Reseeding techniques to be used in organic farming
The principles of reseeding in organic farming are somewhat different to those practised by conventional farmers.
No artificial inputs such as pre or post-emergence sprays or synthetic fertilisers are permitted under organic standards. Instead, special emphasis is placed on:
1.Natural fertilisers such as farmyard manure (FYM) and slurry.
2. High levels of white clover in the seed mix.
3. Good levels of management pre and post-sowing to control weeds.
Teagasc demonstrated how grassland swards could be reseeded under organic conditions in Kilbeggan last year. Prior to reseeding, the plot was mowed tightly and 10t/ac of FYM was spread.
The plot was ploughed and cultivated using a power harrow. With very good ploughing, old grasses and weeds were successfully buried. The demonstration plot received 1t/ac of ground limestone.
The plot was then rolled prior to sowing to consolidate the seedbed and avoid burial of clover seed.
Ploughing aids can help with the release of natural soil nitrogen in an old permanent sod, but it should not be deeper than 15cm. Deeper ploughing will bury any available nutrients out of the reach of the new emerging seed.
As with conventional reseeding, there are many methods for establishing good grass clover pastures under organic conditions. Regardless of the method used, clover seed must not be sown deeper than 1cm to ensure successful establishment.
Seeding method and rate:
In our demonstration, the seed was sown using an Einboch grass harrow. The Einboch avoids burying the seed too deep without leaving the seed with insufficient cover to ensure germination.
Organically-certified grass seed with 20pc white clover in the mix was sourced from a local merchant.
One of the key factors in achieving good levels of production on grassland organic farms is the introduction and maintenance of white clover into the new reseed.
Seeding rate for new organic grassland swards should be approximately 10kg of grass seed and up to 2kg of white clover seed per acre.
Organic farmers must make every effort to use organically-certified seed.
Time of sowing:
Organic swards should be sown in spring or before mid August. Later autumn sowing may result in poor clover establishment.
Post emergence management:
80pc of the success of getting grass-clover swards established is in the post-sowing management. Well managed grass-clover swards can last up to 20 years.
To achieve this, the emphasis needs to be on:
1. Maintaining soil fertility.
2. Good post-emergence grazing and weed management.
In the demonstration plot, watery slurry was spread at a rate of 2,000ga/ac, approximately four weeks after sowing. Along with the FYM spread before ploughing, this met the full N, P and K requirements of the new re-seed.
Grazing and weed management:
The aim in organic grassland reseeding is to produce a uniform, well-tillered, dense sward. New swards should be grazed as soon as the new grass and clover plants are strong enough to withstand grazing.
This is described as the point where roots stay anchored in the ground when pulled between the finger and thumb.
Grazing also encourages tillering, which increases ground cover and further helps to control any emerging weeds.
Grazing with calves or sheep would be preferred initially as ground conditions may be fragile, depending on the re-seeding method used.
Frequent grazing of the reseed in the first year after establishment will have a long term beneficial effect on the sward.
New organic re-seeds ideally should not be closed for silage in their first year of production as the shading effect of heavy covers of grass will inhibit clover and tillering of the grass plant.
In turn, this results in a more open sward that is more liable to weed ingress.
Cost of organic reseeding:
The overall costs of organic reseeding are similar to that of conventional, but with a focus on different input costs.
In organics, there may be higher costs associated with more expensive organic seed, which is often at least 30pc more expensive.
There are also extra costs for spreading and sourcing slurry and FYM, but these are off-set by no costs for sprays and artificial fertilisers.
Tables 1 and 2 show the material and machinery costs of the organic demonstration plot in Kilbeggan.
It is important to remember that extra costs may be incurred where slurry and FYM have to be sourced off-farm.
Organic farmers face similar challenges to conventional farmers in terms of increasing output and maximising their returns.
As with conventional reseeding, there are many methods available to establishing successful grass clover pastures under organic conditions. Unlike conventional farming however, the 'quick-fix' solution is not an option.
Good management in terms of slurry:
FYM, cultivation technique, tight grazing, and avoiding poaching are especially important to produce a long lasting successful organic reseed.