Homework Activity
Jar Test for Soil Texture
Background:
1. Whatissoil?
2. Whatnaturalfactorsinfluencetheformationofsoil?
3. Howwillthedepthofeachhorizoninyoursoilprofileaffectyourplants?
4. Whichhorizondoyouexpectwouldprovidethegreatestamountofnutrientstotheplantsin
yourlandscape?
5. Whydoyouneedtosupplementthecultureofyourplantswithfertilizersormulch?
6. What are the three categories of soil mineral particles that are active in supporting plant
growth?
7. Why is the weathering of the primary soil mineral particles important in supporting plant
growth?
Whatyoushouldbelearning.
Comparetheresultsofthejartestwiththosefromtheribbontesttodeterminethesuitabilityof
yourlandscapesoilinsupportingplantgrowth.
Howlongwillittake?
Thisjartestwilltake2-3days.Youcouldcollectyoursoilsampleforthisactivityatthesame
timeyoudigaholeforthedrainagetest.
Suppliesyouwillneed:
Shovel
Jarwithstraightsides(Ideallyabout1quartcapacitylikeamayonnaisejar)
Rulerortapemeasure
Markingpen
Clock
Calculator
Whattodo:
Thereareseveralonlineprotocolsforperformingthistest.Youcanchoosetouseanyof
thesedirectionsorfollowthedirectionsbelow.
•http://www.dummies.com/how-to/content/urban-farming-how-to-determine-yoursoil-type.html
•https://www.youtube.com/watch?v=AUhOBxVFcFk
•http://www.ext.colostate.edu/mg/gardennotes/214.html
•https://www.youtube.com/watch?v=knrmCbctGEA
•https://www.youtube.com/watch?v=GWZwbVJCNec
Thebasicpremiseforthisactivityistosuspendasampleofsoilthatisrepresentativeofyour
yardorlandscapesoil(andsuspendtheparticles)inwater.Thelargerparticlesshouldsettleout
beforethesmallerparticles.Bycomparingtherelativevolumeofeachparticlecategory,you
shouldbeabletoestimatethetextureofyoursoil.
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Collectarepresentativesampleofsoilfromyourgarden.
Remove any large objects (gravel, rocks, roots, etc.) With your fingers, break up any
dirtlumpsorclods.
Fillthejarabouthalfwaywithyoursoilsample.
Optional:Addonedropofdishwashingliquid,oneteaspoonofTSP,oroneteaspoon
ofpowdereddishwasherdetergenttohelpbreakupclumpsofsoilparticles.
Fillthejartowithinabout1inchofthetopwithtapwater.
Capandshaketocompletelysuspendthesoilinthewater.
Placeonaflatsurfaceandallowthesuspensiontosettleout.
After1minute,markandmeasuretheheightofthesedimentsatthebottomofthejar.
Afterabout1hour,markandmeasurethethicknessoftheadditionaldepositsontopof
thefirstlayerofparticlesinyourjar.
Allowthemixturetosettleoutundisturbedforonetotwodays(atleastovernight).
After about 1 -2 days, mark and measure the thickness of the additional layer that
hasaccumulatedoverthefirsttwolayersofparticlesinyourjar.
Carefully transport your jar to class for analysis trying not to disturb the layers of
soilparticles.
pg. 2
Whatdotheresultssuggest?
8. Fillinyourmeasurementsbelow.
Layer
SoilMineral
Particle
Bottom
Sand
Middle
Silt
Top
Clay
TOTALTHICKNESS
Thicknessoflayer
(mmorinches)
Percentage
9. Calculatethepercentageofheightforeachparticlebydividingthethicknessofeachlayerby
theTotalHeightandmultiplyingtheresultsby100.
𝑡ℎ𝑖𝑐𝑘𝑛𝑒𝑠𝑠
𝑃𝑒𝑟𝑐𝑒𝑛𝑡𝑎𝑔𝑒 = 𝑥100%
𝑡𝑜𝑡𝑎𝑙𝑡ℎ𝑖𝑐𝑘𝑛𝑒𝑠𝑠
10.Plotyourpercentagesonthesoiltexturetrianglebelow.
a. BeginbyputtingamarkonthebottomlegofthetriangleatthepercentofSANDyou
calculatedinyoursoilsample.
b. Fromthispoint,drawalineupwardtotheleft,paralleltotheotherslantedlinesthatstart
onthesandscale(bottom)ofthetriangle.
c. Ontheleftsideofthetriangle,markthepercentofSILTinyoursample.
d. Fromthispoint,drawahorizontallineacrossthetriangletotheright.
e. Ontherightsideofthetriangle,markthepercentofCLAYinyoursample.
f. Fromthispoint,drawalinedowntotheleft,paralleltotheotherlinesthatstartonthe
clayscale.
g. The3linesyouhavedrawnshouldintersectinapoint.Thatpointwill
fallintooneofthesoildescriptionsonthegraph.
pg. 3
11.Atwhichsoilclass(texture)doyourthreegraphlinesintersect?
12.Howdoessoiltextureaffecthowwellplantsgrow?
Conclusion
13. Howissoilstructuredifferentfromsoiltexture?
14. Whyisthestructureimportanttoplantgrowth?
pg. 4
15. Howdosoilmanagementstrategiessuchastillage,irrigationscheduleandcultivationaffect
soilstructure?
16. Howisasoilprofiledifferentfromsoiltexture?
17. Explainwhyadifferenceinsoilprofilesmightaffectplantgrowthdifferentlyforsoilswitha
similartexture?
18.Completethetablebelow.
Characteristic
SandySoils
LoamySoils ClayeySoils
Primary particle size. Surface to volume ratio (high,medium,low).
Generaltextureclass(coarse,medium,fine).
Infiltration. The entry of surface water into the soil–oppositeofrunoffpotential(rapid,medium,
slow).
Percolation. The internal water drainage and leaching(high,good,poor).
Waterstoragecapacity.Abilitytostorewaterfor plantuse(low,medium,high).
Aeration. The ability of oxygen to reach the root zone(good,moderate,poor).
Easeoftillage.Easeofseedbedpreparation(easy, mediumdifficult).
Soilporosity.Theamountofporespaceinthesoil (low,medium,high).
Field capacity. Maximum amount of water soil canholdagainstgravity(low,medium,high).
Nutrientstoragecapacity(low,medium,high).
Cation exchange capacity. The amount of cations thatcanbeadsorbed(low,medium,high).
19. What irrigation and fertilization strategies would you recommend for someone with a soil
textureandstructuresimilartoyoursoil?
20. Later you might conduct a second test to determine the soil texture called the ribbon test.
Howdidtheresultsoftheribbontestcomparetothisjartest?Whatinformationcanthejar
testprovidethattheribbontestmaynot?
pg. 5