As farmers, our primary asset is the land. The success or failure of our farm business is largely determined by the performance of this asset. Somewhere along the way we have forgotten to look after the basics of soil health. Instead of correcting soil deficiencies, we tend to supplement the animal, or crop, on the ground rather than addressing the real problem.

As grazed grass is the cheapest feed we can produce for livestock, maximising its production has to be a primary objective on farm.

Steps to address soil fertility

1. Soil sample

Each of the Farm Profit Programme focus farms have taken soil samples earlier this year to get a handle on the current soil fertility status on farm. Ideally, samples should be taken between December and February and prior to any fertiliser application in spring. Sampling has to be the basis of any soil fertility plan. Spreading fertiliser without knowing the fertility status of the soil is like putting oil in an engine without checking the dipstick.

If starting from a low base in terms of soil samples, it is important to sample a sensible proportion of the farm. There is no point in spending a lot of money sampling hundreds of acres if you don’t have the time or money available to address fertility issues on the whole farm. A soil sample is valid for five years, so sampling 20% of the farm each year will ensure that all fields are kept up to date.

2. Addressing pH

The pH of the soil will determine the availability of nutrients to the growing crop. Optimal pH for mineral soils is 6.3 (6.5 for arable ground). Below this, nutrients start to become “locked up” or bound to the soil and unavailable for use by the plant.

3. Correcting P and K

After pH, phosphorus (P) and potassium (K) are the next nutrients to correct. Remember that P and K availability will increase by correcting pH thus making lime the first port of call. Available P and K reserves in the soil are reported on a six-point scale from very low (VL) to very high (VH). The target for samples should be moderate + (M+). At this level only maintenance application of P and K is required. Below this, there is a need to apply more nutrients to build up soil reserves. Soils with a P index of M+ have the ability to grow 1.5t DM/ha per year more grass than those that are VL or L.

4. Use farmyard manure effectively

Dung is a valuable source of nutrients on farm. Each tonne of farmyard manure supplies 3.2kg of P and 8kg of K according to SRUC figures. Application should be rotated around the farm, not applied to the same fields all the time. Target manure to land with low P and K levels and land with high requirements. Application works best prior to a period of increased growth so early spring or after a cut of silage are optimal.

5. Balancing nutrient shortfall

The yield potential in any field is only as good as its first limiting factor. This is usually P and K in grassland. Once farmyard manure has been allocated, any nutrient shortfall should be made up with chemical fertilisers. Take into account the current P and K status of the land and the offtake of the crop.

Correcting soil fertility is a long-term project that needs to be continually monitored. There is no ‘‘one size fits all’’ approach. Your plan must be tailored to your own farm.