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close this book Soils, Crops and Fertilizer Use
close this folder Appendixes
View the document Appendix A: Useful measurements and conversions
View the document Appendix B: How to determine soil moisture content
View the document Appendix C: Spacing guide for contour ditches and other erosion barriers*
View the document Appendix D: Composition of common chemical fertilizers
View the document Appendix E: Hunger signs in common crops
View the document Appendix F: Legumes for green manuring and cover-cropping in tropical and subtropical regions
View the document Appendix G: Some sources of technical support
View the document Appendix H: A bibliography of useful references

Appendixes

 

Appendix A: Useful measurements and conversions

AREA

1 SQ. METER = 10.76 sq. ft.

1 HECTARE (ha) = 10,000 sq. meters = 2.47 acres = 1.43 manzanas (parts of Latin America)

1 ARE (a) = 100 sq. meters = 0.01 hectares

1 ACRE = 4000 sq. meters = 4840 sq. yards = 43,560 sq. ft. = 0.4 hectares = 0.58 manzanas (parts of Latin America)

1 MANZANA (used in parts of Latin America) = 10,000 sq. varas = 7000 sq. meters = 0.7 hectares = 1.73 acres

LENGTH

1 METER (m) = 100 cm = 1000 mm = 39.37" = 3.28 ft.

1 CENTIMETER (cm) = 10 mm = 0.01 m = 0.4"

1 MILLIMETER (mm) = 0.001 meter = 0.04"

1 KILOMETER (km) = 1000 m = 0.625 miles

1 VARA (Latin America) = 83.7 cm = 32.8"

1 MILE = 1.6 km = 1600 meters = 5280 ft.

WEIGHT

1 KILOGRAM (kg) = 1000 grams (g) = 2.2 lbs. = 35.2 oz.

1 POUND (lb.) = 16 oz. = 454 g = 0.454 kg 1 OUNCE (oz.) = 28.4 g

1 METRIC TON = 1000 kg = 2202 lbs.

1 LONG TON = 2240 lbs. 1 SHORT TON = 2000 lbs.

1 QUINTAL = 100 kg (metric system), 100 lbs. (Latin America)

VOLUME

1 LITER (l) = 1000 cc = 1000 ml = 1.06 U.S. quarts

1 HECTOLITER (hl) = 100 liters

1 CUBIC METER = 1000 liters

1 CUBIC FOOT = 7.48 U.S. gallons = 28.3 liters

1 GALLON (U.S.) = 3.78 liters = 3780 cc (ml)

1 GALLON (Imperial) = 5 U.S. quarts = 4 Imperial quarts = 4.725 liters

1 ACRE-INCH (of water) = 26,928 U.S. gallons

1 BUSHEL (U.S., English) = 1.25 cubic ft. = 9.375 U.S. gallons = 35.4 liters = 66 lbs. shelled, dry maize or sorghum = 60 lbs. dry wheat kernels or beans

1 FLUID OUNCE (fl. oz.) = 30 cc (ml) = 2 level tablespoons (measuring type)

1 TABLESPOON (measuring type) = 15 cc (ml) for solids or 18 cc (ml) for liquids, due to surface tension.

1 TEASPOON (measuring type) = 5 cc (ml) for solids or 6 cc (ml) for liquids, due to surface tension.

MISCELLANEOUS CONVERSIONS

lbs./acre X 1.12 = kg/ha; lbs./acre X 1.73 = lbs./manzana

kg/ha X 0.89 = lbs./acre; kg/ha X 1.54 = lbe./manzana

lbs./manzana X 0.58 = lbs./acre; lbs./manzana X 0.65 = kg/ha

1 LITER PER SQ. METER = a 1 millimeter thickness (layer)

7 U.S. GALLONS PER SQ. METER = a 1 inch thickness (layer)

Temperature:

C° = (F° - 32°) X 0.55

F° = (C° X 1.8) + 32°

 

Appendix B: How to determine soil moisture content


Determining soil moisture by feel or appearance

 

Appendix C: Spacing guide for contour ditches and other erosion barriers*

(See Chapter 3)

% SLOPE

DEGREESSLOPE

DISTANCE BETWEEN DITCHES** IN METERS

5

21.6

6

 

19.3

7

17.7

8

 

16.6

9

15.8

10

 

15.0

11

14.2

12

13.4

13

 

12.7

14

12.1

15

 

11.5

16

11.0

17

 

10.5

18

10º

10.0

19

 

9.5

20

11°

9.0

21

 

8.6

22

 

8.2

23

 

7.8

24

 

7.5

25

14°

7.2

26

 

7.0

27

 

6.7

28

 

6.4

29

 

6.2

30

17°

6.0

31

 

5.8

32

 

5.6

33

 

5.4

34

 

5.2

35

19°

6.0

36

 

4.9

37

 

4.8

38

 

4.7

39

 

4.6

40

22º

4.5

41

 

4.4

42

 

4.3

43

 

4.3

44

 

4.1

45

24°

4.0

* These spacings are suitable for contour ditches, rock walls, and other erosion barriers.

** The distances in column 3 are based on Peace Corps project experience in El Salvador. Check with conservation specialists in your region for their recommendations.

 

Appendix D: Composition of common chemical fertilizers


Table

 

Appendix E: Hunger signs in common crops

NOTE: Before trying to diagnose hunger signs, read over the section in Chapter 7 on their usefulness and drawbacks.

NITROGEN DEFICIENCY

Cereal Grains (Maize, Sorghum, Millet, Rice, Wheat): Young plants are stunted and spindly with yellowish-green leaves. In older plants, the tips of the lower leaves show yellowing first which progresses up the mid-rib in a "V" shaped pattern, the leaf margins remaining green. In some cases, there's a general yellowing of the lower leaves. In severe N hunger, the lower leaves eventually turn brown and die, starting at the tips. This "firing" can also be caused by drought which prevents N uptake. Maize ears are pinched at the tips.

Pulses and Pasture Legumes (Peanuts, Beans, Kudzu, etc.)

Many legumes like peanuts, cowpeas, mung beans, soybeans, and pasture legumes can fix all the N they need if the right strain of rhizobia bacteria is present. Others, such as beans, garden peas, and non-vining lima beans, are less efficient.

N-deficient legumes have pale green leaves with a yellowish tinge, starting first with the lower leaves. In severe cases, leaf drop may occur.

If an efficient N fixer like peanuts or soybeans shows N deficiency symptoms, check for adequate nodulation (refer to the section on pulses in Chapter 10).

