Bio-Intensive Household Food Production - Chapter 3 - Soil Management

Know your soil

Which crops will do well in your garden soil? Aside from trial and crop failure - an expensive proposition at best - testing the soil is the only way to find out. Generally, there are three soil types:

Neutral Soil (pH 7)

Most common vegetables, fruits and flowers do best on soils that have a pH of 6.5 to 7 - slightly acid to neutral.

Soils in this pH range offer the most favorable conditions for microorganisms that convert atmospheric nitrogen into a form available to plants.

This also creates the best environment for bacteria that decompose plant tissue and form humus.

All of the essential mineral nutrients are available to plants at this level.

This soil has good filth because a good crumb structure is easily maintained.

Neutral Soil

Alkaline Soil (pH 7-11)

Very alkaline soil robs nutrients from growing plants.

It ruins soil structure. 

It also breaks humus apart and causes a concentration of salts which inhibit or prevent plant growth.

Alkaline Soil

Recommendations:

1. Alkaline pH can be lowered to the neutral range by adding organic materials.

2. If the garden is located in an area with low rainfall, the high soil pH is probably linked to accumulated salts. These can be flushed below the root zone of sensitive plants (such as beans, carrots, onions and peppers) by watering regularly with non-saline water.

Acid Soil (pH 1 to 6.5)

Bacteria that decompose organic matter cannot live when the soil is too acidic.

Organic matter level gradually declines, resulting in poor soil structures.

Manganese and aluminum can become toxic to plants because these elements are very soluble in highly acidic soils.

Worse, strong acidity limits nutrient availability to plants.

Acid Soil

Recommendations:

1. pH can be raised by working in bone meal, pulverized egg shells, clam shells, oyster shells or a form of fineground agricultural lime. Unleached hardwood ashes are another good material for neutralizing acidic veils.

2. If soil test reveals magnesium deficiency, use the dolomitic form of lime. If calcium is low, choose the calcitic type.

3. Spread the liming material after the soil has been plowed, tilled or spaded deeply. Do not plow the lime under since it leaches down into the soil too rapidly.

4. It is best not to apply lime with other fertilizers.

5. Do not apply lime around acid-loving plants or in any area where runoff water may carry the lime downhill to such plants.

6. When using ground limestone, do not expect a tremendous difference on the first year of application. Changes can be seen only on the second year. Repeat liming every fourth or fifth year, depending on the results of soil tests.

Reference:

Quick Ways To Better Soil. 1990. Organic Gardening Magazine.

Discovering your soil type firsthand

Discovering your soil type firsthand

Soil modifiers

Dolomitic lime

A good source of calcium and magnesium to be used when both are needed. Do not use lime to "sweeten" a compost pile as doing so will result in a serious loss of nitrogen. A layer of soil will discourage flies and reduce odors.

High Calcium Lime (Calcite)

A good source of calcium when magnesium levels are too high. Oyster shell flour lime is a good substitute.

Gypsum (Calcium Sulfate)

Used to correct excess levels of exchangeable sodium. Apply only upon recommendation of a professional soil test.

Crushed Eggshells

High in calcium, especially good for cabbage family crops. Eggshells help break up clay and release nutrients tied up-in alkaline soils. Use up to 1 kg/12 sq m.

Manure (All Types)

A good source of organic matter in the garden. The nutrient levels in each manure will depend on proper management of the curing process and on the amount of straw or sawdust in the manure. Optimally, do not use more than 62 kg of aged manure per year (about 12.7 mm layer). It is best to use manure that contains little undecomposed sawdust. Approximately 23 kg of dry manure applied per 12 square meter can lower the pH one point.

Manures-Solids (Approximate)	N	P	K
Chicken-Fresh	1.50%	1.00%	0.50%
Chicken-Dry	4.50%	3.50%	2.00%
Dairy Cow	0.56%	0.23%	0.60%
Horse	0.69%	0.24%	0.72%
Pig-Fresh	0.50%	0.32%	0.46%
Sheep	1.40%	0;48%	1.20%
Steer	0.70%	0.55%	0.72%

Compost

A good compost is the most important component of garden beds. It aerates soil, breaks up clay, binds together sand, improves drainage, prevents erosion, neutralizes toxins, holds precious moisture, releases essential nutrients and feeds the microbiotic life of the soil, creating healthy conditions for natural antibiotics, worms and beneficial fungi. Use 25 mm of compost each year (124 kg/12 sq m) or up to 75 mm in a first-year garden. Manure may be substituted for compost the first year if you do not have a ready supply of compost.

