Why reseed now?
In order to boost productivity for the year under-performing pastures should be reseeded now to ensure grass growth is good for the rest of the year.
If you are unsure if your sward needs reseeding then think back to the last time you reseeded. In general swards cut twice annually for silage should be reseeded every 5 — 8 years. Reseeding will extend the grazing season and the new ryegrasses sown will have higher yields and better quality which will be reflected both in grazing and silage production.
If you have pastures with low ryegrass content, poor productivity, high weed infestations (docks, thistles etc) these should be targeted for reseeding. If there are appreciable amounts of weed grasses present in swards, silage yields may be reduced by 20-25%. If weed grasses constitute more than 30% of the sward, dry matter (DM) yield and quality will suffer.
If you are reseeding for silage then any fields where there is less than 50% perennial ryegrass in spring need to be reseeded. Investing money in reseeding will leave you with higher output in milk yield, more kgs of milk protein, growth at the shoulders of the year, better response to nitrogen and better growth rates in stock. In Ireland our competitive edge depends on grass growth over the winter and reseeding can help extend our grazing season and make more grass available to cows in the spring.
With fertiliser costs increasing over the last few years it is important to note that new swards will make much better use of nitrogen which will reduce costs. When you are reseeding you can also add clover to the mix and this will help reduce the nitrogen needed for that pasture.
The wet winter may have caused more nitrogen leaching than usual so soil testing should be carried out to see what your fertiliser requirements are. The winter may also have depleted the sward and fewer species may be present with a greater proportion of these being weeds. Leaf diseases like crown rust are becoming more common and will leave swards more susceptible to winter damage, whilst poaching may have been more of a factor in a wet season and frost will have done little to improve survival rates.
Timing your reseed
Reseeding now is a good idea as on most farms the stocking rates should not be so high that you can’t take out a few paddocks now without putting the system under great pressure. During the spring grass growth is good; therefore, grass supply is above demand on most farms.
Also you can reseed now and have plenty of time to control weeds once reseeds are established. Some farmers wait until autumn for reseeding, and end up not being able to spray the new reseeds because it is sometimes difficult to get a spray on in October and November. Spraying after five to seven weeks of growth is well worth it, but must be carried out with the right spray and good spraying conditions.
Methods
A complete reseed is the best way to establish a new sward however you can also opt for spring overseeding as this will minimise the time out of production.
Overseeding
If you are planning to over seed first ensure that soil nutrient levels are adequate and wait until surface soil temperatures are at least 6 degrees C and ideally up to an optimum of 8 degrees C. Whatever the method of overseeding, good seed-to-soil contact will be a key factor in ensuring good establishment.
A complete reseed should be strongly considered if you have any of the following problems: low rye grass content, high weed content, bare patches, lack of thrive of livestock, poor regrowth of pasture following cutting or grazing or reduced silage. If you are cutting your grass for silage twice a year then ideally you should reseed about every 7 or 8 years. If you are primarily using your pasture for grazing then reseeding will lengthen your grazing season.
Seed Bed Preparation
The seedbed preparation should result in a fine, firm and level seedbed. This will give the seed good contact with the soil and moisture conserved in the soil. Rolling after sowing is strongly advocated to help firmness and conserve moisture. Grass and clover seeds are very small so they require a fine firm seed bed to ensure close contact between soil and seed to get adequate moisture for germination and nutrients for establishment.
Traditional ploughing and cultivation is still the most reliable of seed bed preparations but power harrowing and disc harrowing (several runs) also give good results, especially early in the season and on dry soil. Rolling to make an even, firm seed bed before sowing is recommended.
Pastures with docks and bent grass should be burned off with glyphosate before cultivation. Spray with 5.5 litres/ha (4 pints/ac) of the 360g/l product.
There are a number of different methods suitable for sowing grass seed. Which one you pick will depend on how much you want to spend, soil type, elevation, slope, availability of certain machinery and condition of the existing sward.
These methods include:
(1) Plough Till & Sow: This has been the conventional way of reseeding. When ploughing, plough to bury trash and avoid ploughing too deep in order to avoid the fertile top layer of soil being buried. Although expensive, this method provides a good seedbed. Sowing with the one pass is also common and avoids bringing up unwanted stones.
(2) Minimum Cultivation : This method was originally used in areas where ploughing was difficult or undesirable, but has grown very substantially in popularity in recent years. It involves the cultivation of a shallow seedbed, through use of a power-harrow, rotovator or similar type machine. For successful results, it is important to have relatively low levels of debris or stubble and to achieve very good consolidation of the seedbed through rolling.
(3) Direct seeding: This involves the use of a direct drilling machine which may use a tine or disc to cut a slit in the soil onto which the seed is dropped. To help this process the existing sward should be cut as bare as possible to give the new seeds a chance to germinate and establish.
(4) Slurry Seeding: Conditions should be the same as direct drilling ie a bare sward. Generally grass seeds should be covered with 2000-3000 gallons of slurry per acre.
