Urine Patches Research Articles

Comment on ‘An examination of the ability of plantain (Plantago lanceolata L.) to mitigate nitrogen leaching from pasture systems’

ABSTRACT In their review: An examination of the ability of plantain (Plantago lanceolata L.) to mitigate nitrogen leaching from pasture systems, Eady et al. (2024) dispute both the historic estimates of typical urine patch nitrogen (N) load and leaching and the evidence for the N leaching reduction mechanisms of plantain; and question the recommended levels of plantain required to achieve N leaching reduction. We reject the suggestion that the urine patch has little influence on N leaching, and that average annual N leaching from dairy farms is 6 kg N/ha. We agree that the low dry matter content of plantain is the dominant and best documented effect of plantain on urine N dilution. We reject that there is no evidence for the effect of plantain on nitrogen partitioning to urine, and on potential nitrification rate in the urine patch. We point to empirical evidence of statistically significant reductions in nitrate leaching from plantain at paddock scale, at levels as low as 21% plantain of dry matter eaten. Current research will improve understanding of the mechanisms and magnitude of the effect of plantain on N loss, paving the way for recognition of other forage-based N loss reduction options, and ongoing development of mechanistic models that are adaptable to other forages.

The effect of plantain (Plantago lanceolata L.) in pasture swards on gaseous nitrogen emissions from nitrogen-enriched urine patches

The effect of plantain (Plantago lanceolata L.) in pasture swards on gaseous nitrogen emissions from nitrogen-enriched urine patches

Inhibitors application time and pasture canopy capture regulate gaseous losses of urine-N

Technologies have been developed for the in-situ treatment of urine patches deposited by grazing livestock to mitigate nitrogen (N) losses using N transformation inhibitors. For this mitigation to be effective, close contact between the applied inhibitors and the N in the urine patch is required (similar to N-fertilisers coated with inhibitors). This research aimed to determine the proportions of urine-N that mixed with inhibitor at or exceeding the threshold concentration (inhibitor concentration at which the nitrification rate is reduced by at least 40%) when inhibitors were applied to simulated urine patches at 4, 24 and 48 h after synthetic urine application. Three commonly used nitrification inhibitors (NIs) [dicyandiamide (DCD), 3,4-dimethylpyrazole phosphate (DMPP), and 2-chloro-6-(trichloromethyl) pyridine (nitrapyrin)] were applied at 40 mL of inhibitor per urine-patch at two different concentrations. The field studies were undertaken in two dairy-grazed pasture soils with contrasting drainage. Large proportions of applied NIs (38%–59% DCD, 27%–58% DMPP, and 31%–58% nitrapyrin) were retained in the pasture canopy. In most cases, the inhibitor threshold concentration was present only within the top 0–20 mm of the soil, with only 16%–40% of the urine-N present. In some cases, the proportions of urine-N intercepted was 12%–15% higher when inhibitors were applied 4 h after urine application compared to delayed application of 24 and 48 h after urine application. Our results revealed that a substantial proportion of N in the urine-patch remained out of the reach of the inhibitor solution. This is possibly due to the small volume (40 mL per 2 L urine patch, 1:50) of the inhibitors applied, with up to 59% of inhibitor solution retained in the pasture canopy. The time delays (4 to 48 h) between the urine deposition and the inhibitor application could have also contributed to this poor physical mixing between inhibitor and urine. Increasing the volume of water applied with the inhibitor and assessing the effect of rainfall/irrigation on increasing urine-N and inhibitor mixing warrants further consideration.

Reduction of Nitrous Oxide Emissions from Urine Patches from Grazed Dairy Pastures in New Zealand: A Preliminary Assessment of ORUN® as an Alternative to the Use of Nitrification Inhibitor Dicyandiamide (DCD)

