Grass leys did have a lifespan, but when a particular field was not responding there may be other underlying factors limiting performance, said Chris Duller, IBERS Grassland Development Centre (pdf), Aberystwyth, at one of the BGS, DairyCo show seminars.
“Regular soil analysis can identify these areas and improve nutrient efficiency, potentially reducing nitrogen application rates,” said Mr Duller.
“If you simply use less nitrogen, you will get less grass growth, ultimately leading to many farmers having to buy in more cake – forget opting for cheap, poor quality fertiliser or buying less and growing less. The key is to improve nutrient efficiency. There are massive savings to be had by improving soils”
It was not necessary to sample all fields at once, he said, but aim to get round the whole farm every 5-6 years. This would allow you to assess whether soil indices were at the targeted 2 or 2- for P and K and pH 6-6.5.
“If you fail to maintain indices, sward competitiveness will decrease leading to a higher weed burden. Incorrect pH levels will also limit the availability of P and K and other trace elements.”
Field-specific nitrogen application could also save you money. “Many farmers use the same application rates for all fields, but the way individuals leys react to the same level of nitrogen will vary depending on the age of the sward and grass constituents.”
Old leys would not respond as well to nitrogen application as new leys. “If you are going to cut back on nitrogen, do so on old leys not new leys.
“Walk individual fields – dig a hole and assess soil compaction and root depth and react to analysis results to formulate a plan of action for each field.”
First cut was a good time to assess grass for sulphur levels. “Soil sulphur deficiency can lead to suppressed grass growth caused by reduced nitrogen utilisation efficiency. Analysing levels after first cut will allow you to react before second and third cut.”