Soils, Crops and Fertilizer Use. A What, How and Why Guide. Appropriate Technologies for ...

169 Pages·2008·2.85 MB·English

DOCUMENT RESUME
CE 038 582
ED 241 778
AUTHOR
Leonard, Dave
TITLE
Soils, Crops and Fertilizer Use. A What, How and Why
Guide. Appropriate Technologies for Development.
Reprint R-8.
Peace Corps, Washington, DC. Information Collection
INSTITUTION
and Exchange Div.
Feb 80
PUB DATE
171p.
NOTE
PUB TYPE
Guides - Classroom Use
Guides (For Teachers) (052)
MF01/PC07 Plus Postage.
EDRS PRICE
DESCRIPTORS
Agricultural Education; *Agricultural Production;
Agricultural Safety; *Agricultural Skills;
*Agricultural Supplies; Agriculture; Agronomy;
Botany; Entomology; *Fertilizers; *Field Crops;
Grains (Food); Guidelines; Harvesting; Land Use;
Pests; Plant Growth; Plant Pathology; Postsecondary
Education; *Soil Conservation; Soil Science;
Vocational Education; Voluntary Agencies; Volunteers;
Volunteer Training; Weeds
ABSTRACT
This manual, prepared for use by Peace Corps
volunteers in developing countries,; has been designed as an
on-the-job reference for soil management and fertilizer use at the
small farmer level. It provides information on yield-boosting
techniques, especially in the areas of soil conservation, organic and
chemical fertilizer use, and the safe and appropriate use of
agricultural chemicals. The text is written in a "how to" format, in
as nontechnical language as possible, and takes a problem-solving
approach to soil, management and fertilizer use. Organized into nine
sections, the text covers the following topics: soil basics, spotting
and fixing soil physical problems, seedbed preparation, soil
fertility basics, determining fertilizer needs, how to use organic
fertilizers and soil conditioners, chemical fertilizers, liming
soils, and salinity and alkalinity problems. An appendix to the
manual provides conversion tables, composition of common fertilizers,
information on soil moisture content, erosion control approaches, and
hunger signs in common crops. (KC)
***********************************************************************
Reproductions supplied by EDRS are the best that can be made
from the original document.
***********************************************************************
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Peace Corps
3
n
SOILS, CROPS AND FERTILIZER USE
A WHAT, HOW AND WHY GUIDE
by
DAVE LEONARD
Pace Corps
Information gal:action and Exchange
ReprintR78
December 1967
First Edition
June 1969
Second Edition
February 1970
Reprinted
1
March 1976
December 1977
February 1980
Third Edition
September 1981
Reprinted
Author's Foreword
Agriculture cmension work r=equires more than good intentions and
The real challenge is usually establishing
rapport with farmers.
credibility in the agriculture skills area.
Agriculture at the small farmer level in a developing country is
Farmers have 'nue, they can teach you when it comes
a complex endeavor.
to land preparation, planting, harvesting, using tools, and other
Likewise, there are many yieldboosting skills you can
manual skills.
show them, especially in the areas of soil conservation, organic and
chemical fertilizer'Use, and the safe and appropriate use of agricultural
chemicals.
This manual has been designed as an on-the-job reference for soil
management and fertilizer use; hopefully, it will help you along that
sometimes bumpy road to credibility.
I would._!ike to give a special thanks to Susan Cass for the
illustrations V.n this manual.
David Leonard
Any suggestions for revisions or additions are welcome.
Please Note:
Write to
Information Eollection and Exchange, OPTC
Peace Corps
806 ConnecticutAvenue
Washington, D.C. 20525
4
TABLE OF CONTENTS
Emu
2AFT I: STARTIN6 PROM SCRATCH
1. 7
Sc NO important Soil Basics
What is Soil, Anyway? 1, Why do Soils Vary so MUch? 1-2,
Topsoil vs. Subsoil 2, Sand, Silt$ and Clay 2.4i Soil
Organic Matter 4.6, More on Soil Micro-organisms 7..