Agriculture plays a significant role in economic development and livelihood and is a key contributor to food security and nutrition. However, global concerns regarding the sustainability of the agricultural sector (mainly environmental damage) is linked to agricultural activities such as greenhouse gas (GHG) emissions, water pollution, and loss of biodiversity. The aim of this study was to assess the effectiveness of ORUN® (a formulated agricultural chemical mixture) to reduce N2O emissions from urine patches and to improve pasture yield, pasture N uptake, and soil mineral N concentrations. The field trials were conducted during the spring of 2015 on dairy urine patches at Massey University, New Zealand. Treatments consisted of control nil urine, control nil urine + ProGibb®, urine only, urine + ProGibb®, urine + ORUN®, and urine + ORUN PLUS® replicated four times in a randomized complete block design. At 31 days after treatment (DAT), analysis of soil samples in 0–5 cm soil profiles showed that urine + ProGibb® significantly (p = 0.0041) increased the soil nitrate concentration (121.40 kgN/ha) compared with 48.15 kgN/ha from urine only. The urine + ProGib® treatment produced significantly lower herbage N recovery (35% of applied N) compared with the urine only. Throughout the trial period, the urine patches treated with ProGibb® and ORUN® produced significantly higher N2O fluxes compared with urine only and urine + ORUN PLUS®, as well as higher surface soil nitrate and mineral N concentrations.

N Losses from an Andisol via Gaseous N2O and N2 Emissions Increase with Increasing Ruminant Urinary–N Deposition Rate

Agricultural soils account for about 60% of the global atmospheric emissions of the potent greenhouse gas nitrous oxide (N2O). One of the main processes producing N2O is denitrification, which occurs under oxygen-limiting conditions when carbon is readily available. On grazed pastures, urine patches create ideal conditions for denitrification, especially in soils with high organic matter content, like Andisols. This lab study looks at the effects of Urine-urea-N load on the Andisol potential to emit N2O. For this, we investigated the effects of three levels of urea-N concentrations in cow urine on emissions of N2O, N2, and CO2 under controlled conditions optimised for denitrification to occur. Results show total N2O emissions increased with increasing urine-N concentration and indicate that denitrification was the main N2O-producing process during the first 2–3 days after urine application, though it was most likely soil native N rather than urine-N being utilised at this stage. An increase in soil nitrate indicates that a second peak of N2O emissions was most likely due to the nitrification of ammonium hydrolysed from the added urine, showing that nitrification and denitrification have the potential to play a big part in N losses and greenhouse gas production from these soils.

Contrasting response of comammox Nitrospira, ammonia oxidising bacteria, and archaea to soil pH and nitrogen inputs

This study aimed to investigate the effect of soil pH change, and nitrogen amendment on ammonia oxidiser abundance and comammox Nitrospira community composition. The experimental design used soil mesocosms placed in a temperature-controlled incubator for 90 days. A Templeton silt loam was used as its physiochemical properties are typical of the region's dairy farms. The results showed that comammox Nitrospira clade B preferred the natural (pH 6.1–6.2) soil pH with no applied nitrogen. Furthermore, synthetic urine (N700) decreased the abundance of comammox Nitrospira clade B. This may have been because the large amounts of available ammonia in the N700 treatments inhibited the growth of comammox Nitrospira.These results suggest that while comammox Nitrospira clade B are present in New Zealand dairy farm soils, but their role in nitrification in the very high nitrogen environment under a urine patch in grazed pastures may be limited. Further research is needed to confirm this.In contrast to comammox, the AOB community (dominated by Nitrosospira) responded positively to the application of synthetic urine. The response was greatest in the high pH soil (7.1), followed by the natural and then the low pH (4.9) soils. This may be due to the difference in ammonia availability. At high pH, the ammonia/ammonium equilibrium favours ammonia production. Calculated ammonia availability in the N700 treatments accurately predicted the AOB amoA gene abundance.Interestingly, the AOA community abundance (which was predominantly made up of Thaumarchaeota group I.1b clade E) seemed to prefer the natural and high pH soils over the low pH. This may be due to the specific lineage of AOA present. AOA did not respond to the application of nitrogen.

Stacking nitrogen mitigation strategies for future pasture-based dairy farms: impacts on leaching and profit

