 lbs ground limestone• S 33• Mg 50• Fe 3• Mn .45• B .10• Cu trace• Mo trace

Question

• Cost to remove 28,000 CO2/ac from atmosphere? {basis: cost of Nitrogen}

• 675 lb Urea * 45 lb N/100 lb Urea =304lb N

• 28,000 lb CO2/304 lb N =93 lb CO2/ 1 lb N

• 93 lb CO2 /lb N * lb N/ $ 0.30 =310 lb CO2 / $1.00 of N

• Typical topsoil – approximate composition

• Soil• basis Solids liquids

Gases• % by vol 50 25 25• Inorganic Organic• % by vol 40 10• % by wt 95 5

• INORGANIC Fraction ORGANIC Fraction• (decomposed

things)• Sand Silt Clay Humus•• Primary Secondary Colloids• Minerals Minerals• Quartz layer silicate• Feldspar hydrous oxide• mica

Questions

• What are primary minerals?

• What are secondary minerals?

• Soil - Root System

• Rye plant in 1 cu ft of soil for 4 months

• Length –miles surface area – sq ft

• Roots 385 2550

• Root hairs 6600 4320

Questions

• Soil resources in the USA (TN) do not have enough available nonmetals and metals elements for normal growth and development of plants and animals.– TN land area -1980– Cropland 5.1 million ac– Grassland 5.5 million ac– Woodland 11.7 million ac Now 14 million ac– Urban 1.7 million ac– Other 1 million ac– Federal 1.2 million ac

• Non-metal elements human function• N protein• Se antioxidant• P bones & teeth

• Metal human function• Cobalt vitamin B12 • Zn sexual maturity• Mn bone formation, Insulin

Production• Cu red blood cell formation

Questions

• Emphasize– There is a difference between plant available

content and total elemental content– Soil testing; plant available content

Other topics

• Soil Testing, PB 1061 by Dr. H. Savoy

• Liming Acid Soils in Tennessee, PB 1096 by Dr H. Savoy

Additional topics

• Landscape Irrigation by Dr. J Buchanan, CD in the extension office

• Commercial WEB sites– RainBird Irrigation at www.rainbird now look under

landscape irrigation– Toro Irrigation at www.toro.com/sprinklers/index.html– Hunter Industries at www.hunterindustries.com

• Book Source: Simplified Irrigation Design ISBM 0-471-28622-22