Management notes for May 2023

Date published: 22 May 2023

Management Notes are prepared by staff from the College of Agriculture, Food and Rural Enterprise (CAFRE). CAFRE is a College within the Department of Agriculture, Environment and Rural Affairs (DAERA).


Prepared by:  David Mackey

When should I cut grass for silage?

Making good quality silage is key to the feed efficiency of your dairy herd through the winter, but what makes good silage? Cutting date is important as the developing seed head, with its higher fibre content in the stem, reduces silage quality.

For high quality silage, with a ME of 11.5 MJ/kg dry matter (DM) or more, you must cut your silage well before 50% ear emergence. To assess the level of ear emergence, walk your silage swards. Pulling up a grass plant and splitting the sheath allows you to determine how far up the stem the seed head is and plan your cutting date accordingly. As a general guide, early heading perennials reach 50% ear emergence around 10th May, mid-season varieties around 20th May and late heading in the first days of June, but this is weather dependent and can vary a few days either way. Each week of delay after 50% ear emergence results in a 0.4 MJ/kg DM decline in silage ME, requiring an extra 1.2 kg of concentrates to achieve the same daily milk yield.

Good weather conditions make for good silage. Bright sunshine increases the sugar content of grass leading to a better fermentation. Sunshine also promotes a more rapid wilt reducing the amount of water ensiled. Ideally, grass should be mowed dry. Cutting whilst wet, even with dew, means a longer wilt with a reduction in nutrients and a poorer fermentation.

Unused fertiliser or slurry nitrogen can adversely affect fermentation, resulting in poorer silage quality. Nitrogen uptake by grass is typically about 2.5 kg per hectare per day (2 units per acre per day). This is weather dependent and could be less in cold, wet, cloudy weather when the grass is growing less actively. Unused nitrogen decreases the sugar content of grass leading to higher ammonia concentrations in the silage. If you have concerns, consider getting a grass ensilability test carried out to check how well the grass will preserve.

Harvesting and clamp management

The aim of silage production is to preserve grass whilst avoiding loss, maintain feeding value and promote intakes. There are several phases in the production of silage. They are:

Harvesting - aim to ensile grass at 30% DM. This is best achieved through a rapid wilt where the grass is spread out over the entire field straight after mowing. A rapid wilt minimises sugar and protein losses and in ideal weather can be achieved within eight hours. At 30% DM, short chop length promotes better clamp consolidation but should not be less than 25 mm to maintain fibre for rumination in the winter diet. Consider longer chop lengths in wetter crops, closer to 20% DM.

Have a wilting plan. Assess the starting DM of grass. Standing crops can range from 14% DM (lush, early crops) to 23% (maturing, lighter crops in exceptionally dry weather). In average conditions, a crop of grass can increase in DM by 1.0% per hour during the day. Early, lush crops will struggle to achieve 30% within a day.

Rowing a crop greatly reduces, if not stops, wilting. If a crop starts to get over dry, get it rowed up! Make sure the rake is set correctly. Machines that are set too low will pull up debris and dead material from the bottom of the sward, reducing the ME and possibly increasing contamination. Rakes set too high will produce high in-field losses.

If you are not sure about the starting DM, carry out a microwave drying test to assess DM more accurately.

Filling the clamp - this should be done quickly with grass distributed evenly in shallow layers and rolled continuously to eliminate oxygen and start the fermentation process. Pay particular attention to the shoulders of the pit which have the greatest potential for loss. Seal the pit with at least one cover to make it airtight and weigh down the cover with tyres or mats.

Fermentation – micro-organisms in the grass produce lactic acid, which is the primary acid responsible for lowering pH, producing silage and making it stable. Undesirable micro-organisms can dominate if the pH does not drop rapidly. This is more likely with lower DM grass and with high levels of residual nitrogen present. Soil contamination and poor sealing can also be factors.

Use of an additive

Effective silage fermentation produces high levels of lactic acid reducing the crop pH. Silage additives can help this process. Various additives are available including bacterial inoculants, enzymes, acids and sugar sources. It is important to emphasise that none of these are a substitute for good silage making techniques and management, but they should help make a good situation better.

Jobs checklist for May

  • Ensure good grazing management by grazing swards down to 1,600 kg DM per hectare to maintain sward quality.
  • Check silos and carry out any maintenance well in advance of silage making.
  • Check there is adequate storage in tanks to collect effluent produced.
  • Calibrate parlour and out of parlour feeders to ensure accurate feeding.
  • Spray docks/weeds if conditions are suitable and they are at the right stage for control. If spraying silage ground for docks, generally allow an interval of at least 21 days between spraying and harvest. As this depends on the product used and always read the label.


