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Grassland

Although grass is the most dominant crop in Ireland, just 2% of our grassland is reseeded annually. As pastures get older, they on average produce up to 3 tonnes less dry matter (DM) per hectare per year. This is an economic cost to the farmer and this cost occurs mainly in the first half of the grazing season.

A new, well-managed sward, containing a high percentage of perennial ryegrass is essential to maximise forage output, increase grass utilisation and improve overall farm productivity. Spring reseeding is well worth considering as the improving weather conditions at this time of year provide more flexibility in terms of sowing time, soil preparations and establishment of the new sward.

Perennial ryegrass should be the most dominant species in a grass sward. As a rule, pastures with less than 40% perennial ryegrass should be considered for reseeding.

A high level of management and attention to detail is key to a successful reseeding programme and to ensure you get the very best response from your fertiliser application.

Here are our top tips:

Plan ahead

Planning and preparation are key to a successful reseed. For spring reseeding, it is wise to have a recent soil analysis to hand. A soil sample should be taken to a depth of 10cm from beneath the soil surface for min-till or direct sowing methods. When using the plough till sow method, ensure to take your soil sample from the top of the ploughed ground. Soil samples must be representative of the area being sampled and make sure you have no contamination from previous organic and inorganic applications.

A standard soil sample will indicate soil pH and soil Phosphorus (P) and Potassium (K) status. Calcium and Magnesium ratios and levels will determine which type of lime to apply. Where lime is required, it should be spread on top of the ploughed ground and worked into the soil for good incorporation. Lime can be spread at up to 7.5 tonnes /ha in one application. Granulated lime can be used as a short-term quick solution and applied at 3 bags (50 kg) per acre.

The target pH of a mineral soil is 6.3 or for more peaty type soil a pH of 5.5 is adequate. It’s important to contact your local advisor and that planning, preparation and fertiliser application decisions are made based on your recent soil analysis.

Managing your reseed

There are many different cultivation and sowing methods available for reseeding. All methods, when completed correctly, are equally effective.

Desiccation is an essential first step when reseeding. By spraying old swards with a glyphosate spray all weeds (docks, thistles etc.) and weed grasses will be killed. Where the existing sward is cultivated without spraying, weed grasses have a greater ability to regenerate and appear in the new sward.

Seed selection is vitally important. When selecting your grass mixtures for 2020, refer to the recently released Pasture Profit Index (PPI) and the Department of Agriculture, Food and the Marine (DAFM) grass and white clover recommended list. By selecting varieties that are tried and tested, over several years, across numerous locations in Ireland, you can have confidence that you are sowing the best varieties on your farm and maximising the return on your investment. It is advisable to speak to your local merchant or advisor on which mixtures are the most suited to your farming platform.

Following recent changes from 1st January 2020, farms in derogation are required to add in white clover @ 1.5 kg’s/ha. First grazing will be at the two-leaf stage, using younger stock if ground conditions are difficult. This will encourage early tillering and create a dense sward.

It is important to graze reseeds prior to closing for silage, otherwise it will result in a low plant count/m2, leaving an opportunity for unwanted weeds to germinate later. It is also very important to spray weeds with a post emergence herbicide specifically at the cotyledon stage when the weed plant is more susceptible to the herbicide, especially invasive species such as docks. Pest control may also be necessary. Full crop establishment will take 12 months and it is important to manage the crop carefully over this period.

Fertiliser application for root development

If applying organic manure, use it only to complement chemical fertiliser compounds. Organic manure can be spread onto ploughed ground; however, it is not recommended to use excessive amounts as this can interfere with seed placement and germination.

When choosing a suitable fertiliser compound, it is recommended to choose a high Phosphorus (P) and high Potassium (K) compound. P and K are essential for providing energy and encouraging vigorous root development of the young seedling after germination. For this reason, the last Nitrate regulations allow an additional 15 Kg of P/ha at soil index 1, 2 and 3 for each hectare of pasture establishment. Depending on your soil test, a fertiliser with a 1:2 ratio (P:K) may suit your first application.

Using Nitrogen (N) for grass establishment

Nitrogen (N) is essential in aiding good grass establishment however, excessive N during the early stages of establishment will encourage weed dominance and hinder the development of the new grass seedlings. Note considerable amounts of N may be released by mineralisation which will be dependent on the previous crop. A good rule is to limit the amount of N at sowing to a max of 38 kg/ha (30 units/ac) and apply the balance later in line with index requirements.

P & K rates for Grassland: in kg/ha

Soil Index 1 2 3 4
P 60 40 30 0
K 110 75 50 30
Source: Teagasc
 

Target Fertilisers’ compounds for successful establishment of reseeds:    

10-8-25+S

10-7-25+S

10-10-20

12-8-20+S

To learn more about planning for a successful reseeding period, click here.

To view our full range of fertilisers for grassland, click here.

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