Comparison of Summer Forages and the Effect of Nitrogen Fertilizers on \u3ci\u3eBrassica\u3c/i\u3e Forages in Tasmania

Summer forage crops, and in particular Brassica spp., have become increasingly popular in dairy production systems in Tasmania. Field experiments were conducted for 3 years in northwestern Tasmania, in the spring/summers beginning in 1995. The study aimed to compare yield and quality of Brassica and Poaceae forages and the response of Brassica species to nitrogen (N) (50, 100 and 200 kg N/ha) and irrigation. The average total yields of dryland (rainfed) crops in 1995 to 1997 experiments, were turnip (Brassica rapa) 9.3 t/ha, rape (B. napus) 5.9 t/ha, oats (Aevena sativa) 5.2 t/ha, kale (B. oleracea) 5.1 t/ha, short-lived ryegrass (Lolium multiflorum) 5.1 t/ha, pasja (B. campestris × B. napus) 4.3 t/ha, perennial ryegrass (L. perenne) 4.2 t/ha, millet (Echinochloa utilis) 3.8 t/ha, and maize. (Zea mays) 2.9 t/ha. Irrigation increased the yield of turnips by 4.8 t/ha (mainly bulbs) and millet yields by 1.4 t/ha and reduced maize yield by 1.2 t/ha. Brassica species were higher in ME and lower in CP than the Poaceae forages. Nitrogen fertilizer increased the DM yield of tops of all Brassica crops in the 1997/98 experiments under irrigation, but it decreased the yield of turnips bulbs. The total yields with 50, 100 and 200 kg N/ha were 14, 15.2 and 15 t DM/ha for turnips, 7.5, 8.5 and 10 t for pasja and 10, 12 and 12.2 t DM/ha for rape, respectively. With 100 kg N/ha the average concentration of quality attributes of turnips, pasja and rape were CP 14, 22 and 19%, ME 12, 14.6 and 12.6 MJ/kg DM respectively. Nitrogen increased the CP, but had no effect on ME of any Brassica crops. Brassica forage are superior to Poaceae forages for summer feed production and as a part of pasture renovation process. They are higher in their yields, quality and water use efficiency and respond well to N fertilizer

Assessing Resilience of Pasture Production to Climatic Changes

Increasing temperatures and atmospheric carbon dioxide (CO2) concentrations, together with changes to rainfall patterns, will influence seasonal pasture production; however climate change projections for south eastern Australia are uncertain (CSIRO and BoM 2007). Despite this, climate change impact assessments generally rely on specific climate projections, but in this study an alternative approach was developed to test the resilience of production to incremental changes in climate

The Use of Long-Term Modelling in Analysing N\u3csub\u3e2\u3c/sub\u3eO Abatement Strategies in Dairy Pastures

Concerns about the environmental impact of nitrogen (N) losses in Australia, in particular, nitrous oxide emissions are related to the rapid increase in N application on dairy pastures. Computer modelling is the most suitable method available to assess the potential of best management practices (BMP) to reduce field losses, as direct field measurements are frequently limited by the short term nature of many field trials

Modelling Adaptation and Mitigation Strategies for Southern Livestock Industries of Australia

Climate change will impact on the Australian grazing industries both through mitigation policies and the impact of warmer temperatures, increased atmospheric CO2 and changed rainfall patterns (Cullen et al. 2009; Eckard et al. 2010). Mechanistic models are useful tools to inform our understanding of the complex interactions between future climates and the soil, plant, animal and management in livestock production systems. This paper summarises the results of a number of whole farm systems modelling studies investigating likely impacts of climate change, adaptation options and emissions implications for livestock production in southern Australia

Nitrogen Balances in High Rainfall, Temperate Dairy Pastures of South Eastern Australia

Nitrogen (N) fertilizer use on dairy pastures in south eastern Australia has increased exponentially over the past 15 years, causing increasing environmental concerns. Volatilisation, denitrification and leaching of N were measured for one year (1998-1999) in pastures receiving no N fertilizer (grass/clover), or 200 kg N/ha applied as urea (46%N) or ammonium nitrate (34.5%N). Nitrogen balances were calculated for each treatment. Significantly more N was lost through volatilisation and denitrification when N was applied as urea compared to ammonium nitrate. Nitrate leaching losses were significantly greater with the application of N fertilizer, although the maximum loss was only 4.1 kg N/ha due to low rainfall between May and September. Nitrogen balances were -15, +87 and +82 kg N/ha per year for the grass/clover, 200 kg N/ha urea and 200 kg N/ha ammonium nitrate treatments, respectively. Given the large range in N losses and balances, there is opportunity for improving the N efficiency in dairy pastures, through lower stocking rates and more tactical use of grain and N fertilizer