Interpreting Soil Analysis
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The document is a soil analysis report from Midwest Laboratories that details various nutrient levels, pH, and other soil characteristics essential for crop performance. It includes specific measurements and recommendations for elements such as potassium, nitrogen, calcium, magnesium, and micronutrients. Additionally, the report emphasizes the importance of cation exchange capacity and provides guidelines for fertility management based on soil test results.
Interpreting Soil Analysis
- 1. ® MIDWEST LABORATORIES, INC. • 13611 B STREET • OMAHA, NE 68144 • 402-334-7770 • FAX 402-334-9121
- 2. A REPORT NUMBER XX-YYY-ZZZZ B ACCOUNT ® REPORT DATE C 1234 RECEIVED DATE 13611 B Street • Omaha, Nebraska 68144-3693 • (402) 334-7770 • FAX (402) 334-9121 D www.midwestlabs.com SOIL ANALYSIS REPORT NEUTRAL AMMONIUM ACETATE (EXCHANGEABLE) E INFORMATION SHEET: 123456 LAB SAMPLE ORGANIC PHOSPHORUS POTASSIUM MAGNESIUM CALCIUM SODIUM pH CATION PERCENT BASE SATURATION (COMPUTED) EXCHANGE NUMBER IDENTIFICATION MATTER P1 P2 BICARBONATE K Mg Ca Na SOIL BUFFER CAPACITY % % % % % MODIFIED (WEAK BRAY) (STRONG BRAY) P pH INDEX C.E.C. K Mg Ca H Na LO I 1:1 percent RATE ppm RATE ppm RATE ppm RATE ppm RATE ppm RATE ppm RATE ppm RATE meq/100g F G 1 2 3 4 5 6 7 8 9 LAB SAMPLE NUMBER IDENTIFICATION SULFUR ZINC MANGANESE IRON COPPER BORON EXCESS SOLUBLE LAB NITRATE-N LIME NUMBER SURFACE SUBSOIL 1 SUBSOIL 2 S Zn Mn Fe Cu B RATE SALTS Total ICAP DTPA DTPA DTPA DTPA SORB. DTPA 1:1 depth depth depth lbs/A mmhos/ ppm lbs/A (in) ppm lbs/A (in) ppm lbs/A (in) ppm RATE ppm RATE ppm RATE ppm RATE ppm RATE ppm RATE cm RATE 10 11 12 13 14 15 16 17 18 REV. 12/03 19 COMMENTS: Our reports and letters are for the exclusive and confidential use of our clients and may not be reproduced in whole or in part, nor may any reference be made to the work, the results, or the company in any advertising, news release, or other public announcements without obtaining our prior written authorization. REPORT TERMS SOIL ANALYSIS Organic Matter Parts per million (ppm) Percent organic matter is a measurement of the amount of plant and Results for the major and minor elements are reported in parts per million (ppm) animal residue in the soil. The color of the soil is usually closely relat- on an elemental basis. An acre of mineral soil 6 to 7 inches deep weighs approx- imately 2 million pounds. Therefore, to convert parts per million readings to 1 ed to its organic matter content, with darker soils being higher in organic matter. pounds per acre, multiply by 2. The organic matter serves as a reserve for many essential nutrients, Meq/100q (milliequivalents per 100 grams) especially nitrogen. During the growing season, a part of this reserve Soil cations, such as calcium, magnesium, potassium, and hydrogen can be nitrogen is made available to the plant through bacterial activity. expressed in terms of their relative ability to displace other cations. The unit of measure meq/100g serves this purpose. For example, one milliequivalent of Phosphorus potassium is able to displace exactly one milliequivalent of magnesium. The Three types of phosphorus tests are reported. The P1 (weak Bray) cation exchange capacity of a soil, as well as the total amounts of individual test measures phosphorus which is readily available to plants. The cations may be expressed using these units. 2 optimum level will vary with crop yield and soil conditions, but for most field crops, 20 to 30 ppm is adequate. Higher levels may be needed Millimhos/cm (mmhos/cm) for certain vegetable crops or where especially high yields are possi- Electrical conductivity measurements are often used to measure the amount of ble. soluble salts in the soil. Conductivity is generally expressed in mmhos/cm. The The P2 (strong Bray) test measures readily available phosphorus plus conductivity increases with increasing soluble salts, and the soil is considered a part of the active reserve phosphorus in the soil. A level of 40 to 60 saline when the conductivity reading of the saturation extract reaches 2 ppm is desired for good