PART II: SOIL PHYSICAL PROBLEMS
8- 29
V
Mow to Spot 'em and,Fix 'en
Getting to Know your Area's Soils 8, Some Common
Soil Physical Problems 9, HOW TO SPOT AND TREAT SOIL
PHYSICAL PROBLEMS 9 -29: What About Soil Color? 9,
Soil Texture 9-13, Soil Tilth 13 -14, Soil water Hold.
ing Capacity 15.16, How Much Water do Plants Need?
How Often? 17 -18, Soil Drainage 18-19, Soil Depth
19 -20, Slope and Erosion Control 20-29.
PART III: SEEDBED PREPARATION
31 - 36
Getting Crops Off to a Good Start
The What and Why of Tillage 30, Same Common Tillage
Equipment 30-31, -The--Abuses of Tillage.and.HOw to
Making the Right Seedbed for the Soil,
Avoid Them 32
crops, and Climate 32-33, How to Double dig 34, How
to Cope with Soil Crusting 34, How to Make up a Seed-
box Soil Mix 35.
EMI_IMI_AlftlE IMPORTANT SOIL FERTILITY BASICS,
50
37
How Plants Grow 36, Available vs. Unavailable Forms
of Nutrients 37, The Nutrient Holding Ability of a
Soil 37, Soil pH and How it Affects Crop Growth 39-
42i IMPORTANT PACTS ON THE PLANT NUTRIENTSA3 -49:
Macro- vs. Micronutrients 439-Nitrogen 44-45, Phos-
phorus 45.46, Potassium 46-47, Calcium 47, Magnesium
47, Sulfur 47-48, The Micronutrients 48.49
PART Vs DETERMINING FERTILIZER NEEDS
SI - S7
SOIL' TESTING 51-54: Soil TestS Vary in Accuracy 51 -52,
What about Portable Soil Test Kitt? 52, How to.Take
a Soil Sample 52 -54, Plant Tissue Teats 54, Fertili.
sec Trials 55, Spotting Visual Hunger Signs 56, An
Educated ."Guestimatea 56.
HOW TO USE CIRCA=
T
58
70
PER
S AND SOIL CONDITIONERS
The Chemical vs. Organic Controversy 5759, ORGANIC
0
FERTILIZERS & SOIL CONDITIONERS
59..69: Manure 59.61
(Continued)
SI
paaes.
Compost 61-64
,:ther Organic 'Fertilizers & Soil
Improvers 65.6Cv Green Manure Crops 66, Mulching
67, Earthworms :38-69.
PART VII: CHEMICAL FERTILIZERS
71 - 136'
I. Some nmEntrt Odds & Encla
Types of C4emical Fertilizers 7071, How to Read
7
a Fertilizer Label 71-72, What's Chemical Fertili-
zer Made Out of 2 72 -73, Nitrogen Fertilizers 73-74,
?hosphorus Fertilizers 74-75, Potassium Fertilizers
75, Calcium and 'Magnesium 75, Supplying Sulfur 76,
Micronutrient Fertilizers 76, How Some Fertilizers
Affect Soil pH and What to Do abaut it 76.77.
C.mar_y_jLeca
II. 119LtaA
Nitrogen 78.79, Phosphorus 79.80, Potassium 80-811,
Sulfur 81, Calcium & Magnesium 81, Micronutrients
General nicronutrient Rates 82, Fertilizer
31-82,
Application Methods Compared 83.87:'3roadcasting 83,
Localized Placement (Band, Hole, Half-circle) 84-85,
Using a Liquid "Starter" Solution 85, Foliar Applica.
,11114,4
tions 85 -.86, Application through the Irrigation Water
86, Some Specisl Advice for Furrow Irrigated Soils 86,
How to Avoid Fertilizer Burn 86-87.
III. liallAM211_12Amlal
What's the Most Profitable Rate of Fertilizer for a
Small Farmer? 88.90.