Source: Jeavons. J, 1991 How to grow more vegetables. 

Nutrient composition of various organic materials

Organic Matter	% Nutrient Content
Animal Wastes	N	P	K
Cattle	1.50	1.00	0.94
Water buffalo	1.09	0.82	0.70
Horse	159	1.65	0.65
Sheep	2.02	1.75	1.94
Pig	2.81	1.61	1.52
Rabbit	2.40	1.40	0.60
Chicken	4.00	1.98	2.32
Duck	2.15	1.13	1.15
Bat	1.00-12.00	2.25-16.00
Crop Residues
Tobacco stem	3.70	0.65	4.50
Tomato stem	0.35	0.10	050
Wheat straw	0,49	0.11	1.06
Rice straw	0.58	0.10	1.38
Corn stover	0.59	0.31	1.31
Cotton stalks $ leaves	0.88	0.15	1.45
Peanut roots	1.18	0.07	1.28
hulls	1.75	0.20	1.24
Cowpea stems	1.07	1.14	2.54
roots	1.06	0.12	1.50
Sugarcane trash	0.35	0.04	0.50
Banana skin (ash)	-	3.25	41.76
Banana stalk	-	2.34	49.40
N-fixing Trees (Leaves)
Leucaena leucocephala	4.29	0.19	1.37
Acacia ferruginea	2.96	0.13	0.88
Acacia arabica	2.61	0.17	1.20
Gliricidia sepium	1.81	1.80	21.85
Sesbania acullata	2.18	-	-
Sesbania speciosa	2.51	-	-
Crotolaria juncea	1.95	-	-
Crotolaria usarmoensis	5.30	-	-
Vigna sinensis (cowpea)	3.09	-	-
Melitotus indica	3.36	0.22	1.27
Pisum sativum (pea)	1.97
Desmodium trifolium	2.93	0.14	1.30
Calopogonium mucunoides	3.02	-	-
Water hyacinth	2.04	0.37	3.40
Azolla sp	3.68	0.20	0.15
Algae	2.47	0.12	0.37
Other Composting Materials
Ground bone (burned)		34.70
Eggshell	-	0.43	0.29
Feathers	-	15.30
Molasses	0.70	-	4.50
Wood ashes	-	1.00-1.50	1.00-3.00
Compost
Municipal*	0.40- 1.60	0.10-0.40	0.20-0.60
Garbage**	0.40-4.00	0.20- 1.30	0.20-2.10
Garden	1.40-3.50	0.30- 1.00	0.40-2.00

* Includes garbage, paper, household and yard trash
** Food wastes

Composting

This process involves decomposition of a mixture of organic materials to form "smaller bits" of matter called compost. This process does not solely refer to waste disposal; it also relates to the return of wastes to the soil as part of the cycle of life.

Figure 1: Most human intervention results in wastes dumped in waterways rather than resumed to the land.

Decomposers:

Majority of decomposers are microorganisms. Macroorganisms such as earthworms, termites and other insects also help break down organic materials.

Figure 2: Food web of the compost pile (D. Dindal)

Composting Parameters

1. Composting materials

a. Good quality compost contains high organic matter content and a minimum of non-organic material. Some compostable wastes, particularly from industrial areas, can contain high levels of metals such as copper, lead, nickel and zinc and should therefore be removed. Other non-organic materials such as glass, plastics and artificial fibers should also be removed. 

b. Succulent and young plants can be decomposed much faster than old and tough ones because they are high in water and contain relatively more sugars. 

c. If possible, use materials that are high in N. such as residues from leguminous plants because they are preferred by microorganisms since they provide both C and N. They are also easier to break down. The insects, worms, bacteria and fungi found in the compost pile do the work of composting.

