Publication 360, Fruit Production Recommendations: Assessing Nutrient Needs

Excerpt from Publication 360, Fruit Production Recommendations, 2010-11
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Table of Contents

1. Introduction
2. Assessing Nutrient Needs
3. Soil testing
   • Taking a Soil Sample
   • Interpreting Soil Test Results
   • When to Sample
   • Table 3-1. OMAFRA-Accredited Soil Tests (PDF 71 kb)
   • Table 3-2. Soil Test Nutrient Ratings (PDF 66 kb)
4. Plant tissue analysis
   • Sampling
   • Sample Preparation
   • Interpretation
   • Table 3-3. Sample Methods for Tissue Analysis of Fruit Crops (PDF 71 kb)
   • Table 3-4 Nutrient Concentration Sufficiency Ranges for Fruit Crops (PDF 77 kb)
5. Visual deficiency symptoms
6. Other topics in Soil Management, Fertilizer Use, Crop Nutrition and Cover Crops
   • Soil Organic Matter
   • Soil pH and Liming
   • Nitrogen
   • Phosphorus
   • Potassium
   • Calcium
   • Magnesium
   • Micronutrients
   • Cover Crops
7. Chapter 3: Soil Management, Fertilizer Use, Crop Nutrition and Cover Crops - PDF 189 kb
8. Related Links

Introduction

For a complete guide to soil fertility, consult OMAFRA Publication 611, Soil Fertility Handbook.

Crop nutrition is important in the production of high yielding, top quality fruit crops. Nutrients must be dissolved in the soil water for root uptake. Therefore, the most efficient use of fertilizer is intricately tied to soil and water management. The development of a sound soil fertility program begins with the assessment of nutrient needs.

Assessing Nutrient Needs

There are three ways to assess soil and crop fertility:

• soil-testing
• plant tissue analysis
• visual deficiency symptoms

These are not interchangeable methods. For perennial crops, all three methods are needed to assess and monitor the crop's nutritional status.

Soil testing

A soil test using methods suited to the particular soil type is the best measure of plant-available nutrients. OMAFRA accredits specific laboratory methods suited to Ontario soils (see Table 3-1. OMAFRA-Accredited Soil Tests, below). OMAFRA accredited laboratories participate in the North American Proficiency Testing Program and must demonstrate their ability to perform these tests accurately. Soil laboratories may provide additional soil tests not listed in Table 3-1, as well as analyses for greenhouse media, nutrient solutions and water. For other testing services, contact the soil laboratories listed in Appendix C. Accredited Soil-Testing Laboratories in Ontario. Testing for soil organic matter can be useful but is not an accredited test. OMAFRA-accredited soil tests are not available for boron, copper, iron or molybdenum. Tissue analysis of these micronutrients is a better indicator of the nutritional status.

Table 3-1. OMAFRA-Accredited Soil Tests (PDF 71kb)

When to sample

Always take soil samples before you plant fruit crops. Where pH adjustments may be necessary, sample two years before planting so that pH adjustments can be made. After establishment, sample each field once every two or three years. In sandy soils, consider checking soil potassium levels more frequently.Always take soil samples before you plant fruit crops. Where pH adjustments may be necessary, sample two years before planting so that pH adjustments can be made. After establishment, sample each field once every two or three years. In sandy soils, consider checking soil potassium levels more frequently.

Soils may be sampled in the summer or fall. Sample at the same time each year for more consistent sample results. Late summer or fall sampling is ideal for fields to be planted in the spring. Regardless of when you sample, allow time to mail the samples, receive your report and determine fertilizer requirements.

Taking a soil sample

Soil test report accuracy and the recommendations that result depend on the proper collection, preparation and submission of a soil sample. To take a soil sample you will need:

• soil probe or a shovel
• clean plastic pail (avoid galvanized metal pails, which will contaminate the sample for micronutrient analysis, particularly zinc)
• sample bags and boxes, usually available from the soil laboratory
• a pen or marker

Sample each field or individually managed unit separately. Separate large fields, or fields with considerable variation, into smaller sections. Each sample should represent a field or field section with similar soil texture, topography, organic matter and crop history.

