Soil testing best for optimising fertiliser/slurry
Yet it is one of the most neglected practices on Irish farms.
Contact Teagasc, your co-op, or merchant for advice on soil sampling and testing. Incorrect soil sampling can give misleading results.
If samples from areas treated differently in terms of slurry applications, silage cutting, etc, are mixed together, the results might indicate that the area is suitable for lime, P and K. The reality would be different.
Fertiliser recommendations are based on samples taken to four inches deep. Samples taken to any other depth are misleading, because most of the nutrients are in the top layers.
At least 25 cores should be taken in a W pattern in the area to be sampled.
Avoid sampling for P and K within 10 weeks of fertilising with P and K, within 12 weeks of slurry application, or within 18 months of liming.
Avoid sampling around gaps, or areas where cattle gather for shelter or other purposes.
Farmers using soil corers should get good advice on proper soil sampling and recording methods.
Bad soil sampling has been done in the past, due to corers being handed out without instructions.
Ideally, testing laboratories should have a well-trained adviser, or should supply a trained person to take the samples.
This should not cost very much extra, if there was a reasonable minimum number of samples per farm.
Soil Fertility
Proper soil fertility is the basis for efficient and environmentally friendly farming. Based on the low level of soil testing, and the deficiencies showing up, it is clear that this basic and essential element of profitable and good farming is not getting the attention it deserves.
Proper soil fertility is more important than ever to optimise returns from very expensive fertiliser and lime.
About half the recent soil samples are showing up serious deficiencies in P, K and lime.
Because of Nitrate Directive restrictions on fertiliser use, particularly P, it is also very important that fertiliser be distributed properly throughout the farm.
Fertiliser
Every farmer should know the nutrient (lime, P and K) status of his or her entire farm.
This information is essential to optimise production and to make the most economic use of expensive fertiliser and slurry, while minimising any risks to the environment.
In the late 1990s, Teagasc carried out a number of surveys regarding the use of fertilisers on dairy farms.
All of these revealed that many dairy farmers were using the wrong type of, or a lot more, fertiliser than was required.
With hindsight, the high levels of P that some farmers had built up on their farms, while P fertiliser was cheap, were a good economic investment.
Surveys also show farms where too little fertilisers, or unsuitable types of fertilisers, were used.
Some areas of farms may be suffering from a fertiliser deficiency, while other areas may have a surplus or an imbalance.
Due to the rise in fertiliser prices and the nitrate restrictions, there has been a significant reduction in the overall use of P and N in recent years, but this cutback has not always been in the proper areas.
Due to the cutback in fertilisers, P and K deficiencies have become very prevalent, and can seriously reduce production. If all slurry is returned to first- and second-cut silage areas, it will return most of the P and K that was removed from the soil in the silage crop (1,000 gallons of good quality cattle slurry is approximately equivalent to one bag of 0-7-30).
These areas will then require very little chemical fertiliser P and K. As a maintenance dressing for grazing areas, 10 to 15 units of P, and about 30 units of K, per acre should generally be adequate for maintenance, but this will vary with stocking rate and output.
