Friends these days we are having a long debate about farmers and their problems. No one can help you if you do not improve traditional methods and it is very easy to improve your production so here we will learn how to know about health of our motherland.
Sample Preparation
At the laboratory, each sample is assigned an identification number, transferred to a paper bag, and then placed in a metal tray. Every 12th sample is a quality control sample, either a check sample of known chemical properties to ensure accuracy, or a duplicate sample to evaluate laboratory precision.
Samples are dried rapidly under forced air, the temperature not exceeding 95oF.
Dried samples are crushed with a mechanical grinder, and passed through a stainless steel 10-mesh 2.0 mm sieve to remove stones and unwanted debris.
Texture and Organic Matter
The relative amounts of sand, silt, and clay are estimated by the feel of the soil in a moist condition. The soils are then classified into three categories: C (coarse textures of sand, loamy sand and sandy loam), M (medium textures of loam and silt loam), and F (fine textures of clay loam, silty clay loam, silty clay and clay.
A 5 gram NCR-13 volumetric scoop of soil is placed into a tared, Kimax beaker, and is dried for 2 h at 105 degrees Celsius and weighed. The sample is then ashed for 2 h at 360 degrees Celsius and reweighed. The resulting loss of weight, as a percentage of the dry soil, is the estimate of organic matter content.
Soil pH and Lime Requirement
Soil pH is determined on a 1:1 (V/V) soil/water mixture composed of a 10 gram NCR-13 volumetric soil scoop and 10 mL double-deionised water. Samples are stirred both before and after a 15 minute equilibration period. pH is measured on a Mettler Toledo Seven-Multi pH meter with an InLab Routine Pro combination electrode, calibrated to pH buffers 4, 7, and 10. Mineral soils with pH values of less than 6.0 are analysed further for the following lime requirement test.
The Sikora Buffer Index (lime requirement test) is determined by adding 10 millilitres of buffer solution to the above 1:1 sample. The Buffer Index of the suspension is determined with the pH meter, after the sample has been stirred intermittently for 15 minutes.
Extractable Phosphorus
Bray-1 Method
The soil phosphorus measured is that which is extracted by a solution consisting of 0.025 normal HCl and 0.03 normal NH4F, referred to as Bray-1 extract ant. A 1 gram scoop of air-dried soil and 10 millilitres of extractant are shaken for 5 minutes. The amount of phosphorus extracted is determined by measuring the intensity of the blue colour developed in the filtrate when treated with molybadate- ascorbic acid reagent. The colour is measured by a Brink man PC 900 probe calorimeter at 880 nm. The result is reported in parts per million (ppm) phosphorus (P) in the soil. The phosphorus measured does not represent all of the phosphorus that may be available for plant growth; e.g., some fraction of the organic phosphorus not measured may become available upon mineralisation. The upper reporting limit for this test is 100 ppm. For situations such as nutrient management decisions where a higher value is needed, see the nutrient management test below.
Olsen Method
For highly calcareous soils (pH greater than 7.4), the Olsen sodium bicarbonate method is used. A 1 gram scoop of air-dried soil and 20 millilitres of 0.5 molar sodium bicarbonate (NaHCO3) solution are shaken for 30 minutes. Blue colour in the filtered extract is developed with molybdate- ascorbic acid reagent and measured with the Brinkman PC 900 probe calorimeter at 880 nm. Results are reported as parts per million (ppm) phosphorus (P) in the soil. As with the Bray P-1 test, potentially available organic P is not measured by the test. The upper reporting limit for this test is 50 ppm. For situations such as nutrient management decisions where a higher value is needed, see the nutrient management test below.
Available Potassium
Potassium is extracted from the soil by mixing 10 millilitres of 1 normal ammonium acetate, pH7 with a 1 gram scoop of air-dried soil and shaken for 5 minutes. The available potassium is measured by analysing the filtered extract on an atomic absorption spectrometer set on emission mode at 776 nm. The results are reported as parts per million (ppm) of potassium (K) in the soil.
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Soluble Salts
Soil samples are evaluated for salinity by first determining the electrical conductivity (E.C.) of a 1:1 suspension. One 10 gram scoop is mixed with 10 mL deionised water to form a slurry, which is stirred intermittently for 30 minutes. The E.C. is determined by the Accumet model 30 conductivity meter, and is reported in units of millimhos per centimetre. (mmohs/cm).
Slightly to strongly saline soils (conductivity more than 0.9 Mallomars) are subjected to a more precise test. A saturated soil paste is prepared by slowly adding deionised water to about 50 CC’s of soil until the mixture is a thick paste. After an equilibration time of two hours, the saturation paste is filtered under suction. The electrical conductivity is determined on the filtrate with the Acumen Model 30 conductivity meter, and is reported as Mallomars per centimetre (mmohs/cm).
Extractable Sulfate – Sulphur
Readily soluble and adsorbed sulfates are extracted with a mono calcium phosphate [Ca(H2PO4)2] solution containing 500 parts per million of phosphorus. A 10 gram scoop of air-dried soil is treated with 25 millilitres of extracting solution and shaken for 30 minutes. The sulfate in the filtrate precipitates with Barium (added in the form of BaCl2) and the SO4 concentration is determined turbidimetrically on the Lachat QuickChem 8500 Flow Injection Analyser. The results are reported as parts per million (ppm) of extractable Sulfate-S in the soil.
