Teagasc soil specialist, David Law, has dispelled the old myth that spreading lime on conacre ground cannot be justified on economic terms.

Speaking at the first of the virtual Teagasc Tillage Conference 2022 sessions, he said that ground limestone will deliver a plant growth response within two to three months of spreading.

Law said: “Up to 30% of ground limestone will be active within the soil very soon after application.

“This means that limestone can be spread on stubble or applied at sowing in cases where farmers are growing spring barley on conacre ground this year.”

The Teagasc research scientist confirmed that ground limestone can be purchased and spread for between €22/t and €24/t at the present time.

“Lime prices have not risen at all over recent months. This is in total contrast to the situation that is unfolding where N [nitrogen], P [phosphate] and K [potash] prices are concerned.

“Over the past number of months, phosphate prices have increased from €2/kg up to €3.69/kg. Where potassium is concerned, the equivalent figures are 85c/kg and €1.33/kg.”

Teagasc is confirming that N prices have almost tripled over the past 12 months.

Lime and soil pH

Recent surveys indicate that 23% of tillage soils in Ireland have a low pH with 37% being at optimal values.

“As a rule of thumb, spreading lime at a rate of 1t/ha will raise soil pH value by approximately 0.3 of a unit,” explained David Law.

“Crops such as potatoes and oats will tolerate lower pH values. However, the likes of fodder beet and barley require soil pH values to be in the optimal range of 6.5-7.0,” he added. 

Given the current state of the fertiliser market, Teagasc specialists are highlighting the need for tillage farmers to make the best use of the soil nutrients available to them.

“Soil testing will be a key driver in this regard,” stressed the Johnstown Castle-based research scientist.

“Given current circumstances, crops grown on Index 4 soils can get away without the need for applications of P and K this year.

“In cases where P and K are already at optimal levels, it’s a case of implementing a fertiliser plan that primarily takes account of the minerals that will be removed at harvest.

“Repeated trials have confirmed that the best response from phosphate fertiliser will be achieved when it is applied down the pipe in tandem with the seed when the crop is sown out.

“The potential for tillage farmers to use animal manures on spring crops this year is immense,” Law concluded.