Producers in New Zealand’s pasture-based, seasonal dairy sector are striving to reduce nitrogen (N) losses to the environment whilst maintaining or increasing farm profitability. This study examined the cost-effectiveness of stacking different combinations of five N leaching mitigation strategies within the whole farm system; 1) reduced N fertilizer input, 2) off-paddock infrastructure, 3) recycling N by growing maize silage on a dedicated area on the farm using effluent as a fertilizer source followed by a catch-crop, 4) dietary salt supplementation to dilute urinary N, and 5) applying a nitrification inhibitor (NI) to slow the release of nitrate in the soil. The reference point (baseline) was a typical current dairy farm (CF) system in the Waikato region of New Zealand. We modelled four Future Farm scenarios by stacking mitigation strategies as follows: baseline plus reduced N fertilizer input, reduced stocking rate, and off-paddock infrastructure (FF); FF plus a dedicated maize block (FFP); FFP plus dietary salt (FFPS); and FFPS plus NI (FFPSNI). These systems were modelled using the Whole Farm Model coupled with the Urine Patch Framework, and APSIM models, using observed climate and economic input data over five consecutive years from 2013-2018. Relative to CF, the FF system achieved a N leaching reduction of 31% with a reduction in profit of 16%. The FFP system had a smaller N leaching reduction (22%), but the reduction in profit was smaller (11%). The fully stacked system (FFPSNI) demonstrated the largest leaching reduction of 33%, but also the largest profit reduction of 27%, compared with the CF. Stacking these five N mitigation strategies can achieve substantial N leaching reductions at the farm-scale. Including a dedicated, effluent-fertilized maize block followed by a catch-crop as part of the stack can reduce the negative impact on profitability but has a trade-off in N leaching. Farmers will have to weigh up these compromises between profit and leaching, considering risk factors not modelled here.

Ammonia emission factors from cattle production systems in Ireland – a review

Ammonia (NH3) emissions from livestock production contribute to environmental pollution. To address this challenge, the European Union (EU) National Emission Reduction Commitments Directive 2016/2284 (NECD) sets NH3 reduction targets for EU member states. In order to achieve these targets, several strategies have been evaluated under Irish conditions. A compilation of emission factors (EFs) from studies which evaluated these strategies is necessary to assess their effectiveness. This paper reports NH3 EFs from cattle production under Irish conditions. The results from the review show that the mean EFs from the deposition of dung, urine and urea applied to urine patches on grasslands were 4%, 9% and 8% total nitrogen (TN), respectively. EFs from the application of urea to urine patches were reduced by 28% after the addition of the urease inhibitor N-(n-butyl) thiophosphoric triamide (NBPT) to urea. The mean EF of 28% TN reported for urea fertiliser was almost 7 times higher than calcium ammonium nitrate (CAN). The inclusion of urease inhibitors with urea fertilisation on grassland led to EF reduction of up to 86%. The mean EFs from cattle houses, concrete yards, slurry storage pits and slurry landspreading were approximately 13%, 35%, 60% and 59% total ammoniacal nitrogen (TAN), respectively. The most effective NH3 abatement strategies for concrete yards and slurry storage were immediate cleaning of concrete floors (up to 89% reduction) after excreta deposition and the application of chemical amendments (sulphuric acid, acetic acid, alum and ferric chloride) to slurry in storage pits (up to 98% reduction), respectively. Low-emission spreading strategies and slurry acidification were effective at abating EFs after slurry application to land.

The fate of nitrogen in animal urine patch as affected by trees and nitrogen supply on integrated crop-livestock systems

Nitrogen (N) losses by leaching are significant in terms of environmental contamination. Thus, attention has been given to urination points of ruminant urine because they contain high levels of N. Integrated crop-livestock systems (ICLS), in turn, seek to intensify production and, at the same time, make production systems more sustainable. Therefore, it is crucial to know the behavior of N to boost its cycling and, consequently, minimize its impacts (environmental and economic). The objective of this study was to evaluate N leaching from bovine urine in a mixed pasture of Lolium multiflorum x Avena strigosa in two different integrated systems, crop-livestock (CL) and crop-livestock with trees (CLT), and two N doses (90 and 180 kg N ha−1). During the winter 2018, the study was conducted in the Brazilian subtropics, in sandy texture soil. The application of higher doses of nitrogen fertilizer (180 kg N ha−1) causes an increase in the concentration of nitrogen excreted in urine and, consequently, increases nitrate and ammonium contents in the soil at the urine points. Higher nitrogen contents were observed at the urine points, since the uptake of nutrients by the forage plants was reduced due to shading of the plants, leading to a reduction in dry matter production of the pasture. The area of action/diffusion of urinary N does not exceed 25 cm from the center point of urination. No leaching of nitrate or ammonium was observed at the sampled urine points, up to a depth of 40 cm. However, the adoption of more intensified production systems (i.e., with the inclusion of grazing animals and increased nitrogen fertilization) should be conducted under conditions that provide high plant uptake of soil nutrients to reduce the risk of losses.

