Archive for the category: Feature Presentation

Grace S. Cun*, Grant R. Edwards, Racheal H. Bryant

Faculty of Agriculture and Life Sciences, Lincoln University, Lincoln 7647, Christchurch

*Corresponding author email: grace.cun@lincolnuni.ac.nz

Abstract

Pasture management strategies are sought to reduce nitrate leaching by enhancing nitrogen (N) uptake over the winter period. The objective of this study was to determine the effect of five post grazing heights on herbage production, and N uptake of a diverse pasture mixture containing perennial ryegrass, white clover, chicory, plantain, and lucerne during the late autumn/winter season. In late autumn, pastures were defoliated to five residual heights (20, 30, 40, 50, 60 mm), and herbage dry matter (DM) and N accumulated over a 112 d regrowth period was measured. Swards defoliated to 20, 30 and 40 mm accumulated more herbage above ground level (1884, 1508, 1322 kg DM/ha, respectively) than those defoliated to 60 mm (1289 kg DM/ha) over 112 days. Repeated measures analysis on herbage N concentration showed a significant interaction (P=0.012) of defoliation treatment with time. For the 20 mm defoliation, N concentration increased over time from 18.8 to 29.7 g N/kg while for the 60 mm defoliation, decreased from 26.1 to 24.9 g N/kg during the regrowth period. During this 112 d regrowth period, pastures defoliated to 20 mm accumulated more DM and more N than plots defoliated to 60 mm (56 vs. 32 kg N/ha, respectively). The results indicate grazing severely to post grazing heights <40 mm may improve growth and N uptake in the late autumn/winter.

Martin Labadz¹, Clemens Scheer¹, David W. Rowlings¹, Beverly Henry¹, William Parton², Peter Hayman³, Oscar Alves⁴, Griffith Young⁴ and Peter Grace¹

¹ Institute for Future Environments, Queensland University of Technology, 2 George Street, Brisbane QLD 4000, Australia

² Natural Resource Ecology Laboratory, Colorado State University, Fort Collins, CO 80523, United States

³ Government of South Australia, SARDI, 2b Hartley Grove, Urrbrae SA 5064, Australia

⁴ Centre for Australian Weather and Climate Research, Melbourne, Victoria, Australia

Abstract

The DayCent biogeochemical model was used to assess the applicability of POAMA-2 weather forecasts to assist dairy farmers in future nitrogen fertiliser decisions. Simulated soil mineral nitrogen, water-filled pore space, and biomass was calibrated and validated against field measurements from a dairy farm in subtropical Queensland, Australia, for the season 2012/2013 with a ryegrass/kikuyu rotation. DayCent was able to predict water movement in the soil profile, soil nitrogen dynamics and biomass production; however, there were some discrepancies between simulated and measured mineral nitrogen content in the soil and biomass production. This study showed that combining weather forecasts with biogeochemical models as a decision support tool for farmers to estimate mineralisation and assess N fertiliser demand is a promising approach to avoid excessive nitrogen application for dairy cropping systems. However, there are still shortcomings in an accurate simulation of soil nitrogen turnover and plant nitrogen uptake, in particular in highly fertilised systems such as the one presented here. More confidence in the accurate representation of the complex nitrogen transformation processes on dairy farms in biogeochemical models is necessary to use weather forecasts as fertiliser nitrogen decision support tool.

Mark Powell¹, C. Alan Rotz², Peter A. Vadas¹ and Kristan F. Reed¹

¹ USDA, Agricultural Research Service, US Dairy Forage Research Center, 1925 Linden Drive, Madison, Wisconsin 53711 USA

http://ars.usda.gov/pandp/people/people.htm?personid=21056, mark.powell@ars.usad.gov

² USDA-Agricultural Research Service, Pasture Systems and Watershed Management Research Unit, University Park, Pennsylvania 16802 USA

Abstract

Many dairy farms in the USA are growing and feeding more corn silage (CS) and less alfalfa silage (AS) to reduce feed costs. More corn grain (CG)-based concentrates are also being promoted to reduce enteric methane, a potent greenhouse gas. Whole farm simulations illustrate that growing more CS and less AS reduces the land requirement for feed production by approximately 27%, maintains milk production, increases animal N use efficiency (from 20 to 25%), and decreases manure N excretion (from 26.5 to 20.8 g N/kg milk). Growing more CS however, requires more fertilizer N (80 kg N/ha) and increases N losses (by 35 kg N/ha). Feeding more CG does not greatly impact milk production or animal N use efficiency, but requires about 40% more CG land area, more fertilizer N (23 kg N/ha), and increases nitrate leaching (by 10 kg N/ha). CS, AS and CG were labeled with stable isotope ¹⁵N and fed to mid-lactation dairy cows. Consumed ¹⁵N from AS and CS were distributed similarly into milk N and faecal N. Relatively more of the ¹⁵N contained in CG was transformed into milk N compared to ¹⁵N contained in AS and CS. After land application, more of the manure ¹⁵N from AS and CG was taken up by corn silage than manure ¹⁵N from CS. Trade-offs in N use and N loss need to be more fully considered when recommending more CS and CG in dairy cow rations.

