Sowing date and species choice affect the performance of autumn-sown catch crops in Waikato

Residual nitrogen (N) left in the soil following summer cropping or grazing by livestock is at risk of leaching in winter and spring. This study, conducted in Waikato, New Zealand, assessed the performance of different catch crop species and sowing dates in reducing the risk of N leaching. In 2016, Italian ryegrass and oats were sown in late March, April and May. In 2017, Italian ryegrass, oats and triticale were sown in mid March, April and May. In both years, urea fertiliser (400 kg N/ha) was applied immediately before the first sowing to simulate high N loading of the soil following crop grazing. Both years also included a fallow treatment (control) in which no catch crops were established. In both years, catch crops reduced N losses by 11-55% compared with fallow ground. Oats performed the best at earlier sowings, closely followed by triticale, while Italian ryegrass performed better at the later sowing. Sowing in March resulted in the highest reduction in N losses for all species. These results demonstrated that catch crops can be used to reduce N losses in these Waikato systems, and that species selection and sowing date are key to maximise their effectiveness.