Agroecological studies of Desmanthus – a tropical forage legume

The use of forage legumes in tropical regions to improve the efficiency of animal production from grazing has been limited, largely because of the lack of economic incentives. There is a clear need, therefore, to investigate the existing gene pool of tropical forage plants to assess their potential for pasture improvement. Therefore, the present study evaluated the agronomic and ecological aspects of plant development in a set of genotypes of the genus Desmanthus and their relationships\ud with the components of the surrounding environment, at different stages of growth, in a series of laboratory and field experiments.\ud \ud Accessions of the genus Desmanthus formed permanent soil seed banks that ranged from 281 to 1303 seeds/m2, with a large variation between genotypes, in experiments on a duplex soil on the Douglas Campus of James Cook University, Townsville. Genotypes originally collected in Argentina had larger seed banks than those of other tested genotypes, but a small number of surviving plants. Fire increased seedling recruitment in almost all observed genotypes. Temperatures observed during controlled grass-fires reached a maximum of 300 ºC at the soil surface, 80 ºC at 10 mm depth, and around 30 ºC at 30 mm depth suggesting that all seeds located at soil surface were killed, those at 10 mm depth were probably softened, and those at 30 mm or more in soil had no alteration in their seed-coat permeability.\ud \ud Changes in strophiolar structure and germination, in response to the variation of oven temperatures ranging from 25 ºC to 120 ºC were observed in seeds of nine genotypes of Desmanthus. There were two groups with different patterns of responses: genotypes in which strophiolar structures were not significantly affected by temperatures below 80 ºC; and genotypes with significant changes in the strophiolar structures when temperature rose to 60 ºC.\ud \ud Seedlings of 8 accessions of the Desmanthus complex, growing directly under trees in open savanna woodland had higher values of means for number of leaves/plant, height of plant, and number of plants surviving than seedlings growing between trees. Three years after sowing, all plants from the between-canopy environment had died, while many plants of accessions TQ88, CPI 79653, and CPI 91162 were thriving under the tree canopy.\ud \ud Plants of D. virgatus CPI 78382 and D. leptophyllus TQ 88 growing in soils collected from under and between canopies had significantly increased their seedling emergence, by increasing shade levels and watering frequency. A low number of seedlings died in both genotypes, growing in soil from under the canopy but, plant deaths drastically increased in seedlings grown in soil from between the canopy.\ud \ud Growing in soil collected from under-canopies, plants allocated most of their dry matter to the production of aerial, rather than the underground parts, however, when grown in soil from between-canopies environment the largest proportion of the total dry matter was diverted to the underground parts. This diversified behaviour of\ud biomass allocation for shoot and root in the two soils is thought to be controlled by the contents of nutrients in soil.\ud \ud Seven accessions of the Desmanthus complex, sown into a pasture as seeds or seedlings, under two levels of competition with the natural vegetation, showed to have differentiated behaviour according the different treatments. Plant establishment and dry matter yields of plants sown by seed into unaltered vegetation were significantly reduced by competition.\ud \ud The effect on liveweight changes and wool growth of Merino sheep of 200 g hay of four different forms of the Desmanthus complex included as a supplement to a diet of 600 g Mitchell grass (Astrebla spp.) was compared with 200 g hay of Stylosanthes hamata cv. Verano. Verano and D. virgatus CPI 79653 supplemented diets had the highest dry matter digestibility (46.52% and 44.94% respectively). All the legume supplemented diets produced significantly more wool than the control. Clean wool growth was significantly correlated with nutritional parameters. The levels of nitrogen and sulphur present in some Desmanthus genotypes shows the potential of these plants in promoting wool growth.\u

Dormancy releasing mechanisms in soil seed banks of Desmanthus genotypes

Desmanthus is a genus of forage legumes with potential to improve pastures and livestock production on clay soils of dry tropical and subtropical regions such as the existing in Brazil and Australia. Despite this patterns of natural or enforced after-ripening of Desmanthus seeds have not been well established. Four year old seed banks of nine Desmanthus genotypes at James Cook University were accessed for their patterns of seed softening in response to a range of temperatures. Persistent seed banks were found to exist under all of the studied genotypes. The largest seeds banks were found in the genotypes CPI 78373 and CPI 78382 and the smallest in the genotypes CPI's 37143, 67643, and 83563. An increase in the percentage of softened seeds was correlated with higher temperatures, in two patterns of response: in some accessions seeds were not significantly affected by temperatures below 80°C; and in others, seeds become soft when temperature rose to as little as 60°C. At 80°C the heat started to depress germination. High seed production of Desmanthus associated with dependence of seeds on elevated temperatures to softening can be a very important strategy for plants to survive in dry tropical regions

