Reducing environmental N losses and increasing N uptake on grazed dairy farms with simple, low cost detection and treatment of fresh cow urine patches
Pastoral Robotics Ltd
Dairy products produced from cows gaining most of their food intake grazing pastures are becoming increasingly preferred by consumers who are seeking more natural food.A significant environmental concern under grazing, especially under intensive farming under higher rainfall or irrigation is the significant nitrogen (N) losses to the environment from cow urine patches, as nitrate leaching and/or as emissions of nitrous oxide greenhouse gas.These losses come about essentially as a result of the very high concentrations of N applied to the urine 'patch' or deposition area, mainly as urea. Within any one patch, the N application rate typically ranges from 500-1200 kgN/ha, far greater than the amount that can be recovered by the pasture before significant losses to the environment occur.This presentation describes the development of new technology which, towed behind a 4-wheel motorbike or other vehicle, enables the farmer to detect fresh cow urine patches and simultaneously treat them with various products such as N inhibitors and growth promotants, greatly increasing the recovery of urine-N by the pasture and reducing losses of N to the environment.The equipment developed, known as 'Spikey', uses a row of light, spiked metal wheels spaced 10 cm apart to measure the electrical conductivity of the top few mm of the soil, as well as the soil surface resistance, to locate fresh (1-3 days old) urine patches with a very high degree of certainty and accuracy.The ionic content of urine is very much higher than that of the soil solution; each urination is typically applying a 10mm 'irrigation' with urine, which saturates the topsoil, and causing easily detectable 'spikes' in soil conductivity for typically 3 days.Treatment of individual fresh urine patches in this way has been found to increase pasture N recovery by up to 70%, and as a consequence sigificantly reduce N losses to the environment.The Spikey equipment can be scaled up to whatever is the most appropriate for the farmer to do on a given farm. For New Zealand, this is like to be a width of 8m initially. Many farmers follow the cows' paddock rotation or electric fence-controlled strip-grazing with applications of fertilizer N to whatever area has been grazed in the last 1-3 days. For these farmers, the fertilzer hopper and spreader can easily be mounted on the Spikey equipment. For these farmers, the additional time requirement to detect and treat urine patches is minimal. For those that do not, the time requirement is typically 20-30 minutes per day.Treatment of the urine-affected area only, which is typically only 2-5% of the area grazed on any one occasion or area, means that the use of chemicals such as urease and/or nitrofication inhibitors and growth promotants is greatly reduced compared to technologies that involve treating the entire area grazed. The period of the year for which Spikey is used will be a function of local climate and soil conditions, farm mangement practises such as irrigation, and the sensitivity of local receiving waters to nitrate enrichment.The Spikey technology, when combined with fertilizer N application, will allow prevention of fertilizer N to urine patches, with consequent calculated savings in N requirements of 5-15%.