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close this bookSoils, Crops and Fertilizer Use: A Field Manual for Development Workers (Peace Corps, 1986, 338 p.)
View the document(introduction...)
View the documentAbout this manual
View the documentAcknowledgements
close this folderChapter 1: Down to earth - Some Important Soil Basics
View the documentWhat is soil, anyway?
View the documentWhy do soils vary so much?
View the documentTopsoil vs. subsoil
View the documentThe mineral side of soil: sand, silt, and clay
View the documentDistinguishing ''tropical'' soils from ''temperate'' soils
View the documentOrganic matter - a soil's best friend
View the documentThe role of soil microorganisms
close this folderChapter 2: Trouble-shooting soil physical problems
View the document(introduction...)
View the documentGetting to know the soils in your area
View the documentSoil color
View the documentSoil texture
View the documentSoil tilth
View the documentSoil water-holding capacity
View the documentSoil drainage
View the documentSoil depth
View the documentSoil slope
close this folderChapter 3: Basic soil conservation practices
View the document(introduction...)
View the documentRainfall erosion
View the documentWind erosion
close this folderChapter 4: Seedbed preparation
View the document(introduction...)
View the documentThe what and why of tillage
View the documentCommon tillage equipment
View the documentThe abuses of tillage and how to avoid them
View the documentMaking the right seedbed for the crop, soil, and climate
View the documentHow deep should land be tilled?
View the documentHow fine a seedbed?
View the documentSome handy seedbed skills for intensive vegetable production
close this folderChapter 5: Watering vegetables: When? How Often? How Much?
View the document(introduction...)
View the documentIt pays to use water wisely
View the documentSome common watering mistakes and their effects
View the documentFactors influencing plant water needs
View the documentOk, so get to the point! how much water do plants need and how often?
View the documentSome methods for improving water use efficiency
close this folderChapter 6: Soil fertility and plant nutrition simplified
View the document(introduction...)
View the documentLet's Make a Deal
View the documentHow plants grow
View the documentAvailable vs. unavailable forms of mineral nutrients
View the documentSoil negative charge and nutrient holding ability
View the documentSoil pH and how it affects crops growth
View the documentImportant facts on the plant nutrients
close this folderChapter 7: Evaluating a soil's fertility
View the document(introduction...)
View the documentSoil testing
View the documentPlant tissue testing
View the documentFertilizer trials
View the documentUsing visual ''hunger signs''
close this folderChapter 8: Using organic fertilizers and soil conditioners
View the documentWhat are organic fertilizers?
View the documentOrganic vs. chemical fertilizers: which are best?
View the documentSome examples of successful farming using organic fertilizers
View the documentHow to use organic fertilizers and soil conditioners
close this folderChapter 9: Using chemical fertilizers
View the document(introduction...)
View the documentWhat are chemical fertilizers?
View the documentAre chemical fertilizers appropriate for limited-resource farmers?
View the documentAn introduction to chemical fertilizers
View the documentCommon chemical fertilizers and their characteristics
View the documentThe effect of fertilizers on soil pH
View the documentFertilizer salt index and ''burn'' potential
View the documentBasic application principles for N, P, and K
View the documentFertilizer application methods explained and compared
View the documentTroubleshooting faulty fertilizer practices
View the documentGetting the most out of fertilizer use: crop management as an integrated system
View the documentUnderstanding fertilizer math
close this folderChapter 10: Fertilizer guidelines for specific crops
View the document(introduction...)
View the documentCereals
View the documentPulses (grain legumes)
View the documentRoot crops
View the documentVegetables
View the documentTropical fruit crops
View the documentTropical pastures
close this folderChapter 11: Liming soils
View the document(introduction...)
View the documentThe purpose of liming
View the documentWhen is liming needed?
View the documentHow to measure soil pH
View the documentHow to calculate the actual amount of lime needed
View the documentHow and when to lime
View the documentDon't overlime!
close this folderChapter 12: Salinity and alkalinity problems
View the document(introduction...)
View the documentHow salinity and alkalinity harm crop growth
View the documentLab diagnosis of salinity and alkalinity
close this folderAppendixes
View the documentAppendix A: Useful measurements and conversions
View the documentAppendix B: How to determine soil moisture content
View the documentAppendix C: Spacing guide for contour ditches and other erosion barriers*
View the documentAppendix D: Composition of common chemical fertilizers
View the documentAppendix E: Hunger signs in common crops
View the documentAppendix F: Legumes for green manuring and cover-cropping in tropical and subtropical regions
View the documentAppendix G: Some sources of technical support
View the documentAppendix H: A bibliography of useful references


Most vegetables are very low in calories but have a high nutrient density in terms of vitamins and minerals. The dark-green leafy vegetables like kangkong, bok choy, amaranth, and collards are excellent sources of vitamin A (as carotene), Vitamin C, B vitamins, calcium, iron, and potassium. (However, amaranth, spinach, Swiss chard, and beet greens contain oxalates which bind up much of their iron and calcium; they can be partially deactivated by cooking). Dark-green leafy vegetables also provide significant protein.

The deep-yellow and orange vegetables like cantaloupe, carrots, and Hubbard squash are excellent sources of vitamin A, vitamin C, and potassium. For example, one large carrot contains twice the adult daily requirement of vitamin A. Aside from preventing vitamin A deficiency which leads to blindness and death from infections, carotene is now known to play an important role in preventing several type" of cancer.

The Asian Vegetable Research and Development Center in Taiwan is the international research center most involved with tropical and subtropical vegetable production. The AVRDC has developed a number of heat-tolerant varieties of cool-season vegetables like cauliflower and also work" on disease resistance and general production practices. (Bee Appendix G for the address.)

