With focus on water quality and nutrient loss growing in Ireland, Ross Monaghan of Ag Research New Zealand provided some insight into New Zealand’s experience on Teagasc’s latest Signpost webinar.
The soil scientist’s presentation discussed the approaches taken by the NZ agricultural sector in reducing nutrient loss to the environment through a number of land management measures.
Clover-based pasture dominates NZ grazing systems and farmers commonly out-winter stock on a combination of grazed grass and forage crops, explained Monaghan.
Common nitrogen application rates on NZ dairy farms are in the 100kg to 150kg/ha range, with urea the commonly applied fertiliser type.
Less fertilisers, if any, are used in the generally more-extensive drystock sector.
Legislation introduced last year has set a limit of 190kg N/ha on yearly nitrogen application.
Recently suggested national water quality protection measures relate to the exclusion of livestock from streams, necessitating winter housing on heavy soils and catchment-specific waterway monitoring.
The area of grassland farmed in NZ has decreased by approximately 11% since 1995 at the same time that the dairy sector has expanded.
This expansion has more than compensated for the drop in livestock units created by a reduction in sheep numbers over the same period.
When these two factors are accounted for, grasslands in NZ have intensified by approximately 1% per year, explained Monaghan.
Between 1995 and 2015, NZ has reduced phosphorous losses to waterways by 20% to 25%.
Despite increased efforts to improve nutrient management in the country’s dairy industry, nitrates leakage has increased by 25% over the same timeframe.
The changes to nitrates losses have increased the pressure on farmers to maintain and improve water quality.
The researcher claimed that the nitrates problem would have been exacerbated had the industry not acted to implement control measures.
“Being an optimist, I do think there is a lot we can do to practically manage those leakages and at least get us on the right trajectory to improvements,” commented Monaghan.
“We have done a lot of work in the past 10 years to show that we can live on less fertiliser nitrogen if we are quite targeted in the way we use it,” he said.
Plantain inclusion in swards was identified by researchers in NZ to have been a significant development in possible nitrates loss reduction strategies.
It has been established that the plant must make up approximately 30% of the sward for the beneficial impact of the plant to be seen. This has been a difficult achievement for some NZ farmers who have struggled plantain persistency.
Improved forage crop management could greatly reduce nutrient and sediment loss from farming activities, according to Monaghan. Leaving crop residue would help prevent overland losses from bare soils.
Among the other solutions to water quality challenges proposed by Monaghan were the switch to more water-friendly land uses, such as fruit growing, forestry or sheep milking in some water pressure areas.
Regional limit setting
There has yet to be a full compliment of water quality regulations similar to the Irish Nitrates Directive introduced nationally in NZ, as water quality and land use management directives are decentralised to the country’s regional authorities.
There is currently no cross-region exclusion period for organic fertilisers.
The impacts of this regionally delegated responsibility for controlling water quality has had varying results, as larger and more populated regions have more resources to implement their quality control plans.
Areas with higher urban populations also commonly implement stricter measures on water quality when compared with rural ones.