we take samples from field that have sandy soil very lose soil and dry soil after measurement moisture content we find low bulk density around 0.8 g/cm3 , 1.3 g/cm3 and 1.7 g/cm3
https://www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/nrcs142p2_053260.pdf
https://www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/nrcs142p2_050936.pdf
http://www.agriinfo.in/?page=topic&superid=4&topicid=271
Go through these links, it will help you
Dear Ahmed, sandy soils tend to have a higher bulk density that clay or loamy soils and also have a higher critical density for root penetration. This is generally plants can tolerate a higher bulk density in a sandy soil than in a clay soil. A bulk density of 0.8 g/cm3 is indeed very low for a sandy soil. I can only imagine that in Oman this may be due to the influence of other soil constituents that may be making the soil very open and loose such as surface efflorescence caused by salt/gypsum (having ruled out high organic matter content which can also result in low BD). The value of 1.3 g/cm3 would be quite low for a pure sand, but not unreasonable and a value of 1.7 g/cm3 would be on the higher side of normal indicating some compaction/settling and a soil low in organic matter and other less dense soil constituents. As a rule of thumb, root growth in sandy soils (>80% sand) can be start to be restricted at BD >1.6 g/cm3 , but severely restrictedat BD >1.8 g/cm3. There is some evidence in the literature and thorough my own observations that slight compaction (say BD of 1.4-1.6 g/cm3 ) may stimulate root growth.
Hope this helps.
The bulk density (BD) valueof 0.8 g/cm3 is unlikely of a sandy soil. Did you take the gravel content/percentage of the soil? If yes, to get accurate value of BD, there is need to divide the value by correction factor (1+Mstone/Mfine) where Mstone = dry mass of the gravel; Mfine = dry mass of fine soil.
The bulk density of soil is generally influenced by texture, structure, moisture content, organic matter and management practices of soil. In course textured soils bulk densities varies between 1.40 and 1.75 Mg/m3, which we are getting in Indian sandy soils. In fine textured soils, it normally ranges from 1.10 to 1.40 Mg/m3. The bulk density decreases with increase in organic matter content and fineness of soil texture. Higher values of bulk densities indicate more compactness of the soil. The bulk density generally increases with soil depth due to lower organic matter content and overburden of the upper soil layers. In swelling soils, it decreases with increase in moisture content and vice versa.
The soil bulk density is higher in coarse and fine soils because of wider macropores and occupy more volume than the clay soils.The clay soils have fine soil microspores which bring compactness and low soil bulk density .Besides,the bulk density values and soil particle density determine soil porosity which is important in soil hydraulic conductivity .Therefore, it is suggested that addition of organic fertilisers will decrease soil bulk density , increase the negative charges on soil colloids for cation exchange capacity and enhance better root growth network for nutrients and water uptake for bumper crop yield
Bulk density in sandy soils is generally higher than 1.5 g/cc, more proportion of macro-pores although total porosity is generally low, low water holding and rapid release of water, so requires frequent irrigation but with small amounts to avoid drainage losses, oc is generally very low, with lower CEC
Your values of less tan 1 g/cc may be very very rare phenomenon, may be some kind of solid waste lying on the surface or might have drifted below within the sub-soil and might be due to that the bulk density could be low, but not to that extent, you pl recheck the results
regards
I agreed with the statement of Naveen Karla.
Need to recheck the results.
The mentioned bulk density of sandy soils near about 0.80 g/cm3 is really low, however , other soil samples bulk density seems quite ok...This value needs recheck...
Too low value, i.e. 0.80 g/cm3 of sandy soils. Need to recheck this value. This value does not correlate with sandy type of soils.
Yes, Dr Syed , this is too low value as bulk density of sandy soil......
Such a low value is imposible for healty or undisturbed sandy soil. This soil could be plouged recently. I think an error appears during analysing the soil.
Can you please have a recheck on organic matter content of the soil, as a possibility..
If you measured the BD in correct way. This could be related to the mineralogy of the parent materials. If your soil formed on the volcanic tuff in this case you can have a bulk density below 1. Just check the mineralogy of your soils.
Dear Dr. Ahmed,
Please, do you have information about the OM content and the soil texture? Were the samples collected in each depth? Did you use volumetric rings for sampling? Which dimensions? Normally BD for sandy soils ranges from 1300 to 1800 kg/m3.
I endorse the other comments. A useful check would be to pour some of this (dry) sample into a measuring cylinder and tap it a few times then see what density it comes to. I think experimental mistake is most likely, but I have encountered pure silica sand with density on 0.9g/cc. Is the sand made of something other than silica? CaCo3 for example - there arealso a number of ex volcano products which have very low density. Or it may have very high OM content.
To follow up on the comments from Chris and mine at the beginning of this string, Ahmed is based in Oman and having worked there as a soil chemist many moons ago, I can say that many of the soils contain calcium carbonate, not to mention salts (including common salt and gypsum for example). There is also generally very little organic matter except in intensively used irrigated areas. Some soils have been laid down in layers from the times when there is surface water flow and as such texture and salt content can vary dramatically through the profile. I agree with others the values are low and that it would be a good idea to check the calculations, but I would not be surprised if the low values recorded coincided with soils that contain calcium carbonate or salt inflorescence. Again this would be easy to test for. Ahmed can you provide a follow up message to help guide the comments further.
@Ahmed- Please use core sampler for determining the BD. This is the correct way.All the best!
Please give some environmental context for the soils concerned. Andrew mentions carbonates above. Are they in sabkhas? Could they be volcanic? Is there any chance that they were emplaced by low-angle dry-flow runout from a wadi fan? Also what were the morphological changes down the profile as the BD went from 0.8 to 1.7?
Dear all,
I think that for some "sandy" soils there is an important rate of gypse (CaSO4) which make the bulk density to be lower than silica sandy soils.
What do you think about hydrodynamic behaviour of these gypsiferous soils?
Is it naturally formed autochthonous/allocthonous soil? Did you have your sample from the same field? What is the nature/mineralogy of sand fraction? Is there any amendments towards improving soil moisture properties by adding perlite or similar porous materials with low BD? You first answer these questions? If your sand fraction have silica mineralogy you most probably mismeasured the BD. If the sand fraction is a kind of volcanic ash with extremely porous nature and low density you can have a BD below 1 g/cm3. The other point is if all of these soil samples were taken from the same field with differing depth there should be other more complex situation. Some of these a dense layer, amendments with porous materials, wrong sampling procedure, the coverage of allocthonous material differing mineralogy, partial compaction in some part of the field, etc. In short, you should know the genesis and management history of the field to understand such differences in the BD.
May be due to higher fraction of air (volume of air) in the macro-pores is the cause for all sandy soils.
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