Reducing N-Loss from Soils

Whenua Haumanu is a $26.12 million flagship programme supported by MPI’s Sustainable Food and Fibre Futures Fund and is the most comprehensive study of pastoral farming and regenerative agriculture ever undertaken in New Zealand.  

Now in its fourth of a planned seven years, the programme is a partnership between the Ministry of Primary Industries and Massey University. Also involved are Lincoln University, Public Research Organisations (PROs, known formerly as Crown Research Institutes or CRIs) and industry partners.  

The research programme is looking at multiple measures throughout the farm system, exploring how different pasture mixes and management practices impact a number of areas; the environment, animal health and welfare, and levels of production, as well as the quality of milk, meat and wool produced from these systems.  

One of the work strands being undertaken at Te Kunenga ki Pūrehuroa Massey University, is looking into nitrate leaching from soils, and is consistently finding that lower rates of loss occur under a diverse pasture and regenerative management system.  

Massey University’s Dr Lucy Burkitt is an Associate Professor at the university’s School of Agriculture and Environment. She is the soil research lead for the project and supervises the nitrate loss component of the programme and steers a team including colleague and lecturer in soil science, s, as well other scientists, technicians and agriculture students. 

Described by Dr Burkitt as ‘mini farm systems’, two Massey farmlets are focal points in the study – one is a dairy farm and the other is a sheep and beef system. Each has different soil types, with the dairy farmlet sited alongside the ū River, and having a well-drained sedimentary soil type, while the sheep and beef farmlet (part of Massey’s Plant and Crop Research Unit) has poorly drained, heavier soil. 

Conventional ryegrass and white clover, as well as novel/diverse pastures have been set up on each farmlet (containing a mixture of approximately 20 species of grasses, legumes and herbs). In addition, due to the differing soil types across the farmlets, Dr Burkitt and her team have devised different ways of measuring nitrate leaching appropriate to each soil type.  

On the poorly draining sheep and beef farmlet, a tile drainage system has been installed underground. It captures drainage water that is directed into tipping buckets, with the contents measured for volume before being tested and analysed for nitrogen content.   

On the dairy farmlet with its free-draining soils, trench lysimeters are used to measure and analyse any water that drains through the soil.  “Essentially this system uses a wick that’s buried 60-70 cms into the soil,” says Dr Burkitt, adding that the trench is plastic lined so that any nitrate that moves through the soil, including cow urine, is captured.  

Added to this, the cows are fitted with Halter collars, allowing researchers to track where each animal is spending time and how this might influence nitrate leaching.  

Researchers are finding that regenerative farming practices on both farmlets are helping to reduce leaching. These include options such as giving paddocks longer rest periods between grazing and leaving more pasture behind after grazing when the animals are moved to a fresh area.   

There is low to no addition of mineral fertiliser and no chemicals used on the regenerative farmlets, with the only additions being some organic amendments typical of regenerative practice in New Zealand.   

While Dr Burkitt and her team are the first to observe their set up – small sheds on the edge of paddocks with tipping buckets – might not look like it, it is, in fact, state of the art, even ground-breaking.

Massey was the first university in the world to develop a system that enables such accurate onsite measurement and analysis of paddock leaching. There is a university (in Ireland) and a few similar set ups in the Americas that can do the same onsite measurement and analysis, but Massey was the first to install the in-ground system.  

To help illustrate the various ways of reducing nutrient and sediment loss from soils, Massey has had several interactive models crafted which are on display in the foyer of the School of Agriculture and Environment building and often showcased at agricultural field days. 

The models show different types of farmland with options for mitigating nutrient run-off, such as fencing, animal classes, wetlands, riparian planting, and controlled drainage, among other features. There is even push-button irrigation allowing observers to readily understand how the precise application of water is crucial to reducing run off.      

For more about the Whenua Haumanu programme, click here.