Dormancy releasing mechanisms in soil seed banks of Desmanthus genotypes

Desmanthus is a genus of forage legumes with potential to improve pastures and livestock production on clay soils of dry tropical and subtropical regions such as the existing in Brazil and Australia. Despite this patterns of natural or enforced after-ripening of Desmanthus seeds have not been well established. Four year old seed banks of nine Desmanthus genotypes at James Cook University were accessed for their patterns of seed softening in response to a range of temperatures. Persistent seed banks were found to exist under all of the studied genotypes. The largest seeds banks were found in the genotypes CPI 78373 and CPI 78382 and the smallest in the genotypes CPI's 37143, 67643, and 83563. An increase in the percentage of softened seeds was correlated with higher temperatures, in two patterns of response: in some accessions seeds were not significantly affected by temperatures below 80°C; and in others, seeds become soft when temperature rose to as little as 60°C. At 80°C the heat started to depress germination. High seed production of Desmanthus associated with dependence of seeds on elevated temperatures to softening can be a very important strategy for plants to survive in dry tropical regions

Age at first parturition, parturition intervals, and milk production in saanen, marota and crossbred goat's

Com o objetivo de avaliar o desempenho produtivo e reprodutivo de cabras Saanen, Marota e mestiças Saanen + Marota na região semi-árida de Alagoas, foram estudados a idade ao primeiro parto (IPP), o intervalo entre partos (IEP), e a produção leiteira de cabras na Estação Experimental de Santana do Ipanema, Al. O sistema de exploração utilizado foi o semi-extensivo, sendo feito o manejo reprodutivo através de monta natural controlada. O controle leiteiro foi processado duas vezes por semana, durante 168 dias de lactação (1986-1987). A IPP na raça Saanen (824±156 dias) mostrou-se maior que nas raças mestiças (650±157 dias), enquanto foi evidenciado o mesmo IEP para ambas (367±21 dias). As médias de produção total e diária de leite da Saanen (178 e 1,06±0,34 kg) e das mestiças (201 e 1,20±0,29 kg) foram semelhantes, porém superiores às da Marota (66 e 0,39±0,08 kg). Analisando-se as tendências das curvas de lactação observou-se uma diminuição gradativa na produção leiteira, com algumas oscilações.Aiming at evaluating the productive and reproductive performance of Saanen and of Marota goats and of crossbred Saanen x Marota in the semi-arid region of Alagoas, Brazil, the age at first parturition, the interval between parturitions, and milk production of goats raised at the Santana do Ipanema Experiment Station in Alagoas, Brazil, were studied. The management method used was the local one; i.e., the semi-extensive, with controlled natural cross breeding. The milk control was made twice a week during 168 days of lactation (1986-1987). The age at first parturition of Saanen (824±156 days) was bigger than that of the crossbreed (650±157 days), and the interval between parturitions was the same in both breeds (367±21 days). The total production average and daily milk of Saanen goats (178 and 1.06±0.34 kg) and that of the crossbred (201 and 1.20±0.29 kg) were similar, but were higher than for Marota (66 and 0.39±0.08 kg). Ayalising the tendency of the lactation curves, a gradatively/decreasing milk production with some oscillation was observed

Resposta de Macroptilium Atropupureum cv. Siratro a diferenças fertilizações minerais, em quatro solos do estado de São Paulo

Em ensaio de vasos, realizado em casa de vegetação na Estação Experimental de Nova Odessa (SP), estudou-se a resposta do siratro (Macroptilium Atropurpureum cv. Siratro) a três tratamentos de fertilização: tratamento I: testemunha sem adubação; tratamento II; fósforo, cálcio e enxofre; tratamento III, tratamento II mais calagem, potássio, zinco e molibdênio, em quatro solos do Estado de São Paulo (Latosol Vermelho- -Amarelo — fase terraço, série Pinda; Podzolico Vermelho-Amarelo variação Laras; Latool Vermelho-Escuro Orto e Areia Ouartzosa As respostas ás fertilizações em termos de produção de matéria seca e altura das plantas foram significativas para todos os solos, com exceção do Latosol Vermelho-Escuro Orto, coletado no município de Itapetininga. o qual apresentou baixa produtividade das plantas em todos os tratamentos. A produção de matéria seca nos solos LVA — fase terraço e Areia Ouartzosa foi significativamente maior com a fertilização do tratamento III do que com a do tratamento II, e para o Podzólico Vermelho- -Amarelo — variação Laras não houve diferenças entre os tratamentos II e III

