Modelling the surface of a paddock affected by urine and faeces deposition during grazing by dairy cows

HAL Id: hal-02742935

https://hal.inrae.fr/hal-02742935

Submitted on 3 Jun 2020

HAL is a multi-disciplinary open access archive for the deposit and dissemination of sci- entific research documents, whether they are pub- lished or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers.

L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Modelling the surface of a paddock affected by urine and faeces deposition during grazing by dairy cows

Elodie Ruelle, D. Hennessy, C.A. Paillette, Luc Delaby

To cite this version:

Elodie Ruelle, D. Hennessy, C.A. Paillette, Luc Delaby. Modelling the surface of a paddock affected by urine and faeces deposition during grazing by dairy cows. 26. General meeting of the Euro- pean Grassland Federation (EGF), Sep 2016, Trondheim, Norway. Wageningen Academic Publishers, Grassland Science in Europe, 21, 2016, The multiple roles of grassland in the European bioeconomy.

�hal-02742935�

Grassland Science in Europe, Vol. 21 – The multiple roles of grassland in the European bioeconomy

Modelling the surface of a paddock affected by urine and faeces deposition during grazing by dairy cows

Ruelle E.

, Hennessy D.

, Paillette C.

and Delaby L.

1

Animal & Grassland Research and Innovation Centre, Teagasc, Moorepark, Fermoy, Co. Cork, Ireland;

2

INRA, AgroCampus Ouest, UMR 1348, Physiologie, Environnement et Génétique pour l’Animal et les Systèmes d’Elevage, 35590 Saint-Gilles, France; elodie.ruelle@teagasc.ie

Abstract

In grazed grassland, urine and faeces, returned by grazing animals and added to the nitrogen (N) from fertilizer, augments the N fluxes and also the risk of N losses (leaching, ammonia volatilization). Urine and faeces deposition by the grazing animal result in large applications of N to a small area within the paddock. Many agronomic models do not take into account this aspect of grazing systems. As the area affected by urine and faeces at each deposition is reported to be 2 m

, the Moorepark Grass Growth model (MGGm) describes the N fluxes in a grid basis at a 2 m

level. The MGGm assumes that within any given grazing event the localisation of the urine and faeces deposition will be random with overlapping being a possibility. The objective of this paper is to compare the consequences of a uniform deposition over the paddock versus localize at 2 m

individual animal depositions, in four different grazing simulations. At 2 m

level, the urine and dung deposition induces a huge variation in term of mineral N available (maximal difference of 335 kg of N), grass growth (maximal difference of 5,052 kg of DM) and N leached (maximal difference of 134 kg of N leached). At the paddock level, the uniform simulation has a slightly higher net grass growth and N uptake compared to the 2 m

simulation. Finally, within a simulation, the average N leached evaluated between November and April of year 2 are identical between the uniform and a 2 m

localized applications.

Keywords: grass growth, urine patches, N leached, model

Introduction

Nitrogen (N) fertilizer is highly effective at increasing grass growth and hence farm productivity, but it also contributes to nitrogen (N) leaching to groundwater (Delaby et al., 1997). On a grass grazed paddock, urine and dung depositions from grazing animals increase the N added through fertilization which increase the N availability for grass growth and the risk of N losses (leaching, volatilization) on a small portion of a paddock area. Traditionally soil models simulate urine patches uniformly across the whole paddock. The objective of this study is to use the Moorepark Grass Growth model (MGGm – Ruelle and Delaby, 2016) to show the heterogeneity of growth and N leached in a grazed paddock due to grazing animal depositions and to evaluate the consequences of a uniform or a 2 m

localized approach at the paddock level.

Materials and methods

The MGGm is a dynamic model developed in C++ describing the grass growth and the nitrogen flux of a paddock at a 2 m

level. The core model functions are described in Ruelle and Delaby (2016).

The main inputs of the model are the type of soil (in terms of clay, sand and organic matter content),

grassland management (date of grazing or cutting event, number of animals, post grazing cutting height

...), fertilisation management (date and quantity of N applied), and the daily weather (in terms of

temperature, rain and radiation). In this model, the faeces and urine depositions are considered to affect

only a 2 m

area of the paddock. Therefore, the paddock is represented as a grid of 2 m

having individual

mineral N, organic N, grass biomass and grass N content. The localisation of each deposition on that

grid is random with overlaps. The model has been tested for different weather conditions (Table 1). Two

490

Grassland Science in Europe, Vol. 21 – The multiple roles of grassland in the European bioeconomy different N mineral applications have been simulated (zero or 150 kg N per ha (France) /200 kg of N per ha (Ireland) per year, in six or height applications respectively). The size of the simulated paddock is 1 ha and there are a total of seven (France) or eight (Ireland) grazing events. The initial N mineral status of the soil was 80 kg per ha and the N organic level was at 14,400 kg N per ha (6% of OM content). In the simulations, the number of animals for each grazing event was calculated depending on the pre grazing height (calculated by the model) based on a daily intake of the animal of 16 kg of dry matter (DM).