Greenhouse gas emissions from sheep excreta deposited onto tropical pastures in Kenya

To improve the estimate of greenhouse gas emissions (GHG) from tropical rangelands in sub-Saharan Africa, we measured GHG emissions from sheep excreta over two periods of 51 days on a Kenya rangeland. In addition, we measured GHG emissions from potential hotspots in the landscape linked to sheep grazing: overnight enclosures (“bomas”), where sheep are kept at night to protect them from theft and predators, the areas surrounding sheep bomas, and areas surrounding watering troughs. Results showed a short pulse of CO2 fluxes after sheep urine application and a rapid increase of CH4 fluxes following sheep dung application in both rainy and dry season. However, only small increases of N2O fluxes were observed after dung and urine applications compared to controls without excreta. Elevated N2O fluxes mainly coincided with heavy rainfall. Overall, N2O emission factors (EFs) did not vary across excreta type or seasons, but mean N2O EFs for dung (0.01%) and urine patches (0.02%) were only one tenth of the default EFs from the 2019 IPCC Refinement for dry climate. We did, however, find that bomas and watering troughs are sites of herd concentration that are important sources of GHG emissions in the landscape, and that emissions in these locations can remain elevated for months to years, especially when soil moisture is high. This study contributes to more robust estimates of GHG emissions from African livestock systems, which are fundamental to develop targeted mitigation strategies.

N2O emission factors for cattle urine: effect of patch characteristics and environmental drivers

Urine patches from grazing cattle are hotspots of nitrous oxide (N2O) emissions. The default IPCC emission factor for urine patches (EFurine) is 0.77% for wet climates and 0.32% for dry climates. However, literature reports a considerable range of cattle urine EF values and urine characteristics used in experimental studies, revealing contrary results on the effects of urine patch characteristics and seasonal pattern. Therefore, we examined N2O emissions and corresponding EFurine values in relation to urine patch characteristics (urine N concentration, urine volume, patch area, urine composition) and environmental drivers (precipitation, water filled pore space, soil temperature). Ten artificial urine application experiments were performed from July 2020 to June 2022 on a pasture located in Eastern Switzerland. Urine N concentration, patch area, volume and urine N composition showed no significant effects on the EFurine value (p > 0.05). EFurine varied, however, strongly over time (0.17–2.05%). A large part of the variation could be predicted either by cumulative precipitation 20 days after urine application using a second order polynomial model (Adj. R2 = 0.60) or average WFPS 30 days after urine application using a linear model (Adj. R2 = 0.45). The derived precipitation model was used to simulate EFurine weekly over the last 20 years showing no significant differences between the seasons of a year. The resulting overall average EFurine was 0.67%. More field studies are needed across sites/regions differing in climate and soil properties to implement a country-specific EF3 for Switzerland and to improve the quantification of N2O emissions at the national scales.

Simulating Gibberellic Acid Effect on Pasture Yield on Naturally Deposited and Fixed Area Urine

Nitrate (NO3−-N) leaching from urine patches is a serious environmental concern in dairy pastoral systems. In our previous research, we established that application of a plant growth hormone, gibberellic acid (GA), can potentially reduce NO3−-N leaching in urine patches; however, this was investigated in two locations in New Zealand. The performance of GA in influencing pasture nitrogen (N) uptake and NO3−-N leaching needs to be undertaken in multi-locations to draw conclusions. However, multi-location studies are a challenge due to a lack of funding and time constraints, so models such as the agricultural production systems simulator (APSIM) have been used. Therefore, field studies were conducted to determine whether APSIM can be used to quantify and simulate the effect of GA on NO3−-N leaching and pasture yield in three experimental sites known as Ashburton, Stratford, and Rotorua in New Zealand. Treatments examined were control (no urine applied), urine at 600 kg N ha−1, urine + GA at 8 g ha−1. The observed data was used to calibrate and validate the model. APSIM simulated that application of GA reduced NO3−-N leaching (relative to urine treatment) by 4.6, 5.1, and 8.8 kg NO3−-N ha−1 in Ashburton, Stratford, and Rotorua, respectively. APSIM reliably simulated pasture dry matter yield, and this was confirmed by the coefficient of determination ranging from R2 = 0.8562 to 0.995 in all treatments and experimental sites. This study demonstrated that APSIM can effectively be used to simulate the effect of GA application on NO3−-N leaching and pasture yield. Therefore, APSIM can be applied in other areas to simulate NO3−-N leaching and pasture yield.

