Public perceptions of agriculture and the environment A review of survey information

SIGLEAvailable from British Library Document Supply Centre- DSC:GPC/03104 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Opportunities for reducing the environmental impact of dairy farm managements: a systems approach

Dairy farming systems are important sources for the emission of a number of materials that include various forms of nitrogen (NO3-, N2O and NH3) with potential environmental impact. The present paper is a systems synthesis study and assesses the likely impact of changes in management on N flows and losses, These include tactical fertilizer adjustment, slurry injection, maize silage production and the use of white clover as an alternative to fertilizer N. Implications for greenhouse gases (N2O and CH4) and support energy have also been considered. Substantial reductions in inputs and total and proportional losses by all the options considered were predicted by this study, Thus, using a tactical approach to fertilizer application and injecting slurry or using 50% maize silage reduced overall N losses from 160 (under conventional management) to 86 and 109 kg N ha(-1) respectively. Combining both possibilities reduced losses further to 69 kg ha(-1). Although use of white clover, especially at low contents in the sward, was the most effective regime to reduce losses, this was at some cost to production so that losses per livestock unit (LU) did not always differ from those under other managements, Changing the N management had consequences for greenhouse gas emission with an estimated maximum 70% reduction in N2O release. The effects on CH4 emissions were relatively small. Substantial reductions in support energy costs were also obtained: these arose mainly from the reduction in fertilizer N use, which represented 66% of the total support energy in the original system

Rendimento de milho em área de integração lavoura-pecuária sob o sistema plantio direto, em presença e ausência de trevo branco, pastejo e nitrogênio Corn yield on no tillage crop-pasture rotation in presence and absence of white clover, grazing and nitrogen

O trabalho experimental foi realizado no campo, na Estação Experimental da Fundação Agrária de Pesquisa Agropecuária (FAPA), em Guarapuava (PR), Brasil, nos anos agrícolas de 1999 e 2000, com o objetivo de verificar a influência da adubação nitrogenada residual na cultura do milho, em Sistema Plantio Direto, cultivado em seqüência, em áreas que no inverno tinham presença e ausência de trevo branco e de animais em pastejo. O delineamento experimental foi o de blocos ao acaso com três repetições. Os tratamentos foram arranjados em parcelas subdivididas. No inverno, nas parcelas, foram aplicados quatro doses de nitrogênio (N-TI = 0, 100, 200 e 300 kg ha-1 de N) e, nas subparcelas, a combinação de presença e ausência de trevo branco e de pastejo (CT = com trevo; ST = sem trevo; CP = com pastejo e SP = sem pastejo). No verão, em cada subparcela proveniente do inverno, foram aplicadas cinco doses de N (N-TV = 0, 60, 120, 180 e 240 kg ha-1 de N), em cobertura, e cultivado o milho. A máxima eficiência técnica de rebrote da cultura de inverno, avaliada dezoito dias após a retirada dos animais, foi obtida com a aplicação de 231 kg ha-1 de N (N-TI). As áreas CP/N-TI apresentaram maiores produtividades do milho que as áreas SP; contudo, estes resultados não foram estatisticamente significativos. As áreas sem N-TI produziram mais milho em subparcelas SP. As parcelas que receberam 300 kg ha-1 de N N-TI não mostraram resposta do milho ao N-TV, comprovando o efeito residual do N-TI. Conclui-se que a interação entre pastejo e N-TI contribui para a nutrição nitrogenada da cultura do milho.<br>This field experiment was carried out at the Fundação Agrária de Pesquisa Agropecuária [Agrarian Foundation for Agricultural and Cattle Research] (FAPA), in Guarapuava, State of Paraná, Brazil, during the growing seasons of 1999 and 2000. The objective was to verify residual effects of nitrogen fertilization on maize crop under a no tillage system, in presence and absence of white clover and grazing animals. The experimental layout was a completely randomized block design with three replications. The treatments were arranged in split-plots. Four N rates (N-TI = 0, 100, 200, and 300 kg ha-1 of N) were previously applied on the main plots during the winter season, while the treatments of the sub-plots consisted in combinations of presence and absence of white clover and grazing (CT = with clover; ST = without clover; CP = with grazing, and SP = without grazing). During the summer each sub-plot that had been prepared during the winter was cultivated with corn which received five N rates (N-TV = 0, 60, 120, 180, and 240 kg ha-1 of N) top dressed. The maximum re-growth efficiency of winter culture plants occurred eighteen days after the animals had been removed from the plots, obtained with 231 kg ha-1 of N (N-TI). The areas CP/N-TI presented higher corn yields than the SP plots, although these differences were not statistically significant. The areas without N-TI produced most in the SP subplots. On plots that had received 300 kg ha-1 of N N-TI there was no response of corn to the N-TV, confirming the residual effect of N-TI. The conclusion was drawn that the interaction between grazing and N-TI contributes to nitrogen nutrition in maize