This was an interesting question posed to me by a client recently, they provided me with recent soil analysis data and some nutrient analysis from their silages and a recommendation for some commercially available biological supplements, along with the supplementary question “would this help”.

I suspect that the issue of not growing as much grass is not an uncommon issue on a lot of predominantly grass farms. The soil analysis did not give much away. The pH of 6.2 -6.5, phosphorus indices were on the low side and potassium indices OK but magnesium indices of 4 or 5 too high. What the analysis did not tell me was that the soils are heavy clays and probably lacking available calcium. Nor did the analysis give me any clue to soil structure, biological activity, or sward composition.

Knowing the client, I knew that the grass would have received large amounts of slurry over the years and would probably have been heavily trafficked, the swards would have been reseeded over the years with ryegrass only mixtures.

Certainly, some available phosphorus would not go amiss, this might be better if it came in a plant available form as the phosphorous may not be available in a dry spring and these soils are likely to lock it up quickly.

A walk with a spade or fork to try to determine the presence of compaction would be a good first step as would a sward assessment. The swards are all ryegrass and therefore shallow rooting and less likely to have any deep rooting herbs or clovers present.

A more detailed soil analysis showing available nutrients especially calcium and sulphur, soil organic matter (measuring biological activity is more difficult) and soil texture would help to throw more light on the problem and from this a plan of action could be put in place. I would like to see soil analysis from the current root zone i.e., about 4-5 inches and from deeper down at 8-12 inches where we would want the plant to be rooting.

The biological stimulant being advised might have some impact but is probably not the whole answer. This a complex issue that has built up over the last twenty years or so.

For more information or help with soil health, soil fertility and increasing the productivity of your soils, please contact William at w.waterfield@fcgagric.com or your local FCG Office.