Effective Proportion of Plantain (Plantago lanceolata L.) in Mixed Pastures for Botanical Stability and Mitigating Nitrous Oxide Emissions from Cow Urine Patches

Plantain (Plantago lanceolata L.) is recognised for its ability to improve summer feed productivity as well as mitigate nitrous oxide (N2O) emissions from grazed pastoral soils. This study aims to determine the proportion of plantain required in perennial ryegrass (Lolium perenne L.) and white clover (Trifolium repens L.), or RWC, mixed swards to maintain yield stability and to quantify N2O emission reductions. The botanical composition was monitored when plantain was sown at different rates of 0%, 30%, 50% and 70% in RWC pastures under grazing by dairy cows over 2 grazing years. Urine from cows grazing RWC (6.15 g N L−1), 30% (5.40 g N L−1) and 50% (4.40 g N L−1) plantain mixed pastures was used to measure N2O emissions (n = 5) from the pastures of their origin and to assess the impact of the plantain rhizosphere on N2O emissions by applying the RWC urine to the 50% plantain mixed pasture, and vice versa, in late summer–autumn using the static chambers technique. After declining in spring, the plantain content recovered in early autumn and reached a peak of 40% in the 30% plantain mixed pasture and around 50% in the 50% and 70% plantain mixed pastures in winter. A lower N content in urine, and therefore a lower urine N-loading rate from cows grazing in the 50% plantain mixed pasture, resulted in 39% lower total N2O emissions compared to RWC urine treatment. In conclusion, 30% to 50% plantain in mixed pastures was stable throughout the 2 years, and it not only reduced the urinary N concentration in grazing cattle but also contributed to reduced N2O EFs.

Soil denitrification response to increased urea concentration constrains nitrous oxide emissions in a simulated cattle urine patch

Soil denitrification response to increased urea concentration constrains nitrous oxide emissions in a simulated cattle urine patch

The soil microbial community and plant biomass differentially contribute to the retention and recycling of urinary-N in grasslands

Urine patches in grazed systems are hotspots for nitrogen (N) cycling and losses to the wider environment. Retention and subsequent recycling of urinary-N is key to minimise losses and increase ecosystem nitrogen use efficiency. Biosynthesis into the microbial organic N pool is an important N pathway but this has not been directly quantified in a urine patch. Herein, we present the results of a time course experiment using soil mesocosms sown with perennial ryegrass (Lolium perenne L.) and treated with 15N-labelled sheep urine to determine partitioning of the applied N between plant, soil biomass pools and leaching losses following simulated rainfall events. 15N-tracing used bulk and compound-specific 15N-stable isotope probing (SIP) to determine the fate of urinary N. Initial high leaching losses (233 kg N ha−1) were comprised of native soil N, ammonium and nitrate derived from urine by urea hydrolysis and nitrification, respectively. Leaching subsequently decreased whilst uptake into plant biomass and microbial biosynthesis increased during periods of low rainfall. Uptake into above and belowground plant biomass was the largest fate of urinary-15N after 94 d (42%), although assimilation into microbial biomass dominated for ca. 1 month after urine deposition (34%). Compound-specific 15N–SIP of amino acids and amino sugars revealed immobilisation of urinary-N following mineralisation was the dominant pathway for biosynthesis, with incorporation into bacterial organic N pools more rapid than into the fungal biomass. There was also intact utilisation of glycine derived from urine. This study provides clear evidence that direct assimilation of urine-derived N into microbial organic N pools is an important process for retaining N in a urine patch, which will subsequently support plant N supply during microbial turnover.

Dairy Cows Grazing Plantain-Based Pastures Have Increased Urine Patches and Reduced Urine N Concentration That Potentially Decreases N Leaching from a Pastoral System.

