31% reduction in nitrogen loss. Is grass the answer?

Approximately 40 growers and industry representatives gathered to see the AS Wilcox-led Crop Stacking Project in action and hear the latest results firsthand in early June.

This project, a collaboration between AS Wilcox, Plant & Food Research, and Perrin Ag, is trialling and researching this transformational approach to cropping systems to improve freshwater quality by reducing nitrogen losses and minimising soil erosion.

The concept adapts an innovative regenerative cereal farming system in the United Kingdom. The concept involves sowing grass over the paddock after late spring/early summer harvest, keeping the ground covered until planting in winter. Strips of grass are sprayed out prior to planting the crop providing a 20cm wide fallow planting strip for the crop. The grass cover continues to grow two to three weeks after the crop is planted, following this it is desiccated to allow the crop to grow while still protecting the soil.

After three years of refining operations, it’s rewarding to see the collaboration between research and on-the-ground growing delivering real outcomes. The crop stacking approach is emerging as a promising best practice for the future.

Key outcomes to date include:

2023 Trial

·       31% reduction in nitrogen losses in the 2023 trial.

·       Improved structure in the top 15 cm of the soil profile.

·       Improved uniformity of mineralisation down the soil profile. 

2024  Trial

·       Negative value for potential environmental nitrogen losses, indicating the crop accessed nitrogen from deeper soil layers beyond 30cm.

·       200 kg N/ha less nitrogen in the top 90cm compared to baseline, showing active uptake and reduced leaching risk.

The project would like to extend its thanks to Te Tautara o Pukekohe and the Ministry for the Environment for funding the 2025 season trial. The project would also like to gratefully acknowledge the support from the Ministry for Primary Industries, Auckland Council, and Vegetables NZ for their funding of the 2024 season trial.