The effect of situational variability in climate and soil, choice of animal type and N fertilisation level on nitrogen leaching from pastoral farming systems around Lake Taupo, New Zealand

Agricultural systems with grazing animals are increasingly under scrutiny for their contribution to quality degradation of waterways and water bodies. Soil type, climate, animal type and nitrogen (N) fertilisation are contributors to the variation in N that is leached through the soil profile into ground and surface water. It is difficult to explore the effect of these factors using experimentation only and modelling is proposed as an alternative. An agro-ecosystem model, EcoMod, was used to quantify the pastoral ecosystem responses to situational variability in climate and soil, choice of animal type and N fertilisation level within the Lake Taupo region of New Zealand. Factorial combinations of soil type (Oruanui and Waipahihi), climate (low, moderate and high rainfall), animal type (sheep, beef and dairy) and N fertilisation level (0 or 60 kg N/ha/yr) were simulated. High rainfall climates also had colder temperatures, grew less pasture and carried fewer animals overall which lead to less dung and urinary N returned. Therefore, even though a higher proportion of N returned ultimately leached at the higher rainfall sites, the total N leached did not differ greatly between sites. Weather variation between years had a marked influence on N leaching within a site, due to the timing and magnitude of rainfall events. In this region, for these two highly permeable soil types, N applied as fertiliser had a high propensity to leach, either after being taken up by plants, grazed and returned to the soil as dung and urine, or due to direct flow through the soil profile. Soil type had a considerable effect on N leaching risk, the timing of N leaching and mean pasture production. Nitrogen leaching was greatest from beef cattle, followed by dairy and sheep with the level of leaching related to urine deposition patterns for each animal type and due to the amount of N returned to the soil as excreta. Simulation results indicate that sheep farming systems with limited fertiliser N inputs will reduce N leaching from farms in the Lake Taupo catchment.

[1]  J. E. Radcliffe,et al.  VI. Wairakei, pasture and lucerne production , 1975 .

[2]  A. Heathwaite.  Chemical fractionation of lake sediments to determine the effects of land-use change on nutrient loading , 1994 .

[3]  B. M. Petersen,et al.  Evaluating nitrogen taxation scenarios using the dynamic whole farm simulation model FASSET , 2003 .

[4]  W. Parton,et al.  Agricultural intensification and ecosystem properties. , 1997, Science.

[5]  S. Ledgard,et al.  Nitrogen inputs and losses from clover/grass pastures grazed by dairy cows, as affected by nitrogen fertilizer application , 1999, The Journal of Agricultural Science.

[6]  C. Topp,et al.  Modelling environmental impacts of deposition of excreted nitrogen by grazing dairy cows , 2004 .

[7]  A. Jacquet,et al.  Fate of urine nitrogen in three soils throughout a grazing season. , 2003, Journal of environmental quality.

[8]  Elizabeth A. Stockdale,et al.  Research in organic production systems – past, present and future , 2007, The Journal of Agricultural Science.

[9]  S. Ledgard,et al.  Nitrogen fixation by white clover in pastures grazed by dairy cows: Temporal variation and effects of nitrogen fertilization , 2001, Plant and Soil.

[10]  R. Holt,et al.  Meta‐ecosystems: a theoretical framework for a spatial ecosystem ecology , 2003 .

[11]  C. A. Rotz,et al.  Modeling the Nitrogen and Phosphorus Inputs and Outputs of Financially Optimal Irish Beef Production Systems , 2007 .

[12]  I. R. Johnson,et al.  Dynamic model of the response of a vegetative grass crop to light, temperature and nitrogen , 1985 .

[13]  J. Grönroos,et al.  Estimation of the impact of fertilisation rate on nitrate leaching in Finland using a mathematical simulation model , 2000 .

[14]  I. R. Johnson,et al.  The single heterogeneous paddock approach to modelling the effects of urine patches on production and leaching in grazed pastures , 2009 .

[15]  D. Barraclough,et al.  Fate of fertilizer nitrogen applied to grassland. II. Nitrogen-15 leaching results , 1984 .

[16]  T. Prance,et al.  Climate variability effects on simulated pasture and animal production in the perennial pasture zone of south-eastern Australia.1. Between year variability in pasture and animal production , 2003 .

[17]  I. R. Johnson,et al.  Comparison of outputs of a biophysical simulation model for pasture growth and composition with measured data under dryland and irrigated conditions in New Zealand , 2008 .

