Fertiliser advice for second cut silage

With first cuts currently underway across the country, attention will soon turn to fertiliser application for the second cut.

With a challenging spring, high levels of rainfall and poor grazing conditions throughout March and April, silage reserves have become quite low and depleted on many farms. The National Fodder and Food Security Committee (NFFSC) raised a concern of fodder supply issues in drought prone areas if the summer weather trend continues in 2023 in April when they met. A good second cut will be important to not only to replenish winter reserves but also to rebuild a buffer. A rolling reserve of one month’s silage per cow (equivalent of two bales) or more is recommended to manage risk on farm.

Additionally, according to the NFFSC N, P and K applications in 2022 were down 14, 24 & 26% respectively versus 2021, therefore reserves in the soil for growing crops will be lower. According to the recent fertiliser sales data released by the DAFM, fertiliser sales continue to be down compared to last year. If nutrients are not replaced soil fertility will reverse, which farmers have worked hard to build, negatively impacting on grass growth, quality and yields.

Grass silage yield, feeding value and nitrogen use efficiency will decrease rapidly depending on soil type if annually K offtakes are not replaced. Phosphorus is required in relatively large quantities during critical plant development phases such as rooting, seed production and vital for cell division or regrowth. These are important to optimize regrowth’s, quality and yields particularly in year where silage reserves have been depleted.

In many cases, the yield being cut can often be  5t/ha of dry matter (equivalent to approximately 10t of fresh grass/acre). When looking at the fertiliser requirements for second cut with a yield of 10 tonnes fresh weight/ acre this crop will require approximately 80 unit/acre of N, 16 units of P and 100 units of K. It’s important to remember this recommendation assumes a soil index 3. If soil indexes are 1, the P and K requirements increase to 32 units of P and 140 units of K. Heavier crops will have a greater requirement for nutrients, especially K where for every extra tonne of fresh weigh/ acre produced will require an extra 10 units/ acre.

Assuming slurry is available on farm to apply to silage ground, 3,000 gallons of slurry using LESS will supply 15 units of N, 15 units of P and 96 units of K applications. Five days after slurry application, apply balance with chemical fertiliser to support the crop growth.

Apply lime where 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.

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

Further fertilizer recommendations for different crop tonnages can be found in the Gain Momentum booklet

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 fertilizer to match your requirements.

For more information please contact your local Tirlán Farmlife representative, branch or visit Tirlán FarmLife

First Published 22 May 2023

Tagged with: Dairy

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