Vegetables

Tomatoes first show stunted growth and loss of normal green color, first in the younger, upper leaves which stay small and thin. The whole plant gradually becomes light green to pale yellow. The veins begin to change from light green to purple, especially on the underside of the leaves. Stems may turn purple. Flower buds may turn yellow and drop off, and fruits are small.

Cucumbers and squash first show leaf stunting and a loss of deep green color. Stems are spindly, and fruits are light in color (cucumbers).

Potatoes have light green to yellowish-green leaves. In late stages, leaf margins turn yellow and tend to curl.

Other vegetables show a general leaf yellowing.

PHOSPHORUS DEFICIENCY

Cereal Grains

P hunger signs are most likely to occur during early growth. Mild shortages usually cause stunting without clear leaf symptoms . More severe shortages cause a purplish color starting at the tips of the lower (older) leaves which may even turn brown and die. Some varieties of maize and sorghum don't show a purplish color but rather a bronze coloration of the same pattern. Disregard purple stems.

In maize, a purplish color can be caused by either low temperatures or P shortage. Low temperatures make it more difficult for the roots to absorb P; however, the purpling can be caused by low temperature alone even when the plans 'e level of P is adequate.

In maize and sorghum, symptoms usually disappear once the plants reach 40-45 cm, but yields will be severely lowered. Maize ears from P deficient plants are somewhat twisted, have irregular seed rows, and seedless tips.

Pulses and Pasture Legumes: Hunger signs often aren't well defined. Plants lack vigor and have few side branches. Upper leaves become dark green but remain small. Flowering and maturation are retarded.

Vegetables

Leaves of most vegies first fade to a lighter color. In tomato and Crucifer Family plants (cabbage, turnip, etc.). a purple color develops on the undersides of the leaves or along the veins. (On tomatoes, this can be confused with deficiency).

Potatoes have smaller than normal leaves with a darker color than usual; leaves fail to expand normally. Tubers may have rusty brown lesions in the flesh.

POTASSIUM DEFICIENCY

Cereal Grains: Maize, sorghum, and millet, etc. rarely show symptoms the first several weeks of growth. The margins of the lower leaves turn yellow and die, starting at the tip. K-deficient plants have short internodes (distance between the nodes) and weak stalks. Maize stalks sliced length-wise often reveal nodes that are discolored and a darkish brown. Maize ears from K-deficient plants are often small and may have pointed, poorly seeded tips.

Pulses and Pasture Legumes: K deficiency is fairly easy to spot. In broad-leaved legumes like beans and cowpeas, early signs are irregular yellow mottling around the leaflet edges, especially in the lower part of the plant. This turns into a "firing" of the leaf margins that may move inward to cover half the leaf.

Vegetables

Tomatoes will grow slowly and have a dark blue-green color. The young leaves become crinkled; older leaves turn dark green and then develop a yellow-green color around the margins. Blotchy ripening of tomatoes can be caused by K deficiency.

Cabbage plants first show bronzing of the leaf edges which then turn brown and dry out.

Potatoes: The early appearance of unusually dark green, bluish-green, or glossy foliage is a dependable sign. Older leaves become yellowish and develop a brown or bronze color starting at the tips. A number of lower leaves nay dry up at the same time. Plants become stunted and seem to droop due to downward curling of the leaves. Tuber flesh turns dark when cooked.

CALCIUM DEFICIENCY

Calcium deficiencies are very unlikely except in some vegetables and peanuts.

Maize leaf tips become stuck to the next lower loaf.

Beans: Ca hunger is moat likely to occur in combination with aluminum toxicity on very acid soils. Leaves stay green with a slight yellowing at the margins and tips. Leaves may pucker and curl downward.

Peanuts: Light green plants with a high percentage of "pops" (unfilled pods).

Tomatoes: Blossom end rot is caused by calcium deficiency which is promoted by "feastor-famine" watering and severe pruning. The blossom end (bottom end) of the fruit becomes sunken and dark, eventually rotting.

Celery will develop brown, decaying areas in its heart leaves.

Carrot roots will have cavity spots.

MAGNESIUM DEFICIENCY

Where to suspect deficiencies: Very acid soils or soils that have been limed with a material low in magnesium. High K applications encourage deficiencies.

Cereal Grains: A general yellowing of the lower leaves is the first sign. Eventually, the areas between the veins turn light yellow to almost white, while the veins remain fairly green. As the deficiency progresses, the leaves turn reddish-purple along their edges and tips, starting at the lower leaves and working upwards.

Pulses: Interveinal (between the veins) yellowing appears first on the older leaves and then moves upwards. Leaf tips show the first effects.

Vegetables: Cabbage, cucumber, watermelon, tomato, eggplant, and pepper are the most susceptible. Tomatoes get brittle leaves which may curl upwards (caused by other things too). The veins may stay dark green while the areas between turn yellow and finally brown.

SULFUR DEFICIENCY

Where to suspect: Volcanic soils; acid, sandy soils; where low-S fertilizers have been used exclusively for some time.

Cereal Grains: Cereals have relatively low S needs. Stunted growth, delayed maturity, and a general yellowing of the leaves (as distinguished from N hunger) are the main signs. Sometimes the veins may stay green which can be mistaken for iron or zinc deficiency; however, iron and zinc hunger are more likely in basic or only slightly acid soils.

Other Crops: Signs aren't easily recognizable in most crops. In beans ,the upper leaves turn uniformly yellow.

ZINC DEFICIENCY

Where to suspect: Soil pH above 6.8; where high rates of P have been applied, especially if locally placed near the row. Maize is very sensitive to Zn deficiency.

Cereals: Maize shows the most clearly recognizable zinc hunger signs of any crop. If severe, symptoms appear within 2 weeks of of emergence. A broad band of bleached tissue on each side of the mid-ribs of the upper leaves, mainly on the lower part of the leaves, is typical. Mild shortages may cause an interveinal striping similar to manganese and iron hunger. However, in the case of Fe and Mn shortages, the interveinal striping runs the full length of the leaf. Sorghum shows similar signs but with less interveinal striping, and the white band is more defined.

Pulses and Pasture Legumes: Interveinal yellowing of the upper leaves.

IRON DEFICIENCY

Where to suspect: Soil pH above 6.8; sorghum and legumes.

Cereal Grains: Sorghum is much more prone to iron deficiency than maize. Cereals show an interveinal yellowing that extends the full length of the leaf and occurs mainly on the upper leaves.

