Maui County Unversity of Hawaii at Manoa UH Seal Soil Nutrient Management for Maui County College of Tropical Agriculture and Human Resources (CTAHR)
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Soil Fertility Evaluation

Deficiency symptoms

To view illustrations of typical nutrient deficiencies, click on the following link: Deficiency Symptoms of Some Common Crops in Hawaii


  • Plants often have stunted growth.
  • Leaves develop a yellow color, which is a condition known as chlorosis.
    • Since nitrogen is a mobile nutrient within the plant, nitrogen moves from older growth to new growth when deficient.
    • As a result, nitrogen deficiencies first appear in older leaves.
    • Since deficiency symptoms are sometimes difficult to diagnose, the location of the symptom (new or old growth) helps us determine which nutrient, if any, is deficient.
  • When nitrogen is severely deficient, chlorotic leaves may die and fall off the plant.


  • Plants often have overall stunting, particularly during the early stages of growth.
  • Phosphorus is a mobile nutrient; and so, symptoms first appear in older growth.
    • When deficient, older leaves develop a dark green to blue green color.
  • In certain corn and grass species, older leaves may develop a purple coloration.
  • Phosphorus deficiencies can cause poor fruit and seed development as well as delay crop maturity.


  • Plants often experience stunted growth.
  • Like nitrogen and phosphorus, potassium is a mobile nutrient. Older leaves may develop chlorosis along the margin, or edge, of leaves.
  • Certain crops may have weaken stalks, which causes lodging (toppling over).


  • A common symptom of sulfur deficiency is uniform chlorosis of leaves.
    • Sulfur deficiency symptoms may resemble nitrogen deficiencies, except the symptoms first appear on new growth of most crops since sulfur is mostly immobile.
  • Growth may be stunted, with spindly and thin stems.


  • Symptoms first appear in new growth since calcium is immobile within the plant.
    • Areas of active growth, such as buds, new leaves, and root tips, fail to develop, and eventually turn brown and die.
    • Leaf tips are often chlorotic or colorless.
  • Sticky substances may be excreted from the growing points causing leaf tips to stick together as new leaves emerge. This may cause tearing of plant tissue.
  • Young leaves of certain crops may develop a cupped or crinkled appearance.
  • Buds, blossoms, and fruit may rot and fail to reach maturity.


  • Deficiency symptoms first show up on older leaves since magnesium is a mobile nutrient. Commonly, plants develop interveinal chlorosis.
    • Interveinal chlorosis is a condition in which the plant tissue becomes yellow while the veins remain green.
    • Interveinal tissue in some crops may turn reddish, purplish, and bronze.
  • If severe, the entire leaf may become chlorotic and eventually die.


  • Deficiency symptoms first appear in new growth. Leaves may be thickened, curled, and brittle. Stems may also become cracked.
  • Other symptoms include rotting and discoloration of fruits and roots.
  • The plant may also have stunted growth.


  • Plants may have chlorosis, stunted growth, and curling of young leaves.
  • Leaf tips and leaf edges may begin to die back.
  • Leaves may develop a dark bluish-green cast.


  • Deficiency symptoms include interveinal chlorosis, which first appears on young growth. In severe cases, entire leaf may turn white and die.


  • Like iron, interveinal chlorosis may develop on young leaves, except the chlorosis appears as yellow dots.
    • In monocot plants, black spots also appear on the base of young leaves.
  • The plant may have stunted growth.


  • Older growth may become chlorotic.
    • Molybdenum deficiencies may resemble nitrogen deficiency since molybdenum is involved in the major nitrogen processes that occur in plants.
  • The margins of leaves may develop spots of dead leaf tissue.


  • Like iron deficiency, interveinal chlorosis may form on younger leaves. In contrast to iron deficiency, distinctive bands of chlorosis form between the midrib and the edges of leaves.
  • In some crops, interveinal chlorosis develops on older leaves, leading to eventual death of the leaf.

Elemental Toxicity


  • Leaf margins may develop a red or yellow color, which may lead to necrosis, or death of plant tissue.
  • Plant may experience stunted growth.


