soiltesting-120731015754-phpapp02

7/30/2019 soiltesting-120731015754-phpapp02

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Soil Testing

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Introduction:

We all know that health of soil is equallyimportant as health of any person. It ismore applicable when it comes to farming.

But, it is observed that now a day, healthof soildoesnt get enough attention. Peoplecare more about only cash crops andincreasing quantity of the crop. As a resultof this, soil becomes unproductive.Awareness about soil health should beincreased to avoid this.


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Why do we need SoilTesting?

Soil is an important matter for cultivation of any type of crop.

Soil supplies many necessary nutrients required for healthygrowth of a crop. The yield is largely dependent on the soil inwhich the crop grows. So, before cultivation, it is very importantto check the soil for its nutrients. By checking the soil you willknow whether the soil is having enough amount of nutrients or not.

If any nutrient is less or more than the required amount,necessary measures can be taken.

In short following are the benefits of soiltesting:Soil testing encourages plant growth by providing the best

fertilizer recommendations.It diagnoses whether there is too little or too much of a

nutrient.Soiltesting promotes environmental quality.It also saves money that might otherwise be spent on unneeded

fertilizer.


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When and How to take a sample of a soil?

Soil sample must be taken at the right time and in theright way as described here:

Before planting anything in the field and after youtake out the crop

Before application of any organic or chemical

fertilizersThree months after application of any organic orchemical fertilizers.

Do not take soil samples from the

following areas:Where cattle grazeUnder a treeGarbage area


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Only 0.5 kg soil is required for soil testing.

Following is the correct procedure to collect soil for soil

sample.

Procedure1. For soiltesting, soil is taken from 15 different places.2. Dig a V shape pit in the ground which is 15 cm deep. Take

soil sample (2 to 3 cm thick) from one side of it.3. Follow the same procedure to take samples from 15

different places.4. Clean the samples by removing any garbage if present in the

soil.

5. Mix all the samples very well (Make 4 equal parts of themixed sample. Then mix two diagonally opposite parts witheach other. Repeat the procedure for 4/5 times)

6. Take 0.5 kg of the sample for soiltesting.


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Dig the pits as per the following figure. Yellow circles show

location for the pit.


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Dig each pit as shown in the figure. Take soil from thearea shown in brown.

Floor surface


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Plants need 16 essential nutrients for healthy growthand development.

Necessary nutrients for crop growth:Main nutrients:

Nitrogen (N), Phosphorus (P), Potassium(K)Secondary nutrients:

Calcium (Ca), Magnesium (Mg), Sulphur (S)

Micro nutrients:Iron (I), boron (B), zinc (Zn), copper (Cu),molybdenum (Mo), chlorine (Cl), maganese(Mn)

Nutrients from air:Carbon (C), hydrogen (H)

Nutrients from water:Oxygen (O)

Apart from above nutrients, there are some other parameterswhich also affect plant growth. These parameters are: Soil pH, SoilEC (Electrical Conductivity) and Soil OC (Organic Carbon). To judgethe health of soil, these parameters should be checked.


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Signs shown on plants because of nutritionaldeficiency

Nitrogen Tree doesnt get averageheight. Leaves become yellow.

Phosphorus Growth of a plant stops

Potassium Leaves become reddishyellow on the edges while inner partof the leaves remain green.


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Calcium Tender leaves dry and plant dies.

Magnesium Leaves start drying from the tip.

Sulphur Brownish spots on leaves.

Iron Main veins of a leaf become green.

Manganese Younger leaves show chlorotic spots betweenthe veins.

Copper Leaves become yellow and stop growing andthen fall off.

Boron Young leaves become light in colour frompetiole and start folding.

Molybdenum Yellow/orange spots all over on maturedleaves.


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pH of soil

Apart from soil nutrients one more factor affect theyield. That factor is pH.

The soil pH is a measure of the acidity or basicity insoils. It is measured in pH units. The pH scale goes from

0 to 14 with pH 7 as the neutral point.

Hydrogen ions present in the soil decide pH value of thesoil. When +ve ions get washed off through water, soil

becomes acidic. Similarly, when amount of Calcium,Sodium in soil increases, soils become alkaline. Simply wecan say that low pH means sour and high pH means saltysoil.


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pH testing is important becausenutrient mobility ( transfer ofnutrients ) from soil to plant

through roots depends on pH ofthe soil.

