Teagasc is strongly advising tillage farmers to soil test over the coming weeks as Irish soil fertility levels are falling.
Crop yields from Harvest 2022 were above average for most crops. This will have resulted in increased offtakes of phosphorus (P) and potassium (K), so it is very important to now assess crop P and K offtakes and soil fertility over the coming weeks.
Teagasc analysed 3,794 tillage soil samples in 2021 and the results show a slight decline in soil fertility on tillage farms when compared to the previous year.
Soil test
According to the latest figures, 18% of Irish soils have optimal pH, P and K values (a 6% year-on-year decrease); 61% of soils have a soil pH >6.5 (13% decrease); 57% of soils are at P index 1 and 2 (7% increase); and 32% of soils are at K index 1 and 2 (2% decrease).
Soil test results will provide recommended rates of lime to correct soil pH to the optimum pH 6.5 for a cereal crop rotation.
Where crops such as oilseeds, beans or beet are part of the crop rotation, a target soil pH of 6.8 is recommended.
Applying lime
Growers should aim to apply lime over the coming weeks and months to correct soil pH for either winter or spring crops.
Lime is a soil conditioner and delivers many benefits to our soils from soil pH correction to improving soil structure at least cost.
For winter crops, where possible, apply lime to ploughed/pressed soils. Optimising soil pH will provide the right soil conditions for the establishment of winter cereals and ensure such nutrients as P and K are readily available for rapid establishment.
Winter cereals have a demand for P and K, which ensures that crops are well established in terms of rooting and tiller development entering the winter period.
Index 3 soils will have a good supply of P and K for crop establishment, therefore omit P and K applications until springtime.
A fertiliser product such as 0-10-20 or 0-7-30 will supply the correct balance of P and K.
These nutrients should be applied at sowing time and incorporated into the seedbed; fertiliser P applications should be completed by October 31.
Where organic manures are available, they should be considered as a source of P and K for winter cereals. E.g., farmyard manure / cattle slurry / mushroom compost are all suitable organic manures, as they are low in nitrogen (N) and will supply good levels of organic matter.