September 2020 Monthly Management

Agricultural Emissions; Body Condition Scoring; Grass & Grazing

21 September 2020

Agricultural Emissions

Gaseous Emissions from Irish Agriculture are divided into two main categories:

A) Greenhouse Gases
B) Air Pollutants i.e. Ammonia

Greenhouse gases have a negative impact climate change while air pollutants can adversely affect human and animal health while also damaging ecosystems.

Greenhouse Gases (GHG)

Methane and nitrous oxide are the main greenhouse gasses connected to Irish agriculture.

Gas % of GHG emissions Sources
Methane 64% Cattle & Sheep (ruminants) release methane as a bi- product of their digestive process
Nitrous Oxide 34% Nitrogen fertliser use and emissions from animal waste and manure management (slurry storage & land spreading)

Air Pollutants - Ammonia

Ammonia is a gaseous form of Nitrogen and is an air pollutant. The main sources are the storage and application of organic manures, chemical fertiliser applications and from grazing animals. In Ireland, agriculture is responsible for 99% of all ammonia emissions, we have committed to reduce these emissions through EU targets, however since 2016 we have been exceeding our targets.

Emission Reduction Strategies

There are many options available to reduce GHG and ammonia emissions that will at the same time improve on- farm efficiency and profitability. (See Table 1 below).

Mitigation Measure GHG Ammonia
Dairy EBI X
Animal Health X
Nitrogen use efficiency X X
Clover in sward X X
Protected urea X X
Soil fertility X X
Extended grazing X X
Low emission slurry spreading X X
Slurry additives X X

Dairy EBI & Animal Health
Breeding and animal health provide benefits mainly through better animal performance, increased efficency and reduced finishing times which in turn reduces methane emissions.

Soil Fertility & Clover
Optimising soil fertility and incorporation of clover can allow for reducing N fertilisation rate without a yield penalty.

cows grazing

Protected urea is a fertiliser formulation that is proven to reduce ammonia emissions by over 70%, while also maintaining yields, once used as part of a fertiliser plan to maintain pH, P&K levels.

Extended grazing season focuses on manure management, through reducing quantity of animal manure being stored and land spread.

Low emission slurry spreading like the trailing shoe & band spreader have been proven to cut ammonia losses by 50% while also improving nutrient use of the slurry.

Slurry additives are being investigated to see their effectiveness in reducing emissions during storage and land spreading. Through reducing N losses during storage and land spreading, more N is retained in the system and available as nutrient supporting plant growth.

With agriculture in Ireland accounting for one third of total greenhouse gas emissions. The use of the above emission reduction strategies will be hugely important to ensure we meet the European Union target to reduce our Green House Gas Emissions by 30% by the year 2030.

Body Condition Scoring

Now is an important time to assess the Body Condition Score (BCS) of your herd. The target BCS at drying off should be 2.75 to 3.25. If cows are dried off at a BSC below 2.75, they will have an increased risk of calving disorders and reduced milk and reproductive in their next lactation. When thin cows are identified, three management options should be addressed.

  1. Dry off early to allow a long dry period to put on weight.
  2. Milk thin cows once-a-day so that they gain extra weight.
  3. Supplement with good quality meals so that thin cows gain weight before drying off.

In many cases, waiting until thin cows are dried off to commence supplementary feeding will be too late to build body condition. It takes 72MJ of energy to put on 1kg liveweight on a dry cow whereas it takes 50MJ to gain the same weight while she is milking. Hence the value of identifying the thin cows in October and feeding them meals to rectify the problem early.

In working to achieve BCS targets over the dry period, it is also important to know the quality of silage being fed. If quality is low or poor, the right level of supplementation will be needed to build body condition, see table for more details.

body condition scoring ranges

body condition scoring

Grass & Grazing

This month’s feature farm is Charles Hegarty, Caheragh, Drimoleague.

Charles Hegarty
Charles Hegarty
Date 16/09/2020
Average farm cover 1011 kg/dm/ha
Yield (litres/cow) 16 litres
Fat% 4.6%
Protein % 3.75%
Kgs Milk Solids / cow 1.38 kg
Supplement fed(kg/cow) 4kg
Pre-grazing covers 1800 kg/dm/ha

The amount of rain in August made life challenging to say the least. Fertilizer application was delayed, some ground in the rotation had to be skipped to avoid damaging it, silage was introduced to cows at milking time and in-calf heifers had to be housed for two weeks. The result of the difficult weather now is that the amount of grass needed on the farm is behind what I would like to have. Stocking rate (3.22 cows/Ha) is running slightly higher than normal as I have ground out for reseeding, this ground was sprayed off on August 3rd but did not get seeded until September 9th. My plan is to keep in with 4kg of ration, at my stocking rate this will reduce my demand to 42kgs/Dm /Ha. At this level of demand, I hope that I can maintain and even perhaps increase the AFC on the farm over the next few weeks.

Fertiliser: With heavy rain and poor ground conditions, there was a delay of over 2 weeks in fertiliser application across the milking block in August. The last round of fertilizer for 2020 was last Saturday with 35 units of nitrogen/acre applied. Lime is currently being spread at a rate of 2 tonnes/acre on paddocks showing a requirement.

Last rotation: I plan to start the last rotation around the 5th October and around this point I will also start to graze by day only and keep grass in the diet by day for as long as possible. This also suits my system as cows have to travel on the public road to access grazing ground. As the milking platform is fragmented, having cows housed by night at this stage alleviates the potential risks associated with moving cows on a public road following evening milkings.