Pulses: Interveinal yellowing of the upper leaves which eventually turn uniformly yellow.

MANGANESE DEFICIENCY

Where to suspect: Soil pH above 6.8; sandy or highly leached soils.

Cereal Grains: Very uncommon.

Peanuts: Yellowing between the veins of the upper leaves which eventually become uniformly yellow and then bronzed.

Beans: Plants are stunted, and upper leaves become yellow between the small veins and eventually take on a bronzed appearance.

Manganese toxicity occurs on very acid soils and is accentuated by poor drainage. Beans are very susceptible. Upper leaves show an interveinal yellowing which is easily confused with Zn or Mg deficiency, but Zn hunger is very unlikely under acid conditions.

BORON DEFICIENCY

Where to suspect: Acid, sandy soils or high pH soils. Boron is the most common micronutrient deficiency on most vegetables. Cereals rarely show B deficiency.

Peanuts: Foliage may be normal but seeds often have a hollowed out, brownish area in the meat, usually referred to as "internal damage".

Beans: Thick stems and leaves with yellow and dead spots; if less severe, leaves are puckered and curl downward; easily confused with leafhopper damage and virus attack.

Table beets. turnips. and root crops show dark spots on the root, usually at the thickest part; this is known as "brown heart". Plants are stunted with smaller than normal leaves which develop yellow and purple-red blotches. Leaf stalks show a lengthwise splitting. The growing point may die.

Sweet potatoes: Plants are stunted with short internodes and curled petioles (the leaf stems). The edible roots have surface cankers covered with a black exudate.

Lettuce shows malformation of the quicker growing leaves, death of the growing point, and leaf tip burning and spotting.

MOLYBDENUM

Where to suspect: Acid soils. Legumes, Crucifer family (cabbage, cauliflower, etc.).

Pulses, Pasture Legumes: Since Mo is needed by the rhizobia bacteria, Mo-deficient legumes often show signs of N hunger.

Cabbage, Cauliflower. Broccoli, etc.: Interveinal yellowing along with cupping of the leaf margins. Leaves have a whiplike appearance.

COPPER: Copper deficiency is very uncommon but is most likely to occur in peat soils. Tree fruits and pasture legumes (especially stylo) are the most susceptible. Symptoms are varied but partial dying back of terminal shoots in fruit trees is one sign.

 

Appendix F: Legumes for green manuring and cover-cropping in tropical and subtropical regions

NOTE:

• For additional information, refer to the section on green manures and cover crops in Chapter 10.

• Seed innoculation and cross-innoculation groups: See the section on pulses in Chapter 10 and Table 10-3.

• Before using these species, check first with your country's extension service and experiment stations concerning their experience with them.

Seed scarification: The seeds of some tropical legumes such as centrosema, tropical kudzu, and leucaena have hard, impermeable seed coats which must be broken (scarified) to allow moisture absorption for germination. Several methods can be used:

• Hot water treatment: Soaking for 2-3 minutes at 80°C (176°F) or for 3 seconds in boiling water. Higher temperatures or longer immersions will damage the seed. If such accuracy isn't possible, bring water to a boil, allow to cool for 30 seconds, and then pour it over the seeds, allowing them to soak overnight before planting. Expect in the case of overnight soaking, the heat-treated seeds can be stored for several months or more if quickly air-dried.

• Mechanical means: Seed can be rubbed between sandpaper boards or placed in a drum lined with sandpaper and stirred or rotated to abrade the seed. Leucaena seeds can be nicked with toenail clippers.

I. Quick-Growing Legumes for Short-Term Use (40-90 days)

Glycine max (Soybeans): Annual bush or vining pulse crop requiring 130-160 days for seed production. Moisture needs similar to those of maize. Prefer a soil pH of 6.0-7.0. Varieties are highly daylength-sensitive and must be suited to the local photoperiod. Most varieties are susceptible to nematodes. Prone to diseases when grown in humid conditions. Require a very specific type of rhizobia bacteria.

Phaseolus aureus (Mungbean, Green Gram, Colden Gram): Widely grown in S.E. Asia as a pulse crop; adapted as a short-term green manure/cover crop. Stem-rot resistant but susceptible to nematodes and poor drainage. Fair drought tolerance.

Pueraria acutifolius (Tepary Bean): Annual bushy or viny plant well adapted to hot-dry areas with less than 500 mm annual rainfall and in frequent but heavy rains. Needs good moisture from germination to flowering but can often mature its seed without additional rain. Native to Mexico and Southwest U.S. Only moderately tolerant of salinity and alkalinity, but needs good drainage. Not adapted to humid, high-rainfall conditions. Very resistant to common bean blight (a bacterial disease; Xanthomonas phaseoli). Mature seeds are produced in 60-90 days after plant emergence. Dry seeds are edible after soaking and boiling; references disagree as to flavor ("strong-tasting", "mild-flavored"). Leaves and pods can be fed to livestock.

Sesbania macrocarpa (Syn. S. exaltata) [Coffeeweed]: Quick-growing, erect annual suitable as a green manure. Susceptible to nematodes. Can become invasive if allowed to set seed.

Vigna unguiculata (Syn. V. sinensis) [Cowpea]: Grown for edible seeds and young pods, forage, green manuring, and cover cropping. Varieties range in growth habit from bushy determinates (seed produced over a short period) to viny indeterminates (seed produced over several months>. Best adapted to 400-1500 mm annual rainfall. Well adapted to semiarid regions. Better tolerance to heat, drought, and soil acidity than common beans (Phaseolus vulgaris). Poor tolerance of soil salinity. Requires good drainage. Some varieties have good root knot nematode resistance. Makes good hay. Seed matures 60-200 days after planting with bush types being the earliest. V. sesquipedalis (yardlong bean, asparagus bean) is a closely related species widely grown in Asia. Nodulates readily.

II. Bush or Viny Legumes Suited for Long-Term Use (90 days +)

Calopogonium mucunioides (Calopo): Short-lived, vigorus, climbing perennial suited to hot, humid tropical areas with rainfall over 1500 mm. Not very palatable to livestock but may be eaten during dry season.

Clitoria ternatea (Butterfly Pea): Very drought tolerant; small leaved and doesn't cover the ground well. Grows in Central America at sea level.

