Test soil fertility levels

SOIL analysis results indicate that low fertility soils are becoming increasingly common with many samples showing low soil pH coupled with low phosphate and potash levels.

In Kerry the main cause of poor soil fertility is the high rainfall coupled with the soil type. Soil analysis should be used as a tool to protect and manage your soil fertility into the future by drawing up a sound fertilizer plan.

Now is a good time to take soil samples and establish soil fertility levels as soil tests should not be carried out within 3 months of applying phosphorous or slurry to avoid transiently raised levels of phosphorous causing falsely elevated levels of phosphorus (P) on the results.

Many farmers will be considering spreading slurry once the closed season for applying slurry is finished on the 15th January – weather permitting.

Soil tests provide the basic information to allow you correct soils with low lime, phosphorus or potassium (K) levels and put in place one of the key building blocks to maximising grass production i.e. optimum soil fertility.

Ideally soil fertility on your farm should be monitored and maintained through regular soil testing every 3 – 5 years. As a guideline, take one soil sample to represent 2 ha. If the area is very uniform, a sample size may be increased to maximum of 4 ha in size. Under the new (2018-2021) Nitrates regulations the maximum area for soil samples to be taken has been reduced from 5 to 4 hectares.

Addressing soil pH by applying lime should be regarded as the priority action if it is indicated by the results. Efficiency of nitrogen and phosphorous availability will be greatly increased by addressing low pH by liming.

That said, extra care should be taken when applying lime to peat soils or soils in high molybdenum areas. These factors should be taken into account in the recommendations based on the soil tests.

Soils with P Index 1 will produce approximately 1.5t/ha grass dry matter less compared to soils maintained at the target soil P Index 3.

This equates to up to €345/ha loss in feed production compared with a soil at optimum fertility and P Index 3. Early spring growth is particularly affected by low soil P, while silage yields are very sensitive to soil low in K.

Farm level soil tests should be used to develop a lime and fertiliser spreading plan to build and maintain soil fertility levels to optimise production. Be prepared to invest in P and K for this purpose though targeting livestock manures (Slurry / Farmyard Manure) to fields with the lowest soil P & K levels will help build soil fertility more economically.

There have been increases made to the maximum application of phosphorous on Index 2 & 3 soils on farms stocked between 130-170kgN/ha in the recent Nitrates review but special conditions apply. If you fall into this category contact your adviser for details.

Soil fertility is a long term investment and needs to be reviewed every 3 - 5 years to plan future fertiliser applications.