General Fertilizer Needs of Vegetables

Since most Third World small farmers grow vegetables on small plots, this is an ideal situation for using organic fertilizers (see Chapter 8), and responses are excellent. However, in cases where organic fertilizers are in short supply, chemical fertilizer can be used if resources permit and will usually be very cost-effective on well--managed plots.

NPK Needs: The kind and amount of fertilizer needed varies a lot with the soil, the vegetable, and other key factors covered in Chapter 9. Table 10-4 gives a range of NPK rates from a number of research and extension sources worldwide.

TABLE 10-4 Co "on NPK Rates for Vegetables

TABLE 10-5

Susceptibility of Vegetables to Secondary Nutrient Deficiencies




Tomato, celery


Cabbage, eggplant, pepper, tomato, cucumber, watermelon


Asparagus, onions, and the Crucifer family (cabbage, collard, broccoli, turnips, bok choy, kale, cauliflower)

TABLE 10-6

Response of Vegetables to Micronutrients When Soil Levels are Low.


Direct-Planted Vegetables

The band method of application is very suitable for direct-seeded vegetables like turnips, radish, mustard, bok choy, leaf lettuce, spinach, Chinese cabbage, and okra. The halfcircle method works well with cucurbits (cucumber, squash, etc.) and transplants. Apply all the P and K along with 1/3-1/2 of the N at planting; sidedress the remaining N in one or more applications, depending on time to maturity and harvest method. For example, leafy greens, like leaf lettuce, spinach, Swiss chard, and bok choy, can be harvested either all at once or picked a few leaves at a time over a month or two (new leaves keep emerging from the center). In the latter case, 2 or 3 sidedressings can be made at 3-week intervals.

Transplanted Vegies

Tomatoes, peppers, eggplant, cabbage, collard, broccoli, cauliflower, head lettuce, and onions usually do better if first started out in a nursery seedbed, seedbox, or small containers and then transplanted to the field 3-6 weeks later.

Nursery Seedbed or Seedbox: In most cases, manure or compost will supply enough nutrients for the nursery stage. (See Chapter 4 for how to prepare a nursery seedbox mix.) However, there are 3 cases where chemical fertilizer might be needed:

· If the soil has been heat sterilized before planting, there may not be enough beneficial bacteria left to convert the organic N in the manure or compost into available N. However, fresh manure has a good amount of available N.

· If the manure or compost is of poor quality due to poor storage and exposure.

· If plants become N deficient while in the nursery. Watering is often high enough to cause lots of leaching.

If NPK fertilizer is needed, broadcast the equivalent of 60-80 grams/sq. meter (600-800 kg/ha) of 10-20-10 or 10-30-10 and mix it thoroughly into the top 10-15 cm of soil. Don't exceed 60-80 kg/ha of N or plants may become overly succulent and more prone to damping-off fungus disease. Fertilizers with a 1:2:1 or 1:3:1 ratio work best since they allow you to apply sufficient broadcast P without exceeding N or K rates.

NOTE: Disregard the amount of NPK applied in the nursery when calculating NPK rates needed' fro. transplanting onward.

N Deficiency in the Nursery Seedbed: If the plants turn yellow from N deficiency, dissolve a straight N fertilizer in water and apply it over the bed at the rate of 30 kg/ha of N which equals:

15 grams ammonium sulfate (21-0-0) per sq. meter

10 grams ammonium nitrate (33-0-0) per sq. meter

7-8 grams urea (45-0-0) per sq. meter.

Water plants with plain water afterwards to wash off any fertilizer solution from the leaves. If plants are being "hardened" in preparation for field setting (usually done the last 7-10 days before setting), N fertilizer will be counterproductive.

Using a Starter Solution for Transplants: Pouring a liquid starter fertilizer solution around the base of the plants after setting them will help get things off to a good start. Manure tea (see Chapter 8) or chemical fertilizer can be used for this. If using chemical fertilizer, here are the guidelines:

· Since P is the nutrient most involved in stimulating root regeneration and development, choose a formula with a good ratio of P in it such as 12-24-12, 18-46-0, or 10-30-10. Some N is helpful too, since it helps in the uptake of N.

· Except for a few like 18-46-0, most granular NPK fertilizers dissolve poorly in water. Grinding or mashing is helpful and will improve solubility.

· Dosage: Mix up 8-15 cc of fertilizer per liter of water and apply about 1 cup (240 cc) around the base of each transplant after setting.

· The starter solution only supplies enough nutrients for the first week or so of growth; additional organic or chemical fertilizer will be needed.

· NOTE: As in the case of fertilizer applied to a nursery seedbed, this starter fertilizer application is not counted when calculating overall NPK totals.

Applying Solid Fertilizer at Transplant Time: Use an NPK fertilizer that supplies 1/3-1/2 of the total N and all the P needed. If leaching is likely to be high, only about 1/3-1/2 of the K should be applied. The half-circle method works very well for transplants and should be made about 7.5-10 co (about 4 fingers-width) out from the stem and 5-10 cm deep.

How to Sidedress Nitrogen: Review the sidedressing guidelines in Chapter 9 before proceeding. Here are some more specific suggestions for vegetables:

· Long-duration crops like indeterminate tomatoes, eggplant, and peppers may require 3-4 or more sidedressings at 3-4 week intervals.

· Medium duration crops like broccoli and cauliflower will normally need 1-2 at 3-4 week intervals.

· Apply about 30 kg/ha of actual N per sidedressing as a rough figure. It's more accurate to subtract the at-transplanting dosage from the total N and then divide the result by the number of sidedressings needed.

· Apply the N in a band or half circle about 20 cm out from the plant; cover it lightly with soil. (This can be done by weeding with a hoe following the application.)