Grassland and forage crops

Grass mineral analysis can be a useful tool to check nutrient levels, both macro and micro-nutrients levels in grass swards. Silage samples are regularly tested for minerals, but it’s usually with a focus on animal nutrition rather than crop nutrition. So, there is certainly more scope on both grass for grazing and silage to utilise mineral analysis to improve yields and nutrient use efficiency.

A farmer two years ago asked me to have a look at their 1^st cut silage mineral analysis report which highlighted a couple of potential problems. Because it was a composite sample from a number of different fields, it warranted a closer look the following spring, so three silage fields were sampled in May, 10 days before harvest.

The three fields had received the same nutrients, a combination of slurry and YaraMila EXTRAGRASS (27-5-5+6%SO₃) in the spring. Nitrogen, phosphate, potash, sulphur, calcium and magnesium were within the optimum range for two of the fields, while the report on the third field indicated that phosphate, potash, calcium and magnesium were low or very low.

These three fields had the same history of manure applications, and the most recent soil analysis indicated good levels of soil phosphate and potash. The difference was that the field which had the low grass nutrient levels also had a low soil pH (5.4). This makes sense, as soil pH affects nutrient availability. This again highlights the benefit of analysis and in particular acting on soil test results and correcting low soil pH.