Canavalia ensiformis (Jack Bean): A bushy, semi-erect annual 60-120 cm tall; can become a perennial climber; adapted to annual rainfall as low as 650-750 mm; fairly drought tolerant once established; tolerant of acid soils; withstands some waterlogging. Forage palatable to livestock only when dried and needs gradual introduction. Young leaves and pods can be eaten after cooking. The dried seeds are unattractive in flavor and must be soaked and boiled in salted water for several hours to soften them and remove toxins; they can also be detoxified by fermenting into tempeh. Produces green, immature pods in 90-120 days after sowing and mature seeds in 180-300 days.

Canavalia gladiata (Sword Bean): Vigorous perennial climber reaching 4-10 m in length; can be treated as an annual. Grows best under 900-1500 mm annual rainfall; once established, it has some drought tolerance. Most varieties have only poor to fair tolerance of waterlogging. Tolerant of acid soils. Forage palatable to livestock only when dried. Immature green pods widely used as green beans in Asia; mature seeds contain toxins which require soaking and boiling to remove and have a strong flavor and thick, tough seedcoat.

Centrosema pubescens (Centrosema, Centro): Aggressive vining perennial that readily climbs. Best for areas having over 1000 mm rainfall. Tolerant of acid soils and has some tolerance of poor drainage. Moderately palatable to livestock. Seed innoculation recommended as its rhizobia bacteria is somewhat strain-specific. If seeding conditions are secure, the seeds should be scarified with hot water to assure uniform germination. Some varieties can be propagated by stem cuttings. Withstands fairly heavy grazing.

Crotalaria spp.: Most species are erect annual or perennial shrubs reaching 90-180 cm. Green forage, hay, and silage of C. juncea (sunn hemp) and C. spectabilis (showy crotalaria, rattlebox) are toxic to livestock; seeds of all types are toxic. Best adapted to sandy soils and well-drained areas.

Desmodium intortum (Greenleaf Desmodium): Vining perennial best adapted to 900-1500 mm rainfall. Tolerant of acidic soils and waterlogging. Very palatable to livestock. Best as a grazed cover crop. Established by seed or stem cuttings.

Desmodium uncinatum (Silverleaf Desmodium): Lower tolerance to drought and waterlogging than greenleaf but withstands light frosts. Excellent forage. Best as a grazed cover crop.

Dolichos lablab (Lablab Bean, Hyacinth bean): Vigorous annual or biennial vining plants that make good forage. Flowers, leaves, and dried seeds are edible for humans. Adapted to areas with 500-2500 mm rainfall; needs good moisture for establishment. Good tolerance to acid soils and to aluminum toxicity, but needs good drainage. Crows well wherever cowpeas do but has better disease and insect resistance, though it is susceptible to nematodes. Seeds mature in 150-200 days and are unusually large, making them ideal for rough seedbed conditions. Competes well with weeds during establishment. Seeds mature 150-200 days after sowing. Withstands rotational grazing but cattle require time to adapt to it.

Indigofera hirsute (Hairy indigo): Annual shrub growing to 1.2-2 m. Adapted to acid, sandy soils. Makes good hay if cut before 90 cm. Has suppressant effect on root knot nematodes. Nodulates readily with cowpea rhizobia group.

Phaseolus atropurpureus (Siratro): Deep-rooted perennial used mainly for pasture. Best adapted to 750-2000 mm rainfall but has good drought tolerance. Requires good drainage. Resistant to nematodes. Reacts to stress by shedding its leaves. Easily established by seed; stem cuttings can also be used. Nodulates readily with cowpea rhizobia. Susceptible to Rhizoctonia stem rot in high rainfall regions.

Phaseolus lathyroides (Phasey bean): Self-regenerating (by seed fall) annual or bienniel erect plants eventually developing vines. Best adapted to subtropical areas with over 750 mm rainfall. Fair tolerance to waterlogging but susceptible to nematodes. Tolerant of acid, infertile soils. Forage is palatable to livestock. Nodulates readily with cowpea rhizobia.

Phaseolus lunatus (Lima bean): There are 2 groups of lima beans: bushy-erect and tropical vining. Unlike the bushy-erect types, the tropical vining types are especially well adapted to hot-humid conditions and are often the principal pulse crop of the wet rainforest regions of Africa and Latin America; unlike the bushy types, the vining types are efficient nitrogen fixers. However, they are susceptible to nematodes, have poor drought tolerance, and don't do well below a soil pH of 6.0. Seeds, immature pods, and leaves are eaten, but some varieties (especially those with dark-colored seeds) have toxic levels of hydrocyanic acid in these parts which must be removed by boiling and changing the cooking water.

Pueraria phaseoloides (Tropical Kudzu, Puero): Vigorous vining perennial with stems up to 8 m ions" Best adapted to ample rainfall (over 1500 mm). Tolerant of acid soils and somewhat tolerant of poor drainage. Very palatable to livestock and withstands moderate grazing. Fair drought tolerance. Established by seed which should be soaked for 24 hours or treated with hot water. Stem cuttings can also be used. Not to be confused with common (Japanese) kudzu, which is a much more aggressive subtropical species.

Stizolobium spp. (Syn. Mucuna pruriens) [Velvet Bean]: A vigorous annual or perennial climbing vine for forage and green manuring/cover cropping. Best adapted to 1200-1500+ mm of rainfall; not as drought tolerant as C. ensiformis. Grows from sea level to 2000 m in the tropics. Well adapted to sandy, less fertile soils. Fair tolerance of soil acidity but require good drainage. Seed produced in 180-270 days, although the few early-maturing varieties require just 110-130 days. Seeds are unusable for poultry but can be fed up to the 25% level to pigs. Seeds eaten by humans but require soaking and boiling to remove a toxin. Toasted, ground seeds used as a coffee substitute. Some varieties have an irritating, itchy powder on the pods. Relatively free from insect attack but susceptible to some species of root knot nematode. Nodulates with cowpea rhizobia.

Stylosanthes guyanensis (Stylo): A perennial erect small shrub growing up to 1.5 m. Best adapted to rainfall above 900 mm. Very tolerant of low fertility and acid soils but responds well to added P where lacking; sensitive to copper deficiency. Some tolerance of poor drainage. Good livestock forage but less resistant to heavy grazing than centro or siratro. Palatability varies but improves as growth progresses. Not very drought resistant but can re-establish itself through self-sown seed. Established by seed which needs scarification. All varieties except Schofield require a specific strain of rhizobia bacteria.

Stylosanthes humilis (Townsville Stylo): A self-regenerating (through reseeding) annual or biennial erect shrub whose branches can reach 90 cm in length. Needs at least 600 mm annual rainfall. Well adapted to low fertility and acid soils and is a good P extractor. Needs good drainage. Palatable to livestock and makes good hay. Withstands grazing well.

