Effect of dicyandiamide (DCD) on nitrous oxide emissions from cow urine deposited on a pasture soil, as influenced by DCD application method and rate

Animal urine deposited on pastoral soils during grazing is a dominant source of nitrous oxide (N2O) emissions. The nitrification inhibitor, dicyandiamide (DCD), is a potential mitigation technology to control N2O emissions from urine patches on grazed pastures. One delivery option is to include DCD in animal feed so that the DCD is targeted directly in the urine patch when excreted in the animal urine

Effect of plantain use on reduction of nitrous oxide emissions from a Waikato farm

The objectives of this study were to compare the nitrous oxide (N2O) emission factors for urine (EF3, N2O-N emitted as % of N applied) from animals grazing two pasture types: conventional ryegrass (Lolium perenne) /white clover (Trifolium repens) (RG/WC) or a mixed sward of 60% plantain (Plantago lanceolate L.) and 40% RG/WC (P/RG/WC), and to assess whether any differences in EF3 were due to a “plant” effect or a “urine composition” effect. This work was carried out on a free-draining alluvial soil near Waharoa in the Waikato region during the winter of 2019. A static chamber method was used to measure N2O fluxes from urine, collected from cows which had been fed on RG/WC or P/RG/WC diets, applied to five plots of each pasture type. Plots that received no urine were also included. Gas sampling took place once before urine application, and then over the following 3 months until N2O fluxes from the urine-applied soil returned to background levels. The N2O fluxes were integrated over time to estimate the total emissions. EF3 values were then calculated for each urine type applied to each pasture type. The mean net N2O emission from the RG/WC urine was 0.57 kg N2O-N ha-1 when applied to the RG/WC pasture and 0.40 kg N2O-N ha-1 when applied to the P/RG/WC pasture. The mean net N2O emission from the P/RG/WC urine was 0.60 kg N2O-N ha-1 when applied to the RG/WC pasture and 0.41 kg N2O-N ha-1 when applied to the P/RG/WC pasture. Overall, the differences in net N2O emission between the two urine types were not significant (P > 0.05), but the net mean N2O emissions from the P/RG/WC pasture were lower compared with those from the RG/WC pasture (P < 0.05). Accordingly, the EF3 values were not different when either urine type was applied to either RG/WC soil or P/RG/WC soil, but the EF3 values for the P/RG/WC sward (0.10-0.12%) were lower than those for the RG/WC sward (0.15-0.17%) (P < 0.05). These results indicate that the effect that plantain had on reduction of N2O emissions was not due to specific compounds in the urine but most likely due to biological nitrification inhibition caused by substances exuded from plantain roots or due to other differences in soil microclimate such as soil moisture levels

Nitrous oxide emissions during change of land use from permanent pasture to maize cropping and re-establishment to pasture

In recent years the strategic use of non pasture-based supplementary feeds on New Zealand (NZ) dairy farms has contributed to intensification and increased productivity. Maize silage is the dominant source of NZ produced supplementary feeds on farms, as it provides a low cost source of starch and fibre for dairy cattle. Land that is normally in permanent pasture is most often used to produce maize for ensiling. Depending on crop establishment method used, the production of maize silage involves some measure of soil disturbance, which can affect soil nutrient transformation processes. Little is known about the effect of cultivation of permanent pasture and planting of a maize crop on changes in soil nitrogen (N) transformations and nitrous oxide (N2O) emissions. The amount of N2O emitted is affected by many soil factors, such as mineral N content, aeration, water and availability of degradable organic material, which are all affected by cultivation. The objectives of this study were to conduct field measurements of N2O emissions throughout the various stages of maize production on land that had been in permanent pasture (ryegrass/white clover), and to compare with emissions from land maintained in permanent pasture. We included the effect of application of N fertiliser (177 kg N ha-1) or dairy manure (177 kg N ha-1) to the maize crop, and N fertilizer (80 kg N ha-1) only to the pasture. This work was carried out on a well-drained soil on the former Ruakura Number 1 Dairy Research Farm, Hamilton in NZ. Full cultivation was used to establish the maize crop and a direct drilling method for subsequent establishment back into pasture

Effect of plantain use on reduction of nitrous oxide emissions from a Waikato farm