Sample soils with a sampling tube or shovel. Sample each field or uniform section of a field separately. Traverse the sampled area in a zigzag pattern to provide a uniform distribution of sampling sites. Take at least 20 soil cores, 15 cm deep, from any field or area sampled up to 5 ha (12.5 ac.) in size. For fields larger than 5 ha, proportionately more cores should be taken. The more cores taken, the more likely the sample will provide a reliable measure of the fertility in the field. One sample should not represent more than 10 ha.

Where parts of a field differ in soil type, crop grown or previous fertilization practices (manuring or liming), sample separately. This applies even if the areas are too small to fertilize separately. Avoid sampling recent fertilizer bands, dead furrows, areas adjacent to gravel roads, or where lime, manure, compost or crop residues have been piled.

Collect the soil in a clean plastic pail, break up the lumps and mix the soil well, since only about 2 mL of soil from the sample will be used for each analysis. Fill a clean plastic bag with approximately 500 g of soil, place it into the box and forward it for testing. Be sure to clearly mark the sample box with all of the necessary information (i.e. sample number, farm name, date, etc).

Micronutrient deficiencies most often occur in small patches in fields. In these cases, soil or plant samples representing the entire field are unlikely to show a problem. Sample problem areas separately. When you sample a problem area, be sure to take a comparison sample from an adjacent area without symptoms.Micronutrient deficiencies most often occur in small patches in fields. In these cases, soil or plant samples representing the entire field are unlikely to show a problem. Sample problem areas separately. When you sample a problem area, be sure to take a comparison sample from an adjacent area without symptoms.Micronutrient deficiencies most often occur in small patches in fields. In these cases, soil or plant samples representing the entire field are unlikely to show a problem. Sample problem areas separately. When you sample a problem area, be sure to take a comparison sample from an adjacent area without symptoms.

Samples to assess soil nitrogen should be taken following the same sampling method, except they are taken to a depth of 30 cm and must be kept cool or frozen if not submitted immediately.

Interpreting Soil Test Results

The OMAFRA-accredited soil-testing program provides recommendations for nitrogen, phosphate, potash, magnesium, zinc and manganese fertilizer. It also gives recommendations for the amount and type of lime to be applied, if required. These recommendations are specific to the future crop to be grown, specified on the lab submission form. Crop specific details may be found on the following pages:

• Apples
• Berry crops
• Grapes
• Tender fruit

These recommendations can produce the highest economic yields when accompanied by good or above-average crop management.

On a soil test report, each nutrient is reported in parts per million (ppm) or milligrams per litre (mg/L) of soil, a letter rating and a fertilizer recommendation (usually kg/ha or lb/ac). The letter rating of the nutrient indicates the likelihood of a profitable response to applied nutrient for the specified crop. This letter rating system is explained in Table 3-2. Soil Test Nutrient Ratings.

Table 3-2. Soil Test Nutrient Ratings (PDF 66 kb)

A fertilizer recommendation depends on the crop to be grown. Recommended fertilizer rates, especially for nitrogen and phosphorus, should be adjusted if manure or legume cover crops are incorporated. This information is essential for an optimum fertilizer recommendation.

Note: Soil tests from other laboratories

OMAFRA-accredited soil tests provide accurate fertilizer recommendations. Make certain that the service you use is accredited. To be accredited, a laboratory must use OMAFRA-approved testing procedures to demonstrate acceptable analytical precision and accuracy and must also provide the OMAFRA fertilizer recommendations. Ensure that you ask for the OMAFRA fertilizer recommendations. Soil tests for nutrient management plans must be completed at OMAFRA-accredited labs.
Soil tests for exchange capacity, aluminum and copper are not accredited by OMAFRA because they have not been found to contribute to better fertilizer recommendations.

Plant tissue analysis

Plant tissue analysis measures the nutrient concentration in plant tissue. It is most useful if combined with visual inspection of the crop and soil conditions, knowledge of past management in the field and a current soil test to provide information about soil nutrient levels and soil pH. See Table 3-3. Sampling for Tissue Analysis of Fruit Crops, below.

