Sulphur can improve silage quality

For the second installment of the Soil Fertility Series in association with Grassland Agro Clayton Coulter gives us some insight into his farm which is just outside Emyvale in Co. Monaghan.

Clayton is a member of the Breffni Oriel Holstein Club and owner of the Portvale Holstein Herd. Clayton farms with his wife Dianne, and daughters Rebecca (15), Jessica (10) and Emma (6).

The Portvale Holstein Herd is expanding and will grow to 80 cows in 2020. There are also three pedigree Jersey cows in the herd. The herd averaged 8,500L/cow last year and operates a 30:70 (spring:autumn) calving-split.

On the day of the visit in early March the cows were housed due to the inclement weather conditions, but were performing very well, which Clayton contributes to excellent quality grass silage.

Christopher Corrie, a Grassland Agro agronomist in the Co. Cavan and Co. Monaghan area, has been working together with Clayton on the fertiliser plan for the farm for the past three years.

“The fertiliser plan and advice help to maximise forage quantity and quality. Chris soil sampled the farm and provided great advice to help my soil fertility and make fertiliser decisions to maximise silage quality.

We use Sulfammo 30 and I have seen a great increase in protein in my silage and we have great flexibility on the harvest date.

“We have also used this on grazing ground and I am now keeping more cows on the same land area,” Clayton explained.

“I want a big cow, with a wide rump and the capacity for milk,” Clayton noted when asked to describe his ideal cow.

The Role of Sulphur (S) for grazing

The role of sulphur (S) in grass is in the formation of protein and it is a crucial nutrient to optimise nitrogen use efficiency (NUE).

S deposition from the atmosphere has gradually decreased due to improvements in air quality in recent decades.

It is also resulting in S being applied earlier in the season in spring, in addition to summer months. There is no suitable soil test for S, however, it is a nutrient that behaves similarly to nitrogen (N) in the soil.

Sulphur is mineralised throughout the growing season from organic matter. Soils with low organic matter (tillage soils or tillage conversions) will have a higher requirement for S.

While applying enough S is critical for grass growth and quality, it is also important not to over-apply the element as it can be an antagonistic to some trace elements, like copper for example, especially in situations where high levels of molybdenum are also present in the soil.

It is best to drip feed S with N on the grazing ground throughout the year. Balancing nitrogen application rates over the year with S at a ratio of 1 unit of S for every 12 units of N is a good guide.

Sulphur for Silage

Sulphur is just as important for silage crops as it is for grazing. The standard nutrient requirements for a crop of first cut silage are 100-20-90-16 (N-P-K-S) units/ac.

Silage Quantity

The expression “you could never have enough silage” is a common phrase amongst farmers. While this is true it should be amended to “you could never have enough good silage”.

While silage fed to dry cows can often be of average quality, good-quality silage is a very valuable asset to have on a farm, especially in the autumn and spring, or in summer-drought, if the weather and growth conditions restrict the capacity to get grazed grass into the diet.

Silage Quality

The main determinants of silage quality are outlined below.

Harvest date and conditions are often out of our control, but Clayton was able to minimise his risk by using Sulfammo 30 phase release N which allowed harvest date flexibility.

This means sugar content tends to be higher, and free nitrate levels are lower. As a result, the grass has a more consistent high-ensilability quality, allowing more opportunity to be flexible with harvest date and take good weather or contractor-availability opportunities.

Sulphur to increase Protein and Protein Quality

The island of Ireland is world renowned for our capacity to grow grass. The one Achilles heel to our ruminant production systems is the reliance on imported protein.

However, nearly every farm is already producing a protein crop in grass silage, and there is a significant opportunity to increase both the protein quantity and quality in grass silage.

Crude protein is a crude method of measurement of protein and only provides a measure of total nitrogen and not the quality of the protein, to get a better understanding of the quality of protein the PDI system is used.

The aim of the PDI system is to provide a balance of protein and energy to ruminants to optimise rumen function and performance.

Typically, grass silage grown under Irish conditions is very high in PDIN (ruminally degradable nitrogen) and lower in PDIE (metabolizable protein supply).

To increase PDIN and PDIE we can increase the overall crude protein of grass silage, but we can also supply the correct nutrition to the crop to allow for the maximum formulation of PDIE possible within a grass variety at the time of harvest.

The addition of S with nitrogen when applying fertiliser for a crop of silage will help to ensure the maximum quantity and quality protein is achieved in the pit.

Sulphur could help your farm’s sustainability

Decreasing the reliance on imported protein would be very beneficial to Irish agriculture. There would be a significant improvement in NUE which would be beneficial for the environment.

The increase in nitrogen use efficiency would help to increase the economics of N applied, additionally reducing the reliance on high-protein concentrates may also save money.

Back to the farm

Back to the farm and while the weather conditions are difficult, calving is going well. The cows are producing and are in great condition which Clayton contributes to his high-quality silage.