The objectives of this study were to compare the nitrous oxide (N2O) emission factors for urine (EF3, N2O-N emitted as % of N applied) from animals grazing two pasture types: conventional ryegrass (Lolium perenne) /white clover (Trifolium repens) (RGWC) or a mixed sward of 60% plantain (Plantago lanceolate L.) and 40% ryegrass/ white clover (PRGWC), and to assess whether any differences in EF3 were due to a “urine composition” effect or a “sward” effect. This work was carried out on a free-draining alluvial soil near Waharoa in the Waikato region during the winter of 2019. A static chamber method was used to measure N2O fluxes from urine, collected from cows which had been fed on RGWC or PRGWC diets, applied to five plots of each pasture type. Plots that received no urine were also included. Gas sampling took place once before urine application, and then over the following 3 months until N2O fluxes from the urine-applied soil returned to background levels. The N2O fluxes were integrated over time to estimate the total emissions. EF3 values were then calculated for each urine type applied to each pasture type. The mean net N2O emission from the RGWC urine was 0.57 kg N2O-N ha-1 when applied to the RGWC pasture and 0.40 kg N2O-N ha-1 when applied to the PRGWC pasture. The mean net N2O emission from the PRGWC urine was 0.60 kg N2O-N ha-1 when applied to the RGWC pasture and 0.41 kg N2O-N ha-1 when applied to the PRGWC pasture. Overall, the differences in net N2O emission between the two urine types were not significant (P > 0.05), but the net mean N2O emissions from the PRGWC pasture were lower compared with those from the RGWC pasture (P < 0.05). Accordingly, the EF3 values were not different when either urine type was applied to either RGWC soil or PRGWC soil, but the EF3 values for the PRGWC sward (0.10-0.12%) were lower than those for the RGWC sward (0.15-0.17%) (P < 0.05). These results indicate that the effect that plantain had on reduction of N2O emissions was not due to specific compounds in the urine but most likely due to biological nitrification inhibition caused by substances exuded from plantain roots or due to other differences in soil microclimate such as soil moisture levels

Evaluation of the effect of dicyandiamide (DCD) on nitrous oxide emissions from cow urine deposited into a pasture soil, as affected by DCD application rate and delivery method

Research, on whether the nitrification inhibitor, dicyandiamide (DCD), can mitigate N2O emissions from urine patches on grazed pastures, through excretion by cows that are provided DCD-amended feed. Application of DCD, either mixed or in urine from DCD-fed cows, significantly reduced EF3. DCD excreted in urine had the same reduction effect on N2O emissions as DCD that was separately mixed with urine at the same DCD loading rate

Nitrous oxide emissions during maize cropping

The objectives of this study were to conduct field measurements of N2O emission changes through various stages during the production of maize silage on land that had been in permanent pasture and to compare them with emissions from land maintained in pasture. This work was carried out on a Horotiu soil on the former Ruakura Number 1 Dairy Research farm, Hamilton. Treatments were: Pasture control, fertilized pasture, maize control and fertilized maize. Soil temperature, moisture and inorganic N content were monitored and N2O emissions were measured using a closed chamber technique. Soil temperature was generally lower, and soil water filled pore space (WFPS) was generally higher, in the soil under the closed maize canopy than under the adjacent pasture sward. Cultivation for maize crop establishment resulted in elevated soil nitrate levels. The addition of fertiliser N (177 kg N ha-1) enhanced soil nitrate levels until maize harvest time. However, increases in soil ammonium due to cultivation or the application of fertiliser only lasted for relatively short periods. For about 2 months following initial cultivation for maize establishment, the daily soil N2O emissions from the cultivated control (without any N input) were between 0.017 and 0.419 mg N m-2 hr-1. These rates were generally higher than those in the pasture control treatment, which ranged between 0.004 and 0.027 mg N m-2 hr-1. Using “standard” maize and pasture management practices in NZ, during the study period (239 days) the total N2O emission from the cultivated maize growth area, including subsequent establishment of new pasture, was 1.78 kg N2O-N ha-1. This was higher than the 0.74 kg N2O-N ha-1 emitted from the pasture area over the same period (P<0.05). The N2O emission factor (EF1) (% of fertiliser N emitted as N2O) during the maize growth period was 0.10%. The EF1 for fertiliser on the pasture was 0.16%. The EF1 values obtained were below the default IPCC value of 1% for applied fertilizers

Effect of dicyandiamide (DCD) on nitrous oxide emissions from cow urine deposited on a pasture soil, as influenced by DCD application method and rate