  • The plant may have stunted growth.
  • Root growth may be severely restricted.


  • Older leaves may develop small, dark brown spots.
  • Leaf edges and tips also become chlorotic, which leads to the death of the leaf.
  • Like calcium deficiency, young leaves may become cupped and crinkled.


  • Plant develops thickened, rolled leaves.
  • The plant appears to be wilting due to reduced water uptake.

Soil analysis

Soil analysis is a very valuable tool in nutrient management. Most importantly, it enables us to predict and determine the proper amount of nutrients that should be added to a given soil based upon its fertility needs.

To read more about the value of soil analysis, click on the following link:

If correctly done, soil analysis eliminates much of the uncertainty involved in the application of nutrients, as well as reducing wasteful applications of valuable resources.

Soil testing involves two major processes:

  • obtaining a representative soil sample of your soil
  • laboratory testing to determine the nutrient content of your soil

Obtaining representative soil samples

Soil sampling is the most important step in soil analysis. Since the amount of soil sampled is only very small fraction of your field, obtaining a representative sample is critically important. If care is not taken during soil sampling, the nutrient recommendation may not reflect the true needs of your field in its entirety.

Incorrect recommendations could cause:

  • the loss of
    • money
    • time
    • nutrients
  • reduce yields
  • environmental risk

In this section, we suggest ways in which you may eliminate error so that you may obtain reliable nutrient recommendations.

Suggested Method

A common way to reduce error is to take multiple samples and subsamples from various parts in your field.

Sampling steps
  • Make a detailed map of your field or garden.
  • Divide the map into soil sampling areas. Each area should contain a relatively uniform soil.
    • A uniform soil should not differ in soil type, color, slope, drainage, texture, past management, and natural vegetation. It is important that soils with variation be sampled separately.
    • Include no more than 1-5 acres in each test area.
  • Label each test area clearly so that you may recall which areas you sampled to make later comparisons with the nutrient recommendations.
    • For your convenience, you can use the same labeling system to mark the sample bags, which will allow you to correctly identify the soil samples with the appropriate areas.
    • It is recommended that you use a waterproof marker when labeling the bags.
  • Throughout each sampling unit, it is recommended to randomly or systematically collect 10-15 soil cores.
    • A soil core is a sample that covers a one inch square area and extends to a specific depth.
    • The depth to which the core is taken varies upon the field. Usually, soil cores are taken to a depth of 4 inches in pasture, turf, or no-till land, but 8 inches in tilled fields or gardens.
    • If systematically taken, you may choose to develop a zigzag pattern from which to collect cores. A zigzag pattern helps to cover the entire area.
  • Even within one sampling area, there may be some variation. If this is the case, only take soil samples that are representative of the overall area and avoid soils that are uncharacteristic.
  • You may use a spade or shovel to collect samples. If available, a soil “probe,” is a useful tool, because it is designed for collecting soil cores.
    • Tools made out of steel are favored because other metals may contaminate the samples with copper or zinc.
    • When using a shovel or spade, dig a hole to the desired soil core depth. Then, remove a 1 inch slice of soil from the side of the hole. From the 1 inch slice, remove a 1 inch portion to obtain your 1 inch by 1 inch soil core.
  • Collect subsample soil cores in either plastic bucket or bag. It is important to use clean tools and materials to avoid contamination that will result in misrepresentation.
  • At the end of sampling, the 10-15 cores should be thoroughly mixed together into a composite sample. From this, a final sample of approximately 1 pint of soil may be taken and placed in an appropriately labeled, thin plastic bag. You should not use brown paper bags because these bags contain traces of boron.
  • If you are sampling fields used for tree crops, it is recommended that additional core samples are taken from 8 to 24 inches of soil depth.
  • Further recommendations include:
    • soil sample are collected and sent for analyses about two to three months prior to planting
    • soil samples be taken each season for annual crops and every 2 to 3 years for orchard crops

Analyzing samples

While personal test kits are available, samples can be sent to an agricultural testing laboratory. Since laboratories are equipped with professional technicians and the equipment and materials that are necessary to follow the proper procedures for analyses, you can have confidence in the results that you receive. However, it is recommended that you send your samples to an accredited soil testing laboratory.

