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The objective was to evaluate the characteristics of the pasture and the behavior of grazing goats under continuous stocking in a silvopastoral system (SPS) of Andropogon grass (Andropogon gayanus Kunth cv. Planaltina) in comparison to its monoculture (MC). The treatments consisted of two cropping systems: monoculture of Andropogon grass and silvopastoral system—SPS of native trees mixed with Andropogon grass, evaluated in five grazing periods using goats (February, March, April, May and June). Pasture height, leaf/stem ratio and the dry mass of forage, leaf, stem and dead material were evaluated. The grazing behavior of the goats was also assessed. Significant effect of interaction was observed (p 0.05). The Andropogon grass has the potential to be used in SPS with grazing goats under continuous stocking, positively affecting the pasture and animal behavior.

C3 and C4 plants, as their intermediates, respond differently to short-term changes in environmental conditions. This difference is linked to contrasting levels of phenotypic plasticity and photosynthetic apparatus specialization. Phenotypic plasticity is an underexplored topic although its understanding is crucial to predict plant behaviour in future climatic scenarios. In this research, the phenotypic plasticity of anatomical traits and its influence to carbon uptake efficiency was studied in plants with different photosynthetic types, under contrasting water regimes. Oryza sativa cvs. Soberana (drought-sensitive) and Douradao (drought-tolerant) (C3), Homolepis isocalycia (C3 proto-Kranz) and Andropogon gayanus (C4), grown at three water treatments (100, 75 and 50% of substrate water holding capacity), were phenotyped for leaf anatomy and gas-exchange parameters. The results showed that plasticity trends indicated different strategies between O. sativa cultivars to deal with water shortage, explaining their classification as drought-sensitive or tolerant. We also mapped typical characteristics of C3–C4 intermediate plant, H. isocalycia, mainly in the ratio mesophyll:bundle sheath cells and hypothesize how it may influence photosynthesis. Finally, we have confirmed previous claims that C4 carbon uptake advantages may be limited under severe drought conditions, as A. gayanus have drastically reduced its photosynthetic rates at lower water levels. By studying C3–C4 intermediates, this study may also be a starting point to unravel the trade-offs of anatomical changes during the evolutionary process from C3 to C4 photosynthesis, and also improve the understanding of their impact in carbon uptake in different water conditions.

Foliar epidermal studies were carried out on accessions of Andropogon gayanus-Andropogon tectorum complex collected in Southwestern Nigeria with a view to providing additional characters of the two species of Andropogon to enhance the understanding of the taxonomic relationship between the two species. The epidermal preparation of the adaxial and abaxial surfaces of the leaf blade was made from the median part of well-matured leaf samples by the scrapping method. The analysis of both qualitative and quantitative characters revealed that study revealed that the costal zones of both adaxial and abaxial surfaces of all accessions studied showed similar features with little or no variation in their expression; epidermal cells are mostly rectangular with wavy walls, and the stomata encountered are paracytic. There was a unique occurrence of cluster of cells at the base of the macro hairs present in A. gayanus which is a diagnostic feature for its accessions collected. Kiwani, an unidentified polyploid accession, has the highest number of bands, the stomata are bigger, which is consistent with gigas effect occasioned by its polyploidy status. Glandular trichomes were present in both diploid and tetraploid of A. tectorum, a diagnostic feature for the species.

In silvopastoral systems (SPS) canopy height and the existence of shaded and non-shaded environments can provide changes in plant development. The objective in this study was to evaluate the effect of shading and canopy height on morphogenic, structural and biomass production characteristics of Andropogon gayanus in an SPS. It was adopted a completely randomized design in a 2 × 3 factorial scheme, with four replications, being two luminosity intensities (shaded and non-shaded within a SPS) and three canopy heights (45, 55 and 65 cm). The studied area was used for 21 years in SPS and grazed by goats. The luminosity in the A. gayanus canopy in shaded areas was reduced by 40% in comparison to the non-shaded area in the SPS. There was effect of the interaction between heights and environments on the dry forage biomass, with higher values in non-shaded areas and in higher canopy heights. The leaf/stem ratio, as well as the leaf percentage did not differ between the environment luminosities and canopy heights, whereas the number of tillers was lower in the shaded areas, also where final leaf length was higher. The shade from Tabebuia sp. in SPS does not compromise the growth of A. gayanus. In SPS A. gayanus should be managed at a canopy height of 65 cm in order to present higher yield and maintain its sustainability.