Diagrams shows availability ofnutrients according to its pH -


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**We are using a readymade kit from Prerana Lab for all thetests. So, the procedures are given assuming that you havePrerana Lab kit with you to carry out the tests. Contact

Details of Prerana Lab are given on the last slide.**

Checking pH of soil

1. Take 5 ml of pH-1 solution in the test bottle no. 1.

2. By using a funnel, add two teaspoon (approx. 2 gm) soilsample in the test bottle no. 13. Put the cap on the bottle and gently shake it for a minute.4. Then keep the bottle still for 10 minutes. Now the soil will

settle down and there will be a layer of clear liquid on the

top of it.5. Place the test bottle in the pH colour comparator andcompare the colour of the liquid in the test bottle with thecolour on the comparator.

6. Note down the pH accordingly.


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Soil type according to its pH value:

pH value Soil type

Below 4.5 Extremely acidic4.5-5.0 Highly acidic

5.0-6.0 Medium acidic6.0-6.5 Slightly acidic7.0 Neutral7.0-7.5 Slightly alkaline

7.5-8.0 Medium alkaline8.5-9.0 Highly alkalineAbove 9.0 Extremely alkaline


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How to increase pH of the soil?

According to the existing pH of the soil, use Lime powder (Calciumcarbonate or dolomite limestone) to increase the pH. 0.5-2.50 tonsof Lime powder per hector of farm.

Use organic and grass fertilizers.


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How to reduce pH of the soil?

If pH of soil is more, that means ve ion deposited,soil becomes salty (alkaline). For small correction (ifpH is slightly high @ 8 to 8.5) leaching of these ionswill be useful. For leaching these deposited ionspreparing trenches toward slop of land / fixingpurported pipes (earthen / PVC) below 3 ft in soil canbe done.Similarly, green manuring with crops like sunhemp(dencha) , Jute (Tag) etc are also helpful.

For highly alkaline soils ( pH more than 8.5), gypsum(Sulphar) can be used. (Quantity of Sulphar isdecided on the basic of soil type and pH of soil).


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How to reduce the salts in the soil?

Scratch out all the salts which are there on thesurface of the soil.

Make small compartments (of a height of 1 feet)of the field and fill it with water.Keep the water there for some time and let itgo at once through an outlet. This way all saltswill be washed off.

Make sure that water is draining out properly.Use plenty of organic fertilizers.


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Checking Nitrogen content in the soil

We are using a readymade kit from Prerana Lab for this test.

1. Take 6 ml AN-1 solution in the test bottle no. 1.2. By using a funnel, add one teaspoon (approx. 1 gm) soil sample in the

test bottle no. 13. Put the cap on the bottle and gently shake it for a minute.4. Then keep the bottle still for 5 minutes. Now the soil will settle

down and there will be a layer of clear liquid on the top of it.5. Now, in an another test bottle (test bottle no. 2), take 2 ml clear

liquid from test bottle no. 1 with the help of a dropper. Make surethat there wont be any traces of soil from test bottle no. 1 in thedropper.

6. Add 4 drops of AN-2 solution in test bottle no. 2.7. Put the cap on the bottle and shake it gently.8. Keep the bottle still for 5 minutes.9. Now shake the bottle and compare the colour of the solution in the

bottle (test bottle no. 2) with the colour screen given in the kit.10. Note down the Nitrogen content in the soil accordingly.


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Checking Phosphorus content in the soil


1. Take 6 ml of EP-1 solution in the test bottle no. 1.2. By using a funnel, add one teaspoon (approx. 1 gm) soil sample in the test

bottle no. 1.3. Put the cap on the bottle and gently shake it for a minute.4. Then keep the bottle still for 5 minutes. Now the soil will settle down and

there will be a layer of clear liquid on the top of it.5. Now, in an another test bottle (test bottle no. 2), take 3 ml clear liquid

from test bottle no. 1 with the help of a dropper. Make sure that therewont be any traces of soil from test bottle no. 1 in the dropper.

6. Add 6 drops of AP-2 solution in test bottle no. 2.

7. Put the cap on the bottle and shake it gently.8. Now add 2 drops of AP-3 solution in test bottle no. 2.9. Put the cap on the bottle and shake it well.10. Now, the solution in test bottle no. 2 will look blue in colour.11. Compare this colour with the colour on Phosphorus colour chart and

accordingly note down the available phosphorus content in the soil.


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Checking Potassium content in the soil:

We are using a readymade kit from Prerana Lab for this test.1. Take 6 ml of AK-1 solution in test bottle no. 1.

2. By using a funnel, add two teaspoon (approx. 2 gm) soil sample in the testbottle no. 1.

3. Put the cap on the bottle and gently shake it for a minute.4. Then keep the bottle still for 5 minutes. Now the soil will settle down

and there will be a layer of clear liquid on the top of it.5. Now, in an another test bottle (test bottle no. 2), take 2 ml clear liquid

from test bottle no. 1 with the help of a dropper. Make sure that therewont be any traces of soil from test bottle no. 1 in the dropper.

