Anibal de MORAES 7 RESUMOA grande maioria do rebanho brasileiro de bovinos é criado a pasto e apresenta baixa produtividade, dado pelo baixo suprimento e qualidade das pastagens. O objetivo foi avaliar a produtividade e composição química do Capim Mombaça (Panicum maximum) sob doses crescentes de nitrogênio. O experimento foi conduzido na Estação Experimental do Cangüiri localizada em Pinhais-PR, pertencente à Universidade Federal do Paraná. O delineamento experimental foi o de blocos ao acaso com quatro repetições e cinco tratamentos (0, 85, 170, 320 e 510 kg de N ha -1 ) aplicados a lanço em novembro de 2007. Os parâmetros avaliados foram produtividade de matéria seca (MS), teor de clorofila na folha e concentrações totais de N e C. A pastagem obteve incrementos na produção de MS, teor de clorofila e concentração total de N. A adubação nitrogenada propiciou incrementos lineares na produção de MS e PB, variando de 585 a 10.310 e de 45 a 1.279 kg ha -1 , após 85 e 161 dias da aplicação, respectivamente. Os incrementos na produtividade de matéria seca foram lineares com 19 kg de MS para cada kg de N aplicado. Cada kg de N também propiciou as seguintes variações lineares: 0,5x10 -5 mg kg -1 de N -teor de clorofila, 0,015 g kg -1 de N -concentração de N; 2,52 kg kg -1 de N -PB; 7,98 kg kg -1 de N -C total, e -0,025 -relação C/N. A adubação nitrogenada aumentou a produtividade, bem como as concentrações de PB e clorofila, além de diminuir a relação C/N. Palavras-chave: produtividade; forrageira; nitrogênio; clorofila. ABSTRACTThe majority of Brazilian livestock is raised under pasture which usually has low productivity. This is due to both low biomass offer and low quality of pastures. The objective of this study was to evaluate the Nitrogen fertilization on yield and quality of Mombaça grass (Panicum maximum cv. Mombaça). The experiment was carried out at Canguiri Experimental Station located Pinhais county-Parana state, belonging to Federal University of Paraná. An oxissol with high organic matter content, low acidic, and without limitation of available P and K was used for the study. The experimental design was a randomized complete block with four replications and five N rate treatments (0, 85, 170, 320 e 510 kg of N ha -1 ) applied broadcast in the first week of November 2007. The pasture was evaluated for yield dry matter (DM), chlorophyll leaf contents, and total concentration of nitrogen and carbon. The nitrogen fertilization resulted in great improvement on DM and protein yield, varying from 585 to 10.310 and from 45 to 1279 kg ha -1 , after 85 and 161 days fertilization application, respectively. The DM increment showed to be linear with 19 kg DM for each kg N applied. Each kg N applied also provided the following linear variation: 0,5x10 -5 mg kg -1 -chlorophyll leaf content; 0,015 g kg -1 -N concentration; 2,52 kg ha -1 -total protein yield; 7,98 kg ha -1 total C yield, and -0,025 -C/N ratio. The nitrogen fertilization enhanced productivity and forage quality for developed grass under good condition of s...

-Phosphorous application effects were evaluated on ryegrass dry matter (DM) accumulation, root development and plant tissue concentration of phosphorus, nitrogen and carbon aiming to determinate the nutritional status of the pasture, as well as to verify the possibility to establish a phosphorus dilution curve for this pasture. Also, the development of phosphorus and ryegrass cultivated with the residual effect of phosphorus fertilization was determined. The experiment was carried out in Pinhais County -Paraná State on a Cambisol with very low phosphorus levels. The experiment was of random blocks design and treatments consisted of five phosphorus rates of triple superphosphate (0, 45, 90, 180 and 360 kg P 2 O 5 ha -1 ) applied to soil surface with four replications. Phosphorus fertilization promoted linear increments in the soil phosphorus availability and resulted, in the first year, in early pasture production and higher phosphorus content in the plant. Nitrogen and carbon contents were not affected. Phosphorous application increased ryegrass DM accumulation in all periods, ranging from 16 to 2826 kg DM ha -1 at flowering stage, for zero and 360 kg P 2 O 5 ha -1 , respectively. Root density was positively influenced by phosphorus supply, and the rate of 45 kg P 2 O 5 ha -1 was effective for maximum root development. The residual effect of phosphorus fertilizer provided enhancement of yield and phosphorus plant concentration for both sorghum and ryegrass in the second year.