Cultural Practices Soil Tests
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Soil tests provide the best way to determine lime and fertilizer requirements. The shotgun approach to vegetable crop fertilization is not practical or economical. The vegetable grower must know the nutrient status of the soil and then match application rates of lime and fertilizer to crop needs. This is important for cost effectiveness and to achieve optimum yield and quality and to safeguard water quality. Following is a list of soil test laboratories in New England. It is best to use local labs because they are calibrated for local soils and recommendations and are tailored to New England conditions. The nutrient recommendation tables for vegetable crops in this guide are applicable to the New England soil test results given as Very Low, Medium, High (Optimum), and Very High (Above Optimum or Excessive). Tests are designed to measure nutrient levels in the soil which are available to plants. Generally, nutrients should be in the High (Optimum) range for good yield and quality. When levels are below this range, the addition of more of the nutrient will usually improve production. However, factors other than nutrients may limit crop growth, and simply adding more nutrients will not improve yield. If a nutrient is in the Very High (Above Optimum or Excessive) range, additional amounts should not be added in most cases. If levels are in the "High" (Optimum) range) additional application of that nutrient is generally not necessary, but some amount may be added to replace crop uptake. In the nutrient tables for the crop sections, this is indicated by a range such as 0 to 50 lb/A. Crops vary in their requirements for nutrients, and this is accounted for in the nutrient tables. This is shown in Table 6 on page 10. In addition to standard soil tests, other services are available in some of these laboratories including: Pre-Sidedress Soil Nitrate Test (PSNT), soluble salts (conductivity), manure analysis, compost analysis, water testing and plant tissue analysis. Call your laboratory to find out which services it offers or where they are available. SOIL HEALTH TESTStandard soil tests traditionally measure several chemical indicators such as pH, extractable phosphorus and potassium, and minor elements, to determine lime and fertilizer requirements. Researchers at Cornell have expanded upon this concept in the Soil Health Test by adding biological and physical indicators to help determine the relative healthiness of a soil and its ability to sustain crop productivity. For biological soil health indicators they measure organic matter content (%), active carbon, potentially mineralizable nitrogen, and use a root health index or rating system (scale of 1-10). For physical soil health indicators, they include aggregate stability, water holding capacity, and surface and subsurface compaction. Although many more potential indicators were investigated to come up with this list, these 12 indicators were determined to be the most critical and most practical to measure. Some of these indicators require a brief explanation. Organic matter content is the amount of decomposing plant and animal material in a given volume of soil. Active carbon is the portion of the organic matter that is available to feed beneficial soil organisms. Potentially mineralizable nitrogen is the amount of N that can be made available to plants in the near future. The root health rating is conducted after growing beans in the soil for four weeks and then washing and inspecting the roots for size, color and disease. Aggregate stability measures how well soil clumps hold together after wetting. Water holding capacity varies depending upon the size and number of soil pores and the amount of organic matter present and is measured by determining the difference between the soil at field capacity and at the permanent wilting point. Surface and subsurface compaction is measured on the farm with an instrument called a penetrometer. When soil moisture is near field capacity (ample water, but not saturated), the penetrometer is pushed slowly through the top 18 inches of soil and maximum measurements (p.s.i.) are recorded for the top 6 and lower 12 inches of soil profile. Soil Health Test sampling is similar to a conventional soil test except that it involves collecting more soil (1.5 quarts) which must then be kept shaded and cooled, both in the field and during shipping, to preserve the microorganisms. It also requires access to a penetrometer and involves recording compaction readings from 10 separate locations within each field or sampled area. Samples must be sent to the lab by over-night shipping. Results are reported on two separate pages: a standard soil test results sheet for the chemical indicators (pH, P, K, Ca, Mg, micros), and a follow-up Soil Health Report on the chemical, biological and physical indicators, which is sent after the root health rating is completed. Lab measurements for each of the 12 indicators are converted into a color-coded rating system for poor, medium and healthy soils, and an overall soil health score is provided. Soil Health Test sampling protocol, current prices, and submission forms are available at www.hort.cornell.edu/soilhealth/. SOIL TESTING LABS OF NEW ENGLANDConnecticut:Soil Nutrient and Analysis Lab Email: This e-mail address is being protected from spambots. You need JavaScript enabled to view it Gregory Bugbee, State Laboratory Maine:The Analytical Laboratory, 5722 Deering Hall, Room 407 Email: This e-mail address is being protected from spambots. You need JavaScript enabled to view it Massachusetts:Soil & Plant Tissue Testing Laboratory New Hampshire:UNH Cooperative Extension Soil Testing Program Vermont:UVM Agricultural & Environmental Testing Laboratory Private:Woods End Research Lab, Inc. Email: This e-mail address is being protected from spambots. You need JavaScript enabled to view it |
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