Lincoln Ag: reducing nitrate leaching on the farm

Drilling the catch crop trial plots with a variety of oats, triticale, and Italian ryegrass at Craigmore Farming’s Te Awa farm near Te Pirita, Canterbury. Photo: Lincoln Agritech.

Lincoln Agritech has recently been awarded two three-year Ministry of Primary Industries Sustainable Farming Fund (SFF) contracts to investigate the use of catch crops to reduce nitrate leaching; and assess the feasibility of using optical sensors for nitrogen fertilised dairy pastures. The first project builds on research by Dr Peter Carey at Lincoln University and aims to upscale this applied research into working winter crop rotations in Canterbury and Southland. The second project will assess using optical sensors for biomass and N-status monitoring in pastures. Both projects will ultimately lead to improved N-use efficiency on dairy farms and reduced nitrate leaching.

Catch crops for reduced nitrate leaching is a project that continues Dr Carey’s PhD studies  where he studied the use of catch crops to mitigate nitrate leaching under winter forage grazing. In autumn and winter, non-lactating dairy cows are eating large quantities of feed over a relatively short period of time to build up body condition and depositing large volumes of urine onto often bare soil at a time when there is minimal plant growth. The conversion of the nitrogen (N) present in urine to soil mineral forms, such as nitrate, can lead to large N leaching losses (80-120 kg N/ha per annum) through field drainage.

However, Dr Carey says that while sowing a crop immediately following winter forage grazing can be problematic, hardy cereals (such as oats) can still establish in these cool conditions.  Once the soil warms, these cereal ‘catch’ crops can then rapidly mop up some of this soil-N, reducing the amount available for leaching - by as much as 40%, according to field trials, as well as improving N-use efficiency and farmers’ profitability.

With the aid of the Sustainable Farming Fund, the aim is to upscale this applied research into working winter crop rotations in Canterbury and Southland; adapt it to various soil and climatic conditions; and communicate the alternative techniques, best practice methods, and findings to the farming communities.

“Ultimately, success will be measured by establishing the practice of sowing winter catch crops as a normal part of winter forage management and demonstrating effective alternatives to farmers that lower nitrate leaching losses after winter forage grazing,” says Dr Carey.

The catch crops SFF programme is supported by industry and leading dairy farm companies including: Plant and Food Research, Craigmore Farms, Dairy Holdings, Ballance Agri-Nutrients, Ravensdown, Agricom, Luisetti Seeds, DairyNZ, Foundation for Arable Research (FAR), South Island Dairy Development Centre (SIDDC), Irrigo Centre Ltd, and Lincoln University’s Centre for Soil and Environmental Research.

New Zealand’s intensive dairy-farming systems rely heavily on N-fertiliser to maintain pasture production; however, these fertilisers are often applied uniformly over the paddock - irrespective of the variability that might exist in the paddock. This results in poor use of N-fertilisers, with under or over application in some areas of the paddock, causing unfavourable economic and environment consequences, such as lost yield and nitrate leaching to the groundwater. 

Lincoln Agritech’s second SFF-project, Optical sensors for N-fertilising dairy pastures, will assess using optical sensors for variable rate application (VRA) of N-fertilisers on dairy grazed pastures. This type of sensing technology is commonly used for assessing biomass and N-status in arable crops; however, at present they are not used for monitoring pastures.

Lincoln Agritech’s previous research has demonstrated that using optical sensors for pasture systems can reduce N-fertiliser amount by up to 30% and nitrate leaching by up to 13%, whilst maintaining the same pasture yields. The aim of this research project will be to assess and adapt current commercial sensor systems for VRA of N-fertiliser in pasture systems. 

This research programme is supported by Stratford Farms in Temuka, Irrigo Centre Ltd, MHV Water, North Otago Irrigation Company, Advanced GPS Ag, Topcon, Ballance Agri-Nutrients, DairyNZ, AgResearch, and Plant and Food Research.

More information can be found in the Lincoln Agritech July 2018 newsletter. The newsletter also reports on Lincoln Agritech’s development of an automated sensor known as the ‘PAWS pest identification sensor pad’ that will detect and identify pests reinvading islands and mainland sanctuaries where possums, stoats and rats have previously been eradicated. The research is part of the Department of Conservation’s ‘Predator Free by 2050’ programme.

Date posted: 21 August 2018

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