The objective of this study was to determine the effect of grazing plantain-based pastures on urine volume, urination frequency, and urinary nitrogen (UN) concentration of dairy cows under a typical pastoral dairy practice offering approximately 25% supplemented feeds. The experiment was a completely randomised design with three pasture treatments (perennial ryegrass-white clover (RGWC); RGWC + low plantain rate (PLL); and RGWC + high plantain rate (PLH)), five replicate plots, and repeated in two sequential grazing periods. Forty-five lactating Friesian × Jersey cows were randomly assigned into three groups of 15 animals each to graze over six days in adaptation paddocks and three days in experimental plots. Urine flow sensors were used to measure urine volume and urinary frequency, while spot urine sampling was conducted to determine nitrogen (N) concentration in cow urine. The results showed that including 25% plantain in the diet (PLH) increased daily urine volume by 44% and the daily number of urinations by 28%, compared to grazing the RGWC pasture. In addition, N concentration in cow urine was decreased by 18 and 29% when the diet contained 18% and 25% plantain, respectively. In conclusion, under a typical dairy farm practice, incorporating plantain into the RGWC pasture with the proportion of 25% plantain in the diet can increase the number of urine patches and reduce the concentration of N in the urine, thereby providing the opportunity to decrease N leaching from pastoral systems.

Nitrification rate in dairy cattle urine patches can be inhibited by changing soil bioavailable Cu concentration

Ammonia oxidation to hydroxylamine is catalyzed by the ammonia monooxygenase enzyme and copper (Cu) is a key element for this process. We investigated the effect of soil bioavailable Cu changes induced through the application of Cu-complexing compounds on nitrification rate, ammonia-oxidizing bacteria (AOB) and archaea (AOA) amoA gene abundance, and mineral nitrogen (N) leaching in urine patches using the Manawatu Recent soil. Further, evaluated the combination of organic compound calcium lignosulphonate (LS) with a growth stimulant Gibberellic acid (GA). Treatments were applied in May 2021 as late-autumn treatments: control (no urine), urine-only at 600 kg N ha−1, urine + dicyandiamide (DCD), urine + co-poly-acrylic-maleic acid (PA-MA), urine + LS, urine + split-application of LS (2LS), and urine + combination of GA plus LS (GA + LS). In addition, another four treatments were applied in July 2021 as mid-winter treatments: control, urine-only at 600 kg N ha−1, urine + GA, and urine + GA + LS. Soil bioavailable Cu and mineral N leaching were examined during the experimental period. The AOB/AOA amoA genes were quantified using quantitative polymerase chain reaction. Changes in soil bioavailable Cu across treatments correlated with nitrification rate and AOB amoA abundance in late-autumn while the AOA amoA abundance did not change. The reduction in soil bioavailable Cu induced by the PA-MA and 2LS was linked to significant (P < 0.05) reduction in mineral N leaching of 16 and 30%, respectively, relative to the urine-only. The LS did not induce a significant effect on either bioavailable Cu or mineral N leaching relative to urine-only. The GA + LS reduced mineral N leaching by 10% relative to LS in late-autumn, however, there was no significant effect in mid-winter. This study demonstrated that reducing soil bioavailable Cu can be a potential strategy to reduce N leaching from urine patches.

Varying plantain content in temperate ryegrass-white clover pastures affects urinary-nitrogen excretion of non-lactating dairy cows

Dairy cow urine patches contain high rates of nitrogen (N; >500 kg N/ha) and represent the main source of N loss from grazed pastoral systems. Emerging research has identified plantain (Plantago lanceolata) as a key forage to potentially reduce urine N (UN) losses from dairy cows. This experiment examined the effect of increasing proportions of plantain in the diet of dairy cows on UN excretion relative to a ryegrass-white clover diet. Twenty mixed aged non-lactating dairy cows were randomly assigned to one of five treatment diets; 0 %, 20 %, 40 %, 60 % or 100 % plantain (dry matter basis), with the remainder comprised of ryegrass-white clover pasture and grass-silage. Cows were fitted with urine sensors to measure urination event N concentration, volume and frequency. Daily N intake increased with increasing proportions of plantain in the diet due to the greater N concentration of plantain. Conversely, mean UN concentration was reduced as the proportion of plantain in the diet increased. Urine-N concentration was >40 % lower for cows on 100 % plantain compared with 0 % plantain (0.46 and 0.81 % N respectively). There was no treatment effect on the total daily amount of UN excreted, indicating a dilution effect of plantain as total daily urine volumes markedly increased with increasing plantain diets. Nitrogen load per urination event was lower for cows on 100 % plantain than 0 % despite greater N intake, with no significant difference for the intermediate treatment groups. The reduced N load per event for cows on >60 % plantain could help to reduce N leaching losses at the urine patch level. This experiment suggests that a reduction in UN concentration can be achieved on low levels of plantain (20 % of the diet), but >60 % plantain diets are required to reduce N load per event.

