However, there are several factors that farmers can control, especially soil fertility status. Late February/early March is a good time for soil sampling provided there has been no organic manure, lime or bagged fertiliser applied in the previous three months.
A soil sample will be adequate for 4ha (10 acres) provided it has been under similar management. This service costs £10.44 sterling including VAT and represents excellent value for money to enable you get more production from grass. Soil sampling augers are available from local Department of Agriculture and Rural Development (DARD) Direct Offices. When collecting a soil sample, approximately 20 cores should be taken in a W pattern across the field to ensure representative sampling.
Results should arrive in approximately one week and will indicate soil pH, lime requirement and Phosphate (P) and Potash (K) indexes. It is important to address lime requirement quickly as up to 50 per cent of nitrogen fertiliser is wasted at low soil pH. Continuous use of a field for silage can very quickly deplete soil P and K reserves and this will result in poor yields.
Slurry should be targeted towards these fields and a suitable compound fertiliser applied. On the other hand, applying compound fertilisers to fields with higher P and K indexes is a waste of money and results in no extra yield, luxury uptake by plants or loss of nutrients into groundwater.
To assist you in making good decisions regarding soil improvement and grassland management practices, there is a crop nutrient requirement calculator on the DARD website or alternatively contact your local College of Agriculture, Food and Rural Enterprise Development Adviser (Telephone 0300 200 7843).
Dr Norman Weatherup Senior Grassland Technologist, CAFRE, Greenmount