Extractable Zinc, Copper, Iron, and Manganese
Concentrations of zinc, copper, iron, and manganese (Zn, Cu, Fe, and Mn) are determined by treating a 10 gram scoop of air-dried of soil with 20 millilitres of DTPA (Diethylenetriamine-pentaacetic acid) extracting solution. After shaking for two hours, the sample is filtered and the extract analysed by an inductively coupled plasma atomic emission spectrophotometer (ICP-AES). The results are reported as parts per million (ppm) for each metal in soil.
Nitrate-Nitrogen
Nitrate-nitrogen is determined by adding 60 millilitres of KCl extracting solution to a 2 gram scoop of soil and shaken for 15 minutes. The nitrate level in the filtered extract is measured on a Lachat Quick Chem 8500 Flow Injection Analyser by the cadmium reduction method. The results are reported as pounds per acre (lbs/A) of nitrate-nitrogen (NO3-N) in the top 2 feet of soil or as parts per million (ppm) nitrate-nitrogen (NO3-N) in the soil for all other depths.
Hot Water Extractable Boron
A 10 gram scoop of air-dried soil and 20 millilitres of 0.01 M CaCl2. H2O (calcium chloride dehydrate) solution are boiled in a metal container for 5 minutes under reflux using a fiber digestion condenser apparatus. Boron in the filtered extract is determined with an inductively coupled plasma atomic emission spectrometer (ICP-AES). The results are reported as parts per million (ppm) of boron (B) in the soil.
Exchangeable Calcium and Magnesium
Calcium and magnesium are extracted from the soil by mixing 10 millilitres of 1 normal, pH7, ammonium acetate with a 10 gram scoop of air-dried soil and shaking for 5 minutes. The filtered extract is analysed with an inductively coupled plasma atomic emission spectrometer (ICP-AES) for calcium and magnesium. The results are reported in parts per million (ppm) calcium (Ca) and magnesium (Mg) in the soil.
Environmental Lead
This measure of lead in the soil is determined from 3 grams of air-dried soil that is shaken in 30 millilitres of 1 molar nitric acid (HNO3) for 1 hour at 180 opm. The mixture is then centrifuged and the supernatant is analysed for lead with an inductively coupled plasma atomic emission spectrophotometer (ICP-AES). Results are reported in parts per million (ppm) lead (Pb) in the soil. Although this method does not measure total lead, it measures the fraction that is environmentally available and that which is potentially harmful to human health upon ingestion.
Nutrient Management P
For situations involving soil phosphorus and nutrient management decisions where extractable P is likely to exceed 100 ppm on the Bray test and 50 ppm on the Olsen test. The range for the nutrient management P test is 20-250 ppm. This test is basically the same as the Olsen P test, but with a dilution of the extract before colourimetric analysis. In detail: A 1 gram scoop of soil and 20 millilitres of 0.5 molar sodium bicarbonate (NaHCO3) solution are shaken for 30 minutes. The mixture is filtered and the filtrate is diluted 5 X with sodium bicarbonate. Colour is developed with the molybdate-blue/ascorbic acid method. The intensity of blue colour, corresponding to the amount of P in the extract, is measured with the Brinkman PC 900 Probe Calorimeter at 880 NM. Results are reported as parts per million (ppm) extractable phosphorus (P) in the soil.
Spurway
The Spur way extract is a weak acetic acid extraction of the potting media. A representative sample of the media is sieved through a 2 mm sieve to remove the larger pieces of bark, stones and other relatively inert materials. A 5 cc sub sample is placed into a 50 mL Erlenmeyer flask and 25 mL of 1% acetic acid solution is added with a volumetric buret. The mixture is shaken for 1 minute and then filtered. The filtrate is analysed for important plant nutrients: nitrate and ammonia levels are determined by calorimetry, and phosphorus, potassium, calcium, magnesium, sodium, iron, manganese, zinc, copper, molybdenum, and boron are analysed by ICP-AES. Results are reported as ppm (mg/L) in the media extract. A separate 15 g subsample is wetted with 75 mL of deionised water, stirred every 10 minutes for 40 minutes and the solution analysed for electrical conductivity. The media pH is determined on a separate 5 cc subsample that is wetted with 5 mL of deionised water, allowed to stand for 15 minutes, and the pH determined using a pH meter with reference and glass electrodes.
Saturated Media Extract (SME)
The Saturated Media Extract is a water extract of the entire media sample. No attempt is made to sieve the sample before analysis. A representative sample of the media is wetted with deionised water until water just barely stands on the surface. The mixture is allowed to stand for 90 minutes and then filtered under suction. The filtrate is analysed for important plant nutrients: nitrate and ammonia levels are determined by calorimetry, and phosphorus, potassium, calcium, magnesium, sodium, iron, manganese, zinc, copper, molybdenum, and boron are all analysed by ICP-AES. Results are reported as ppm (mg/L) in the media extract. The electrical conductivity is also determined on the above filtrate. The media pH is determined on a separate 5 cc subsample that is wetted with 5 mL of deionised water, allowed to stand for 15 minutes, and the pH determined using a pH meter with reference and glass electrodes.
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