Returning paddocks to pasture after summer cropping is a year-long commitment, advises Murray Lane, a Technical Consultant at Ballance Agri-Nutrients.
‘After such a great season for cropping in many regions, with final yields pushed higher by late summer rain, it’s time to plan for regrassing harvested areas. There are several key factors to consider when you want to return cropping paddocks to pasture,’ advises Murray.
‘You have to get your timing right first, allowing time to control weeds before planting. The new pasture will then need careful management for at least 12 months.’
After the crop, allow time for weeds to germinate, particularly perennial weeds that weren’t well controlled prior to sowing the crop. It’s a trade off – the later you leave it to sow new grass the poorer the winter production will be.
Autumn weed sprays are more effective than spring applications so control perennial weeds with a broad-spectrum herbicide such as glyphosate. Summer weeds such as fathen, nightshade and amaranthus generally succumb to the winter conditions, but be mindful of winter annual grasses such as poa annua, and apply the herbicide as near as possible to sowing date.
Don’t wait too long. The bigger the weeds get the more moisture they will take out of the soil, which could be significant if the season goes dry. Ideally, the new pasture crop would be established using no-tillage as cultivation of the soil leads to moisture loss.
The most important consideration in grass seed selection is getting the right endophyte. Endophyte is a fungus that lives inside ryegrasses and tall fescue. It produces toxins that limit the effects of certain insects. Talk to your seed representative about common pasture pests in your region, and what the most appropriate novel endophytes are for reducing the impact of these pests.
Seed treatments do not control the other major autumn pest – slugs. Slug baits have to be used.
If the seed is not new season’s seed and has been stored incorrectly, the endophyte fungi may have died in the seed, in the bag. Check with your seed supplier that 85-90% of the seed in the bag has live endophyte when you buy it.
In the black beetle zone, always use treated seed. New grass failure can and does occur in the rest of NZ due to Argentine stem weevil and damping off diseases, so reduce the risk of failure by always using treated seed.
Then there is clover selection, small-medium leaf size for sheep/beef, medium to large leaf size for cattle/cows. Check for clover inoculums; is it within its shelf life? Consider whether to add herbs such as chicory or plantain.
Finally, do you want all of the seed types in one bag, or should the clover/chicory be in a separate bag to the grass seed. Largely this decision depends on the gear you will be using. If roll-seeding the seeds should be mixed. If drilling ideally sow the small seeds (clover/chicory) separately to the ryegrass. They struggle to compete when sown deep with the ryegrass.
Depending on the crop grown, large amounts of nutrient might have been removed from the paddock at harvest. Soil testing should be carried out and lime applied if required to lift pH.
The other two key elements to aid the new pasture establishment are phosphate and nitrogen. Early phosphate enhances early root and leaf development. Recent work has shown the value of drilling 30 kg/ha phosphate near to the seed.
Three to four weeks after sowing apply 30-40 kg/ha nitrogen to encourage greater tillering and leaf expansion, leading to faster leaf canopy cover. The sooner this happens the sooner germinating weeds are suppressed.
New pasture crops should take priority in the grazing round. Graze earlier rather than later to stop the clover being over shadowed. After regrassing, it takes up to 18 months for clovers to fix sufficient nitrogen to feed themselves and their companion grasses. Hence, regular nitrogen fertiliser application should be a priority over the first 12 months. Light rates of nitrogen after each grazing will encourage the pastures to tiller; in addition, healthy, non-stressed plants will be more resilient against pests and diseases.
Murray recommends farmers avoid cutting hay or silage from new pastures – wait until the pastures are at least 12 months old.
‘Remember that pasture is a long-term crop. The establishment phase (10-12 months) is just as important as the few weeks establishment phase of a cereal or brassica crop,’ says Murray.
‘Make the right decisions during planning and implementation and look after it during the first year or so to get the most out of your investment.’
10 March 2010
