Soils & Plant Nutrients

San Diego County Master Gardener Class February 4, 2014By Claire EhrlingerMiraCosta College

Oceanside campusNew HORT building dedicated in 2007

SLandscape ArchitectureSLandscape ManagementSNursery/Crop ProductionWhen combined with General Education

Requirements leads to an Associate Degree

Certificates of Achievement

Employment - Advancement - Transfer

∗ Irrigation Technology∗Wine TechnologyShort-term certificates, requiring fewer than 18 units, which

introduce students to one aspect of a trade.

Certificates of Proficiency

Some of our classes

• Intro to Sustainable Horticulture• Arboriculture• Vineyard Production & Mgt.• Landscape Irrigation• Wines of California• Plant Identification• Subtropical Fruit• Soil Science

∗ “To be a successful farmer one must first know the nature of the soil.” - Xenophon, Oeconomicus, 400 B.C.

∗ “Be it deep or shallow, red or black, sand or clay, the soil is the link between the rock core of the earth and the living things on its surface. It is the foothold for the plants we grow.” --- Roy W. Simonson, USDA Yearbook of Agriculture, 1957

Let’s Go!

∗ Soil Formation

∗ Soil Physical Properties∗ Soil Chemical Properties

∗ Soil Management∗ Soil Fertility

∗ Test Results: Texture, Drainage, pH

Today’s Class

Soils defined

Soil is a Life-supporting Layer of Material

Soil is a Life-supporting Layer of Material

Soils Perform Vital FunctionsSustaining plant and animal life below and above the surface

Regulating and partitioning water and solute flow

Filtering, buffering, degrading, immobilizing, and detoxifying

Storing and cycling nutrients

Providing support to structures

Rain

RunoffSoilInfiltration

Soil is the Basis of the EcosystemThe living systems occurring above and below the ground surface are determined by the properties of the soil. We often ignore the soil because it is hard to observe.

desertification and siltation

Lessons from History

∗Anchorage∗Water∗Oxygen∗Nutrients

Soil is a Medium for Plant Growth

Soil: A Three-Phase System

Root Growth

Five Factors or Soil Formation

Soil Formation

http://www.eoearth.org/upl oad/thumb/b/b8/Soil_pedogenesis_fac tors.jpg/300px-Soil_pedogenesis_fac tors.jpg

Rocks and Minerals

Residual soils form in place versus transported soils such as:∗ Glacial ice∗ Wind (eolian)∗ Loess soils, Dunes

∗ Water (alluvial)∗ Floodplains, levees, river terraces, alluvial fans∗ Marine sediments and deltas – Imperial Valley

∗ Gravity (colluvium)∗ Talus

Parent Material

∗ Temperature controls the rate of chemical reactions

∗ Temperature affects plant growth and moisture retention

∗ Temperature influences the rate of organic matter decay and nutrient availability

Climate - Temperature

∗Amount of rainfall influences chemical weathering, plant growth and erosion/deposition

∗Wind is significant erosive/transporting factor

Climate – Rainfall and Wind

∗ Actively affect soil formation∗ Examples that live in the soil:∗ Plants∗ Animals∗ Insects∗ Microbes

Organisms

∗ Slope∗ Gradient∗ Length∗ Moisture retention

∗ Aspect∗ Solar energy∗ Wind exposure

Topography

Soil Forming Factors:Parent Material (acted upon by)

Climate, Topography, Organisms

http://www.eoearth.org/upload/thumb/6/6c/Soil_forming_factors.JPG/350px- Soil_forming_factors.JPG

∗ http://forces.si.edu/soils/

∗ Chef ’s Challenge video clip on Soil Formation∗ http://youtu.be/hDfFrhL1gl8

Smithsonian Institute

∗Texture∗Structure∗Color∗…affect how soils are used to grow

plants and serve engineering purposes.

Soil Physical Properties

∗ Soil color is indicative of: ∗ Nutrient composition ∗ Organic matter∗ Drainage in soils

∗ The Munsell system of color notation can be used to classify soils according to color.

Soil Color

∗ The proportion of soil separates in soil determines its texture.

∗ Soil separates∗ Sand (large)∗ Silt (medium)∗ Clay (small)

Texture

Affects two important features:• Specific surface area• Number and size of pores–Macropores (aeration pores) — large–Micropores — small

Particle Size

∗ Division of mineral particles used by soil scientists

∗ Consists of three broad classes:∗ Sand (divided in four subcategories)∗ Silt∗ Clay

Soil Separates

Soil Separates (continued)

∗ Largest of the soil separates∗ Particles range in size from 0.05 to 2.00

millimeters in diameter∗ Spaces between particles are large and allow for

aeration of the soil.