III. Legume Trees and Shrubs Suited for Cut-and-Carry Green Manuring

DANGER: Some of the the species below, such as Sesbania bispinosa, are aggressive and quick-growing; they may become invasive. Use native species of known behavior whenever possible.

Cajanus cajan (Pigeon pea): Short-lived perennial shrub often grown as annual since seed yield declines after the first year. Used for cut-and-carry green manuring, soil improvement, forage, firewood, and for its edible seeds and young pods. Deep rooted and drought tolerant. Best adapted to annual rainfall of 600-1000 mm. Requires good drainage. Some tolerance to salinity. Mature seed produced 100-250 days after sowing. Can be cropped for 2-3 years, but yields decline quickly after that. Can be maintained up to 5 years as a forage or green manure crop. Some varieties susceptible to root knot nematodes. Readily nodulates with cowpea rhizobia.

Calliandra calothyrsus (Calliandra): A small tree (up to 10 m tall) used for firewood, erosion control, windbreaks, cut-and-carry green manuring, and beautification. Reaches 2.5-3.5 m in 6-9 months. Best adapted to rainfall over 1000 mm but withstands several months of drought. Some tolerance of poor drainage. Competes well with weeds. Coppices (regrows) readily after cutting. Established by seed or large cuttings. Nodulates freely with cowpea rhizobia. Seed needs hot water treatment.

Gliricidia septum (Madre de Cacao, Quickstick, Madera Negra): A quick-growing tree for timber, live fencing, shade, forage, cut-and-carry green manuring, and honey foraging. Best adapted to rainfalls of 1500-2300 mm. Leaves are palatable to cattle but poisonous to most other animals. Roots, bark, and seeds are toxic; leaves can be toxic to humans. Leaves drop during dry season. Coppices (regrows) readily after cutting; can be trimmed every 1-2 months. Established by seed or large cuttings which readily root.

Leucaena leucocephala (Leucaena, Ipil-Ipil): Multi-purpose, deep-rooted shrub or tree suitable for cut-and-carry green manuring. Best adapted to areas below 500 m elevation with 500-2000 mm rainfall. Needs good drainage and a soil pH of 5.0 or above. Can be seriously attacked by psyllid insects (jumping plant lice). Makes slow initial growth and is easily wiped out by weeds, termites, ants, and rodents. Growth becomes very rapid after the first few weeks and can reach 4-6 m in 12 months. Quickly regrows new foliage within 2-3 weeks. Its high-protein leaf forage contains mimosine which is toxic to non-ruminants unless fed at low levels. Some low-mimosine leaucaena varieties have been identified. Innoculation with leaucaena-specific rhizobia is sometimes recommended. However, the Nat. Academy of Sciences states that seed innoculation isn't normally needed even when leucaena is planted on new ground, especially if other leguminous trees like Calliandra, Gliricidia, Sesbania, and Mimosa are present; however, specific rhizobia strains for Leucaena are now available. Seed scarification is needed for good germination, due to the hard seed coat. Other uses: firewood, edible seeds, poles, reforestation, living fence. Can become an aggressive weed.

Mimosa scabrella: Rapid-growing thornless tree used for firewood, beautification, live fencing, and cut-and-carry green manure. Can reach 5 m height in 14 months. Native to the cool subtropical savanna of S.E. Brazil but can grow in warmer areas; stunted by wet soils. Good nitrogen fixer.

Sesbania bispinosa (Prickly Sesban): Quick-growing shrub up to 4 m tall that can produce firewood in 6 months. Good drought tolerance but does best at 550-1100 mm rainfall and up to 1200 m elevation. Good tolerance of saline and alkaline soils. Tolerates wet soils but not long periods of waterlogging. Palatable to cattle. Suitable for cut-and-carry green manuring. Can become an invasive weed due to its abundant seed production. Freely nodulates with cowpea rhizobia.

Sesbania grandiflora (Agati, Katurai, West Indian Pea Tree): Small, fast-growing tree up to 10 m tall. Used for firewood, reforestation, forage, food, and cut-and-carry green manure. Best adapted to rainfall over 1000 mm and elevations below 800 m. Adapted to wide range of soils; some tolerance to waterlogging. Very susceptible to nematodes. Young leaves, young pods, and giant flowers are popular vegetables in Asia. Established by seed. Freely nodulates with cowpea rhizobia group.

Sesbania sesban (Sesban): Fast-growing, short-lived shrub 4.5-6 m tall used for wood, forage, food, and green manure. Requires 350-1000 mm rainfall. Tolerates acid soils, saline soils, and periodic waterlogging. Forage is very palatable. Regrows readily after cutting. Flowers, leaves, and seeds are edible for humans; seeds require soaking and cooking to remove a toxin. Widely used in the tropics as a green manure for rice and should be turned under at least 3 weeks before transplanting. In double-crop rice areas, it can be interplanted at a late stage of the first crop and then used as a green manure for the second crop.

 

Appendix G: Some sources of technical support

• The International Agricultural Research Institutes

• Private and Voluntary Organizations (PVO's)

I. THE INTERNATIONAL AGRICULTURAL RESEARCH INSTITUTES

In the early 1960's, the growing realities of the world food problem helped stimulate worldwide interest in the agricultural and nutritional dilemma faced by the developing countries. There are now some 9 major international research institutes dealing with food crops in developing countries and 2 dealing mainly with livestock. Most of them were initially sponsored by international foundations like Ford, Rockefeller, and Kellogg. However, in 1971 the Consultative Group for International Agricultural Research (CGIAR) was formed to provide broad-based financial support for the institutes. The CGIAR is jointly sponsored by the Food and Agric. Org. (FAO), the International Bank for Reconstruction and Developuent (IBRD), and the United Nations Development Program (UNDP).

Role of the International Institutes

• To undertake multidisciplinary, field-oriented research for developing yield-increasing technologies.

• To cooperate with appropriate national crop and livestock improvement programs in the developing countries; this includes training programs, providing new varieties for field testing, and supplying professional personnel.

• To collect and preserve crop and livestock genetic material vital for the development of improved varieties and stock.

• To provide training programs for agricultural personnel from developing countries.

Due to the many variations in soils, climate, and pests, etc., the development of suitable improved technologies is a very location-specific endeavor that requires adaptive research on a region-by-region basis within each country. Unfortunately, such country-sponsored efforts tend to be the weak link in the system, because they are often underfinanced and understaffed.

