Daniel Portella Montardo

Produção agronômica de uma coleção de acessos de Paspalum nicorae Parodi

This study was carried out to evaluate a collection of 53 accessions of Paspalum nicorae, introduced in two physiographically distinct regions over two years, with the objective of characterizing production and quality of forage of access for subsequent phases of a forage plant breeding program. The accessions were established in lines in randomized block design with three replications and the evaluations were performed from October 2007 to February 2009 by using cuts. There was variation of forage production among access over time and among sites. The majority of the accessions of P. nicorae presented high forage yield when compared with the control (P. notatum cv. Pensacola) and some accessions presented very expressive performances. The percentages of crude protein obtained from accessions in the collection were similar to the ones found in the control access. The accessions 28B and 26A of P. nicorae are indicated for subsequent stages in a program of forage plant breeding.

Morphoagronomic variation in natural populations of Trifolium riograndense (Burkart)

Several species of Trifolium are widely cultivated as forage for animals and green manure. This work aimed to characterize and estimate through morphological and agronomic traits the genetic diversity of natural populations of T. riograndense, an important forage legume from native pastures of the state of Rio Grande do Sul, Brazil. Plant height and diameter, number of primary and secondary stolons, stolon length, number of nodes per primary stolon, internode length, primary stolon diameter, leaf area, petiole length and dry matter production were analyzed in 29 accessions. The first five attributes and dry matter production were evaluated twice. A broad phenotypic variability was observed for almost all characteristics. Positive correlations occurred between petiole length and leaf area (r = 0.68), petiole length and plant height in the first evaluation (0.63), stolon length and plant height (0.58), total dry matter and plant diameter (0.61), and total dry matter and plant height in the second evaluation (0.55). The two most divergent accessions were collected in the same physiographic region and the two less divergent ones in different regions. A dissimilarity dendrogram separated four groups. Accessions collected in a region where T. riograndense is abundant were found to belong to different groups outlining the great variability of this native forage legume. Dry matter production in the first cut was the characteristic that most contributed (20.80%) to accessions divergence followed by number of secondary stolons (12.30%), leaf area (11.07%), and number of nodes per primary stolon (10.93%).

Desempenho animal e produtividade de pastagens tropicais no noroeste do Rio Grande do Sul

Productivity of dwarf elephantgrass (Pennisetum purpureum Schum. cv. Mott) and tifton 85 (Cynodon dactylon x Cynodon nlemfuensis) pastures was evaluated under continuous grazing, in the Northwest area of Rio Grande do Sul. Twelve multiparous Holstein cows, at 100 days of lactation were evaluated and the put-and-take technique was used to regulate the stocking rate to maintain 4% of leaf lamina on offer. In the first year, dwarf elephantgrass and tifton 85 were different in leaf accumulation rates (31.2 vs 22.6kg/ha/day) and animal production (17.4 vs 20kg of milk/cow/day). In the second year, tifton 85 had higher leaf accumulation rates (38.8 vs 21.9kg/ha/day), stocking rate (2,157 vs 1,084kg of live weight/ha), and production per area (70 vs 41.3kg of milk/ha/day) than dwarf elephantgrass. Comparing the second to the first years, tifton 85 maintained 88% of stocking rate and 80% of production per area, while dwarf elephantgrass only 46% and 56%, respectively. Average individual production of 17kg of milk/cow/day indicates an unexplored potential of tropical grasses in dairy production systems, especially in the South of Brazil.

Avaliação agronômica de linhagens de aveia-branca em duas regiões fisiográficas do Rio Grande do Sul

Realizou-se neste estudo uma avaliacao inicial em diversas linhagens de aveia-branca (Avena sativa, L.), com o intuito de verificar o desempenho agronomico e identificar os genotipos promissores para o lancamento de cultivares para producao de forragem. Os experimentos foram conduzidos em duas regioes fisiograficas do estado do Rio Grande do Sul, Depressao Central e Campanha Gaucha, nos anos de 2008 e 2009. Foram implementados em blocos casualizados com quatro repeticoes. Cada parcela foi constituida por uma linha de 2 m de comprimento, espacadas a 40 cm entre si, considerando parcela util o metro linear central, cortadas a uma altura de 10 cm. Foram avaliadas 21 linhagens de aveia-branca mais a testemunha (IPR126). No primeiro ano, tambem foram avaliadas duas linhagens de triticale, as quais apresentaram baixo potencial forrageiro e foram excluidas dos experimentos no segundo ano. Na avaliacao do potencial produtivo das linhagens de aveia-branca, nao houve diferencas ocasionadas pela interacao dos fatores local, ano e linhagem. No primeiro ano, os valores medios de producao na Depressao Central e Campanha Gaucha foram de 82,3 e 76,3 g por metro linear de materia seca total, respectivamente. Na avaliacao do segundo ano, as medias de producao para esta especie na Depressao Central e na Campanha Gaucha foram, respectivamente, 80,0 e 119,8 g m-1 de materia seca total. As linhagens de aveia-branca, em sua maioria, apresentam bons resultados e sao promissoras para o programa de melhoramento genetico dessa especie.