Resposta de Macroptilium Atropupureum cv. Siratro a diferenças fertilizações minerais, em quatro solos do estado de São Paulo

Em ensaio de vasos, realizado em casa de vegetação na Estação Experimental de Nova Odessa (SP), estudou-se a resposta do siratro (Macroptilium Atropurpureum cv. Siratro) a três tratamentos de fertilização: tratamento I: testemunha sem adubação; tratamento II; fósforo, cálcio e enxofre; tratamento III, tratamento II mais calagem, potássio, zinco e molibdênio, em quatro solos do Estado de São Paulo (Latosol Vermelho- -Amarelo €” fase terraço, série Pinda; Podzolico Vermelho-Amarelo variação Laras; Latool Vermelho-Escuro Orto e Areia Ouartzosa As respostas ás fertilizações em termos de produção de matéria seca e altura das plantas foram significativas para todos os solos, com exceção do Latosol Vermelho-Escuro Orto, coletado no município de Itapetininga. o qual apresentou baixa produtividade das plantas em todos os tratamentos. A produção de matéria seca nos solos LVA €” fase terraço e Areia Ouartzosa foi significativamente maior com a fertilização do tratamento III do que com a do tratamento II, e para o Podzólico Vermelho- -Amarelo €” variação Laras não houve diferenças entre os tratamentos II e III

Productive characteristics of the grass Digitaria umfolozi subjected to defoliation frequencies

Foi realizado um experimento com o objetivo de avaliar a produção de matéria seca, disponibilidade total de massa seca, taxa de acúmulo diária de matéria seca, interceptação luminosa, índice de área foliar, taxa de acúmulo diário, disponibilidade de matéria seca dos componentes morfológicos (lâmina foliar, colmo+bainha e material morto), relação lâmina/colmo, proteína bruta, fibra em detergente neutro e fibra em detergente ácido do capim Faixa-Branca submetido a sete frequências de desfolhação (14, 21, 28, 35, 42, 49, 56 dias). As frequências mais longas de desfolhação reduziram os percentuais de lâmina foliar e aumentaram colmo+bainha. A frequência de desfolhação influenciou positivamente a disponibilidade de lâmina foliar, colmo+bainha, material morto e matéria seca total. No intervalo de 42 dias de defoliation o capim faixa branca atingiu 95% de interceptação luminosa. Nas frequências de 14 e 21 dias de desfolhação os teores de proteína bruta das folhas foram acima de 20%. Verificou-se que a maior eficiência de utilização do capim Faixa-Branca é alcançada quando a forrageira é manejada com intervalos de corte de 40 a 46 dias. As maiores frequências de desfolhação contribui positivamente para o aumento do número de folhas totais do capim Faixa-Branca e apresentam maiores teores de proteína bruta das lâminas foliares e colmo+bainha.An experiment was carried out to evaluate the dry matter production, total dry matter availability, daily dry matter accumulation rate, light interception, leaf area index, daily accumulation rate, dry matter availability of the morphological components (leaf blades, stems + sheaths and dead material), leaf/stem ratio, crude protein, neutral detergent fibre and acid detergent fibre of Faixa-Brancagrass under seven defoliation frequencies (14, 21, 28, 35, 42, 49, and 56 days). Longer defoliation frequencies reduced the percentage of leaf blades and increased the percentage of stems + sheaths. The defoliation frequency positively influenced the availability of leaf blades, stems + sheaths, dead material and total dry matter. In the range of 42 days of defoliation, light interception reached 95%. At frequencies of 14 and 21 days of defoliation, the crude protein content of the leaves was above 20%. The highest utilization efficiency of D. umfolozi grass is achieved when the forage is managed with cutting intervals of 40 to 46 days. Higher defoliation frequencies positively contribute to the increase in the number of total white band grass leaves and higher crude protein content of the leaf blades and stems + sheaths