Composting materials

2. Particle size - The smaller the size of the particles of organic material, the greater surface area available for attack by the microorganisms. If the particle size is very large, the surface area for attack is smaller, and the reaction will then proceed slowly or may stop altogether. It is necessary to chop or shred bulky material to reduce the particle size to a range of 10-50 mm.

3. Moisture - All organisms require water for life. The optimum moisture content of ingredients for composting is 50-60 percent. At too low a moisture content, the biological reactions in a compost heap slow down considerably. Excess water on the other hand, leads to waterlogging of the spaces between the particles of the materials. The maximum practical moisture content depends on the structural wet strength of the materials. For practical purposes the material should be as damp as a squeezed-out sponge.

4. Aeration - An adequate supply of air to all parts of a compost heap is essential in order to supply oxygen for the organisms and to flush out the carbon dioxide produced. Absence of air (anaerobic conditions) will lead to the development of different types of microorganisms causing either acidic preservation or putrefaction of the heap, producing bad odors.

Aeration is achieved through the natural movement of air into the compost heap, by turning the material over regularly.

5. Temperature - When organic material is gathered together for composting, some of the energy released by the breakdown of the material is given off as heat. This causes a rise in temperature. The higher the temperature within certain limits, the faster the activity of microorganisms.

At the beginning of the process the material is at ambient temperature. In the first stage, warming up, the microorganisms present on the materials multiply rapidly and the temperature rises. During this period all the very reactive compounds such as sugars, starches, and fats are broken down. When the temperature reaches 160°F the fungi stop working and the breakdown is continued by actinomycetes and spore-forming strains of bacteria. The breakdown slows and the temperature peak is reached. At this period, the heap is losing as much heat as the microorganisms produce.

When cooling down, the straws and stalks are decomposed, mainly by fungi. This is because as the temperature falls below 160° F the fungi re-invade from the cooler regions of the heap and attack less reactive compounds such as hemicelluloses and cellulose, breaking them down into simpler sugar compounds, which become available for all the other microorganisms. The actinomycetes also help during this period. At the end of the cooling down period most of the available food supply has gone, competition starts among the microorganisms, antibiotics are released, and larger soil organisms, especially worms, move in for a few weeks.

The increase in temperature is one of several factors in the composting process which act against the survival of pathogenic organisms. Table 1 shows that the common pathogens which cause diseases in humans and domestic animals are readily destroyed at temperatures of 55 to 60°C for periods of a few minutes to a few hours under the moist conditions used in composting.

Experimental Compost Data

Temperature Comparison

Ideal Temperature Curve

Table 1. Pathogen survival in composting and agricultural application of human wastes

Organism	Survival in: Composting	Agricultural Application
Enteric viruses	Killed rapidly at 60°C	May survive up to 5 months on soil
Salmonellae	Killed in 20 hours at 60°C	On soil, S. typhi up to 3 months;  other species up to 1 year
Shigellae	Killed in 1 hour at 55°C or in 10 days  at 40°C	Up to 3 months
E. cold	Killed rapidly above 60°C	Several months
Cholera vobrio	Killed rapidly above 55°c	Not more than 1 week
Leptospires	Killed in 10 minutes at 50°C	Up to 15 days on soil
Hookworm ova	Killed in 5 minutes at 50°C and 1  hour at 45°C	Up to 20 weeks on soil
Ascaris ova	Killed in 2 hours at 55°C 20 hours  at 50°C and 200 hours at 45°C	Several years
Schistosome ova	Killed in 1 hour at 50°C	Up to 1 month, if damp

Source: Health Aspects of Excreta and Sillage Management, World Bank, 1980. 

6. Acidity (pH) - Compost material becomes slightly acidic at the start of composting due to the simple organic acids produced at the initial phase of decomposition. The heap then turns slightly alkaline after a few days as proteins are attacked and ammonia is released. Highly alkaline conditions will lead to excessive loss of nitrogen as ammonia; accordingly it is wise not to add lime to a heap. Highly acid initial conditions may lead to a failure of the heap to warm up. If careful attention is paid to the mixing of materials, moisture content and aeration, there is no necessity to influence the pH of the process. The amount of ammonia lost from a compost heap can be reduced by adding a little soil, about 1% of the weight of the heap.

