----- Original Message ----- From: Liz Davis <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Friday, November 01, 2002 12:00 PM Subject: studying soil tests
> Hi all, > Was wondering if any of you may take the time and make comments towards my > interpretation of soil tests. (Testing myself for the exam) > Wanting to see if I'm getting the hang and where I'm not making links. > There is no physical assessment of the soil, just the data to work from. > (I've already given them an ear full of not treating the test but the soil, > the cause not the symptom, but this hoop I must jump through) > Hi Liz > Incitec Soil Test Analysis They sell fertiliser but their lab results, are pretty consistent and out of a couple of hundred that I have seen for our area there have been no obvious stuff ups. > > 0 - 15 cm Ca - 76.8% Mg - 8.69% K - 13.04% Na - .72% Al - .72% Potassium a bit high but I am used to that - I believe this indicates a high degree of weathering. Ca/Mg ratio looks good, Na low > > OC - 1.2 CEC 6.9 pH (CaCl2) 6.9 EC - .6 Ca/Mg - 8.2 P - 18 Organic carbon 1.2 % on an incitec test is reasonable - would translate to about two at the Perry lab - and is about in the range of better class wheat soils - CEC 6.9 says this is a nice light loam soil . pH ? Incitec tests usually give both CaCl2 and water pH? > > OM - .72 Cl - 13 Cu - 1 Zn - .8 Mn - 12 Fe - 43 B - .5 Whats the first one here OM? Traces are low particularly Zn and B > > > 20 + cm Ca - 70.1% Mg - 23.1% K - 6.1% Na - .34% Al - .34% > > P - <5 CEC 14.7 pH(CaCl2) 14.7 EC - .5 Ca/Mg - 3 > > Organic matter levels need to be increased. You will need to say how to increase OM > The pH increases from mod. acid > to a weakly alkaline. The nitrate N is 12 mg/kg in the top and 0 in the > 20+cm zone. S at 9 mg/kg in the top and again 0 in the lower zone. P is at > 18 mg/kg followed by 4 at 20 +cm. K is at .9 in both soils. Mg, pH and CEC > Increase with depth. figure the increase in CEC may be due to more clay > content, seeing no OC -Yes! > > the first 15 cm appear to be a sandy clay loam the lower being a light clay. > the CEC indicates a poor shrink swell potential, No - shrink swell characteristics of a clay are related to the TYPE of clay (smectites)not the amount, the layers are held together weakly and water can easily enter the interlayer spaces swelling the clay crystals - Illite clays have potassium (K) in the interlayer space and dont allow much water to enter, they are stable and dont expand -you probably need to do some revision on this, it is almost a guaranteed question in soil exams, > whilst the Ec indicates a likelihood of dispersion. You need to work on this too - learn the difference between dispersion and slaking and what causes each - learn the chemistry behind this. > Negligible salinity with ECe at .77 & .68. > the levels of Mg in the subsoil indicate leaching Yes - slow leaching of clay particles down the profile > and may be causing K > deficiency, the K in the topsoil could result in Mg deficiency. I think the extra K in the topsoil is because of weathering of an Illite type clay and leaching > The drop in Ca/Mg ratio has me stumped. Why? you have a clay loam subsoil with higher magnesium, low sodium, ideal potassium, > Would liming be required, but that would then No definitely not there is plenty of calcium showing on this soil test > impact on the Ca/Mg ratio especially on the top 15cm. The cations are below > to take up the Ca when it gets down there. ? > Tend to think that there should be more P available below for the rhizosphere, but > also see this as moving > slowly through the profile. Availablility of P being affected by pH, which > if increased in top 15 cm from lime application would make more P available > up top, but not necessarily in bottom sample. P is at reasonable levels for crop and pasture growth - would require maintence applications. > Zinc could be lacking due to climatic conditions cold winters / wet springs > (not this year) more required especially for high productive crops such as > fruit and Veg. > Nitrogen fertility is rated at moderate fertility in the top 15 cm, thinking > the drop in Ca/Mg ratio has decreased the N in the lower sample. Dont think so. remember how mobile and expendable nitrate N is, once it starts to move down the profile it will keep on heading for the water table, also the release of N thru mineralisation is tremendously variable in our climate.Paddock history is a far more reliable indication for N. > > Any indications of where I'm not linking or looking would be helpful. > Thanks > L&L > Liz > > > > >