How to Utilize the International Institutes

Some suggestions:

• Your first contact should be to request the institute's brochure describing its activities. Also request a catalog of their publications. These institutes are one of the best sources of up-to-date research and production information. Some excellent troubleshooting guides are available for specific crops like maize (CIMMYT), millet/ sorghum (ICRISAT), rice (IRRI), and beans/cassava (CIAT). (Some of these are available through PC/ICE; refer to Appendix H.)

• The institutes are not set up to respond to general queries regarding appropriate production information for your specific area. They operate with a limited staff.

• Check with your Ministry of Agriculture to see what cooperative research efforts are being conducted in your country with the help of the international institutes.

• Most of the institutes offer short and long-term training courses which might be of great value to research and extension personnel in your area. Perhaps you could help a host country extension worker or technician obtain a scholarship or government grant for such training.

Major International Research Institutes

Funded by CGIAR

CIAT: The International Center for Tropical Agriculture focuses on beans, cassava, maize, rice, and tropical pastures. Address: Apartado Aereo 6713, Cali, COLOMBIA, S.A.

CIMMYT: The International Maize and Wheat Improvement Center Address: Londres 40, Apdo. Postal 6-641, Mexico, D.F.

CIP: The International Potato Center is conducting innovative research in potato breeding, storage, alternative propagation practices (i.e. other than using seed pieces), warm weather adaptation, and other areas. Address: CIP, Apartado 5969, Lima, PERU, S.A.

ICARDA: The International Center for Agric. Research in Dry Areas focuses on chickpeas, pigeonpeas, and other arid land crops. Address: P.O. Box 5466, Aleppo, SYRIA.

ICRISAT: The International Crops Research Institute for the Semi-arid Tropics, focuses on millet, sorghum, peanuts, chickpeas, peanuts, and pigeonpeas. It has recently established a Sahelian center in Niger, West Africa for work on millet and peanuts. Address: Patancheru P.O., Andhra Pradesh, 502-324, INDIA.

IITA: The International Institute for Tropical Agriculture focuses on maize, pulses, rice, and root and tuber crops. Address: P.M.B. 5320, Ibadan, NIGERIA.

ILCA: The International Livestock Center for Africa works mainly in the area of integrating Livestock and crop production, and also does breeding work. Address: P.O. Box 5689, Addis Ababa, ETHIOPIA.

ILRAD: The International Laboratory for Research on Animal Diseases focuses on the eradication of trypanosomiasis (sleeping sickness) and theileriosis. Address: P.O. Box 30709, Nairobi, Kenya.

IRRI: The International Rice Research Institute developed the first high-yielding, semidwarf rice varieties back in the 1960's. Now it's focusing on developing types that need fewer production inputs. Address: P.O. Box 933, Manila, PHILIPPINES.

WARDA: The West Africa Rice Development Association works to promote rice selfsufficiency in 15 countries in West Africa. Address: P.O. Box 1019, Monrovia, LIBERIA.

Non-CGIAR Supported International Research Centers

AVRDC: The Asian Vegetable Research and Development Center focuses on tomatoes, Chinese cabbage, peppers, sweet potatoes, soybeans, and mungbeans. Address: P.O. Box 42, Shanua, Tainan, 741, TAIWAN, Republic of China.

ICRAF: The International Council for Research on Agroforestry. Address: P.O. Box 30677, Nairobi, Kenya.

IRIWB: The International Research Institute for Winged Beans, recently established in Sri Lanka. Address unavailable.

NFTA: The Nitrogen Fixing Tree Association promotes the use of N-fixing trees for Third World small farmers for the purpose of green manure, erosion control, firewood, and timber. Annual membership is U.S. $10 (developed countries and U.S. $5 (Third World). Members receive 2 research journals ("Leucaena Research Reports" and "Nitrogen Fixing Tree Research Reports"), 6-10 "NFTA

Highlights" (focusing on tree species), and 2 issues of "NFTA News". Other publications include "Leucaena Wood Manual" and "Leucaena Forage Manual". Address: NFTA, P.O. Box 680, Waimanalo, Hawaii, USA 96795. Tel. (808) 259-8685.

WINROCK INTERNATIONAL: Created in 1985 through a merger of the Internat. Agric. Devel. Service, the Winrock Internat. Livestock Research and Training Ctr., and the Agric. Development Council. It is involved in crop and livestock research/extension programs throughout the Third World. Headquarters address: Route 3, Morrilton, AR 72110, USA; Washington address: Rosslyn Plaza, 1611 N. Kent St., Arlington, VA, USA 22209.

II. PRIVATE AND VOLUNTARY ORGANIZATIONS (PVO's)

Several PVO's provide unusually good technical support services for grass-roots agricultural development efforts.

ECHO: The Educational Concerns for Hunger Organization, Inc. is a non-denominational Christian organization that works with ag missionaries and other ag development workers. ECHO actively promotes grass-roots ag experimentation and technical networking. It publishes Echo Development Notes (EDN) at least quarterly, which provides very relevant technical information on small farmer crop and livestock production. EDN also serves as a valuable technical information clearinghouse and informs readers of useful references and sources of technical support. EDN is sent to Peace Corps country offices; for others involved in Third World ag development, a subscription is free. A set of back issues since 1981 costs $10, postage paid and is well worth it. ECHO also maintains a seedbank and will send small trial packets. It welcomes visitors at its experimental/demo farm. ECHO intends to develop auto-tutorial ag training materials. Address: ECHO, RR #2, Box 852, North Ft. Meyers, FL 33903, USA; telephone (813)543-3246.

VITA: Volunteers in International Technical Assistance is a private, nonprofit, international development organization that provides a number of informational and technical services (by mail and through on-site consulting) that promote self-sufficiency. VITA's main areas of focus are agriculture, food processing, renewable energy, water supply and sanitation, housing, construction, and small business development. It also publishes a quarterly magazine and a variety technical papers, manuals, and bulletins. Address: VITA, 1815 N. Lynn St., Suite 200, Arlington, VA 22209, USA.

WORLD NEIGHBORS: A non-sectarian, international development organization that promotes grass-roots, self-help initiatives utilizing local leaders and local volunteers. They have developed an impressive collection of books, manuals, filmstrips, and flipcharts on agriculture, health, nutrition, family planning, and community development; these materials are available in English, French, and Spanish and are designed especially for comprehension by villagers in the Third World. World Neighbors produces 2 newsletters: 1) World Neighbors in in Action, a quarterly how-to-do-it newsletter for $5 a year (airmail postage); 2) Soundings from Around the World, a twice-yearly communications exchange newsletter that reviews World Neighbors' development materials. A catalog of their materials is available on request. Address: World Neighbors, 5116 North Portland Ave., Oklahoma City, OK 73112, USA; telephone (405)946-3333.