Sand

∗ Medium-sized soil separate∗ Particles range in size from 0.002 to 0.05

millimeters in diameter∗ Provides transitionary pores between macro-

and micropores

Silt

SSmallest of the soil separatesSConsists of tiny, sheet-like crystalsSPores between particles are very small, hold

moisture, and are called micropores.

Clay

SSurface area! SFor water holdingSFor nutrient holdingSFor aeration

SSmaller particles have more surface area

Why does particle size matter?

∗ Classifications usually consist of more than one soil separate.

∗ All three separates are found in most soils.∗ Actual percentages are called soil texture.

Textural Classification

Soils can generally be classified as fine, medium, or coarse. These classifications are indicative of a number of soil properties:• Infiltration• Percolation• Water-holding capacity• Strength• Specific surface area

Textural Class Characteristics

Jar Test

Soil Textural Triangle

Internet-Based Tool - USDA:

¨ USDA Soil Texture Calculator

Ribbon Test

SWatering habitsS Irrigations schedules are based on textureSShorter run times for _________

SSoil Amendments including SThe amount of additives like sulfur or lime

depends on texture. More ## for clay

Texture class influences…

∗Add more sand?

∗Add more clay?

∗Something else?

How do you improve texture?

∗…add Organic Matter

∗Or look at Structure

When in doubt…

•Macropores Contain Air and Water•Micropores Contain Mainly Water

Micropores and Macropores

http://www.landfood.ubc.ca/soil200/images/16images/16.1.1macro&micropores.jpg

∗ Soil clumps together to form aggregates. Naturally occurring aggregates are called “peds.” Clumps of soil caused by tillage are called “clods.”

∗ Type – refers to shape∗ Class – refers to ped size∗ Grade – refers to ped distinctiveness and strength

Structure

Soil Peds

http://www.lanfaxlabs.com.au/images/struc ture-dr op-ped.j pg

Type of Soil Structure

http://www.youtube.com/watch?v=vmo0FRAVgkM&feature=youtu.be

Water Movement in the Soil

∗ Sand soils without structure are called single-grain soils.

∗ Fine textured soils that lack structure or function as a soil mass are called massive soils.

Structureless Soil

∗Anything that encourages plant growth or microbes improves structure∗Manage pH

∗ Proper watering

∗ Proper nutrients

How do you improve structure

Results when pressure is applied to the soil surface and can create:• Reduced porosity and permeability• Reduced air exchange• Decreased infiltration rates• Increased erosion• Reduced percolation• Reduced oxygen availability

Compaction

Soil Compaction

∗Nutrients∗pH

∗Fertilizers

Soil Chemistry

∗The ability of the soil to supply nutrients for plant growth is known as soil fertility.

Soil Fertility

∗ Include 17 essential elements∗ Are defined as those that:∗ A lack of stops growth/reproduction/interrupts life cycle∗ Are directly involved in plant nutrition∗ A shortage of can only be corrected by supplying the

nutrient∗ Carbon, oxygen, and hydrogen make up most of the dry

weight of a plant

Plant Nutrients

S MacronutrientsS Primary: nitrogen, phosphorus, potassiumS Secondary: calcium, magnesium, sulfur

S Micronutrients (trace elements)S Boron, copper, chlorine, iron, manganese, molybdenum,

nickel, zincS Beneficial elements

S Sodium, silicon, cobalt

Plant Nutrients (continued)

S Water – Comprises nearly 90% of plantS C H OS N P K S Mg, Ca, S S Cl, Fe , Mn, B, Mb, Ni, ZnS Na, Si, Co

Nutrients to Know

SCharged atoms/moleculesS + CationS - Anion

SAbsorbed by plant rootsSAbsorbed by soil particles

Nutrient Ions

Sources of Elements in Soil

Ionic forms of nutrients

∗ Are tiny clay and humus particles that carry a slight electrical charge that collects nutrients

∗ Cation Exchange Capacity (CEC)—the importance of colloids is their chemical and electrostatic reactivity; they attract and adsorb ions of plant nutrients. Capacity is based on the number of cations the soil can attract.

Soil Colloids

∗Cations are attracted to negatively charged ions so strongly that their downward movement in soil is stopped, capturing them for plant use.

