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Research In Agriculture

Soil Testing

Soil testing is the base for management decisions about fertilizer requirements. It involves the estimation and evaluation of the available nutrient status and acidic reaction of a sample of soil. After testing, a fertility map is prepared where the available nitrogen, phosphorous and potassium is marked as low, medium or high. Areas of sufficient and insufficient nutrients are marked out and nutritional requirements are determined. Fertilizers such as NPK, lime or gypsum are recommended to improve soil fertility. Fertilizer addition, which is based on soil testing, usually leads to an increase in yields and profits by providing the correct amounts of needed nutrients. It also leads to uniform application of nutrients in a field. As nutrient availability becomes less variable, the crop growth is more uniform. Regular soil testing also contributes to environmental sustainability as the use of excess fertilizers can be avoided. Here is a list of soil testing laboratories in some States of Nepal.



A method of fertility evaluation - to understand the capacity of the soil for crop production - helps for the efficient and economic use of fertilizers - helps for increased production of crops - to maintain the soil health in a sustainable manner - helps for adopting integrated nutrient management system for increased crop production and soil health - soil test values are of little value if they are not calibrated against nutrient rate experiments conducted in green houses.


Soil Test Results- Contain 3 parts.


First part contains the: (i) pH of the soil (ii) organic carbon (as a measure of available N), (iii) total soluble salts (as a measure of salinity), available P, (v) available potassium, (iv) any other pertinent information.


Second Part - Fertilizers recommendation based on the analytical results, history of the field and recent research work - indicates quantities of N2 P2 O5 and K2O. Lime and organic manures to be applied for the crops.


Third Part - The methods and time of application of fertilizers and other practices required to make the fertilizer use more efficient and effective.




Water Testing


Aesthetic Objective (AO) - levels of substances or characteristics of water that can affect its acceptance by consumers or interfere with practices for supplying good quality water.


Alkalinity - is not a specific substance but rather a combined effect of several substances. It is a measure of the resistance of water to a change in pH. The alkalinity of most prairie waters is in the range of 100 to 500 mg/L, which is considered acceptable. Water with higher levels is often used. Alkalinity is a factor in corrosion or scale deposition and may affect some livestock when over 1,000 mg/L.


Calcium and Magnesium -  cause "hardness" in water. They are not hazardous to health but are undesirable because they may be detrimental for domestic uses such as washing, bathing and laundering. It also tends to cause encrustations in kettles, coffee makers and water heaters.


Coli forms (Fecal) or (E. Coli) or (Escherichia coli) - E. coli is a member of the total coli form group of bacteria and is the only member that is found exclusively in the feces of humans and other animals. Its presence in water indicates not only recent fecal contamination of the water but also the possible presence of intestinal disease-causing bacteria, viruses, and protozoa.


Coli forms (Total) - The presence of these bacteria may indicate contamination in a water supply. This group of bacteria is found in feces, soil, and vegetation and is used as an indicator of the bacteriological quality of water. Coli forms are useful indicators of the possible presence of pathogenic bacteria and viruses.


Conductivity (E.C.) - is measured in decisiemens/meter (dS/m). It can be used to estimate the total dissolved solids in the water. Multiplying the conductivity in dS/m by 640 will give a good approximation of the total dissolved solids in mg/L. Conductivity tests are often used to assess water suitability for irrigation. Conductivity is sometimes expressed as microSiemens/cm (µS/cm OR uS/cm), which is 1000 times smaller as a unit than deci siemens per centimeter. (Eg 0.75 decisiemens/m=750 microsiemens/cm=0.750 millisiemens/cm). We have used the letter "u" within our tool to represent the "micro" prefix "µ". We have used the conversion of 1dS/m = 700 mg/L TDS within the tool because the federal guidelines have used this conversion for their guidelines values for TDS.


Fluoride - occurs naturally in most groundwater wells and can help prevent dental cavities. Between 1 and 1.5 mg/L is desirable. As fluoride levels increase above this amount, there is an increase in the tendency to cause tooth mottling. Fluoride levels less than 2 mg/L are not considered a problem for livestock. 


Hardness - caused excessive soap consumption and scaling. Hardness is caused primarily by calcium and magnesium, but is expressed as a mg/L equivalent of calcium carbonate. Hard water causes soap curd, which makes bathroom fixtures difficult to keep clean and causes graying of laundry. Hard water will also tend to form scale in hot water tanks, kettles, piping systems, etc. Iron - levels as low as 0.2 to 0.3 mg/L will usually cause the staining of laundry and plumbing fixtures. The presence of iron bacteria in water supplies will often cause these symptoms at even lower levels. Iron gives water a metallic taste that may be objectionable to some at 1 to 2 mg/L. Most water contains less than 5 mg/L iron, but occasionally, levels over 30 mg/L are found. 


Maximum Acceptable Concentration (MAC) - levels of substances that are known, or suspected to, cause adverse effects on health.


NO3 nitrogen (Nitrate) - is often an indicator of contamination by human or livestock wastes, excessive fertilization or seepage from dump sites. The maximum acceptable concentration in drinking water is 10 mg/L. This figure is based on the potential for nitrate poisoning of infants. Adults can tolerate higher levels, but high nitrate levels may cause irritation of the stomach and bladder. The suggested maximum for livestock use is 100 mg/L.


Nitrate is converted to nitrite in the body. Nitrite causes asphyxiation by entering the bloodstream and reacting with hemoglobin (the red, oxygen-carrying pigment of the blood) to form met hemoglobin, which is not able to carry oxygen to the body's tissue. Nitrate in water is approximately 10 times more soluble than in feed. Caution is needed to differentiate between nitrate and nitrate-N or nitrate as N. Nitrate = Nitrate-N * 4.4


NO2 nitrogen (Nitrite) - has an element of toxicity. Nitrite is usually an indicator of direct contamination by sewage or manure because nitrites are unstable and quickly become nitrates.


pH - expresses the intensity of the acid or alkaline condition of a solution. A pH of 7 indicates neutral conditions on a scale of 0 (acidic) to 14 (alkaline). The generally accepted range for pH in water is 6.5 to 8.5 with an upper limit of 9.5.


Sodium - is not considered a toxic metal. 5,000 to 10,000 milligrams per day are consumed by normal healthy adults without adverse effects. The average intake of sodium from water is only a small fraction of that consumed in a normal diet. 

People suffering from certain medical conditions such as hypertension may require a sodium restricted diet, in which case the intake of sodium from drinking water could become significant. 

Sodium is a significant factor in assessing water for irrigation and plant watering. High sodium levels affect soil structure and a plant's ability to take up water. 


Sulphate (SO4) - concentrations over 500 mg/L can be a laxative to some humans and livestock. Sulphate levels over 500 mg/L may be a concern for livestock receiving marginal intakes of certain trace minerals. Very high levels of sulphates have been associated with some brain disorders in cattle and pigs. 


Total Dissolved Solids (TDS) - comprise inorganic salts and small amounts of organic matter that are dissolved in water. The principal constituents are usually the cat ions calcium, magnesium, sodium and potassium and the anions carbonate, bicarbonate, chloride, sulphate and, particularly in groundwater, nitrate (from agricultural use).


Turbidity - Particles of matter are naturally suspended in water. These particles can be clay, silt, finely divided organic and inorganic matter, plankton and other microscopic organisms. Turbidity is a measurement of how light scatters when it is aimed at water and bounces off the suspended particles. It is not a measurement of the particles themselves. In general terms, the cloudier the water, the more the light scatters and the higher the turbidity. The treated water turbidity target is 0.1 NTU (nephelometric turbidity units)