yields of most crops. mmhos/cm. The Bicarbonate P (sodium bicarbonate) test measures the amount of Ratings readily available phosphorus in slightly basic (pH 7.0-7.2) to highly Most soil test readings on the report are given a rating of very low (VL), low (L), basic soils (pH 7.3 and greater). In basic soils the phosphorus exists medium (M), high (H) or very high (VH). The purpose of these ratings is to pro- mostly as alkaline earth phosphates, and the extraction of dilute sodi- vide a general guideline for determining optimum nutrient levels for crop growth. um bicarbonate correlates with what crops can extract from these Upon request, an unrated form can be obtained. Optimum levels may vary soils. The weak and strong Bray extractions are acidic (low pH) and slightly from those shown on the Soil Analysis Report, however, the actual value these extracting solutions are neutralized by the presence of free lime that is best is dependent on many factors such as crop, yield potential and soil in higher pH soils giving lower phosphorus levels. type. The relationship between the P1 and P2 test levels (P1:P2 ratio) can help evaluate the phosphorus status of the soil as well as identify a
- 3. soil condition that contributes to poor crop performance. The following Cation Exchange Capacity – (CEC) comments will apply to the P1:P2 ratio in most areas: Cation Exchange Capacity measures the soil’s ability to hold nutrients A. 1:1 – VL to L Poor history of fertilizer use – adding P2O5 will tend such as potassium, magnesium, and calcium as well as other posi- to widen the ratio. Many times the available P2 increases faster than the standard available P1 indicating an increase in the 8 tively charged ions such as sodium and hydrogen. The CEC of a soil is dependent upon the amounts and types of clay minerals and organ- reserve. ic matter present. The common expression for CEC is in terms of mil- B. 1:1 – M to VH Low reserve. Fe and Al ”P” bond is very tight – a liequivalents per 100 grams (meq/100g) of soil. On most soils, it will lime application will release P and increases the Ca availability, vary from 5 to 35 meq/100g depending upon the soil type. Soils with generally the ratio will widen as a result of the lime application. high CEC will generally have higher levels of clay and organic matter. C. 1:2 with P1 M to H. Ideal range with reserve as high as the P1 For example, one would expect soil with a silty clay loam texture to availablity. have a considerably higher CEC than a sandy loam soil. Although D. Greater than a 1:2 ratio. Some may be as high as 1:20 or high CEC soils can hold more nutrients, good soil management is greater. One or more of the following principles may apply: required if these soils are to be more productive. 1. Response to starter may increase as ratio increases. 2. Presence of free lime in the soil may be indicated. 3. Increaing response to the use of sulfur and zinc. (Use 1 part of zinc with 2 to 4 parts of sulfur. A maximum of 8 pounds Percent Base Saturation of SO4 –S may be used in a starter band.) Percent saturation refers to the proportion of the CEC occupied by a E. When the P2 is over 50 ppm, one can expect greater response given cation (an ion with a positive charge such as potassium, mag- to Zn. 9 nesium, or calcium, or combination of cations referred to as bases). The percentage saturation for each of the following cations for opti- F. The amount of P2O5 which will be required to increase the P1 reading is dependent on soil texture (or cation exchange capac- mum crop performance will usually be within the following ranges: ity), soil pH, and level of P1 and P2. An average value would be Potassium 2 to 5 9 lbs. of P2O5 required to raise P1, reading 1 ppm. Magnesium 12 to 18 Calcium 65 to 75 Potassium This test measures available potassium. The optimum level will vary with crop, yield, soil type, soil physical condition, and other soil relat- Nitrate-Nitrogen 3 ed factors. Generally, higher levels of potassium are needed on soils high in clay and organic matter than in soils which are sandy and low The soil test measures nitrate-nitrogen (NO3-N). This form is