Replenishing soils after first cut silage

Silage stocks on farms have dwindled over the past number of weeks, a good second cut of silage will be important to replenish winter forage and to rebuild a silage buffer.  A rolling reserve of one month’s silage per cow, which is the equivalent of two bales or more, is recommended to manage risk on farm.

According to the recent fertiliser sales data released by the CSO, fertiliser sales continue to be down compared to last year. If nutrients in the soil are not replaced, grass growth and soil fertility will be negatively impacted, this will have a knock-on effect on grass quality and yields.

After first cut silage it’s important to replace what has been taken out of the soil in terms of N, P and K to ensure we maintain good soil fertility and drive grass growth.

Nitrogen: In many cases the second cut can often be a 5t/ha of dry matter (equivalent to approximately 10t of fresh grass/acre) when nutrients are available. Nitrogen requirements for second cut with a yield of 10 tonnes fresh weight/acre this crop will require approximately 80 unit/acre of N. Four to five bales an acre will remove around 40-50 units of N/ac.

Teagasc and AFBI research has shown that Protected Urea is an effective N source growing the same levels of grass as CAN and Urea, with an added benefit of having the largest and quickest potential to reduce in greenhouse gas (GHG) and ammonia emissions within agriculture. Decreasing ammonia emissions by 80% when compared to Urea and decreasing greenhouse gas emission by 74% when compared to CAN. As a result on a per unit of Nitrogen, Protected Urea continues to be better value than traditional CAN products, while more expensive than standard Urea. Protected Urea will provide the same “effective N” for the plant as standard urea at a lower spreading rate, which is more sustainable for nature and your pocket.

Protected urea products are available not only as straight urea but also in a number of formats with sulphur and as N:K:S compounds. If slurry is used a straight N or an NP compound should follow. The way to get the most out of your slurry and fertiliser is to get your slurry tested to determine its nutrient value and balance thereafter. Variability can exist in terms of the nutrient content of cattle slurry.

Phosphorus & Potassium: Other nutrients play an important role in N utilization. Phosphorus is required in relatively large quantities during critical plant development phases such as rooting, seed production and is vital for cell division or regrowth. Grass silage yield, feeding value, and Nitrogen use efficiency will decrease rapidly depending on soil type if annually K offtakes are not replaced. These are important to optimise regrowth, quality and yield particularly in a year where silage reserves have been depleted. 

*Assuming P & K applied in 3000 gallons slurry.

Increase or decrease P by 1.6 units for each t/acre increase or decrease

Increase/decrease K by 10 unit/ac for each t/acre increase/decrease

A 10t of fresh grass/acre depending on soil index will require the following:

Second Cut Silage: The role of sulphur in second cut silage crops should not be overlooked, as it plays an important role in increasing yield, Nitrogen efficiency and reducing Nitrogen leaching. Apply approximately 8-12 units/acre of S per cut of silage.

An added benefit of using protective urea when it comes to spreading lime is that it can be spread straight after. Unlike ordinary urea, it is recommended to leave approximately three months between spreading lime and applying urea. If soil pH is not adequate, P, K & N are not being utilised fully and applied nutrients are at risk of being lost to our waters or air and a poor return on your investment. Apply lime where necessary.

In Tirlán we have a wide variety and range of fertilisers available to suit all needs. Our team will be happy to help you find the best fertiliser to match your requirements.

Products available that may match your requirements are listed below:

• Protected Urea: 46% N
• Protected Urea: 38% N + 7 S
• Protected Urea: 29-0-14 + S
• Protected Urea: 27-2.5-5
• Protected Urea: 24-2.5-10
• Protected Urea: 28-2.5-5
• Protected Urea: 25-2.5-10

When spreading PU products it is important to adjust your spreader as PU products are lighter than the conventional products.

For more information please contact your local Tirlán Farmlife representative, branch or visit Tirlánfarmlife.com.  

First Published 24 May 2024