Prepared by:  Jack Friar

Spring clean housing

If you have noticed scour in calves pre-turnout or especially if you have had confirmed cases of cryptosporidiosis or coccidiosis now is the time to take action. The transmissible part of the parasite that causes scour is known as the oocyst. It has a very hard outer shell and can survive in damp conditions for up to a year. To protect your next calf crop and reduce the environmental load, now is a good time to ‘spring clean’ sheds. Although May is a busy time for getting other jobs completed, cleaning sheds and allowing them to properly dry out over the summer is time well spent. It reduces the survivability of these infectious causing parasites in the environment. 

As bedding provides an ideal environment for these parasites it is important it is all removed. Removing manure and pressure washing is not enough to destroy oocysts. The following steps are recommended:

  • Remove all bedding material/manure from the house.
  • Use a foaming detergent designed to remove soiling and grease.
  • Thoroughly rinse the house and allow time for it to dry out completely.
  • Apply a target disinfectant that is effective. Many commonly used disinfectants cannot penetrate the outer shell of these scour causing parasites. Therefore, ensure when choosing a disinfectant that it is effective against cryptosporidiosis and/or coccidiosis. Also, take note of the contact times required and always follow the manufacturer’s instructions.

Grassland management

The grazing season provides an opportunity for inexpensive weight gain from grazed grass. Peak grass growth occurs in the May to June period. Good grassland management is vital. To maximise animal performance, it is not too late to start rotational grazing. 

Subdividing fields into paddocks offers several benefits including giving stock access to leafy grass on a consistent basis. This will improve performance and allow for forward creep grazing young stock in the build up to weaning. It will also help to improve grass utilisation and provides more control on grazing management. It also allows for a more targeted fertiliser programme.

Ensure grass covers are grazed down tight to avoid a buildup of dead material at the base of the sward. Monitor the grazed area and be prepared to ‘pull out’ paddocks where covers are strong. Do not delay cutting these paddocks to increase silage yield as this may lead to a grass shortage later in the rotation.

Things to consider before cutting silage

First cut silage is just a few weeks away and there are a few things to take into consideration before you start cutting.

  • Herbicide applications

Always read the label and product information before using herbicides for controlling weeds, especially if you are planning to cut silage this month. Adhere to label recommendations regarding product application rate, cutting and grazing intervals. Consult a BASIS registered agronomist for the latest information on product availability and application advice. Anyone who uses pesticides in agriculture is legally required to have a Certificate of Competence in the Safe Use of Pesticides (PA1, PA2A Boom Sprayer, PA6A Knapsack etc.). 

  • Nitrogen levels

Due to the wet conditions during late March and April, nitrogen applications onto silage swards may have been delayed. Grass converts nitrogen into protein and if it has not been fully converted this can result in high nitrate levels. This causes a reduction in sugars and an increase in ammonia, both of which will make fermentation more difficult. Therefore, before you cut your silage consider testing the grass sward for nitrate levels.


Prepared by: Conor Gallinagh

Irrigation in ornamental crops

Water management is fundamental for ornamental crop production. As the move continues towards peat free growing media, a new understanding of irrigation is required. Peat free growing media has a lower water holding capacity than peat growing media. Water holding capacity is the ability of the media to hold on to water particles that can be absorbed for plant growth. It is also connected to leaching of nutrients from the growing media. Due to the poor capabilities of peat free media to retain and hold on to water a ‘washing out’ effect of the nutrients can occur. This happens especially where overwatering occurs and this can further impact on pest and disease pressures.

It is best to water a peat free media little and to grow it on the drier side. This will encourage root development and for the roots to travel throughout the container. Also, maintaining a drier surface in the container will help prevent the establishment of weeds such as liverwort and hairy bittercress.

Also consider the percentage of different substrates in a mix as this will have an impact on irrigation. Wood based substrates tend to have a very poor water holding capacity.

Apple scab monitoring

With a decrease in the number of pesticides available, it is important they are applied at the correct time to maximise their efficacy. To help with this, several computer-based decision support systems (DSS) have been created. These model the pest and disease risk based on environmental conditions such as temperature and humidity.

An example of a DSS is RimPro. This was started over 20 years ago to help growers identify high risk periods for a range of pests and diseases in everything from vegetables to top fruit. Over the years models have been developed for diseases and pests in apples including scab, sawfly and codling moth. For sawfly and codling moth, RimPro requires a ‘biofix’ date to trigger the start of the model. For sawfly this is based on the date of full bloom in orchards and for codling moth the biofix is the date when more than five moths are found in lures baited with mating pheromones. Using the biofix, RimPro can predict when the start of egg laying or emergence of larvae will occur. This can help target the application of suitable pesticides to maximise their efficacy. With scab, the model starts at green tip stage and by combining data from the weather station and weather forecasts it can predict potential spore releases three to four days ahead.