7. Nutrients - The composting process depends upon the action of microorganisms which require a source of carbon to provide energy and material for new cells, together with a supply of nitrogen for cell proteins. Nitrogen is the most important nutrient and, in general, if sufficient nitrogen is available in the original organic matter, most other nutrients will also be available in adequate quantities. It is desirable that the ratio of carbon to nitrogen (C/N) is in the range of 30-35/l in the initial mixture. If it is much higher, the process will take a long time before sufficient carbon is oxidized off as carbon dioxide, if it is lower, then nitrogen, which is an important fertilizer component of the final compost, will be given off as ammonia. The simplest method of adjusting the C/N ratio is to mix together different materials of high and low carbon and nitrogen contents. For example, straw materials which have a high C/N ratio can be mixed with materials such as manures which have low C/N ratio.

References:

Bautista, O.K. et al. 1983. Introduction to Tropical Horticulture. pp. 205-206

Cosico, W.C. 1985. Organic Fertilizers: Their Nature, Properties and Use. pp. 39 - 50

Dalzell, H.W. et al. 1987. Soil Management: Compost Production and Use in Tropical and Subtropical Environments. FAO Soils Bull. 56: 22-27,162.

Conventional method of compost preparation

1. Choose a spot that is at least partially protected from rain.

2. Gather the crop residues, animal manures and other wastes and bring them to the preparation site.

3. Pile the crop and other plant residues (15 cm thick) first. For the next layer, spread the animal manure to a thickness of about 8 cm, followed by about 3 cm of good soil. Pile another layer of the materials in the same sequence and repeat until a height of about 1.5 meters of the compost pile is attained.

4. Water the pile until it is sufficiently moist. Water regularly.

5. Turn over or mix the pile with spading fork after 3 weeks, then again after five weeks.

6. Harvest the compost in three to four months.

Conventional method of compost preparation

The 14-day method of composting

1. Chop the vegetative materials/plant wastes (dry or green or both).

2. Thoroughly mix these with an equal amount of fresh manure.

3. Pile the mixture into a heap measuring at least 1 m × 1 m × 1 m. (However, 1 m is the maximum height.)

4. Cover the heap with banana leaves or damaged burlap sacks.

5. By the third or fourth day, the inside of the heap should be heated up. If not, mix more manure into it.

6. On the same day (3rd or 4th), turn the heap inside out so that the materials from the center will appear outside and vice versa.

7. Turn the heap every two days thereafter.

8. In 14 - 18 days, the compost should be ready for use.

The 14-day method of composting

Composting in triple-compost bin

Making three compartments permits us to keep adding to our compost pile. The compartment at left is ready for the fields while the others are still rotting.

1. Fill compartment one with composting materials.

2. Add a small amount of soil or animal manure.

3. Continue in this way till the compartment is full.

4. After a month, empty the contents of compartment one into compartment two, mixing, watering and breaking up the compost in the process

5. Cover the second compartment with a layer of soil, which has to be kept humid and loose.

6. Once compartment one is empty, the process of filling it should begin again as before.

7. After another month, fill compartment three with the contents of compartment two, airing the contents well without turning over.

8. Cover the third compartment with a layer of soil.

9. Fill compartment two with the contents of compartment one and cover with soil.

10. Fill compartment one with refuse and the cycle goes on.

Composting in triple-compost bin

Deep bed composting

Garden Layout

Cross-section of Composting Bed

Bed Construction

Lay out garden beds at least 12 cm wide.

Dig trench 8 cm wide and 5 cm deep along center line of bed. Place spoil (dirt from trench) on both sides of trench.

Bed Construction

Addition of Organic Materials

Place 15 - 30 cm layer of leguminous leaves and other vegetative materials.

Spread layer of animal wastes over vegetative materials.

Cover with layer of soil. Use ½ of spoil pile along side of trench.

Pile another layer of the materials in the same sequence, returning all of spoils in or on trench.

Shape bed by raking.

Planting

Soak bed thoroughly with water.

Plant seeds or transplant seedlings around the trench.

