Planning for Autumn Reseeds - 10 Point Plan to consider for Water Quality

Many of you are planning to carry out reseeding this Autumn. Reseeding needs to carried out correctly in order to have no negative impact on the streams and rivers in your area. Claire Mooney, ASSAP Advisor, Teagasc Nenagh outlines a 10 Point Plan to consider for Water Quality.

Many of you are planning to carry out reseeding this Autumn – it’s an expensive investment, one that can yield a lot of benefits to your farming system – but one that needs to carried out correctly in order to have no negative impact on the streams and rivers in your area.

While reseeding is very important for improving grass production we need to be mindful that any cultivation of soils in the Autumn can lead to an increase in mineralisation of N in the soils and if crop demand is low, this nitrate can be leached into groundwater. This can subsequently lead to a spike in Nitrogen levels in water especially in periods of heavy rainfall if it is flushed through the soil.  Autumn reseeds are especially prone to this flushing effect of Nitrogen as the newly sown grass can have a low demand for Nitrogen in the initial period after sowing.

Checklist for reseeding in Autumn to reduce the negative impact of autumn reseeding

1. Plan to reseed early, this will ensure the grass seeds get well established early and have an increased demand for nitrate from the soil in the period most at risk from nitrate leaching . It also ensures that a good root depth is got with the new crop (4-5 cm). Crops that are sown late will only have a root depth of 1cm and  therefore won’t take up nitrogen further down in the soil
2. Soil test before reseeding The key nutrients for a good reseed are P, K & Lime - correcting any deficiency in pH  (lime) P and K is the best way of improving efficiency of nutrients you use – therefore reducing their risk of loss to water courses. Remember you can be working on this point long before you start the physical reseeding job itself. Recommend using ½ of the N allowances for reseeds at establishment and judge the crop again before 15^th Sept to see if it needs additional N.
3. Spray off paddock and adhere to appropriate buffer zones as prescribed by the product you are using – remember different chemicals may have different buffer zone requirements. By spraying and power harrowing the field less Nitrogen is available for leaching as against ploughing.
4. Always minimise the amount of time that the soil is bare while cultivation of the field is ongoing - this will help ensure that nutrients and sediment are at less risk of leaching or being washed off while there is no crop in place
5. Use Pasture Profit Index to help choose the variety of grass you want established and when you are looking to have grass available. Consider the use of multi species swards as these have a deeper rooting system, and can take up nitrogen at a deeper level in the soil.
6. Consider incorporating some clover so as to reduce the amount of chemical N that will be needed in the future
7. We also need to be mindful of buffers when it comes to ploughing beside streams and watercourses. A minimum buffer of 1.5m should be maintained so as to provide a sediment trap for break the potential for nutrient runoff .
8. Roll after sowing to prevent large sediment losses if high rainfall occurs
9. Post emergence spray, again stick to the buffer zones as prescribed on the label of the product you are using
10. Graze early this will again ensure best utilisation of the crop and promote tillering and active root systems but will reduce the risk of poaching / soil damage by late grazing in poor ground conditions.

If you take all of the above into consideration you will be doing your best to protect water quality in your farm.