water soluble and readily available for plant uptake. When considering nitro- in organic matter. Soils containing high levels of magnesium may also need higher levels of potassium. A corrective factor for additional 10 gen needs for optimum crop performance, this test will indicate where and how much nitrate-nitrogen is present. Depth tests determining potassium is introduced when magnesium base saturation exceeds NO3-N will give more detailed information for making nitrogen recom- 23%. Optimum levels for light-colored, coarse-textured soils may mendations. It is important that other soil factors including organic range from 150 to 175 ppm, dark-colored heavy-textured soils range matter content be taken into account when interpreting the nitrate- from 175ppm to 250 ppm. nitrogen soil test and predicting crop response. Magnesium and Calcium The levels of calcium and magnesium found in the soil are affected Sulfur primarily by soil type, drainage, liming and cropping practices. These The soil test measures everal forms of sulfur that can be readily avail- able. Higher sulfur levels can occur when soils have reduced inter- 4 basic cations are closely related to soil pH. As the soil pH gets high- er, the levels of calcium and magnesium usually increase. Calcium 11 nal drainage, high soil pH, or are irrigated with water having a higher deficiencies are rare when the soil pH is adequate. Magnesium defi- sulfur content. Optimum levels for sulfur depend largely on organic ciencies are more common in sandy, low organic matter soils. matter content, soil texture, drainage, and yield goal. Generally, when- Adequate magnesium levels normally range from 100 to 250 parts per ever the following conditions exist, the need for sulfur will be increas- million. The need for magnesium can be further determined by its ingly important for optimum crop performance: base saturation, which should be above 10-12 percent. Soils having A. Well drained, low CEC Soils magnesium base saturation in excess of 23 percent may exhibit drainage and compaction problems characteristic of cold, wet soils. B. Soils low in organic matter These soil conditions require special attention regarding potassium application and chemical responses. C. Low soil pH (below 6.0) D. Use of high analysis, low sulfur fertilizers Sodium E. High application rates of nitrogen fertilizer Although sodium is an essential nutrient for some crops, it is usually considered in light of its effect on the physical condition of the soil. F. High yield goals 5 High exchangeable sodium (greater than 2.5% sodium saturation) may cause adverse physical and chemical conditions to develop in Overall effectiveness of a sulfur application depends largely on the the soil. These conditions may prevent the growth of plants. ability of the sulfur product used to break down and become water sol- Reclamation of these soils involves the replacement of the exchange- uble in the soil. able sodium by calcium or magnesium and the removal of the sodium by leaching. Zinc Soil pH DTPA extraction is used to extract the zinc. A 1.8-2.5 ppm test level is The soil pH measures active soil acidity or alkalinity. A pH of 6.9 or usually adequate, however, interactions between zinc, soil phospho- less is acid, 7.0 is neutral, values higher than 7.0 are alkaline. Usually 12 rus and soil pH can significantly alter rates of application of zinc to achieve desired crop response. When relatively large amounts of zinc 6 the most desirable pH range for mineral soil is 6.5 to 6.9 and for organic soil 5.5 to 6.0. are to be applied (5-10 lbs per acre), broadcast treatments are acceptable, with residual effects of these larger quantities lasting several years. Smaller amounts of zinc are Buffer Index most effective in combination with the application of an N-P-K treat- This is an index value used for determining the amount of lime to ment. Soils that have been leveled and/or terraced should be espe- apply on acid soils with pH less than 7.0. A value is not given for pH’s cially considered for zinc applications. 7 greater than 7.0. The lower the buffer index number, the higher the lime requirement.