Tom Misselbrook¹, Alison Carswell¹, Graham McAuliffe¹, Taro Takahashi^1,2, Laura Cardenas¹, Michael Lee^1,2

¹ Rothamsted Resesarch, North Wyke, Okehampton, Devon EX20 2SB, UK, tom.misselbrook@rothamsted.ac.uk;

² University of Bristol, School of Veterinary Sciences, Langford, Somerset BS40 5DU, UK

Abstract

The North Wyke Farm Platform comprises three 22 ha beef and sheep grazing ‘farmlets’ which are highly instrumented to monitor hydrology, weather, nutrient flows and productivity. Typical management for lowland UK grazing systems, based on permanent pasture, was applied to all three systems for an initial two-year baseline period. Following that, the platform has been progressively modified with the underlying principle being to improve the sustainability (economic, social and environmental) of two of the three farmlets, by reseeding of one with a grass-clover sward to drive production through nitrogen (N) fixation and one with a grass monoculture utilising the latest grass breeding advancements and higher yield potential. The third farmlet continued under permanent grassland. This paper presents the framework to be used in assessing the impacts of the reseeding period and to estimate system scale N budgets for the three systems. Data are being compiled with no results yet available, but will consist of a combination of measurements and modelled N pools and flows based on detailed management and production data. N use efficiency will be evaluated at the partial (forage production) and full (livestock product output) system level. A range of metrics expressing N flows on a product and land area basis will be derived. For a more complete understanding of the impacts of the system interventions and potential for future interventions to further improve NUE, further measurement data are required including N losses though denitrification, ammonia volatilisation and total N losses to water and N inputs through fixation.

Aimable Uwizeye^1,2,3*, Pierre J. Gerber^1,2, Rogier P.O. Schulte³, Imke J.M. de Boer¹

¹ Animal Production Systems group, Wageningen University, PO Box 338, 6700 AH, Wageningen, the Netherlands

² Food and Agriculture Organization of the United Nations, Animal Production and Health Division, Viale delle Terme di Caracalla, 00153 Rome, Italy

³ Teagasc – Crops, Environment and Land Use Programme, Johnstown Castle, Wexford, Ireland

Abstract

Pig supply chains are developing rapidly in East and Southeast Asia (ESEA), fuelled by population growth, growing incomes and urbanization that lead to increased demand for animal produce. Pig supply chains, however, are associated with losses of reactive nitrogen (Nr) to the environment at various stages of the chain. To benchmark livestock supply chains and identify improvement options, we previously developed a framework to assess Nr use efficiency at chain level. This framework compromises three indicators: life-cycle nitrogen use efficiency (life-cycle-NUE_N), life-cycle net nitrogen balance (life-cycle-NNB_N), and nitrogen hotspot index (NHI_N). The aim of this study is to apply these three indicators to pig supply chains in ESEA. Preliminary results showed that the computed Life-cycle Nr use efficiency indicators vary greatly between backyard, intermediate and industrial supply chains. Industrial supply chains had relatively higher estimates of life-cycle-NUE_N than intermediate and backyard supply chains. Our data showed a negative relationship between life-cycle-NNB_N and NHI_N demonstrating the presence of hotspots of Nr losses in backyard and intermediate supply chains, as compared to industrial supply chains. These differences between supply chains result from differences in the origin of feed material, feed conversion, manure management system and animal health status. This study demonstrates that there is a scope to improve the Nr use efficiency in pig supply chains in ESEA, especially by focusing on the optimization of fertilization of local feed crops and manure management systems. Further research is required to assess the potential effectiveness of each of these interventions.

Luis Lassaletta¹, Lex Bouwman^1,2, Fernando Estellés³, Henk Westhoek¹, Arthur Beusen^1,2, Jonathan Doelman¹, Salva Calvet², Elke Stehfest¹, Hans van Grinsven¹.

¹ PBL Netherlands Environmental Assessment Agency, 3720 A H Bilthoven, The Netherlands. http://www.pbl.nl/en/. luis.lassaletta@pbl.nl

² Department of Earth Sciences – Faculty of Geosciences, Utrecht University, PO Box 80021, 3508 TA Utrecht, The Netherlands

³ ICTA, Universitat Politécnica de Valencia, Camino de Vera s/n 46022, Valencia, Spain

Abstract

In this study we model the global feed and land demand, nitrogen excretion and nitrogen use efficiency (NUE) for pig production systems in 2050 under different scenarios for pork demand, production performance and dietary composition. We developed a new pig module for the IMAGE integrated assessment model and we constructed a set of scenarios following the storylines of the Shared Socio-economic Pathways. Our model outcomes suggest that pig production systems will play a significant role in the global agro-food system in 2050 including protein supply, land demand and N fertilization. The sustainability of future pig production systems will strongly depend on the livestock production performances, feed rations and manure recycling efficiency. Scenario analysis suggest that the replacement of part of the soybeans by swill and industrial by-products in the feed ration of pigs is a promising solution to increase NUE as well as to reduce the land demand associated with pork production.