 

Appendix H: A bibliography of useful references

NOTE: The International Research Institutes listed in Appendix G have some excellent references and troubleshooting guides available. The following catalog is a comprehensive guide to their publications and costs about $10 (U.S. ) :

Publications on Internat. Agric. Research and Development, 1983, GTZ-CGIAR-IRRI, available from the Agribookstore, Winrock International, 1611 N. Kent St., Arlington, VA 22209, USA.

AGRICULTURAL EXTENSION AND DEVELOPMENT

Africa in Crisis, L. Timberlake, 1985, Earthscan, 1717 Massachusetts Ave. NW, Washington, DC 20036.

Agricultural Extension, Manual M-18, PC/ICE, 1983.

Coming Full Circle: Farmers' Participation in the Development of Technology, P. Mation et. al., 1984, available from Agribookstore, Winrock International, 1611 N. Kent St., Arlington, VA 22209, USA. $12.15.

Planning Technologies Appropriate to Farmers, D. Byerlee, 1980, available from Agribookstore (same address as above). $7.60.

Two Ears of Corn, Roland Bunch, World Neighbors, 5116 N. Portland, Oklahoma City, OK 73112. 2nd ea., 1985. Cost: $7.50 plus postage ($0.50 overseas surface, $5 overseas air. Also available through PC/ICE as publication AG-49.

AGROFORESTRY (See also Windbreaks)

Agroforestry in the Sahel, Fred Weber and Marilyn Hoskins, Virginia Polytechnic Institute and State Univ., 1983. Available through PC/ICE as publication FC125

Agroforestry In-Service Training, PC/ICE manure T-16, 1984.

Casuarinas: Nitrogen-Fixing Trees for Adverse Sites, 1984, National Research Council. Available from Nat. Academy Press, 2101 Constitution Ave., Washington, DC 20418, USA. Also available from PC/ICE as publication FC46.

Forestry for Food Collection, Food and Agric. Org., United Nations, 1979. Reprinted by PC/ICE as publication FC35.

Leucaena: A Promising Forage and Tree Crop for the Tropics, 2nd ea., 1984, National Academy of Sciences, available from Nat. Academy Press, 2102 Constitution Ave., Washington, DC 20418, USA. Also available from PC/ICE as publication FC15.

Proceedings of the Kenya National Seminar on Agroforestry, International Council for Research in Agroforestry, 1981. Available from PC/ICE as publication FC86

Workshop on Agroforestry Systems in Latin America, CIAT, 1979. Reprinted by PC/ICE as publication FC87.

CROP AND FORAGE PRODUCTION Field Crops (General reference)

Guide for Field Crops in the Tropics and Subtropics, USAID, 1976. Reprinted by PC/ICE as publication R-10.

Handbook of Tropical Food Crops, ed. by F. Martin, 1984. Covers cereals, pulses, root crops, vegetables, and fruits. CRC Press, 2000 Corporate Blvd. N.W., Boca Raton, FL 33431, USA. $94.50.

Traditional Field Crops, PC/ICE Manual M-13, 1981. Covers maize, sorghum, millet, cowpeas, beans, peanuts.

Cereal Crops

A Farmer's Primer on Growing Rice, IRRI, 1979, available from UNIPUB, 345 Park Ave. S., New York, NY 10010, USA.

Modern Corn Production, Aldrich and Leng, 2nd. ea., 1978. Available from Thompson Publications, Box 9335, Fresno, CA 93791, USA.

Pearl Millet, Rachie and Majmudar, Penn. State Univ., 1980.

Training Manual for Rice Production, IRRI, 1976, available from UNIPUB, 345 Park Ave. S., New York, NY 10010, USA.

Legumes (for food)

Food Legumes, Crop and Product Digest #3, 1979; Tropical Products Institute, 56/62 Grays Inn Rd., London WC1X8LU, U.K. Also available from PC/ICE as publication A&85.

Modern Soybean Production, Scott and Aldrich, 1979, Thompson Publications, Box 9335, Fresno, CA 93791, USA.

Tropical Legumes: Resources for the Future, 1979, National Academy of Sciences, Printing and Pub. Ofc., 2101 Constitution Ave., Washington, DC 20418. Available from PC/ICE as publication AG21. Covers leguminous root, pulse, fruit, and tree crops.

The Winged Bean: A High-Protein Crop for the Tropics, 1981 Nat. Academy of Sciences; available from Nat. Academy Press, 2101 Constitution Ave., Washington, DC 20418, USA.

Mixed Gardening and Fruit Trees

Handbook of Tropical Fruits and Spices, H. Bittenbender, 1984, Dept. of Horticulture, Michigan State Univ., East Lansing, MI 48824, USA..

The Propagation of Tropical Fruit Trees, R. Garner, 1976, Commonwealth Agric. Bureau, Central Sales, Farnham Royal, Slough, SL2 3BN, UK. Cost: $32.75 + $12 overseas airmail. Available free from PC/ICE as publication FC111 only on a single-copy basis to PC offices/resource centers.

Techniques and Plants for the Tropical Subsistence Farm, 1980, Mayaguez Instit. of Tropical Agric., P.O. Box 70, Mayaguez, Puerto Rico 00708. Available from PC/ICE as publication AG40.

Tropical Horticulture for Secondary Schools, Book Two, PATS Educational Foundation of Mirconesia, P.O. Box 39, Ponape, Caroline Islands 96941. Has sections on banana, breadfruit, and coconut.

The UNICEF Home Gardening Handbook, P. Sommers, 1981, UNICEF, United Nations. Available from PC/ICE as publication AG 66.

Pastures

A Guide to Better Pastures for the Tropics and Sub-tropics, 4th ea., L.R. Humphreys, 1980. Available for about $5 from Public Sales Officer, Tropical Grassland Society of Australia, 306 Carmody Rd., St. Lucia, Queensland 4067, Australia. Covers pasture management and specific pasture grasses and legumes.

Better Pastures for the Tropics, 1975, Arthur Yates and Co., P.O. Box 72, Revesby, NSW 2212, Australia. $5. Covers pasture management and specific pasture grasses and legumes.

Root Crops

Cassava Cultural Practices, 1980, Internat. Devel. Research Center, P.O. Box 8500, Ottawa, Canada K1G 3H9.