After harvesting, remove the contents of the trench and work the compost into the soil around the trench. Place new compost materials in the trench for the next crop.

Semi-sunken composting

1. Clean the area selected for building the compost pile. Dig a hole one-half meter deep.

Clean the area

2. Cut composting materials into small pieces. Mix them with manure at 5:1 ratio.

Cut composting materials into small pieces

3. Place the mixture in the hole until it reaches one to two meters above the ground. Use a shovel or your hands to keep the edges square.

Place the mixture in the hole

4. Cover the pile with straw or smear it with mud to protect it. Add a layer of soil on top of the pile and make a series of holes on top of the finished pile. The compost should be ready is 1 to 2 months.

Cover the pile

Basket composting

Basket composting is the process by which decomposable home garbage, garden and farm waste and leguminous leaves are allowed to rot in baskets half-buried in garden plots as a method of producing organic fertilizer.

Basket composting

Benefits

1. Basket compost can be used immediately without waiting for the usual 34 month period as is necessary in other methods of composting.

2. Baskets hold the composting materials in place, hence minimizing nutrient depletion by runoff.

3. Stray animals and fowls are prevented from scattering the compost materials.

4. Since garbage and wastes are collected and utilized, home and surroundings will become cleaner.

5. It serves as reservoir and collector of the moisture and nutrients.

6. More nutritious vegetables can be produced at less cost.

Preparation of Materials

Preparation of Materials:

Long bamboo strips, 2-3 cm in width.

Bamboo stakes at least 30 cm in length.

Home organic garbage, farm and garden wastes, leguminous leaves.

Manure.

Preparation of Garden Plots

Clean garden site, save weeds and grasses for composting.

Dig at least 30 cm deep and raise the bed.

Dig holes along the center of the plots at least 15 cm in depth and 30 cm in diameter.

Space them 1 m apart

Preparation of Garden Plots

Construction of Baskets

Drive 7 stakes around the holes; uneven number of stakes (5,7 or 9) makes perfect brace for weaving.

Weave the long strips of bamboo around the stakes to form a basket. Without bamboo strips, closely space the stakes (about 1 cm apart).

Construction of Baskets

Addition of Organic Wastes

Place the most decomposed garbage and manure into the basket first.

Place the undecomposed materials like leguminous leaves, grasses and weeds next.

Fill to the brim with other organic wastes.

Earthworms maybe added to speed up decomposition.

Addition of Organic Wastes

Planting and Care and Maintenance

Plant seeds or transplant seedlings around the basket. The distance from the basket should be 15 - 20 cm to prevent the decomposing materials from "burning" the plants.

Water the seedlings while young. Eventually just water the basket. The plant roots will later move toward it.

Planting and Care and Maintenance

Incorporation of Decomposed Materials into the Soil

After harvesting, composts are already used up. Remove the decomposed materials from the basket and incorporate them into the soil while cultivating.

Add new composting materials to the basket for the next plants.

Incorporation of Decomposed Materials into the Soil

Reference

Laquihon, W. A. and H. R. Watson. 1983. A Manual on FAITH Garden. MBRLC, Bansalan, Davao del Sur, Philippines.

Liquid fertilizer

Liquid fertilizer is made by immersing a sackload of fresh animal manure in a drum of water and allowing it to ferment. When used to water the plants, the "tea" makes possible the easy nutrient extraction by the plants. Depending on the availability of materials, animal manure can be substituted with fresh leaves of nitrogen-fixing trees like Leucaena (ipil-ipil) and/or Gliricidia (kakawate) or with green grass clippings and/or fresh weeds.

Preparation

1. Fill the burlap bag ¾ full of wet manure or fresh leaves or compost.

2. Tie the open end then place the bag info the empty drum (regular size, 55 gallon capacity).

3. Place a big stone to hold the bag down.

4. Fill the drum with water. Cover.

5. After 3 weeks, remove the bag from the drum.

6. Dilute solution at a ratio of 1 part liquid fertilizer to 4-6 parts fresh water.

7. Apply the liquid fertilizer around the base of the plant (avoid any direct contact with the plant) 2-3 weeks after germination or Immediately after transplanting. Repeat after 3-4 weeks.

