Heather McKay, Beef + Lamb New Zealand’s Environmental Policy Manager, says farm-scale trials has shown that catch crops can reduce nutrient losses from the soil by up to 40% in some soil types.
“Sown as soon as ground conditions allow, catch crops such as oats or rye corn can be really effective at capturing nutrients and turning them into valuable drymatter.”
Trial work carried out by Plant & Food Research has shown oats to be an ideal catch crop in that they are cold tolerant and germinate at five degrees and above. They reduce water in the soil and capture soil nitrogen (N) left in the wake of winter grazing.
Catch crops in the trials were taking up as much as 40kg of N/ha in the first couple of months after establishement and by late November, early-sown crops of green-chop silage in both Canterbury and Southland were yielding 8-10tDM/ha and capturing 100-150 kg N/ha.
Heather says in the amended winter grazing regulations, which don’t come into effect until November, there is a requirement for farmers to minimise the time a paddock is left fallow after forage crops have been grazed.
“This reflects good practice management and we encourage all farmers to think about the post-grazing management of their paddocks this winter, to ensure nutrients stay in the paddock and are not lost to the environment.”
She says free draining soils and soils with subsoil drainage are more at risk of nutrient losses and these soils are typically the most suited for catch crops, as machinery can usually get on the paddocks earlier than would be advisable with heavy clay waterlogged soils.
“It is important to protect the integrity and structure of the soil, so it can be a balancing act to get the catch crop sown early enough to the reap their benefits while protecting the soil structure.”
She says farmers could consider direct-drilling, heli-cropping or broadcasting and on heavier soils such as those in Southland, spader drills have proved to be very effective.
Heather says there a number of factors farmers need to consider when considering growing a catch crop such as their crop and pasture rotations and whether the crop with be harvested and conserved or grazed in-situ.
In summer-dry dryland situations, thought should be given to availability of moisture for subsequent crops as catch crops will remove moisture from the soil through transpiration.
Heather says information covering all aspects of intensive winter grazing, including the amended regulations, is available on the B+LNZ website at https://beeflambnz.com/wintergrazing.