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Soil Sampling

on Tuesday, 08 December 2015. Posted in Blog, Property, Tillage, Sheep, Dairy, Beef

Soil analysis will tailor fertilizer application to match crop requirement ensuring optimum crop production, by reducing nutrient loss to the environment and growing farm profitability.

Soil analysis is a very small farm expense costing in the region of €1.25/ha/yr. and will be valid for 5 years. A standard soil test will give the soils fertility status as follows; soil pH, lime requirement, soil phosphorus (P), soil potassium (K), soil magnesium (Mg) together with nutrient advice based on soil sample details and results.  It’s essential to take all nutrients into account in order to get the correct nutrient balance in the soil so that applied fertilizer is taken up by the growing crop.

1. Guidelines to taking a soil sample

  • For sampling purposes divide the farm into fields or areas of between 2 – 4ha.
  • Take separate samples from areas that differ in soil type, previous cropping history, slope, drainage or persistent poor yields.
  • Avoid any unusual spots such as old fences, ditches, drinking troughs, dung or urine patches or where organic manure or lime has been heaped or spilled in the past.
  • Do not sample a field for P and K until 3 - 6 months after last application of fertilizer P and K (now is a good time to soil sample).  Where lime has been applied allow a time lag of 2 years before sampling for lime requirements.
  • Follow a ‘W’ soil sampling pattern to ensure that the sample is representative of the entire field.  Ensure that all soil cores are taken to the full 100mm depth.  Place the 20 cores in the soil box to make up the soil sample.
  • Write the field number and sample number on the soil box.
  • Recommended Soil Sampling Pattern:

2. Soil sample details

Now that the soil sample is taken it is essential to sit down with your agricultural advisor and supply as much accurate information as possible such as - soil type, crop to be fertilized, stocking rate, cropping history, application of organic manure (slurry, FYM) etc. 

3. Having the basics right is the key ingredient to soil fertility

It is essential that when you get your soil sample results back that they are applied to improve the soils productivity and farm profitability with improved farm production and fertilizer management.  The cost of fertilizer has increased due to raising energy costs. Soil analysis is a useful tool that can provide the vital information that is required to optimize nutrient efficiency and reduce nutrient loss to the environment.

Applying Lime to Land

The optimum use of fertilisers is obtained when soil pH is between about 6.2 and 7.2.

 Lime is a soil conditioner.  It corrects soil acidity so that the microorganisms can thrive and break down plant and animal residues.  It helps in the release of Nitrogen and other nutrients from organic matter; it increases earthworm activity, which improves soil structure and assists the growth of clover and the survival of Nitrogen fixing bacteria. Recent soil samples are showing 50% of samples requiring lime.

Surface acidity

Liming soils improves the availability of all fertilisers especially nitrogen and phosphorous and many trace elements.

Surface acidity (in the top 50mm) often occurs in grassland due to our high rainfall and high usage of nitrogenous fertilisers.  This reduces the availability of fertiliser Phosphorous. For this reason it is better to have frequent small applications of lime than one large application.  Keeping the pH above 6.0 in grassland improves Nitrogen recycling and reduces total Nitrogen requirements. 

Little and often

In grassland soils which are high in molybdenum (Mo), it is important not to raise the pH above 6.2, as increasing the pH above this level increases the availability of Mo and this in turn induces Copper deficiency in the animal by reducing Copper absorption.

 If the lime advice exceeds 3t/acre for grassland, only 2 tons/acre should be applied initially and the remainder after two years.  Lime applications should be based on a recent soil analysis.

Best time to lime

There is no best time to lime, provided lime is spread evenly and left near the surface of the soil.  Ground limestone can be spread any time and pasture fields can be limed in rotation.  Grass can be grazed as soon as the lime has been washed off the leaves by rain. When reseeding grassland 3 tons lime/ acre should be applied.

Silage fields should not be limed until the final cut is taken.

 Lime and urea

If lime is spread in spring don’t spread urea on that field till the following year

 Liming Peats

Be careful when liming black peaty land. The ideal pH for peat soil is 5.5.

Bag Lime

Bag lime is finely ground lime.  It is very fast acting, however it is much more expensive than ground limestone.  It is very suitable if small amounts are required to maintain soil pH, however if using bag lime it should be applied every year.   It is also convenient when reseeding small amounts of grassland.

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