[18]  H. Di,et al.  Nitrate leaching in temperate agroecosystems: sources, factors and mitigating strategies , 2004, Nutrient Cycling in Agroecosystems.

[19]  N. P. McMeniman,et al.  Feeding Standards for Australian Livestock Ruminants. , 1990 .

[20]  S. E. Simmelsgaard.  The effect of crop, N‐level, soil type and drainage on nitrate leaching from Danish soil , 1998 .

[21]  V. Snow,et al.  A functional evaluation of virtual climate station rainfall data , 2008 .

[22]  Keith Paustian,et al.  Nitrogen pools and fluxes in grassland soils sequestering carbon , 2005, Nutrient Cycling in Agroecosystems.

[23]  V. Snow,et al.  Simulation of mitigation strategies to reduce nitrogen leaching from grazed pasture , 2007 .

[24]  A. Parsons,et al.  Use of a model to analyse the effects of continuous grazing managements on seasonal patterns of grass production , 1985 .

[25]  Tom Addiscott,et al.  A SIMPLE COMPUTER MODEL FOR LEACHING IN STRUCTURED SOILS , 1977 .

[26]  Wilfred M. Post,et al.  The use of models to integrate information and understanding of soil C at the regional scale , 1997 .

[27]  David Scholefield,et al.  Use of SIMSDAIRY modelling framework system to compare the scope on the sustainability of a dairy farm of animal and plant genetic-based improvements with management-based changes , 2008, The Journal of Agricultural Science.

[28]  P. Williams,et al.  Nutrient cycling and soil fertility in the grazed pasture ecosystem , 1993 .

[29]  H. Keulen,et al.  Reducing Nitrate Leaching to Groundwater in an Intensive Dairy Farming System , 2005, Nutrient Cycling in Agroecosystems.

[30]  S. Ledgard,et al.  Nitrogen inputs and losses from New Zealand dairy farmlets, as affected by nitrogen fertilizer application: year one , 1996, Plant and Soil.

[31]  M. Wachendorf,et al.  Performance and environmental effects of forage production on sandy soils. II. Impact of defoliation system and nitrogen input on nitrate leaching losses , 2004 .

[32]  I. R. Johnson,et al.  DairyMod and EcoMod: biophysical pasture-simulation models for Australia and New Zealand , 2008 .

[33]  I. E. Coop.  A review of the ewe equivalent system. , 1965 .

[34]  A. Prado,et al.  Principles of Development of a Mass Balance N Cycle Model for Temperate Grasslands: An Irish Case Study , 2006, Nutrient Cycling in Agroecosystems.

[35]  Wu,et al.  Simulation of nitrogen uptake, fixation and leaching in a grass/white clover mixture , 1999 .

[36]  Anthony J. Parsons,et al.  Use of a model to optimize the interaction between frequency and severity of intermittent defoliation and to provide a fundamental comparison of the continuous and intermittent defoliation of grass , 1988 .

[37]  I. R. Johnson,et al.  Vegetative crop growth model incorporating leaf area expansion and senescence, and applied to grass , 1983 .

[38]  B. M. Petersen,et al.  Modelling spatial heterogeneity in grazed grassland and its effects on nitrogen cycling and greenhouse gas emissions , 2007 .

[39]  S. Polasky,et al.  Agricultural sustainability and intensive production practices , 2002, Nature.

[40]  B. Dear,et al.  Effect of pasture management on the contributions of fixed N to the N economy of ley-farming systems , 1998 .

[41]  A. Tait,et al.  Generating Multiyear Gridded Daily Rainfall over New Zealand , 2005 .

[42]  N. B. Edgar,et al.  Land use in the Taupo catchment, New Zealand , 1999 .

[43]  A. Groen,et al.  Definition of animal breeding goals for sustainable production systems. , 2000, Journal of animal science.

[44]  Stewart Ledgard,et al.  Using the OVERSEER nutrient budget model to estimate on-farm greenhouse gas emissions , 2008 .

[45]  Catriona J. MacLeod,et al.  Intensification and diversification of New Zealand agriculture since 1960: An evaluation of current indicators of land use change , 2006 .

[46]  C. Mclay,et al.  Predicting groundwater nitrate concentrations in a region of mixed agricultural land use: a comparison of three approaches. , 2001, Environmental pollution.

[47]  Rasmussen,et al.  Long-term agroecosystem experiments: assessing agricultural sustainability and global change , 1998, Science.