Tropical Horticulture for Secondary Schools, Book Two, PATS Educational Foundation of Micronesia, P.O. Box 39, Ponape, Caroline Islands 96941. Has section on sweetpotatoes, taro, yam, and cassava.

Tropical Root Crops: Production and Uses in Africa, 2nd Symposium of the Internat. Soc. for Tropical Root Crops, available from Agribookstore, Winrock International, 1611 N. Kent St., Arlington, VA 22209, USA. $15.00.

Vegetables

All about Tomatoes, Ortho Books, 1981, Chevron Chemical Co., 575 Market St., San Francisco, CA 94105, USA.

Amaranth: Modern Prospects for an Ancient Crop, 1984, Nat. Research Council; available from Nat. Academy Press, 2101 Constitution Ave., Washington, DC 20418, USA.

Gardening for Better Nutrition, A. Pacey, 1978, Intermediate Technology Publications, 9 King St., London WC2E 8HN, UK. Available through PC/ICE as publication AG74

Getting the Most from Your Garden, 1980, Rodale Press, Emmaus, PA 18049, USA. . Available from PC/ICE as publication AG 75 only to PC offices/resource centers.

Growing Vegetables in Fiji, Kirk Dahlgren, 1982, 120 pp. Available as a reprint from ECHO, RK #2, Box 852, North Ft. Meyers, FL 33903, USA. $4.00 per copy plus postage ($1.00 overseas surface, $3.50 overseas air).

Guide to Vegetables and Fruits, 1982, Rodale Press, Emmaus, PA 18049, USA.

Handbook of Tropical Vegetables, H. Bittenbender, 1983, Dept. of Horticulture, Michigan State Univ., East Lansing, MI, 48824, USA.

Knott's Handbook for Vegetable Growers, Lorenz and Maynard, 2nd ea., 1980, John Wiley and Sons, New York. Available from PC/ICE.

Tomatoes in the Tropics, R. Villareal, 1980, Westview Press, Boulder, Colorado. Also available fro. the Agribookstore, Winrock International, 1611 N. Kent St., Arlington, VA 22209.

Tropical Horticulture for Secondary Schools, Book One, 2nd. ea., 1975, P.E.A.C.E. Foundation, 40 E. 49th St., New York, NY 10017. Available through PC/ICE as publication AG86.

Tropical Leaf Vegetables in Human Nutrition, Oomen & Grubben, 1977, Koninklijk Instituut voor de Tropen, Amsterdam, the Netherlands. Available from PC/ICE as publication AG88.

Vegetable Growing Handbook, W. Splittstoesser, 1979, AVI Publishing Co., Westport, Connecticut, USA.

Vegetables for the Hot-Humid Tropics, Martin, 1978, Mayaguez Tropical Agric. Research Service, P.O. Box 70, Mayaguez, Puerto Rico 00708, USA. Available from PC/ICE as publication AG 140. Covers amaranth, chaya, eggplant, pepper, okra, winged bean.

Vegetables in the Tropics, H. Tindall, 1983, AVI Pub. Co., 1983. Available free from PC/ICE as publication AG29 only to PC offices/resource centers.

IRRIGATION

Drip Irigation, Publication 2740, Univ. of Cal. Agr. Expt. Station, available from ANH Publications, Univ. of California, 6701 San Pablo Ave., Oakland, CA 94608-1239. $1.00.

Drip Irrigation Management, Publication 21259, Univ. of Cal. Agr. Expt. Station, same address as above. $3.75.

Improving Irrigated Agriculture, World Bank Staff Working Paper #531, World Bank, 1818 H St. N.W., Washington, DC 20433, USA.

Irrigation Principles and Practices, PC/ICE Manual R-5, 1969.

Small Scale Irrigation, Peter Stern, International Technology Publications Ltd., address unknown.

The following 4 publications are available from the Water Management Synthesis Project, University Services Center, Colorado State University, Ft. Collins, CO 80523, USA:

Land Levelling Planning Guide #1, D. Lattimore, 1981.

Small Farm, Self-Help Irrigation Projects, Planning Guide #5, Embry and Adams, 1983.

Water Management on Small Farms: A Training Manual for Farmers in Hill Areas, L.J. Salazar, 1983.

Water Management on Small Farms: A Training Manual for Farmers in Hill Areas: Instructor's Guide, L. Salazar, 1983.

SOIL CONSERVATION, WINDBREAKS General Soil Conservation

A Manual on Conservation of Soil and Water, USDA, 1954. Available as reprint R-38 from PC/ICE.

Conservation in Arid and Semi-arid Zones , F.A.O. Conservation Guide #3, 1976. Available through PC/ICE as publication FC02.

Manual of Reforestation and Erosion Control for the Philippines, published by the German Agency for Technical Cooperation, 1976 but available from PC/ICE as a reprint.

Windbreaks (See also Agroforestry)

Agroforestry in the Sahel, Fred Weber and Marilyn Hoskins, Virginia Polytechnic Institute and State Univ., 1983. Available through PC/ICE as publication FC125.

Conservation in Arid and Semi-arid Zones, listed under Soil Conservation.

Environmentally Sound Small-scale Forestry Projects, CODEL/ VITA, 1983. Available from PC/ICE as publication FC123.

Eucalypts for Planting, Forestry Series No. 11, Food and Agric. Org., United Nations, 1979. Available free through PC/ICE as publication FC122 only to PC offices/resource centers.

Firewood Crops, Vols. I and II, National Acad. of Sciences, 1980. Available through PC/ICE as publications FC42, FC46.

Reforestation in Arid Lands, Peace Corps/ICE Manual M-$, 1976. Available in English or French.

SOIL MANAGEMENT AND FERTILIZER USE

Hunger Signs in Crops, H. Sprague, 1979, David McKay Co., New York, USA.

The Nature and Properties of Soils, N. Brady, 8th ea., 1974, Macmillan Pub. Co., New York, USA.

Organic Farming: Current Technology and its Role in a Sustainable Agriculture, Amer. Soc. of Agronomy Special Pub.

#46, 1984, Amer. Soc. of Agronomy, 677 S. Segoe Rd., Madison, Wisconsin 53711, USA.

Southern Gardener's Soil Handbook, W. Peavy, 1979, Pacesetter Press, Box 2608, Houston, TX 77001, USA.

Western Fertilizer Handbook, 1982, Interstate Printers & Publishers, Danville, IL 61832. Available from PC/ICE as publication AG44.