Wetting Pattern of Cow Urine Patch in an Andisol Assessed through Bromide Concentration Distribution: A Pilot Study

Cow urine is a rich source of mobile nutrients such as nitrate (NO3−) and potassium (K+). The aim of this experiment was to evaluate the wetting pattern distribution through soil profile of cow urine patch in an andisol. Two field experiments across two consecutive years were carried out to compare cow urine patches in relation to initial wetting pattern and volume of soil affected. Bromide (Br−) has successfully been used as an inert hydrologic tracer to indicate the movement of NO3− and K+ in soil–water systems. The distribution of Br− (used as a urine tracer) on the soil surface and down the profile was irregular in all the patches. Cow urine patches covered a surface area of 0.27 and 0.35 m2, respectively, and penetrated to a depth of 70 cm. The rapid downward movement of urine occurred through macropore flow but even so, between 27% and 40% of the applied Br− was detected in the 0–5 cm soil layer. Br− showed concentrations greater than 1500 mg kg−1 and up to 3000 mg kg−1, and as the concentration of Br− decreases, the frequency and depth of affected layers increases. Despite the differences in moisture and in the distribution of the Br− concentration in both years, the concentration frequency of 500 to 1500 mg kg−1 represented around 37% of the affected volume of soil (bulb of urine) in both years. Up to 40% of the bulb represented N equivalent rates between 187 and 975 kg N ha−1. These values can potentially be emitted in gases such as NH3, N2O, and N2. It is suggested that the presence of N in the volume of affected soil could vary due to the moisture content of the soil, and that in andisols of southern Chile under permanent grasslands there are a large number of macropores that would induce preferential flows.

Soil carbon stocks and nitrous oxide emissions of pasture systems in Orinoquía region of Colombia: Potential for developing land-based greenhouse gas removal projects

Improving grassland conditions under grazing has the potential not only to accumulate carbon in soils, but also to reduce nitrous oxide (N2O) emissions from animal urine deposition. However, measurements in developing countries are still scarce. In the Orinoquia region, permanent grasslands (PG; this unimproved, native pasture is considered as at some state of degradation) based on unimproved grasses are found due to extensive, inefficient grazing combined with annual burning of pastures. We hypothesized that, compared to PG, improved grasslands (IG) managed through rotational grazing of introduced, productive and deep-rooted pasture grass species promote soil organic carbon (SOC) accumulation and reduce N2O emission from urine deposited by grazing cattle. We determined SOC and N2O emissions from urine deposited on soils in an area of PG and in a 6.5 year-old IG area of Urochloa (Syn. Brachiaria) humidicola grass pasture in a beef cattle ranch in Orinoquía region (Colombia). In both areas, we sampled soil for chemical/physical analysis, and measured N2O emissions by simulating urine deposition over 21 days. We applied two-way analysis of variance considering pasture type and soil depth as fixed factors. Estimated SOC stocks (0–100 cm) were in the range of 224.8 Mg C ha−1 for the PG and 259.0 Mg C ha−1 for the IG, with a significant (p &amp;lt; 0.05) average accumulation of 2.0 Mg C ha−1 y−1 (0–20 cm) in the IG area. N2O emissions were 10 times lower in the IG compared to the PG. The introduction of U. humidicola grass influenced SOC accumulation probably through its more abundant root system and greater turnover together with higher (14%) forage dry matter production compared to PG. The reduced N2O emissions observed from urine patches in IG were attributed to biological nitrification inhibition ability and greater nitrogen uptake of U. humidicola grass. Compared to the reference default value of IPCC for, the SOC stock found in PG was almost 40% higher, whereas the N2O emission factor (5%) was within the uncertainty range (0.7–6%). The Orinoquía region shows significant potential for SOC storage and reduced N2O emissions in improved pastures with deep root systems. Thus, scaling the implementation of land-based SOC storage practices/projects could significantly contribute to reducing net emissions from beef production from this region.