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Plan spring fertiliser applications for tillage crops

Considering the cost of nitrogen in 2022, it’s a good year for farmers to look at ways to reduce nitrogen use on farm. There are a number of ways to reduce nitrogen use including; growing your own nitrogen (using legume crops), reduce nitrogen inputs and more options as discussed here

Ways to reduce nitrogen use include; growing your own nitrogen (using legume crops), reduce nitrogen inputs (by using less and increasing the precision of application), use an alternative source of nitrogen (by using organic manures), and changing the source of your nitrogen.  We will look at these one by one.

Grow your own nitrogen from legume crops

 Beans are a crop many people may have tried over the past 10 year.  The crop can suffer from yield inconsistency and when the crop is poor it can be very poor (think of 2018) however growers who plant the crop on time (on the correct land) and manage it carefully are achieving quite consistent yields, year on year.  Increasing the area of beans can significantly reduce fertiliser requirements. Take an example of an 80 hectare farm, growing winter barley (20 ha), spring barley (56 ha) and a small amount of beans (4 ha).  If the cropping is adjusted, where winter barley would stay the same (as its already planted) and the farm maximises the area of beans ( e.g. beans at one in five years) and reduce the amount of spring barley sown, this reduces the farm’s nitrogen requirement by 14% or close to 7 tonnes of CAN (or €4,000 @ €600/t for CAN).  These are significant savings and the overall profitability of the farm will not be compromised. 

Reducing nitrogen below the optimum rate for yield is always tricky

Nitrogen recommendations for crops are based on the economic optimum.  This rate generally builds in a little extra nitrogen to ensure high yield, but not necessarily the highest yield.  By increasing nitrogen above this level does not guarantee a higher yield, rather it’s a sum of diminishing returns.  Based on this, and knowing the cost of fertiliser and the sales price for grain, we can calculate the break-even return or BER for crops. 

Teagasc calculations, where CAN is €620/t and grain can be sold for €200/t, then growers should apply 33kg/ha less nitrogen to crops.  Where grain rises to €220/t, then growers should only use €27/ha less nitrogen.  Given the projected cost of nitrogen and the sales value of grain, reducing nitrogen will be profitable for most growers.  

Using organic manures

Where growers can get organic manures and maximise the embedded nitrogen then significant savings can be made.  For example, a grower applying good quality cattle slurry 33m3/ha (3,000 gal/ac) to 20 ha (50 acres) can save €6,000 on chemical fertiliser (not including the costs of slurry spreading). 

Changing from CAN to protected urea

Changing from CAN to protected urea can help to marginally reduce emissions on a plough based system. Research shows some reductions are possible but other considerations such as achieving the correct spread width (out to 24m or beyond) may be more problematic.   

This farm advice is part of the Climate Actions for January being promoted by the Signpost Programme . Get more advice by clicking on these links. Subscribe to the Signpost newsletter, by cliking on the button below, so that you never miss out on the up-to-date advice.