8. Start over again with fresh materials following steps 1-6.

9. Smaller quantities of liquid fertilizer can be produced in smaller containers (if a 55-gallon drum is not available), using the same ratios.

Preparation

Fish emulsion as plant food for bio-intensive garden

Made from a blend of saltwater fish wastes, fish emulsion is a thick, gooey concentrate with about five percent nitrogen and small but significant amounts of trace minerals. It also contains a lot of fish oil. Most of the nitrogen in fish emulsion is present as amino acids from the breakdown of protein or as ammonia and nitrate. These amino acids can easily be absorbed by the leaves or roots. Diluted in water, fish emulsion can be either sprayed on leaves or poured around the base of plants.

Significant Findings from Research

1. Fish emulsion applied once a week to greenhouse soil stimulated vegetative growth and delayed flowering and fruit ripening in tomatoes by over a week. (Virginia Polytechnic Institute of State University in Blacksburg, Virginia)

2. Fish emulsion fertilizer added to the soil reduced nematode population. (Biological Testing and Research Laboratory, California)

Preparation

1. Put any kind of scrap fish or unused fish-parts in a glass jar or plastic container. Fill with water.

2. Cover the top with a cloth, securing firmly to keep out insects and animals.

3. Place the container in a storage bin and let it ferment for two to three months.

4. After this period, a layer of mineral-rich oil will float on top, water underneath and the bones and scales on the bottom. Skim off the oil and store in a container.

5. When ready to use, dilute one cup of oil with five gallons of water. The remaining sludge may be sun-dried and then mixed with the soil.

Preparation

(introduction...)

Green manuring is of special relevance to small gardens. It is a practice of using plants as source of organic matter incorporating them into the soil for decomposition before the planting of crops. Garden fertility can be sustained entirely on the nutrients from green leaves.

Nitrogen-fixing trees

Sources of Green Manures

1. Nitrogen-fixing trees - trees that fix nitrogen from the atmosphere. These can be intercropped with the main crop or used as fence. The leaves are incorporated into the soil or used as mulch.

Benefits

a. increases soil nitrogen

b. helps control weeds when used as intercrop

c. serves as windbreak/controls erosion

d. provides feed for livestock and firewood for the home

e. increases available moisture by improving infiltration and reducing runoff

f. reduces cost of inputs such as fertilizers and herbicides

g. improves soil structure

h. may also provide cash income

Characteristics of N-fixing trees ideal for green manuring

a. should be fast-growing

b. high production of herbage

c. high nitrogen content

d. fast decomposition of leaves

e. tolerant to pruning

f. pest-resistant

g. tolerant to a wide range of soil conditions

Characteristics of Some Nitrogen-fixing Trees

	Herbage	Tolerance to	Adaptability
Scientific Name	Common Name	Growth Rate	Dry Matter Drought	Water	Low logging	Soil Fertility	Rainfall	Remarks (annual)
			Yield	(t/ha.)
Calliandra  calothyrsus	Calliandra	fast	3.70	very  good	poor	good	well- drained	750 mm	Cut 50 to 65 cm from the ground
Desmodium  rensonii	Rensonii	fast	2.50-4.00	fair	fair	good	well- drained	1,000  mm and  over	Cut 0.5-1 m from the ground
Flemingia  macrophylla	Flemingia	moderate	2.65	good	fair	good	well- drained	800 mm	Cut 0.5-1 m from the ground
Gliricidia  septum	Kakawate	moderate	2.60	good	fair	good  drained;  slightly  acidic	well- drained	1,000  mm	Cut 1m from the ground
Leucaena  diversifolia	Acid ipil-  ipil	fast	6.00-9.00	good	fair	good	well- drained	50 mm	Cut 1m from the ground
Leucaena  leucocephala	Ipil-ipil	fast	7.00-24.00	very  good	poor	good	well- drained;  slightly acidic  to slightly  alkaline	760 rnm  pruning.	Cut 1m from the ground, susceptible to Problem  of psyllid flies
Sesbania  grandiflora	Katuray	moderate	15.0022.50	very  good	very  good	very  good	wide range   of conditions

References:

FAO-RAPA. 1988. Nitrogen-Fixing Trees for Wasteland. FAO, Bangkok.

