Bhal Debate

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mikhurram
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Re: Bhal Debate

Post by mikhurram » September 4th, 2013, 4:40 pm

Sir the layer of 20 cm leaf mold would have to be mixed in with the soil.

I believe how much to add Gypsum would depend on the ph of the soil and the % of sodium content.

As I understand the reason for adding Gypsum is to improve the drainage of the soil by making it more porous. Sodic soils in which the ph is more than 8 and % of sodium is very high , the calcium in the soil is not soluble enough to be of any value of the plants. Gypsum being Calcium Sulphate when applied releases the soluble calcium which displaces the sodium ions from their bonding sites in the clay soil.

The question then arises that if our ordinary soil having a PH of 7 has more than adequate Calcium content then do we need to add any Gypsum the answer to which is in the negative.The addition of further Gypsum would further increase the more than sufficient calcium content in the soil. Too much of calcium can tie all the other necessary trace elements like magnesium, zinc, boron, etc and thus the uptake of these essential trace elements by plants would be effected. This is the only side effect I can think of. Based on this we can deduce that addition of Gypsum would be counterproductive in this scenario.

The points raised by Arif Sahib made me realize that by making a statement only on the basis of a soil being clay in nature we can't make an assertion that Gypsum has to be added in without conducting the soil tests first. Only if the Ph is more than 8.5 and high sodium % then application of Gypsum would make sense. Otherwise No.

A safer option would be to mix organic compost like leaf mold in our soil.

newton
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Re: Bhal Debate

Post by newton » September 5th, 2013, 6:23 am

Arif Sb if you feel it would be of any use to you or any other readers I can include a reference chart, diagrams and instructions on how to do some fairly simple home tests for soil and if the addition of gypsum would be beneficial or harmful.

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Re: Bhal Debate

Post by Muhammad Arif Khan » September 5th, 2013, 10:23 am

Others, I cant say but it will be very use full to me.
Thanks

newton
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Re: Bhal Debate

Post by newton » September 5th, 2013, 6:35 pm

Arif SB for you....anything :) :) :)

Home testing of problem soils before gypsum application
Two simplest assessments of clay soil and its suitability for gypsum application are described here. These are:
• using field observations, and
• using a simple dispersion test.

Field observations
Soils likely to be structurally degraded (lose their crumb structure when wet), and likely to be gypsum-responsive may:
• be hard when dry or have a surface crust (note that not all crusting soils are gypsum-responsive);
• become sticky or non-trafficable after light rainfall; puddles of water will have a milky appearance from the suspended clay;
• be difficult to cultivate because they are too hard or too wet;
• collapse after heavy rainfall;
• have low water infiltration and high run-off,
• produce patchy crop emergence and early growth, particularly in poor seasons.

please bear in mind though that compacted loam or sandy soil above clay can exhibit some similar character which is where the next formula comes in.

Visual dispersion test
Apart from looking at the condition of the soil and crop, you can do a simple test on site to determine if your soil is likely to respond to gypsum. The dry aggregate dispersion method described below includes photographic standards for providing a scale of the degree of dispersion (see Figure 1).
f05790a.jpg
f05790a.jpg (36.49 KiB) Viewed 4615 times

Faigure 1. Varying degrees of clay dispersion in soils. The higher amounts of dispersal (4 and 5) indicate a soil's suitability for gypsum application. No.0 displays slaking (breaking off of soil particles), compared to 1 to 5 which show clay dispersion . note the shadows you see in the samples are actually the dispersal of clay into the water as like a milky or cloudy matter. in 0 it is absent and in 5 it is the most cloudy.

The process of clay dispersion is a reliable indicator of unstable soil structure. Highly dispersive (structurally unstable) soils are likely to be more gypsum-responsive than those soils that are less dispersive.
Materials
• 100 mL beakers or 500 g glass jars (Glass jars/beakers are suitable)
• distilled water or fresh rainwater (treated or underground sourced water is unsuitable as its likely to contain chemicals that will influence the dispersal rates)
• dry soil aggregates (small clods, or clumps)
• black surface (bench, cloth or paper)

Method
1. Take about ten dry soil samples from the area to be tested, half from the soil surface and half from a depth of 15 cm. Highly dispersive topsoil is far more limiting in terms of potential productivity than dispersive subsoils.
2. Label each soil sample and break the sample into aggregates, or amounts about 5 mm in diameter.
3. Pour 50 mL of distilled water into ten separate, clean containers and place on the flat, dark surface. (If you are using 500 g glass jars, add 100 mL of distilled water to each. You will then be able to place five aggregates in a jar without affecting the results.) However, make sure you do not have samples of both topsoil and subsoil in the same jar.
4. Label the containers to identify each sample.
5. Gently place one aggregate into the centre of each beaker or jar and allow to stand for 24 hours without disturbance. (Make at least two tests for each sample to ensure the results are consistent.)
6. Rank the degree of dispersion on a scale from 0 to 5. Use Figure 1 to estimate this.
The results of the test are explained in Table 1.

Table 1. Likely response to gypsum of soils with varying levels of clay dispersion

Ranking .....Dispersion (%) .....Aggregate stability .....Response to gypsum
0 ..................0 ............................Very high .......................Nil
1 ..................20 ...........................High .............................Very low
2 ..................40 ...........................Moderate .......................Low
3 ..................60............................Low...............................Moderate
4 ..................80............................Very low.........................High
5 ..................100...........................Nill.................................Very high

A soil is likely to respond to gypsum if from field observations it shows the characteristics associated with poor soil structure and will readily disperse (ranking of 4 or 5).

All clays swell on wetting and the process of swelling causes particles to mechanically break off from the aggregate. This process is called slaking. This is a different observation to dispersion where the clay disperses to form a milky cloud around the aggregate.

It is the dispersiveness of a soil that determines its likely response to gypsum.

There are recommended rates of application based upon the results above. It can take two applications per year over three eyars to produce effective long lasting results. Test strips are recommended on the targeted area in the year preceding a blanket application to observe any responses to gypsum. If there is no response, continue observing the strip for a further season to account for seasonal variation.

Some soils are non-trafficable after rainfall and yet will not be dispersive. The sign to look for in this situation is a sandy to sandy loam-surfaced soil with a massive tight clay subsoil. Waterlogging is invariably the problem on these soil types. The clay subsoil prevents surface water from draining deep into the profile. Where this happens, to minimise degradation you can take the following steps:

1. Reduce tillage.
2. Avoid working the soil if it is saturated.
3. Reduce the volume of surface water flowing onto the soil, for example, by installing recommended drainage works.

There are also government run laboratories in most areas of Pakistan where for a nominal fee you can have the chemical and nutrient composition of soil and water samples analysed. This should give accurate results and indications of what essential fertilisers if any you need to apply. It can also indicate if the water source is actually the source of increasing soil salinity as can occasionally happen, however that is a separate subject requiring a detailed response out of the scope of this reply.

Regards
Ifzal

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Re: Bhal Debate

Post by talha.bin.ayub » November 24th, 2015, 10:04 pm

This thread should be refreshed. Some basic threads should be 'pinned' for all times to come


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Muhammad Arif Khan
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Re: Bhal Debate

Post by Muhammad Arif Khan » November 25th, 2015, 10:43 am

Afzal, Strange I Missed your post, It is never too late to say thank you.
In short as they say in Punjab GILLI GOYA TAY SUKKI LOYA.

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