6. Add one tablet of AK-2 in the test bottle no. 2.7. Let the tablet dissolve in the solution. (Do not put the cap on the bottle.

It will take 5 to 6 minutes for the tablet to dissolve completely)8. By now, colour of the solution in the test bottle no. 2 will change to light

purple.9. Now, take 1 ml of AK-4 solution in the red coloured syringes (available in

the kit).10. Add this solution (AK-4) in the test bottle no. 2 drop by drop till the

colour of the solution in the bottle becomes blue.

Continued


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Colour

change

Drop count of AK-4 Available Potassium(kg/hector)

Potassium contentin the soil

More than 22 drops Less than 100 Very less

21 to 22 drops 100-150 Less

19 to 20 drops 150-200 Medium

17 to 18 drops 200-250 Average

15 to 16 drops 250-300 High

Less than 15 drops More than 300 Very high

Continued from last slide11. Keep a count of no. of drops of AK-4 solution added in the test

bottle no. 2 to change the colour of the solution.12. Refer the following chart to know the potassium content in the soil.


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Organic Carbohydrates (OC)

OC is a measure of organic matter available in the soil.It shouldnt be less than 2% and shouldnt be more than30%. Bacteria grow properly if OC is in a proper limit.Carbon-Nitrogen (C:N) ratio also remains good in properOC limit.

*C:N ratio - C:N ratio means ratio between Carbon present in thesoil to the ration of nitrogen present in the soil. Say for example ifC:N ration of soil is 10:1 that means there is 10 part of carbon toeach part of nitrogen in the soil. All living organisms require to

produce energy for their survival and for that they need carbon astheir main source of energy. But if carbon (OC) contain in soil isvery less then micro-organisms will try to use nitrogen for theirenergy needs. This will lead to reduction in nitrogen content of soil,which is very important for plant growth.


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Checking OC content available in the soil


1. Take 100 mg sample soil in test bottle no. 1.2. Take 0.5 ml of OC-1 solution with the help of Green syringes and

add that to test bottle no. 1.3. Then add 80 drops of OC-2 solution in the same test bottle. (Do

this very carefully as this contain concentrated acid).4. Put the cap on the bottle and shake the bottle gently.5. Take 5 ml of OC-3 solution and add it in the test bottle no. 1.

Now keep the bottle still for 5 min. so that soil will set down andyou will get a clear layer of liquid on the top. This liquid will havea colour.

6. Place this bottle in organic carbon colour comparator to comparethe colour of the liquid in the bottle with matching colour on thecomparator.

7. Note down the percentage of organic carbon available in the soilaccordingly.


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Suggesting fertilizers according to the soiltesting results

Main objective of soil testing is to know the content or amount ofnutrients (for eg. Nitrogen, Phosphorus, Potassium, pH, Organic carbonetc.) available in the soil. Balanced amount of all these nutrients are veryimportant for healthy growth of any crop.

Fertilizers are suggested depending upon the amount of nutrientsavailable in the soil as well as requirement of the same for the crop. Soil

nutrients are generally measured as low, medium and high.

If available soil nutrients are very low, increase the dose of fertilizer by50%.

If available soil nutrients are low, increase the dose of fertilizer by 25%.If available soil nutrients are medium or slightly more than medium, no

need to change the fertilizer dose.If available soil nutrients are very high, reduce the dose of fertilizer by

50%.If available soil nutrients are high, reduce the dose of fertilizer by 25%.


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Contact Details of Prerana Lab:

Prerna Laboratory,Prerna house,Plot No- 8, Near Chatrapati Bank,Vishal Nager (Jagtap dairy),Aundh-Wakad road,Pune -411028.

Phone 27274958 / 9371015199.

References:

www.vasat.icrisat.orgwww.faculty.rpcs.orghttp://www.terragis.bees.unsw.edu.au/terraGIS_soil/sp_soil_reaction_ph.html
http://www.terragis.bees.unsw.edu.au/terraGIS_soil/sp_soil_reaction_ph.htmlhttp://www.terragis.bees.unsw.edu.au/terraGIS_soil/sp_soil_reaction_ph.htmlhttp://www.terragis.bees.unsw.edu.au/terraGIS_soil/sp_soil_reaction_ph.htmlhttp://www.terragis.bees.unsw.edu.au/terraGIS_soil/sp_soil_reaction_ph.html

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