For perennial crops, tissue analysis is an important addition to soil tests. Tissue analysis results are compared against established normal ranges for the crop and indicate whether a specific nutrient is deficient. The tissue test can indicate whether the plant is obtaining adequate nutrients for optimum growth. If soil levels are known to be adequate, tissue tests that indicate nutrient deficiencies should trigger a search for other causes. Plant analysis is particularly useful for the evaluation of phosphorus, potassium, magnesium and manganese. It is the main tool for assessing the status of boron, copper, iron and molybdenum, as there is no reliable soil test for these micronutrients.

Sampling

The time a sample is collected and the stage of growth can have a major impact on the results of plant analysis. The concentrations of some nutrients vary considerably with the age of the sampled tissue and the date of sampling. Results are difficult to interpret if samples are taken at times other than what is recommended for the crop.

Table 3-3. Sampling Methods for Tissue Analysis of Fruit Crops (PDF 71 kb)

• Collect tissue samples into labelled paper bags. Plant tissues will rot if stored in plastic bags.
• Avoid collecting damaged leaves or leaves from plants that appear abnormal.
• If variable areas are large enough to fertilize separately, they should be sampled separately.
• Avoid contamination of the sample with soil. Even a small amount of soil will cause the results to be invalid, especially for micronutrients.
• Plants suspected of nutrient deficiency should be sampled as soon as a problem appears. Take tissue samples from a problem area and submit a separate sample from an adjacent, non-affected part of the field. Also collect and submit a soil sample from both affected and non-affected areas to aid diagnosis.

Sample Preparation

Fresh plant samples should be delivered directly to the laboratory. If they cannot be delivered immediately, they should be dried to prevent spoilage. Samples may be dried in the sun or in an oven at 65°C or less.

Take precautions to prevent contamination with dust or soil. Avoid contact of samples with brass, copper or galvanized (zinc-coated) metal.

Plant analyses may be obtained from several laboratories in Ontario. Refer to Appendix C. Accredited Soil-Testing Laboratories in Ontario. Tissue analysis is not part of the OMAFRA accreditation program. However, OMAFRA-accredited labs have the necessary skills and equipment to perform accurate tissue analysis.

Interpretation

Tissue analysis has limitations and expert help is sometimes needed to interpret the results. Tissue analysis does not indicate how much fertilizer is required to correct a deficiency or even whether a deficiency is related to fertility problems. Tissue test results in the deficiency range may also be due to factors such as climate, pest pressure or disease, and therefore should be used in conjunction with a soil-testing program. Table 3-4. Nutrient Concentration Sufficiency Ranges for Fruit Crops, below, shows the range of tissue nutrient concentration that should result in optimum productivity for various fruit crops.

Table 3-4a. Nutrient Concentration Sufficiency Ranges for Apples^{1 (PDF 77 kb)}

¹ Leaf N should be 0.2% higher for apple trees on M.9 or M.26 rootstocks and for all non-bearing trees.

Table 3-4b. Nutrient Concentration Sufficiency Ranges for Berry Crops

Table 3-4c. Nutrient Concentration Sufficiency Ranges for Grape Petioles

Table 3-4d. Nutrient Concentration Sufficiency Ranges for Tender Fruit

Visual deficiency symptoms

Leaf symptoms can help evaluate some nutrient deficiencies, but have limitations. By the time deficiency symptoms are visible, yield losses may already have incurred. Visual deficiency symptoms are easily confused with other production problems such as pesticide injury, leaf and root diseases, nematodes, insect damage, compaction or air pollution. Suspected visual deficiencies should always be confirmed by tissue analysis. Specific nutrient deficiency symptoms are described in Apple Nutrition; for Berry Crop Nutrition; Grape Nutrition; and, Tender Fruit Nutrition.

Related Links

• OMAFRA Publication 611, Soil Fertility Handbook
• Soil Management
• Soil Fertility & Crop Nutrition
• Soil Water Management
• Best Management Practices: Soil Management
• Cover Crops
• OMAFRA Publication 505: Ontario Weeds
• OMAFRA Publication 75: Guide To Weed Control