To test the impact and the importance of modelling at a 2 m

level, the simulations have been run either with the normal feature of the model or either with the urine and faeces deposition considered as uniform applications across the paddock. The simulations were completed across 2 years with the same weather and management conditions allowing the quantification of the impact of the first grazing year on the leaching that occurred during the winter and spring of the second year. The N leaching results presented are the corresponding N leaching between 1 November of year one to 30 April of year two (called the winter period). All the other results concern only the first grazing year of the simulation. To highlight the heterogeneity within a paddock for the 2 m

simulation, results in the Table 2 are presented on the form of minimal (Min), maximal (Max) and standard deviation (SD). The Min and Max represent the 2 m

with the lower or higher value of the variable considered, the SD represents the standard deviation of those values within a paddock. Due to the variable considered (net growth, N mineral and N leached), the Min for each variable corresponds to an area of 2 m

which received no urine or faeces deposition.

Results and discussion

Table 2 describes the variability in terms of grass growth across the year and the mineral N content in the soil on the first of November and N leached during the winter period within a paddock when simulated at the 2 m

scale. According to the number of grazing days realised, the surface of a paddock affected by a urine deposition was of 52, 63, 65 and 78% for the French study with 0 N, French study with 150 N, Irish study with 0 N and Irish with 200 N, respectively. When there was an increase in mineral N fertilisation, Table 1. Description of the two annual weather data applied in the simulations.

Location Year Annual average temperature (°C)

Monthly rainfall (mm) Annual total

rainfall (mm)

J F M A M J J A S O N D

France Normandie 10.2 61 32 136 68 64 12 35 72 42 80 102 41 743

Ireland Co. Cork 8.7 107 39 88 59 38 53 143 23 102 83 98 37 869

Table 2. Internal heterogeneity of the paddock in grazing condition. The maximal (Max), minimal (Min) and standard deviation (SD) of the net grass growth, N mineral and the total N leached, of the 2 m

within a paddock.

Net growth (kg of DM) N min at 1 Nov. N leached

N (France / Ireland) 0 150/200 0 150/200 0 150/200

France Normandie Min 6,575 8,544 86 119 34 45

Max 10,909 12,080 201 454 67 116

SD 829 732 15 39 4 9

Ireland Co.Cork Min 8,226 11,564 91 125 54 72

Max 13,278 16,573 194 411 102 206

SD 901 902 13 35 7 18

Grassland Science in Europe, Vol. 21 – The multiple roles of grassland in the European bioeconomy

there was an increase in grass growth, N mineral soil and N leaching. Accumulation of urine patches induce a huge increase in grass growth between 3,536 and 5,052 kg of DM per ha in the simulations.

Similarly, the N leaching differs between the different 2 m

areas with a maximal difference in the Irish simulation at 200 N (increase of 134 kg N leached). The lowest maximal difference in N leached is in the French simulation with no fertilisation with a difference of 33 kg N leached. At the paddock level, when comparing the localized with the uniform simulation (Table 3), the grass growth is slightly higher in the uniform simulation (average of 118 kg of DM per ha higher over the year) which led to a higher number of grazing days. This difference is slightly higher in the simulation with mineral N fertilization than in the one without. When looking at the N leached and the N mineral at the start of the winter, both simulations are strictly identical.

Conclusions

Integrated at the paddock level, the impact of uniform or localized urine and dung patches has been very small under those grazing conditions. However, it would be interesting to investigate the impact in a system where the cows are supplemented and stay on a paddock with a relatively small amount of grass in the diet.

Acknowledgments

The authors acknowledge the funding from the Research Stimulus Fund 2011 administered by the Department of Agriculture, Fisheries and Food (Project 11/S/132).

References

Delaby L., Decau M.L., Peyraud J.L. and Accarie P. (1997) AzoPât: Une description quantifiée des flux annuels d’azote en prairie pâturée par les vaches laitières. I – Les flux associés à l’animal. Fourage 151, 297-311.

Ruelle E. and Delaby L. (2016) The Moorepark Grass Growth Model – application in grazing systems. Grassland Science in Europe 21.

Table 3. Comparison between the uniform and the localized simulation on the total net grass growth, the total N uptake, the number of grazing day, the N in the urine of the animal the N mineral in the soil and the total N leached of the year on the weather and the N mineral fertilisation (N)

Net growth (kg dry matter)

N uptake (kg N/ year)

Number of grazing days

N urine (kg per year per ha affected)

N min at 1 Nov. N leached

N (France / Ireland) 0 150/200 0 150/200 0 150/200 0 150/200 0 150/200 0 150/200

France Normandie Uniform 7,412 9,453 141 243 381 507 51 98 97 150 37 52

Localized 7,336 9,350 139 237 376 501 98¹ 153² 97 151 37 52

Ireland Co. Cork Uniform 9,243 12,972 173 336 531 770 56 135 103 157 61 90

Localized 9,146 12,777 169 327 524 758 88³ 171⁴ 103 159 61 91

1 On 52% of the paddock.

2 On 63% of the paddock.

3 On 65% of the paddock.

4 On 78% of the paddock.