Sample form

Soil samples can be sent to the CTHAR’s Agricultural Diagnostic Service Center for laboratory analysis (ADSC). The following link is the web address to the ADSC:

The ADSC requires that a sample form be completed and submitted along with the samples. The sample form contains information that is helpful in assisting the ADCS make recommendations. Thus, it is important to fill out the sample form as completely and accurately as possible.

In addition to the ADSC, the following web addresses are linked to other laboratories that perform soil analyses:

Agri-Food Canada
Spectrum Analytic Inc.
North Caroline State University
A&L Canada Laboratories

Types of soil analyses at the ADSC

Routine analyses
  • Sample Preparation
  • Soil pH
  • Soil Salinity
  • Extractable P
  • Extractable cations
Special Analyses
  • Organic C
  • Total N
  • Extractable Al
  • Extractable B
  • Extractable micronutrients


In approximately two weeks after submission, the ADSC will send you a nutrient recommendation.

A good recommendation includes:

  • Type of nutrients that your field or garden lacks, or doesn’t lack
  • Proper timing for nutrient additions
  • Suggested rates for nutrients application if the calibration information is available for your soil type and crop choice
    • When calibration data is not available, general recommendations for nutrient application rates may be given. However, there is a chance that the general recommendation will be inaccurate. To inaccuracies, see calibration section.

It is important to keep in mind that nutrient supply is just one of many factors that can limit plant growth. For instance, it is possible that other soil properties, such as soil compaction, may be responsible for poor crop performance. Thus, there are many factors that must be considered when identifying the source of limited growth and implementing the correct management strategies to resolve these growth problems.


Soil conditions: Even when nutrients are sufficiently present in the soil, unfavorable soil conditions will affect nutrient availability. Soil compaction, waterlogging, acidity, and alkalinity are among the many soil conditions that can limit nutrient availability.

Visual symptoms: While visual symptoms of nutrient deficiencies can be helpful, they do not always provide an accurate description of the problem.

  • For instance, a nutrient deficiency does not necessarily provide a visual symptom.
  • Nor is the presence of a symptom always sufficient. Distinguishing between a particular nutrient deficiency and mechanical, insect, disease, and pesticide damage can be difficult.

Tissue and soil analyses: Plant and soil analyses are important tools in nutrient management and are the basis for nutrient recommendations. Together, these analyses make the connection between the nutrient needs of plants and the nutrient availability in the soil, and indicate the adjustments that are needed. However, tissue and soil analyses, too, can be compromised by other soil factors that limit crop production.

To read more about how fertilizer recommendations are made, click on the following link:

Critical levels

ADSC nutrient recommendations are accompanied by a generalized statement “very low,” “low,” “sufficient,” “high,” or “very high.”  Although these statements do not tell you how much of a particular nutrient should be added (or not added) to your soil, it may indicate which action you may need to take. Understanding the statements is the first step in evaluating the fertility of your soil.

  • The categories “low” or “high” generally indicate that a particular nutrient simply should or should not be added.
  • In contrast, “very low” or “very high” nutrient levels usually suggest that the nutrient management program is in need of change.

To learn more about what the recommendation levels mean and what action you should take, click on the following link:

Tissue analysis

Tissue sampling allows us to determine whether plants are receiving proper nutrition.

  • A tissue analysis is useful because it can indicate the possibility of particular nutrient deficiencies.
    • Perhaps your crop requires a larger amount of a particular nutrient or a lesser amount.
  • Most importantly, tissue analyses can be compared with soil analyses. Such comparisons help evaluate your present soil fertility program.

Tissue sampling

Tissue sampling is the most crucial step in tissue analysis. Like soil sampling, a representative tissue sample must be taken, which characterizes the entire plant population.

Accurate soil sampling may be achieved by sampling a multitude of plants.

It is recommended that you:

  • identify which plant part is recommended for sampling
  • sample healthy plant parts, and not plants that are damaged or dead
  • remove any soil and dust from sampled parts
  • place samples in plastic bag protects it from dirt and contamination

As with soil sampling, an information form must also be submitted along with the sample, which provides the ADSC with the information needed in making sound nutrient recommendations.

