Agronomists have confirmed that Nitrogen Use Efficiency (NUE) is a strong indicator of both yield potential and the overall efficiency levels generated by cereal crops. This intrinsic measure of crop performance is also strongly linked to the carbon footprint generated by a tillage operation.
According to Colin Lloyd, the technical agronomy manager at Agrii, an agronomy services company based in the UK, the average NUE figure achieved on an international basis comes in at around 52%. However, the work at Stow Longa in Cambridgeshire has shown that it is possible to push this figure up to 90%. “Cultivation methods and the creation of suitable seed beds play a key role in making this happen,” he said.
The Agrii team calculate the NUE of a crop by including a grain analysis of the final crop and the use of nitrogen probes that are placed in the soil during its growth phases. According to Lloyd, grain analysis is an important management tool that tillage farmers must use on a consistent basis. Research and follow-up field trials have confirmed that grain sampling and subsequent analysis at harvest is an extremely accurate measure of true nutrient offtakes throughout an entire growing season.
The current Agrii trials have indicated that a switch to ploughing after five years of min-till establishment will serve to boost yields and NUE efficiency levels. Lloyd said: “This opens an argument regarding the use of ploughing within a cropping system plus the associated sustainability-related benefits of securing higher yields. Higher grain yields reflect directly on crops’ ability to take carbon dioxide out of the atmosphere.”
Lloyd believes this is the missing link when it comes to determining the carbon footprint of a cropping exercise. He added: “Currently, no recognition is taken of a cereal crop’s ability to absorb carbon dioxide from the atmosphere. Carbon footprint calculations take account of gross emissions only. In reality, it is the net emissions’ figure that should be used to determine the environmental sustainability of all cropping enterprises.”
The ongoing blackgrass trials at Stow Longa in Cambridgeshire are seeking to identify the NUE of the cereal crops grown for the purposes of quantifying the impact of cultivation options and crop rotations on final yields. Spring oats, as opposed to spring barley, are the preferred cropping option for grain growers in East Anglia.
Evidence suggests that tillage enterprises in Ireland have an extremely low carbon footprint, relative to other farming enterprises. The Irish government has committed to expanding the tillage area across the country and is one of its key responses to the climate change challenge.