IV. EgatUrsuft 1ixer Practices: How to S_Pot_teM and
Fix 'am 91.93
V. Getting the Most Out of Fertilizers
Factors that Affect the Response You'll Get 51-95,
Use the "Package" Approadhi 95
VI. Coping with Fertilizer Math
Converting Fertilizer Recommendations from an N, F205,
K20 Basis to Actual Kind and Amount of Fertilizer(s)
Needed 96.98, Choosing the Most Economical.Fertilizer
98-99, Mixing D;fferent Fertilizers 99.6200, Calculating
per Length of
How Much Fertilizer is Noodad per Are
Row, or per Plant 102-107, Converting Fertilizer Dosages
from a Weight to a Volume Basis 107
r S ecif c C 108-235
VII. Fe
Gui elfin
i
1.12.11-1 Rice 113-
Corn 108.112, Grain & Forage Sorghums
7119, Peanuts 119-
116, Field Beans 116-117, Soybeans 11
Sweetpotatais 121,
120, Cassava (Manioc, Yuca) 120-121,
Pa5tures 126131,
Potatoes 122-123, Vegetables 123-126,
Coffee 131433, Bananas 133-135.
7
(Continued)
4.6
pules
PART VIII: LIMING SOILS
137 - 143
How Acid Soils Harm Crop Growth 136, Recommended
Soil pH's for Common Crops 136, How to Tell if Lim-
ing is Needed 137, Types of Liming Materials and their
Neutralizing Values 137-1389 Fineness of Liming Ma-
terials is Importantt 138-1399 Purity 139, How Soil
Exchange Capacity Affects the Amount of Lime Needed
139-1409 "Tropical" vs.' "Temperate" Soils 140, "Guesti-
mating" the Amount of Lime Needed 140.:X419 How and
V
When to Lime 141-:129 Don't Overlimei'142.,
PART IX: SALINITY AND ALKALINITY PROBLEMS
144
150
Saline, Saline-Sodic, and Sodic Soils 143 -144, How
Salinity and Alkalinity Harm Crop Growth 144, Lab
Diagnosis of Salinity and Alkalinity 144 -145, Mleasur-
ing Irrigation Water Quality 145, Relative Tolerance
of Crops to Salinity 146, Relative Crop Tolerance to
Boron 147, How to Manage and Reclaim Saline and Sodic
Soils 147-149.
Appendix
1. Some Handy Conversions
IS1
2. Composition of Common Fertilizers 152
3. Determining Soil Moisture Content by
Feel or Appearance 1S3-
4, Spacing GUide for Contour Ditches or
Other Erosion Barriers 1.54 -155
5. Hunger Signs in Common Crops 156 - 160
.4
O
PART I
STARTING FROM SCRATCH
Some Important Soil Basics
WHAT IS SOIL ANYWAY?
Most soils evolve slowly over centuries from the weather-
ing of underlying rock material and decomposing plant matter.
Some'soils are formed from deposits layed down by rivers and
seas (alluvial soils) or by wind (loess soils).
1. Mineral particles (sand,
Soils have '4 basic components:
silt', clay)
2. Organic matter
3. Water
4. Air
i
A typical.saiple of topsoil contains about 50% pore
space with .varyirig proportions of air and water dependifig on
.31
The other 50% of the volume is
the soil's moistdre content.
made up of mineral particles (sand, silt, clay/ and or anic
n
er
mat er; most7MITEil soils range from 2-6% organic ma
Organic soils like peats are formed 1.
t e topsoil by weight.
in marshes, bogs, and swamps, and contain. 30-100% organic
matter.
WHY DO SOILS VARY SO MUCH ,
veaetation
ra h
Climate
rod:, t
, type of Rprcnt
inter-
ormation ana
and tIme,an influence zo
manaaiMe
n countlesi-Faterns to produce an amazing variety of
act
It's_not uncommon to find 2 or 3 differdnt soils with-
in one Small farm that differ markedly in management problems
and crop yield potential.
9
2
TOPSOIL vs, SUBSOIL
Dig down a couple feet in most soils, and you'll nctice
The TOPSOIL is the darker, upper layer
2 distinct layers.
Most of a crop's roots (like 60-80%) are
about 6-12"thick.
found here, since topsoil offers much better conditions for
root-growth.