∗Anion storage—some nutrients are negatively charged and are available through anion exchange

Soil Colloids (continued)

SSilicate clays: mica, smectite, chlorite, kaolinite, vermiculite

SOxide clays (sesquioxides): iron and aluminum oxides

SHumus: residues of organic matter decay

Three Types of Colloids

∗Major source of soil supplied nutrients (Except Nitrogen)

∗ Long term storage in soil∗ Freed from parent material by weathering,

dissolved and freed in ionic form

Source of Soil Fertility: Soil Minerals

∗Nitrogen, micronutrients, freed by decay∗ Intermediate to long term storage∗ Some released quickly, some slowly

Source of Soil Fertility: Organic Matter

∗Held in the soil and attracted by electric charge to clay and humus particles

∗Many plant nutrients are positively charged thus stick to these negatively charged particles.

∗Absorbed by plant through cation exchange

Source of Soil Fertility: Absorbed Nutrients from Soil Colloids

SThe term used to describe the acidity or alkalinity of a soil is soil reaction. It affects plant growth greatly.

SReaction is measured using the pH scale; pH measures acidity/alkalinity.

S6.0 is 10 x more acidic than 7.0S5.0 is 100 x more acidic that 7.0

pH

pH Scale

• Scale runs 0 to 14.0;

• 7.0 = neutral,

• Strongest acidic soils have a pH of 3.5;

• Strongest basic soils are about 10.5.

pH Scale (continued)

∗Nutrient availability (affects solubility) ∗ Element toxicity – some elements are

overly available under certain conditions∗ Soil organisms – prefer neutral conditions

Effects of pH on Soil

pH affects Nutrients

Another View

SPhotosynthetic Enzymes – 50% of N in leafSEssential part of protein – good N nutrition

increases protein content of food/forage SMore present in younger leaves: SYoung blade of grass C:N ration of 15:1SOld blade of grass C:N ration of 80:1

S In nature: primary limiting nutrient

Plant Uses of Nitrogen

∗Slow growth, stunting∗Lack of dark green color (pallor,

chlorosis)∗Small leaves, overall yellowing∗Older leaves lose green color first

Nitrogen Deficiency

Nitrogen Deficiency

tobacco Oil palm

Nitrogen Deficiency

Rice

Nitrogen Deficiency

Turfgrass

Corn

Plant responses to adequate supply• Early and rapid root growth• Efficient water use• Better resistance to cold and disease• Fast blooming, fruiting, crop maturity, and quality• In nature, P is primary limiting nutrient in Tropical

Land systems with highly weathered soils

Primary Macronutrients—Phosphorous

Problems from phosphorus deficiency• Stunted growth• Foliage too dark green or purpling of plant

stems and leaves• Delayed maturity• Lack of flowering

Primary Macronutrients—Phosphorous (continued)

25-90% of available P is in Soil OMPhosphorous comes form the weathering of minerals in

the soil, but most is fixed and unavailable because of pH (6.0 to 7.0 is best)

Forms of phosphorous in the soil• Calcium phosphate• Orthophosphates• Clay particles – can bind in clay particles

Primary Macronutrients—Phosphorous (continued)

∗ Phosphorous does not move much in the soil.∗ It does not leach downward unless storage is

saturated, then it can become a pollutant.∗ Most free at pH 6.5 to 6.8∗ Plant only uses 10-30% of phosphate fertilizer applied

to it, the rest goes into storage for later.

Primary Macronutrients—Phosphorous (continued)

Phosphorous Deficiency

Canola

Reduces VigorDelays MaturationReduces Bloom

Phosphorous Deficiency

Coconut Palm

Phosphorous Deficiency

Corn

Tomato

Plant responses to adequate supply• Good ripening• Activation of enzymes• Strong growth• Better disease resistance

Primary Macronutrients—Potassium

Problems from potassium deficiency• Water stress – K is involved in opening/closing of

stomata• Delayed maturity• Poor root system• Reduced cell pressure• Marginal scorch – browning of the tips

Primary Macronutrients—Potassium (continued)

∗ Potassium moves more readily in soil than Phosphorous but not as much as Nitrogen.

∗ K and N in good ratios promotes less succulent growth with good dry mass

∗ Proper K supply helps plants resist infections.∗ Excess supply beyond plant needs does not increase

hardiness, it may inhibit uptake of Ca and Mg

Primary Macronutrients—Potassium (continued)

Potassium Deficiency

Soybean

Potassium Deficiency

Soybean

Potassium Deficiency

Barley

Sugar Beet

Plant responses to adequate supply• Essential ingredient in chlorophyll• Increased uptake• Enzyme activation

Secondary Macronutrients—Magnesium

∗ Problems from magnesium deficiency∗ Less resistance to drought, cold, disease∗ Interveinal chlorosis∗ Leaf mottling

∗ Forms of magnesium in the soil∗ Minerals∗ Clay

Secondary Macronutrients—Magnesium (continued)

