Work out your costs before deciding on re-sowing

I considered replacing my 64ac of hybrid winter oilseed rape but after a detailed look at the finances involved, I have decided to manage it to harvest

Decisions: Tom Tierney in a field of winter oilseed rape on his farm at Ballinafagh, Prosperous, Co Kildare. Photos: Damien Eagers

An accurate double disc air seeder used on Tom’s farm

Decisions: Tom Tierney in a field of winter oilseed rape on his farm at Ballinafagh, Prosperous, Co Kildare. Photos: Damien Eagers

An accurate double disc air seeder used on Tom’s farm

Decisions: Tom Tierney in a field of winter oilseed rape on his farm at Ballinafagh, Prosperous, Co Kildare. Photos: Damien Eagers

Tom Tierney

February 27 2023 09:27 PM

The wet conditions after planting in the autumn have taken their toll on many of my winter crops. I am trying to see if my 26ha (64ac) of hybrid winter oilseed rape (WOSR) is worth keeping, or should I replace it with a crop of malting barley.

I have companion-cropped my oilseed rape over the last number of years with good success in an effort to reduce crop N requirements and improve soil health.

In deciding on what to do, I first had a look at the costs I have incurred to date with the crop, such as soil cultivation (1 x disc), sowing (Duncan direct drill), rolling and seeds (OSR and companion crop seeds) — and the total spend is €315/ha.

My advisor Ivan Whitten and I walked the crop last week and we established that there were 5-25 viable plants per square metre (GAI 0.5 to 1.5).

However, as with many Irish tillage fields there were numerous small areas missing plants due to pest damage and poor weather conditions. In total, we estimated that 2ha were not viable out of the 26ha.

We have decided not to replant the 26ha with a malting barley crop due to the distribution / management of the affected areas in the field.

An accurate double disc air seeder used on Tom’s farm

In addition the crop would have to carry its own growing costs plus the €315/ha costs incurred to date on oilseed rape inputs.

Based on the Teagasc Crop Costs & Returns it will cost €1,569/ha to grow a new crop of spring barley. This gives a total cost of €1,884/ha, which would require 7.0 t/ha to cover production costs at a grain price of €270t/t… leaving very low returns.

So the crop of rape will be managed to harvest; it has so far received an application of 8-5-18 +S+B at 250kg/ha. This help will kick-start the crop, delivering a balanced supply of both major and minor nutrients to aid the manipulation of plant buds on the main raceme.

We estimated that the WOSR crop has the potential to yield 2.5-3.2t/ha. The crop has received an application of Astro Kerb at 1.7 L/ha to control weeds.

Remaining crop inputs such as nitrogen and fungicides will be tailored during the growing season to reflect the projected final yield.

Remaining crop costs are estimated at €609/ha giving a total spend €924/ha, which will require around 1.6t/ha to cover growing costs at oil seed price of €570/t.

I am conscious of the changes in the new nitrates directive, in particular the requirement for soil sampling all tillage fields. The above field were intensively soil-sampled in October 2021 and results indicated soils at K index 4.

Based on the results, last year’s crop of winter barley received no potassium (K), with a final crop yield of 10.2 t/ha. This crop will have removed 102kg K/ha (grain and straw).

The field was re-sampled in October and results indicate that soil K levels have moved back into a high Index 3 (av 140mg/L) after one year.

The oilseed rape crop received 45kg/ha (compound fertiliser) K based on a crop yield potential of 3t/ha to maintain soil K fertility.

Tom Tierney farms at Prosperous, Co Kildare. Advisors: Mark Plunkett and Ivan Whitten