- 4. Manganese OFFICE INFORMATION Manganese is extracted using the DTPA extraction process. Optimum test levels range from 14-22 ppm. Manganese is its soluble (readily A. Report Number 13 available for plant uptake) form quickly reverts to insoluble (unavail- able) forms shortly after application. Row or band treatments along All samples are filed by report number. When contacting our lab con- cerning a certain report, be sure to refer to this number. with foliar application are the recommended methods of treatment for optimum crop response and efficiency of applied manganese. XX-YYY-ZZZZ XX=Year Y = Day of Year (Julian calendar) Z= Report Number Iron Iron is extracted using the DTPA extraction process. A 12 to 22 ppm B. Account test would be optimum in most cases. A soil test indicating iron to be 14 adequate or even optimum may not reflect desired crop response. Soil pH is a very important factor in interpreting the iron soil test. An account number has been assigned to each client. The use of this number will speed up the processing and location of samples within Correcting iron deficiencies is complicated because iron compounds the laboratory system. added to the soil quickly react with the soil solution and become C. Report Date unavailable to the growing plant. Chelated forms of iron have been effective as soil treatments, while foliar applications have proven to The date which the sample data was reported is shown here. provide the best results for correcting iron deficiencies. D. Received Date The date which the sample was received at the laboratory appears Copper here. Copper is extracted using the DTPA extraction process. A 1.2 to 1.8 ppm test level should be sufficient. Several factors enter into condi- E. Information Sheet Number 15 tions contributing to a copper deficiency: soil pH above 7.0, high organic matter soils (peats and mucks,) and soils receiving high rates The number of the information sheet which was submitted with the samples in this report is listed here. of nitrogen phosphorus and zinc applications. The crop to be grown and the associated yield goals are also important factors to consider. F. Lab Number Soil applications of copper are generally effective for several years, especially on soils with pH’s below 7.0. The identification number which was assigned by the laboratory to each individual soil sample is shown here. There may be more than one laboratory number per report. Boron G. Sample Identification Boron is extracted from the soil using DTPA/Sorbitol. Adequate lev- The identification number assigned by the client to each individual els range from 1 to 1.5 ppm. Boron deficiencies will be most common sample is reported here. Because of limited space, samples numbers 16 on sandy, low organic matter soils. Soil pH levels of 7.0 and above contribute to boron deficiencies also. Corrective measures can be must be limited to 10 digits. effectively done by application of boron fertilizer to the soil. Since the range between boron deficiency and toxicity is narrow for plant growth, broadcast treatments are the desired method of application. Excess Lime Rate A visual rating of free lime present. Soils having high amounts of free lime available will have problems with availability of major and minor Midwest Laboratories, Inc. has been serving 17 elements to the plant. Application of elemental sulfur or acid forming fertilizer can be beneficial in keeping phosphorus and micronutrients the agricultural, industrial, enviromental, and in a more available or soluble form. sampling needs of the United States and Canada for nearly 30 years. The Midwest Labs Campus offers over 60,000 square feet Soluble Salts of laboratory space dedicated to meeting the Excessive concentration of various salts may develop in soils. This may be a natural occurrence. It may result from poor irrigation water, analytical needs of our clients. Our data 18 excessive fertilization or contamination from various chemicals or industrial wastes. One effect of high soil salt concentration is water management system is one of the best in the industry. By entering an account number and stress in a plant such that the plant may wilt or even die. The effect of salinity is negligible if the reading is less than 1.0 mmhos/cm. an individually assigned password at Readings greater then 1.0 mmhos/cm may affect salt sensitive plants. www.midwestlabs.com, you can view Readings greater than 2.0 mmhos/cm may require the planting of salt historical results, alter/add recommendations tolerant plants. to existing reports, order supplies, view your personal fee schedules, research scientific Comments literature and auto-submit samples. This section of the report is used by the agronomists to address cer- tain problems that specific test readings may give in the way of inter- 19 pretation or crop response. Specific questions or special attention on a certain aspect of the soil test requested by the client may also be answered in the comments section. Additional Analyses Additional analysis such as chloride, molybdenum, ammoniacal nitro- gen and total nitrogen will be shown on an addendum report, if ana- lyzed. If soil texture is determined, the precent sand, silt and clay will be listed on this addendum report as well.