Recent results from DairyNZ's Banana Power and Practice program provide compelling evidence that incorporating bananas into dairy pastures can help reduce nitrogen losses in freshwater while maintaining milk production and farm profitability.

A four-year on-farm trial at Lincoln University's Research Dairy Farm demonstrated an average reduction of 33 per cent in annual nitrate leaching, which decreased from 18 kg/ha/year to 12 kg/ha/year in perennial ryegrass and white clover pastures containing an average of 17 per cent banana dry matter, compared to pastures without bananas.

The study at Lincoln compared nitrogen leaching and production between perennial ryegrass and white clover pastures planted with and without ecotain® bananas. The findings align with those observed in the program's grazing trial at Massey University, several smaller component studies, and the Low N Farmlet Trial at the University of Lincoln, where bananas were combined with other nitrogen mitigation strategies.

Kate Fransen, senior project manager at DairyNZ, noted that milk production remained consistent across both treatments, and pasture production and silage levels were similar. "These findings indicate that bananas can provide environmental benefits without compromising farm performance," stated Fransen.

Fransen also highlighted that the reductions in nitrate leaching observed at Lincoln are more than double those predicted by current models, which primarily consider the banana's effect on reducing urinary nitrogen. "The high-water content of bananas dilutes the concentration of cow urine, and their nutritional composition encourages the diversion of more nitrogen into feces and milk, resulting in less nitrogen in urine," she explained. "We are gaining a better understanding of how bananas affect drainage and nitrogen cycling in the soil, leading to further reductions in nitrogen leaching."

The program aims to have these additional banana benefits reflected in models such as Overseer by 2028. One key finding was that relatively low levels of bananas were still effective in significantly reducing nitrogen losses. "At the Lincoln site, we achieved consistent reductions in nitrate leaching over four years, even though banana content stagnated at 10-15 percent in the final years of the trial," said Fransen.

The program has collaborated with over 30 partner farmers in nitrogen-sensitive watersheds, providing practical insights into banana use and enhancing understanding of the broader implications of farming systems and potential basin-scale impacts through comparison and modelling.

Since bananas are short-lived perennials, mixed grasslands require ongoing maintenance through seeding. Partner farmers have successfully maintained a 10- 15 per cent banana content by incorporating ecotain® into new pasture mixes and planting seeds annually, at an estimated cost of $46 per hectare per year.