Planning for Spring Success

Grassland farmers will need to start preparing their soil for spring,  to ensure that it is in the optimum condition to sustain good grass growth. In particular at this time of year you need to be looking at whether your soil is deficient in phosphorus and potassium, as well as checking the pH level.

Measure for accuracy

The best starting point is a soil test - this will give you all the information you need to make informed decisions. This isn’t always about buying more inputs, it can also help you make decisions on where reductions on input costs can be made. Some farmers may choose to apply lime every four years, but if your pH level is already above 6, then you can save money by foregoing the lime.

Once you know what your starting point is, you can be more confident that the decisions you make on what inputs to invest in will deliver the best return on your investment. You may even want to consider undertaking a broad spectrum soil analysis which will go beyond the basic analysis of phosphate, potassium, magnesium and pH level. As Liebig’s law of the minimum states ‘A deficiency of any single nutrient is enough to limit yield.” Crucially, you need to ensure that any investment in valuable inputs such as nitrogen is not undermined by the lack of another nutrient or soil suffering from a low pH level.

It’s worthwhile putting in place a soil testing plan for your farm. We recommend at least a four year cycle, or testing 25% of the farm area at the same time each year. You need the full picture before you are able to develop an accurate nutrient management plan - fluctuations happen within a field, so relying on the results of one soil sample taken from one field is unlikely to increase your accuracy as much as you need it to.

Correct soil index level

The optimum index level of phosphate and potassium to achieve the best grass growth is index 2. AFBI research has shown that at this index level you can produce an extra 1.5t/ha of grass dry matter over soils with an index level of 1. Just think of the saving you can make in concentrate costs by increasing grass yields by this amount?

The importance of spring phosphate

In the spring, when grass is starting to grow, phosphate availability can be limited, and often overlooked. Phosphate is an important nutrient for growing grass, and a key time to ensure good phosphate availability is April and May, where a plant’s requirement can be as much as 0.6kg per day. Soil phosphate availability is lowest in the spring, so it makes sense to target a proportion of any mineral phosphate requirement for this period. Slurry applications in spring are also a good source of phosphate for grass crops.

The rate you apply will greatly depend upon your soil index level, so again your soil analysis will inform this decision. If you just need to maintain your phosphate index at 2, then 20 kg/ha is required for grazed grass, a 1st cut silage will require 40 kg/ha and 25 kg/ha for a 2nd cut.

New research has also revealed that good phosphate levels in soil has a positive impact on reducing N2O emissions.

Optimise pH level

You need to be aiming for a pH level above 6. Anything below that will impact the availability of nutrients within your soil. This not only impacts nutrients already in the soil (for example locking up phosphate in an unusable form to plants) but will also undermine any investment you make in additional mineral nutrients.

Get your pH level right before anything else to maximise any subsequent investment in mineral fertilisers - it’ll make your inputs go much further and maximise nutrient use efficiency.

Offset costs with slurry

Waste not, want not - use waste products such as slurry, but do it intelligently. Get an analysis done of your slurry so you know what nutrients it contains, you can then offset this against any additional mineral fertilisers you buy to reduce your input costs, whilst maximising accuracy and returns.

Ultimately, measuring and planning will help you make informed choices and save costs without threatening grass yields. Autumn is the perfect time to correct soil pH and develop a nutrient management plan.