To evaluate the RimPro model under local conditions, DAERA has installed a METOS weather station at Loughgall. The weather station uses a mobile SIM card, which means the data is freely available through the company’s website or via an app (Android or Apple) after completing a simple registration process and proving a serial number and ‘key’ for that station.

The weather station records environmental data. This is used by RimPro to create pest and disease models that are interpreted by the Fruit Advisory Service Team to create bi-weekly pest and disease bulletins. Over the next year, the scab alerts generated by RimPro will be compared to data produced by AFBI and reviewed at grower events. In addition, the RimPro system will be used to help interested growers target sprays for codling moth and sawfly in DAERA monitored orchards.

If you are interested in either accessing the data generated by the weather station or getting more information on the RimPro system, please contact Mark Huey on 07885 344244 or email on


Prepared by: Leigh Mc Clean


The wet weather during much of March and April has made crop protection challenging, putting crops under pressure, providing ideal conditions for disease to develop and giving limited opportunities to get spray and fertiliser applied at the right time. Keep an eye on crop growth stage and have products and plans in place to spray when the time is right to protect what yield potential there is. 

Winter barley disease control

Following a T1 spray at early stem extension, barley will be due its T2 fungicide three to four weeks later. Target when the flag leaf and the first few awns have emerged. Best control of the main yield robbing barley diseases, rhynchosporium, net blotch and ramularia, is achieved with a mix of active ingredients rather than straight products alone. In the absence of Chlorothalonil, ramularia is difficult to manage, particularly in crops under stress. Teagasc trials on ramularia show both prothioconazole and mefentrifluconazole perform consistently better than other leading actives when applied protectantly. 

Winter wheat disease control

A well timed T2 fungicide gives a bigger yield response in wheat than any other spray timing. Apply at GS 39 flag leaf fully emerged no later than four weeks after the T1 spray. AHDB fungicide trials show that active ingredients mefentrifluconazole (Revysol) or fenpicoxamid (Inatreq) give best septoria control and may be worth the extra spend at T2, particularly for high yield potential crops under high disease pressure. Yellow rust has been a common problem on susceptible varieties in recent seasons. AHDB trials show benzovindiflupyr and prothioconazole (Elatus Era) are particularly effective on yellow rust, but all good mixtures perform well.

To maintain longevity and efficacy of cereal fungicides, it is important you use them responsibly as part of fungicide programmes which minimise the risk of resistant septoria strains developing. This means follow label advice on applications per season, only use where necessary, keep up dose rates of actives in mixes and always use in combination with a multisite protectant such as Folpet which protects other active ingredients in the mix. 


A dry February saw some spring crops sown by early March, though persistent rain has left the majority sown considerably later. For early sown cereals that have not received herbicide, apply a mixture of at least two broad-spectrum herbicides ideally when weeds are at the two-four leaf stage. Tank mixing a low rate fungicide will prevent disease becoming established and protect yield potential. Apply nitrogen top dressing once tramlines are visible at the two-three leaf stage (GS 12 to 13). Later sown crops will require the same treatments, however warmer temperature and longer day length means they will develop quicker than early sowings, so check regularly to avoid missing key timings.

Protein crops should be inspected for grass weeds and volunteers. If necessary, apply a graminicide (grass weed herbicide) once grasses have emerged and before the crop canopy closes over. A fungicide is recommended for beans at mid-flowering to control chocolate spot and bean rust, usually applied in mid-June.  


Plans should be in place for early weed control. Where using pre-emergence herbicides, check regularly to ensure they are applied on time to avoid crop damage.

For later plantings take the shorter growing season into consideration and reduce nitrogen by 1.0 kg per hectare per day past the target planting date and apply the remaining nitrogen pre-crop emergence. Careful nitrogen management now will encourage earlier natural senescence and improve the probability of a successful burndown using PPO inhibitors.

In recent seasons, blight sampling has shown a prevalence of the A37_2 strain in Northern Ireland. This strain has reduced sensitivity to fluazinam (Shirlan), meaning this active can no longer be relied upon for blight control. With new resistant strains emerging in Europe, you are advised to remain vigilant and submit blight samples for genotype testing to either potato inspectors or your local CAFRE Crops Adviser.

Notes to editors: 

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