Friday, K. 1989. Species Choice for SALT. Lecture Notes. Peace Corps Philippines.

NFTA. 1986. Sesbania - A Treasure of Diversity. NFT Highlights 86 04, Nitrogen-fixing Tree Association, Waimanalo, Hawaii, 2 pp.

NFTA. 1989. Flemingia macrophylla - A Valuable Species in Soil Conservation. NFT Highlights 89-04, Nitrogen-fixing Tree Association, Waimanalo, Hawaii, 2 pp.

NFTA. 1989. Gliricidia Production and Use. Nitrogen-fixing Tree Association, Waimanalo, Hawaii, 44 pp.

Cover crops

2. Cover crops are creeping and bushy plants with dense vegetative growth, grown mainly to cover and protect the soil.

Benefits

a. provide large quantities of nitrogen (more than 200 kg N/ha)

b. Some cover crops like Centrosema, Pueraria and Crotalaria develop deep root systems on acid soils and may, therefore, help to recover nutrients leached to the subsoil.

c. increase soil's organic matter content up to 30 tons or more per hectare, thereby improving topsoil depth, water-holding capacity, nutrient content, friability and soil texture

d. shade the soil for as long as 11 months, , keeping the soil temperature as much as 10°C lower than uncovered soils. Therefore microorganisms remain active and organic matter is preserved.

e. Dense foliage of cover crops protects the soil from wind and water erosion.

f. Vigorous growing foliage competes well with weeds and suppresses their growth, thereby reducing or eliminating costly weeding operations.

g. provide high protein fodder for animals

h. provide human food and additional source of income

i. help sustain garden plots during dry months when other crops are hard to grow

Characteristics of cover crops ideal fur green manuring

a. rapid, prolific growth habit

b. ability to fix significant amount of nitrogen

c. tolerant to a wide range of soil conditions

d. good drought-tolerance

e. resistant to pests

f. ability of the plant to produce its own seed

g. fast decomposition of leaves

h. easy to control; some cover crops can be very aggressive and may be difficult to eliminate.

Some cover crops successfully used by farmers

Canavalia ensiformis (jackbean, habas)

drought-tolerant

180-300 days growth period

shade-tolerant

fairly tolerant of waterlogging and salinity

tolerant of a wide range of soil types provided the pH is between 5 and 6.

Voandzeia subterranea (Bambara groundout)

120-150 days growth period

tolerant of excessive rain

adapted to a wide range of soils, but light sandy, welldrained loams with a pH of 5.0-6.5 are preferred.

Cicer arietinum (chick pea, garbansos)

115-125 days growth period

can tolerate shade but for high yields bright sunshine is required

drought-tolerant

can be grown on a wide range of soil types provided the drainage is good.

Crotalaria sp. (sun hemp)

determinant growth habit

produces high herbage yield (1.4-2.42 tons dry matter/ha)

does not tolerate shading.

Cyamopsis tetragonoloha (cluster bean)

110-165 days growth period

sun-loving, intolerant of shade

drought-tolerant; cannot stand waterlogging

grows on a wide range of soils provided they are welldrained and not acidic

Sandy or sandy loams, pH 7.5 to 8.0, are generally preferred.

Dolichos lablab (hyacinth bean, batao)

75-300 days growth period

drought-tolerant; intolerant of waterlogging

grows on a wide variety of soil types provided they are well-drained

does particularly well on sandy loam, pH 6.5.

Lathyrus salivas (grass pea, chick pea)

150-180 days growth period

very tolerant of drought conditions

tolerates waterlogging

grows on a wide range of soil types, including very poor soils and heavy clays.

Macrotyloma uniflorum (horse gram)

120-180 days growth period

drought-tolerant; cannot stand waterlogging

grows on a wide range of soil types provided they are well-drained and not highly alkaline

thrives on light, sandy soils, red loams and gravels.