That's because:
1. Topsoil is :pork fertile than subsoil because of its
higher organic matter content (that's why it's darker)
and because most fertilizer nutrients don't move down-
ward after being applied to the topsoil layer.
1. Topsoil islooser,(less compacted) than subsoil because:
plows and hoes usually don't reach the subsc,i1-; organic
matter aids looseness; subsoils tend to be more clayey.
So what good is SUBSOIL., if most of the action takes place
in the topsoil?:
1. An average subsoil is much thicker than the topsoil
and provides a zittiallturgrasaLie during dry
It's estimated that about half the moisture
spellS.
needed to grow a crop of corn in the Corn Belt is al-
ready in the subsoil at planting time, while average
rainfall during the crop's growth provides the other
half.
2. Subsoil characteristics like drainage ability and
nutrient content have a,big influence on crop yields.
Making topsoil out oi subsoil: Exposed subsoil (i.e. due to
erosion) can be converted into productive topsoil over several
years through large additions of organic matter (compost, ani-
mal manure, etc.) as long AS there's enough total depth left
More on this in Part la.
(at least 18" or so).
THE MINERAL SIDE OF SOILS: SAND,_ SILT: AND CLAY
It would take about 10,000 average size clay particles
to equal an inch vs. only about 125 average sand grains.
Silt is midway between in size.
Sand and Silt
Both sand and silt are JOE broken down rock fragments,
.
Silt partiCles are miniature
mainly Quartz (silicon dioxide).
They don't usually contribute much soil fen«
sand particles.
tility since quartz contains no plant nutrients and the par-
ticles carry no negative charge like clay and humus (see be-
Some sands contain sizeable Amounts of micas and feld-
low).
1 0
O
3
spars which aid soil fertility, but this is uncbmmon.
Des-
pite their lack of nutrients, sand and the larger of the silt
particles are very beneficial to soil tiaft (ease of working),
drainage, and aeration if present in moderate amounts.
giaz
Aside from their much smaller size, clay particles are
uniquely different from sand and silt:
A
icles have a ne ative char e: They act like,
1,;
magnets by attracting and hold ng those plant nutri-
ients that have a plus (+) charge like ammonium nitro-
gen (NH4), potassium (1(4), calcium (Ca++), magnesium
(ft++), and several others.
This greatly cuts down
on nutrient losses from the downward movement of rain
or irrigation water (called 11ACALga losses),
sot
Each :clay par.
Theyy have.a tremendous surface area:
a laminated structure of platelike units.
tic le is
This lattice makeup plus small size means a huge sur-
One
face area for attracting plus charged nutrients.
cubic inch of clay particles easily has 200500 sq,
ft. of surface area.
ney furnish some
: Unlike the
en
sand
1 n nut
and silt partic es, clays are aluminum - silicate minerals
and also contain varying amounts of potassium, calcium,
anti
other nutrients.. A good part of
magnesium, iron,
a soil's natural fertility comes from its clay fraction,
but this varies a lot with the type of clay (see below).
How Clays Differ
There are a number of different clay types, and most soils
Theclays found in most temperate zone
contain at least 2.
soils differ in several important respects from those that
predominate in many tropical soils where weathering has been
more intense.
dominate the clay portion of most
The 2:1 silicate clay
temperate zone soils (the ratio refers to the proportion of
Soils'with a high Content:of 2:1
silicate to aluminum).
lastic when wet and,May fora large
and
clays are very stick
ey a so have a eaU..tr-l-tel*Iln-ative
cracks upon dry ng.
larje amounts of
charge
Chi e (good, for holding
ents).
In many well drained and weathered tropical and sub-tropical,
soils, the clay fraction is dominat4by the 1:1 silicate clays
That s be.
and the hvdrous oxide clays, of iron end aluminum.
dause centuries of weathering and leaching have removed a lot
Unlike the 2:1 clays, these "tropical clays"
of silicate.
have better tilth cony.
are much less sticky and plastic and
Howevertthey tend to have much lower natural
paratively.
ele
11