Types of tissue analyses

Routine analyses

  • P
  • K
  • Ca
  • Mg
  • Fe
  • Cu
  • Zn
  • Mn
  • Mo
  • Al
  • Na

Total N


  • Nitrate
  • Sulfur
  • Silicon

Recommended nutrient levels for various crops

Click on the link below to obtain recommended nutrient levels for some common Hawaii crops. The following information has been complied by the College of Tropical Agriculture and Human Resources.


Once you receive a nutrient recommendation from the ADSC, how do you know how much nutrients to add to your soil? Certainly, the terms “sufficient” or deficient” mean nothing without the following information:

  • Nutrient levels that are considered sufficient for the crops that you intend to grow.
  • The application rate of nutrients to obtain the sufficient levels in the soil to support crop growth.

We obtain this knowledge through a process called calibration. Luckily, calibration information is available for some crops grown in a few of Hawaii soils.

Calibration data enables us to:

  • Acquire the recommended nutrient levels for a specific crop grown in a specific soil type
  • Compare calibration data with the nutrient levels of your soil as indicated by soil analyses
  • Apply any nutrients that are not sufficiently present as recommended

Unfortunately, calibration data is not always available for every crop grown in all of Hawaii’s soil. While a general recommendation may be available, it is not always wise to adhere to a general recommendation. If a nutrient is applied in too great of a quantity, it may result in the waste of resources, potential environmental harm, and possible nutrient toxicities.

As a way to prevent possible economic and environmental damage, a calibration experiment can be performed. By performing a calibration experiment, we answer the question, “How much of a particular nutrient is enough for sufficient growth?

A calibration experiment allows us to:

  • determine the sufficiency, deficiency and critical levels for plant growth in a particular soil
  • interpret soil test analyses and make an appropriate nutrient/fertilizer recommendation

Calibration Experiment


The easiest way to perform a calibration is through simple comparison. Through your experience, you may choose to:

  • gather information about plant and soil nutrient levels from successful plant growth in a particular soil
  • compare your soil and plant nutrient levels with this information. If your nutrient levels are not sufficient, you may consider adding additional nutrients.

Field Experiments

Instead of relying upon personal experience, you may take a more scientific approach to determine the appropriate nutrient levels for a crop of interest. This approach involves an experiment. Therefore, it is advisable to keep detailed accounts and maintain consistency.

Design of the Experiment

The following calibration experiment is not commonly performed by farmers alone. Instead, farmers can work with university research personnel and perform ‘on-farm research.’ If you are interested, contact your extension agent.

Nutrient Levels

  • Choose at least three different nutrient levels, or treatments, that you will apply to your soil.
    • You may choose to double (0,100, 200, 400 lb/acre) or triple (0, 50, 150, 450 lb/acre) each increment.
    • In a graphical representation of yield versus nutrient additions, the maximum yield is the point at which the curve begins to plateau.


  • In order to minimize the random effects within the experiment, it is important to have a set of at least two replicates for each nutrient level.
    • The variance between the two replicates can be determined statistically.
    • Replicated treatments also allow you to determine significant differences between nutrient levels with greater certainty.

Random Assignment

  • Within one set of replicates, the plots that receive a specified fertilizer addition should be randomly assigned.
  • Random assignments reduce the chance that certain plots are treated differently (i.e greater sunlight, more water, more disturbance).

Collection of soil samples before and after experiment

  • Soils samples should be taken and analyzed before the experiment is installed.
  • After harvest, soil samples should be collected and analyzed again from each plot.
  • From these analyses, you can determine the significant effects of various nutrient applications on both yield and soil fertility.

Collection of plant tissue

  • You can also compare how different levels of soil nutrients affect the nutrient levels in plant tissue.
  • We can use this information to determine sufficiency and deficiency levels of the plant of interest.

Collection of yield data

  • Yield data can be used to establish deficiency, sufficiency and toxicity ranges of nutrients. You can also include crop quality information in your report.