Mucuna pruriens (velvet bean, kokua)

180-270 days growth period

tolerant of drought conditions; cannot stand waterlogging

grows on a wide range of soil types, including heavy clays tolerant of fairly acid soils, but for optimum yields light sandy loams with a pH of 5-6.5 are required.

Phaneolus aureus (mungbean, munggo)

80-120 days growth period

fairly tolerant to drought; cannot stand waterlogging

grows on a wide range of soil types tolerant of alkaline and saline conditions

well-adapted to clay soils, but for optimum results a deep loamy soil is required.

Phaseolus calcaratus (rice bean, tapilan)

120-130 days growth period

fairly tolerant of drought conditions

grows on a wide range of soil types

cannot withstand waterlogged conditions.

Psophocarpus tetragonolobus (winged bean, sigarilyas)

economically productive from 5 years or more

does not survive prolonged drought

cannot tolerate waterlogging or salinity

Well-cultivated, rich, sandy loams are best for optimum yields.

Vigna unguiculata (cowpea, paayap)

60-240 days growth period

well adapted to semi-arid regions

grows over a wide range of soil types cannot tolerate waterlogging and salinity

Although reasonably tolerant of acidity, a pH of 5.5 to 6.5 is preferred.

Reference:

Bunch, R. 1986. What We Have Learned to Date About Green Manure Crops for Small Farmers. World Neighbors - Honduras 12 pp..Produced by the International

Cover crops as soil conditioners

In heavy clay, cover crops add humus and stimulate microorganisms to-loosen rock-hard compaction and create a crumbly, well-aerated and well-drained soil structure.

In heavy clay

In sandy soils, the extensive, deep-penetrating roots of cover crops bring up needed nutrients that have leached into the subsoil. As the nutrients decompose, the matted roots give the soil enough body to hold onto nutrients and water that otherwise would quickly drain below the reach of plants.

In sandy soils

In nitrogen-deficient soils, velvet bean, hyacinth bean, jackbean and winged bean treat nitrogen deficiency.

In nitrogen-deficient soils

In dry conditions, cover crops maintain lower soil temperatures and, thereby, conserve microorganisms and earthworms, and generally conserve the soil's organic matter and humus.

In dry conditions

Reference:

Quick Ways To Better Sail. 1990. Organic Gardening Magazine. 16 pp.

Nutrient requirement of vegetables

Vegetable	Nit.	Phos.	Pot.	PH Requirement
Asparagus	EH	H	EH	6.0-7.0
Beans,bush	L	M	M	6.0-7.5
lima	L	M	M	5.5-6.5
Beets, early	EH	EH	EH	5.8-7.0
late	H	EH	H	same
Broccoli	H	H	H	6.0-7.0
Cabbage, early	EH	EH	EH	6.0-7.0
late	H	H	H	same
Carrots, early	H	H	H	5.5-6.5
late	M	M	M	same
Cauliflower, early	EH	EH	EH	6.0-7.0
late	H	H	EH	same
Corn, early	H	H	H	6.0-7.0
late	M	M	M	same
Cucumbers	H	H	H	6.0-8.0
Eggplant	H	H	H	6.0-7.0
Lettuce, head	EH	EH	EH	6.0-7.0
leaf	H	EH	EH	same
Muskmelons	H	H	H	6.0-7.0
Onions	H	H	H	6.0-7.0
Parsnips	M	M	M	6.0-8.0
Parsley	H	H	H	5.0-7.0
Peas	M	H	H	6.0-8.0
Potatoes, white	EH	EH	EH	4.8-6.5
sweet	L	M	H	5.0-6.0
				6.0-7.0
Radishes	H	EH	EH	6.0-8.0
Rutabaga	M	H	M	6.0-8.0
Soybeans	L	M	M	6.0-7.0
Spinach	EH	EH	EH	6.5-7.0
Squash, summer	H	H	H	6.0-8.0
winter	M	M	M	6.0-8.0
Strawberries	M	M	L	5.0-6.0
Tomatoes	M	H	H	6.0-7.0
Turnips	L	H	M	6.0-8.0

Nutrient Requirements
EH= Extra Heavy
M= Moderate
H= Heavy
L= Light

 Reference Source: International Institute of Rural Reconstruction