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Ken Gill May Update

Managing grass in May

Managing grass in May

  • Target a pre grazing yield of ~1400 kg DM/ha to ensure good quality grass for grazing
  • Take out stronger paddocks for silage
  • Spread slurry on red clover paddocks after cutting to replace P and K offtakes
Analysing slurry nutrients

Analysing slurry nutrients

  • Test slurry on your farm
  • Over-dilution of slurry will reduce nutrient content
  • Rule of thumb: Spread 1000 gallons slurry/acre for every 4 bales silage cut per acre, but this can vary depending on the nutrient content in slurry


The latest grass wedge for the farm shows a farm cover of 634 kg DM/ha. The growth is 44 kg DM/ha and the demand is 48 kg DM/ha which is well balanced. There were 13 days of grass ahead on the farm which is on target for the month. The main crop silage and strong paddocks will be cut when weather allows which will bring more grass into the system. The pre grazing yield for the farm is 1500 kg DM/ha which ensures that the cattle are constantly eating good quality grass.

The red clover silage was cut on 12th May and yielded 8 bales/acre which Ken was quite happy with. This has since been spread with slurry and Ken is planning to take his second cut around the end of June.

Soil Fertility

Slurry samples were taken on the farm from the cow’s slatted tank and from the stores’ slatted tank. The results were as follows;

SampleDry matter


(Units/1000 gallons)


(Units/1000 gallons)


(Units/1000 gallons)

1 (Cows) 8.04% 8.8 5.24 23.06
2 (Stores) 3.48% 5.2 3.85 24.15

While the slurry from the store cattle appears to have less nutrients than the sample from the cows, the dry matter is a lot lower. However it does show that if slurry is too dilute, the nutrient content will be lower than expected when fertilising silage crops.

Every 4 bales/acre cut from a paddock will require 6 units of phosphorus and 40 units of potassium per acre to replace nutrient offtakes. Therefore 2,000 gallons of the cows slurry/acre should be spread for every 4 bales/acre yielded from silage ground or strong paddocks on the farm. The slurry from the stores can be spread on grazing ground to replace nutrient offtakes there.

Greenhouse Gases

A sustainability plan was completed for Ken’s farm focusing on the key mitigation actions he can take to reduce greenhouse gas emissions on his farm. This involved assessing technical performance in areas such as soil fertility, slurry applications and timing, grazing management, cattle weight gains at grass and over winter, silage quality, breeding performance and the age at slaughter. By improving all of these areas on farms, it can help to cut emissions.

Improving soil fertility can reduce nitrous oxide emissions by improving grass production, which leads to improved profitability. Getting the pH right (target 6.2 for grassland) by spreading lime is the first step to achieving this. 97% of the farm has a pH of over 6.2 which is excellent. When the soil pH is on target, the focus should be to build up P and K indexes on the farm through spreading slurry on silage and low index fields.

Ken uses a trailing shoe to spread slurry on his farm, which is a low emission slurry spreading method. This results in less nitrogen (N) volatilisation and increases the N fertilizer value of slurry by retaining an extra 3 units of N/1,000 gallons of cattle slurry. It can reduce ammonia emissions from slurry by up to 30% and nitrous oxide emissions through reduced chemical N use which doesn’t apply to Ken’s organic farm, but would be useful to conventional farmers who use chemical fertiliser. Spreading slurry using a dribble bar produces similar results. Spreading slurry using a splash plate results in higher emissions, particularly during the summer.

Animals grazing better quality forage produce less methane. Therefore, better grazing management and less silage in the diet is beneficial, while shorter housing also leads to less slurry and improved performance. Every extra tonne of grass dry matter (DM) grown and utilised/ha is worth €105 to beef farmers. Ken walks his farm weekly and measures grass using PastureBase Ireland. He minimises poaching where possible and targets pre-grazing covers of 1400 kg DM/ha to ensure cattle are grazing the best quality grass. He also aims to make over 70% DMD silage which reduces his need to feed concentrates over winter and maximise animal performance.

Improving animal health can result in increased animal performance, reduced replacement rate and a reduced number of non-productive animals and reduced mortality. At farm level reducing health problems will improve efficiency, reduce costs and increase profitability. It will reduce GHG emissions per unit of meat. Implementing a health, plan/vaccination programme can help to achieve this, which Ken has as part of his organic plan. He faecal samples regularly and consults with his vet if any health issues arise on the farm. As 100% AI is used on the farm, the biosecurity risk with buying in stock is greatly reduced.

Ken’s replacement index for his cows is €112. The replacement index works by delivering better, reducing GHG emissions from non-productive animals and improving efficiency. At farm level, the progeny of 5 star females improve pro­fitability by €60/animal compared to 1 star animals. High replacement animals have a lower methane output/animal than lower replacement index animals, up to a 20% difference in total methane output. His target is to continue increasing this value by €5/year by breeding his best replacement heifers to high replacement AI bulls.

Reducing the age at slaughter reduces methane emissions, feed required and slurry produced by cattle on the farm. Ken is currently slaughtering his heifers at 23.2 months of age and the bullocks at 25.1 months off of grass. Each month earlier in slaughter age increases profitability by approximately €30/head and reduces CO2equivalent by approximately 350 kg CO2e/head. This reduces the total emissions from the farm. This can be further improved by using the Euro Star Index for breeding replacements (replacement index) and finishing cattle (terminal index), through good grassland management, implementing a health plan and making >70% DMD silage.

How can you reduce GHGs on your farm?

How can you reduce GHGs on your farm?

  • Consider how you can reduce the amount of greenhouse gases produced on your farm
  • Cattle that eat better quality grass and silage produce less methane
  • Spreading slurry by LESS will reduce ammonia emissions (which is not a GHG but still damages the environment), which leaves more nitrogen available for grass on the farm