With the challenge New Zealand is facing with increased nitrogen leaching that has come with intensifying of dairy, there is understandably a tendency to ‘look over the fence’ and see how we compare with others. New Zealanders have applied our knowledge of pasture-based systems in a number of other countries, including several in South America.
Given the Morgan Foundation has commented on water quality I have had a few questions aimed at me from farmers and their lobby groups about the farm I am involved with in Brazil. So I asked one of our directors, Craig Bell to pen the article below about the farm.
I must stress that Fazenda Leite Verde (our name means, pasture-based farm) is a farm in the tropical belt of Brazil, and as a result has very limited direct comparison to the issue farmers face here at home. But, I find it pretty interesting stuff nonetheless.
In the article below, Craig summarises the nature of the nutrient budget for the farm. You will see the issues are very different but the basic challenges are the same – the impact on the environment is determined through the farmer’s decision of how vigorously to pursue ecological balance.
Fazenda Leite Verde’s philosophy is “to have islands of dairy farms in a sea of wilderness” in order to preserve sufficient, meaningful, and interconnected areas to allow native flora and fauna to flourish. The farm was designed with the help of biologists to create “ecological corridors” that connect through neighbouring properties with the same philosophy to a nearby national park.
Figure 1 – Ecological Corridors on Fazenda Leitíssmo
Within the farm boundaries, various types of environment can be found including vereda (riverside peat swamp), Cerradão (heavy bush), Cerrado (light bush/ savannah), campo sujo (open grassland with some trees), and campo limpo (open grassland). In laying out the farm, the ecological corridors were designed to include all of these types of environment, as each has an important role to play for the native fauna.
6 pivots are supplied with river water and 14 pivots will eventually be supplied with well water. Even though it is legally permitted to be within 30 metres of a river and the pumping cost would have been considerably lower by placing pivots close to the river, the minimum distance between the closest edge of a pivot and the river is 400 metres. This minimises the amount of nutrient lost to the waterway.
Brazilian law requires 20% of a farm’s area in the Cerrado region to remain as a permanent reserve. In the case of Fazenda Leite Verde, the owners have decided to preserve at least 50%, while irrigated pivots comprise just 20% of the farm’s total area.
When the project is fully implemented, livestock will only be managed on irrigated pivots, which will have a stocking rate of 9.8 Animal Units/irrigated hectare. The overall stocking rate on the property is therefore just 2.00/hectare, which is 30% lower than the average in NZ of 2.85/hectare (2012/13 NZ Dairy Statistics).
Additionally along the river basin in which the farm is located there are currently no other dairy farms and a minimal number of beef cattle. The individual farm and regional pressures on nitrate loadings into groundwater are low compared with New Zealand.
Our Pasture – Tifton 85
Fazenda Leite Verde uses Tifton 85. There is no legume in the pasture system.
Tifton 85 is a cross between a Bermuda grass [Cynodon dactylon, specifically cv. Tift 292 (an armyworm resistant plant introduction in the USDA-ARS collection)] and a closely related Cynodon species called stargrass [Cynodon nlemfuensis, specifically cv. Tifton 68 (highly digestible, but cold susceptible). Tifton 85 is a high-yielding, highly digestible hybrid Bermuda grass that also has a tremendous number of environmental benefits. It produces substantially more dry matter per unit of rainfall/irrigation or unit of fertilizer, has a much deeper root system than other Bermuda grasses, improves soil organic matter content, increases carbon sequestration, reduces the carbon footprint of pasture-based livestock production, and reduces nitrate leaching through the soil into the groundwater.
Compared with ryegrass Tifton 85 has a root system which is several times deeper, and which also gives the plant more root mass area and time to absorb nitrogen passing through the soil profile. The superior ability of Tifton 85 to absorb nitrogen can be seen in nitrogen response rates. Typical New Zealand response rates to nitrogen applications are:
Source: DEXCEL, 2006.
By comparison, observations at Fazenda Leite Verde show nitrogen response ranging between 30 kg DM/kg N in winter and 80 kg DM/kg N in summer, averaging 55 kg DM/kg N across the year. For the non-farmers out there, this means that each dollop of nitrogen creates 4-5 times more grass than you’d get in New Zealand.
Brazilian Nitrogen Studies
A study by Primavesi et al (2002) looked at high levels of nitrogen application on tropical grass using ammonium nitrate and urea as nitrogen sources. The application of nitrogen was either 100 or 200 kg N/grass cut.
By comparison, the maximum nitrogen applied at Fazenda Leite Verde is around 120 kg N/grazing in August when there is no rain and only pivot irrigation of the pastures. During summer N application drops to 30 kg N/grazing, and the average application during the year is 50 kg N/grazing.
As can be seen in the graph of the results below, measurements at 60 cm of soil depth and below showed there was no significant difference from the control of 0 kg N/grass cut for any of the fertiliser treatments. Again for the non-farmers – this means that none of the nutrients make it past the deep roots of the grass, so there is no threat to waterways.
Source: Primavesi et al. (2002)
There are at least three reasons why there is less risk of high nitrate groundwater levels occurring when using tropical pastures compared with temperate pastures:
Higher N extraction capacity for tropical grasses due to their deep root systems and high dry matter production potential
Use of urea in Brazil as the main nitrogen source which have less leaching losses than ammonium nitrate fertilisers used in other countries
Urine patches from cows will of course produce higher spot nitrogen concentrations than the levels researched above, but the deep root structure of the highly efficient Tifton 85 plant is a major advantage that farming in the tropics enables for minimising leaching of urine-derived nitrogen. We are monitoring this issue as the farm continues to expand.
Using a highly efficient nitrogen absorbing pasture with a deep root structure, a farm layout with grazed areas located well away from waterways, operating the farm with conservative nitrogen applications based on good science, and using a low overall stocking rate on the property, Fazenda Leite Verde believes that its nitrogen management is as good as any pasture-based dairy farm in the world. Of course every country has to develop its own approach to nitrogen loss that accords with climate and soils of that location so there are few direct lessons from farming in the tropics in Brazil to the temperate farming here.