Magnesium Deficiency

Phoenix roebelenii

http://www.upf.com/news/images/P33.j pg

http://msucares.com/crops/comhort/tomatodisease/images /mag.j pgTomato

Sago

Metallic trace elements: Iron, Manganese,Zinc, Copper, NickelS Interact with enzymes as keys to activating biological

reactionsSAre taken up as simple cationsSForm chelatesSAdsorb to colloid surfacesSExcesses can cause toxicitySCopper deficiency = lack of sweetness in citrus

Micronutrients

Anionic trace elements: Boron,Molybdenum, Chlorine∗Boron—functions are not well

understood; deficiency causes weakened cell walls, death of terminal buds, bushy growth, blackened hearts, may hurt pollination; too much causes toxicity

Micronutrients (continued)

∗Molybdenum—needed for nitrogen metabolism and nitrogen fixation; crops in the mustard family may be sensitive to it

∗Chlorine—role not well understood; plays a role in photosynthesis; acts as a solute; can occur in toxic levels

Micronutrients (continued)

∗Common in alkaline soils or with acid-loving plants

∗ Iron is less available in higher pH∗Usually shown by younger leaves being

pale and older leaves being green (vs. Nitrogen is opposite) or by green veins and yellow margins.

Iron Deficiency

Micronutrient Deficiencies

Iron Deficient Palm Zinc Deficient Corn

Micronutrient Deficiencies

Boron deficient RoseBoron Deficient Cauliflower

http://www.umassvegetable.org/images /soils_crops_pest_mgt/disease/br occoli_boron_deficiency.jpg

http://www.mobot.org/gardeni nghelp/images/Pests/Pest741.jpg

Micronutrient Deficiencies

Molybdenum Deficient Melon Zinc Deficient Citrus

http://aggie-horticulture.tam u.edu/cucurbit/leaf/36.2.jpeg

http://www.ctahr.hawaii.edu/nelsons /Misc/1_citruszi nc_1.JPG

Micronutrient Deficiencies

Manganese Deficient CornManganese Deficient Schefflera

http://aggie-horticulture.tam u.edu/cornMn/leaf/36.2.jpeg

http://hort.ufl.edu/nutdef/images/thy9556.jpg

Manganese deficiency is common in calcareous soils.

Phytotoxicity

http://www.ctahr.hawaii.edu/nelsons /coffee/burn1.JPG

Coffee

http://www.ag.auburn.edu/aaes/communications/highlights/winter98/images/rosetwo.gif

Rose

Phytotoxicity/Herbicide Damage

http://www.mobot.org/gardeni nghelp/images/Pests/Pest741.jpg

Sugar maple

Malus

Ginko

Mosaic Virus

http://www.extension.umn.edu/projects /yardandgarden/YGLNews/images2/Sept1507/rosemosaic184.jpg

Rose

Field Test: Percolation Test: Day 11. Dig one cubic foot hole (12” x12” 12”)2. Fill the hole with water to saturate the soil. Let drain

overnight.

Soil Drainage Test

Field Test: Percolation Test: Day 23. Refill the hole with water4. Measure the depth of water5. Measure every hour

Soil Drainage Test

∗ If water still remains after 8 hours, drainage is considered poor

∗ Poor drainage can be addressed by ∗ adding organic matter∗ installing drainage systems∗ judicious plant choices

Soil Drainage Test

Before You Plant Drainage

Inches / Hr. Drainage Solutions

Less than 1”

Slow Add organic matter & judicious plant selection

2”

Ideal

1”- 3”

Acceptable

More than 4”

Fast Add organics

pH Problems

∗ Too Acidic∗ Add lime

∗ Calcium carbonate∗ Dolomite∗ Wood ashes

∗ Results in a few months

∗ Too Alkaline∗ Add sulfur (2-4#/100 ft2)∗ Must be incorporated

into rootzone∗ Results in several months

or longer- depends on microorganisms, temp & water

∗ Usually builds up in drier areas∗ Poor water quality∗ Often with high pH∗ Leaching with extra water∗ Use mulches to reduce surface evaporation∗ Gypsum can be added to help leach out sodium

Excess Salts

∗ Usually Nitrogen is most limited∗ Add extra nitrogen to feed microbes that help break

down organic matter∗ Organic fertilizer are usually < 5% N but helps

structure∗ Can use foliar applications for micronutrients

Nutrient Deficiencies

∗ Fourteen mineral nutrients and three beneficial elements are needed for plant growth.

∗Nitrogen, phosphorus, and potassium are the most critical for strong, healthy plants.

∗ Some plant nutrients exist predominately in organic matter while others are primarily adsorbed on colloids.

∗ Solubility and mobility are important traits.

Summary

Internet-Based Tools - USDA:

http://websoilsurvey.nrcs.usda.gov