Whatever method of sowing is used make sure you follow the same preparation of the pasture before sowing. Spraying the existing sward with glyphosate in advance of ploughing or tilling is strongly advised. It removes weeds such as scutch and bent grass, docks, thistles etc, it provides for easier ploughing and tilling, resulting in less cloddy seedbeds.
New pasture aftercare
Reseeding a sward is only the first step, you will need to manage the pasture after it has been sown to protect your investment. Reseeded swards are particularly vulnerable to damage from pests and weeds during early establishment. Carefully monitor your swards and use appropriate actions against pests and weeds when required.
Slugs may be a problem in wet areas or during prolonged rain. Use baits to see if you have a problem and if there is significant damage use slug pellets. Leatherjackets should be tackled using Chlorpyrifos (Dursban/Clinch) if damage is noted or high population of leatherjackets are seen.
Weed control should start at the early seedling stage. Excessive competition from weeds will result in patchy swards. Glyphosate spraying before cultivation will only control established weeds and has no effect on ungerminated seeds. Other weeds may be controlled by grazing and/or topping provided populations are relatively low. With a high number of these weeds however and the presence of problem weeds such as docks, chickweed, thistles and cleavers, chemical control will be needed. The choice will depend on the importance or otherwise of clover and the weeds present.
Recommended for ‘09
No single grass variety will have all the desired traits so you will need to pick a variety mix which balances out the different traits to produce good dry matter production in spring and autumn, increased digestibility and high sward density. When choosing a mix try to keep the heading dates relatively close to each other. If a wide range in heading dates is used, then the heading period will extend longer than necessary. All varieties will head out, some will continue to progressively re-head, which is not desirable.
Clover should be incorporated into grass seed mixes of farms stocked at low stocking rates and farms already in REPS or anticipating joining REPS in the future. When choosing a silage mix, high overall dry matter production and density will be the underlining traits, with the timing of harvest now an important consideration. About three to four varieties is sufficient in a seed mix. Mixes are a better bet than using a single variety because they offer more stability than single stands which can be exposed to large annual variation in DM production. Grass and Clover Recommended List Varieties for Ireland 2009 can be found on the Department of Agriculture’s website:www.agriculture.gov.ie enter the website and click on Publications.
Look at the information for each variety to ensure a balanced mix for your needs.
Varieties for grazing
Teagasc research has shown that cows grazing later heading varieties produced on average 190kg/cow (40ga/cow) more milk than their intermediate heading counterparts. The extra milk production came from swards offering higher selected herbage which positively increased grass dry matter intake.
There are some excellent late-heading tetraploids available with high early spring/autumn growth. Tetraploid varieties have DM high yields and large leaf area, however a drawback is their upright open growth habit and lower tiller density.
Tetraploids should be combined with high ground cover, and high digestibility diploids, which will provide the base grass to the sward and give it its wear tolerance. Seed mixes should not have more than 40% tetraploid. Higher levels can be used, but the management of the sward should be tailored to protect it from damage during the shoulder periods of the grazing season. Tyrone, Tyrella, Portstewart, Soriento, Mezquita, Denver, Cancan and Twystar are the late heading diploid varities. The late tetraploid varieties are Orion, Delphin, AberCraigs, Glencar, Navan and Twymax.
Varieties for silage
For silage swards cut twice-a-year, intermediate heading varieties should be included in the seed mix, making up about 40%. Tetraploid varieties should be used in silage mixes making up to 30%.
For swards cut once-a-year and then grazed, the amount of intermediate may be reduced. This is very much dependant on time of harvest.
The very low growing late diploids should be avoided on the land targeted for continued silage harvests. Anaconda, Donard and January are recommended early perennial ryegrasses.
The recommended intermediate heading diploid ryegrasses are Shandon, Spelga Cashel Premium and Aberstar. The tetraploid intermediate heading ryegrasses recommended are Trend, Magician, Lismore, Edda, Dunluce and new for 2009 Malone.
CLOVER SWARDS
Clover can be divided into three categories depending on its leaf size; small, medium and large leaf clover. Small leaf varieties are lower yielding but more persistent than large leaf varieties and vice versa. Medium-leaf varieties are intermediate in yield and persistency.
In grazing swards, small and medium leaf clover varieties are recommended in combination with late-heading perennial ryegrass varieties. Care must be taken with the larger leafed clovers as their aggressive growth habit can dominate swards over time.
The white clover varieties on the 2009 recommeded list are Aran, Alice, Chieftan, Avoca, AberHerald, Barblanca and Crusader. Barblanca and Crusader have been added to the list for the first time this year.
Large leafed clover varieties are Aran and Alice, Crusader is the only small leafed variety on the list the rest are all medium leafed.
The recommended varieties for 2009 also include Italian ryegrasses and hybrid ryegrasses.
There are three Italian ryegrass varieties on the list; Nabucco, Fabio and AberEpic.
The four hybrid ryegrass varieties are Mamota, Redunca, AberEve and new to the list for this year Pirol.