Animal urine deposited on pastoral soils during grazing is recognised as a dominant source of nitrous oxide (N2O) emissions. The nitrification inhibitor, dicyandiamide (DCD), is a potential mitigation technology to control N2O emissions from urine patches on grazed pastures. One delivery option is to include DCD in animal feed so that the DCD is targeted directly in the urine patch when excreted in the animal urine. The hypothesis tested in this study was that DCD in urine, excreted by cows that were orally administered with DCD, would have the same effect as DCD added to urine after the urine is excreted. The study also aimed to determine the most effective DCD rate for reducing N2O emissions. Fresh dairy cow urine (700 kg N ha-1) was applied to a free-draining silt loam pastoral soil in Waikato, New Zealand, in May (late-autumn) or July (winter) of 2014, and was mixed with DCD at rates of 0, 10, 30 and 60 kg ha-1. In late-autumn, there was an equivalent treatment of urine (containing 60 kg DCD ha-1) from DCD-treated cows. A static chamber technique was used to determine gaseous N2O emissions. An annual emission factor (EF3; the percentage of applied urine N lost as N2O-N) of 0.23% or 0.21% was found following late-autumn or winter applications of urine without DCD. Late-autumn application of urine containing DCD from oral administration to cows had the same significant reduction effect on N2O emissions as DCD that was mixed with urine after excretion, at the equivalent DCD application rate of 60 kg ha-1. Application of urine with DCD mixed with the urine after excretion at varying DCD rates showed a significant (P < 0.05) linear decrease in both N2O emissions and EF3 values

Increasing the spread of urine to reduce nitrogen leaching risk

The majority of nitrogen (N) in a grazed pastoral system is cycled through the urine patch. The N loading rate in the dairy cow urine patch can be greater than 600 kg N/ha which exceeds pasture requirements, leaving urine N vulnerable to leaching or gaseous N loss, particularly in autumn-winter when pasture growth is slow. It is important to understand N cycling processes in the urine patch for modelling and N management on farms. New technologies for reducing N losses include increasing the spread of urinary N via devices attached to the cow. It is hypothesised that increasing the spread of urine will lead to increased pasture uptake of urinary N and reduced risk of N leaching loss by (a) reducing the urine patch N loading rate (increasing patch size), and (b) increasing the potential diffusion of N out of the urine patch through a non-uniform pattern of return (patch shape). A plot study was conducted comparing the effect of urine spreading (patch size and shape) on N leaching risk from urine applied in autumn to a volcanic soil in the Waikato region of New Zealand. Two litres of urine (6 g N/L) was applied in late April to three urine patch sizes (0.2, 0.6, 1.0 m2) and two urine patch shapes (square, rectangle). Urine patches were labelled with the stable isotope 15-N to track the movement of N through the soil profile. Regular monitoring of pasture N uptake and soil mineral N measurements were undertaken from three urine patch zones: the wetted, edge (+20 cm) and outer areas, for approximately 5 months after urine application. The results from the study will be presented

Dung and farm dairy effluent affect urine patch nitrous oxide emissions from pasture

Urine patches in grazed pastures are an important source of nitrous oxide (N2O) emissions. Significant areas of ruminant-grazed pastures are simultaneously covered by excreted urine and dung or farm dairy effluent (FDE). An additional increase in N2O emissions is possible where urine patches coincide with dung patches or FDE applications

Dung and farm dairy effluent affect urine patch nitrous oxide emissions from a pasture

Urine patches in grazed pastures have been identified as important sources of nitrous oxide (N2O) emissions. An increase in the N2O emissions is possible from urine patches, due to concurrence with dung patches and farm dairy effluent (FDE) applications. The aim of this study was to quantify the effects of dung additions and fresh FDE applications on N2O emissions from urine patches. A field experiment was conducted on a pasture site at the AgResearch’s Ruakura dairy farm in Hamilton, New Zealand. A closed soil chamber technique was used to measure the N2O emissions from a free-draining volcanic soil which received urine (492 kg N/ha, simulated urine patches), with or without dung (1,146 kg N/ha) and fresh FDE (100 kg N/ha) and compare these with controls receiving no urine. The addition of dung delayed the peak N2O fluxes from the urine patches by approximately 30 days. This could be due to temporary nitrogen (N) immobilization during decomposition of carbon (C) from the dung. Over the whole measurement period (271 days), dung addition increased the N2O emission factor (EF, % of applied N emitted as N2O) for the urine from 1.02 to 2.09%. The application of fresh FDE increased the EF to 1.40%. We conclude that when EFs are used in calculations of N2O emissions from urine, consideration should be given to the likelihood of concurrence with dung or FDE applications