- - AGRICULTURE CORE CURRICULUM - - (CLF7000) Advanced Core Cluster: PLANT AND SOIL SCIENCE (CLF7450) Unit Title: ELEMENTS NECESSARY FOR PLANT GROWTH ____________________________________________________________________________ (CLF7458) Topic: DETERMINING NUTRIENT Time Taught in Year(s) DEFICIENCIES 2 hours 3 and 4 ____________________________________________________________________________ Topic Objectives: Upon completion of this lesson the student will be able to: Learning Outcome #: (H-11) - Identify three general methods for testing soil deficiency. (H-12) - Perform a soil test and complete a report on the test. (H-16) - Interpret a commercial soil test report. Special Materials and Equipment: Soil testing kits, samples of commercial soil and/or tissue test reports. References: Interstate Printers and Publishers, Inc. WESTERN FERTILIZER HANDBOOK. Pages 149-155. Evaluation: Quiz by instructor **************************************************************************** Note for Instructors: It is suggested that the emphasis on testing be shifted from soil to plant tissue related to the elements listed under (CLF7457). Only P, K and Zn have reasonable soil tests whereas plant tissue testing is good for all elements. **************************************************************************** TOPIC PRESENTATION: DETERMINING NUTRIENT DEFICIENCIES A. Soil and plant tissue analyses are the grower's best guide for efficient use of fertilizers and soil amendments. 1. These tests require accurate sampling, analyses, and interpretations based on local experience and sound research. 2. Each of these diagnostic techniques has advantages and limitations. B. The most commonly used techniques for determining nutrient deficiencies are soil tests, tissue analysis, observation of plants, and field or orchard trials. C. Soil analyses are most useful in evaluating soil pH and salt problems and the availability of nutrients related to these conditions. D. Soil samples must correctly represent the area of soil being sampled. A field may have several different soils and/or levels of crop productivity. Sample each area having a different level of productivity, dividing the field into 2 to 4 separate areas. 1. The proper method of collecting and handling samples is determined by: a. The use to be made of the analyses. b. The pattern and ease of recognizing soil variability. c. Previous and purposed management practices. 2. Soils are heterogeneous. Varying in both horizontal and vertical dimensions. a. From 10 to 20 subsamples should be collected to make one composite sample. b. The depth from which the sample is taken is determined by the crop, use of the analyses, and known facts of the profile. E. When sampling plant tissues we must consider the crop, its stage of growth, part of the plant to be analyzed, and variations within the field. 1. For most perennial crops (fruit trees, grapevines) their nutritional status can be evaluated from a single growth stage. 2. For annual crops (vegetables, cereal, sugar beets) sampling at several stages of growth is more helpful. 3. Samples should be collected in each area that plant growth is different then 30 to 50 plant parts should be collected from each of these specific areas. 4. Research has shown that specific plant parts are best for analyzing for a specific nutrient or a green plant specie. Example: a. petioles of leaves for N content of grapevines, b. whole mature leaves for all nutrients of the prunus species, c. petioles of sixth leaf from growing tip for cantaloupes. F. When you plan to send in soil or tissue samples for analysis you should: 1. Obtain containers, information and instruction sheets from the lab with which you are dealing. 2. Follow collection and preparing of sample instructions carefully. 3. Keep accurate records of: a. areas sampled, b. fertilizers used, c. crop yield, and d. dates of sampling. G. A soil sample will tell you what is present in the soil, whereas a tissue sample will tell you what the plant was able to take from the soil. H. Probably the most widely used means of determining whether or not a plant is in need of a particular element is the deficiency symptom. 1. The type of symptom, when it occurs, and where it occurs are important. 2. Observations in growth, chlorosis, change in size and shapes of the leaves and fruit, necrotic areas, dropping of buds or fruit, will help determine specific deficiencies. 3. Training and especially experience is important in making these judgements. I. Orchard and field trials are also used to determine deficiencies. 1. The plants either respond or they don't. 2. The final criteria for the use of any product (fertilizer) is "if it does not pay for its cost, it is not economical." a. Obviously this is easy to say, but hard to determine. b. Whether or not a product is cost effective is determined by many factors including amount of production, quality of the product, and market price received. J. pH is a measure of soil reaction. 1. In order to distinguish between the relative degrees of acidity or alkalinity of a soil, a pH scale of 0 to 14 is used. a. At the middle of the scale (pH 7.0), soil is neutral. b. Below pH 7.0 soil is acidic. c. Above pH 7.0 soil is alkaline (basic). 2. The soil reaction is important in plant growth for several reasons: a. It has an effect on nutrient availability. b. It effects the solubility of toxic substances. c. It has an effect on soil microorganisms. d. It has a direct effect on root cells which then effects the water and nutrient uptake. 3. Soil reaction can be changed with the use of soil amendments. a. Calcium carbonate (lime) can be used to decrease the acidity (raise the pH). b. Most common nitrogen fertilizers contribute to soil acidity (lowers the pH). __________________________________________________________ ACTIVITY: 1. Have students perform the various soil or plant tissue tests and report on them. 2. Give each student in the class a sample of a commercial soil (or tissue) test report. Have them read and interpret the findings. __________________________________________________________ 6/21/90 sg #%&C