Grasses are amongst the most abundant and environmentally damaging invasive weeds worldwide. Biological control is frequently employed as a sustainable and cost-effective management strategy for many weeds. However, grasses have not been actively pursued as targets for classical weed biological control due to a perceived lack of sufficiently specialised and damaging natural enemies to use as biological control agents. There are also concerns that the risk posed to economically important crop/pasture species and closely-related native species is too great to consider implementing biological control for invasive grasses. In this paper, we review the literature and demonstrate that grasses can possess suitably host-specific and damaging natural enemies to warrant consideration as potential biological control agents. The risk of grass biological control is no greater than for other weedy taxa if practitioners follow appropriately rigorous risk assessments protocols.

Gamba grass (Andropogon gayanus), a forage biomass, was used as carbon source for cellulases production by Fusarium verticillioides. A Plackett Burman design was employed to evaluate the effects of different factors over enzymatic production and two different media composition, M1 and M2, were found. In M1 media, endoglucanase and cellobiase activities were 6.5 and 0.39 U/mL, respectively. By another hand, the activities of endoglucanase and cellobiase in M2 conditions were 2.6 and 6.8 U/mL, respectively. Blends of these two extracts were tested on a sugarcane bagasse saccharification and M1 presented the best performance, indicating that higher ratios endoglucanase/cellobiase (12:1) improved sugarcane bagasse hydrolysis. Different dosages of protein (10, 20 and 40 mg/g of dry biomass) were tested intending to improve the hydrolysis performance of M1 extract. Saccharification rates of 43.4 and 73.1% were observed for glucan and xylan fractions respectively when 40 mg/g was used. Some non-productive factors such as enzyme adsorption, sugar inhibition and thermostability were evaluated to get a better understanding about saccharification bottlenecks related to Fusarium verticillioides enzymatic extract. This paper showed, for the first time, that gamba grass can be an efficient inductor for cellulase production in the endophytic fungus Fusarium verticillioides. It was also showed that, in Fusarium verticillioides, the induction of enzymes specialized on plant biomass degradation is highly dependent on carbon source concentration. Endoglucanase was mostly induced in middle concentrations while cellobiase is induced in high concentrations.

A major challenge in sorghum intercropping systems is maintaining their yields compared to the yields of the solo crops, especially in arid and semi-arid regions. This study aimed to test the hypothesis that intercropping systems using sorghum (Sorghum bicolor (L.) Moench.) and Brachiaria sp. are viable means to increase sorghum production and soil carbon in the conservation systems. Field trials were conducted in the semi-arid region of Minas Gerais, Brazil, during two crop cycles of sorghum associated with different grasses (Andropogon gayanus—AG; Cenchrus ciliaris cv. Aridus—CCA; Cenchrus ciliaris cv. 131—CC; Brachiaria decumbents—BD; Brachiaria brizantha—BB; Brachiaria ruziziensis—BR; Panicum maximum—PM), using row spacings of 0.4 and 0.8 m. Panicles of sorghum (yield) and grass dry matter were collected to determine yields. Results showed that the addition of grasses in systems decreased the grain yield in all systems, except in the systems using sorghum with CCA in 0.4 m, AG in 0.8 m, or BR in 0.8 m. In the 0.4 m row spacing, the sorghum associations with CC, BB, or PM are greater alternatives to increase soil carbon. However, when the row spacing was increased, the sole sorghum was the best alternative to increase the carbon. In machine learning, sorghum systems with CCA and AG are better alternatives to increase the yields, while sorghum with CC, PM, BR, and BB increases the grass dry matter in soil.

The objective of this study was to evaluate the morphogenic and structural characteristics, and demographic patterns of Andropogon gayanus subjected to different cutting frequencies and intensities. A completely randomized design was adopted in a 3 × 2 factorial arrangement, corresponding to three cutting heights (50, 70, and 90 cm), and two cutting intensities (50 and 70%) with four repetitions, totaling 24 plots of 7.50 × 6.25 m. For morphogenesis, there was no interaction effect (P ≤ 0.05) of treatments on stem elongation rate, leaf appearance rate, and phyllochron rate. The highest rate of leaf elongation was observed at a height of 90 cm and cut intensity of 50%, with 1.69 and 0.84 cm tiller-1 d-1 of leaf elongation at heights of 50 and 70 cm, respectively. For forage production, there was no interaction (p > 0.05) between cutting intensity and cutting height. When the pasture was managed to a cutting height of 90 cm, there was a greater increase in dry leaf mass, stalk dry mass, dead forage dry mass, and total dry forage mass, which was 50.89% and 53.29% higher than pasture heights of 50 and 70 cm, respectively. There was no interaction between factors on demographic characteristics (p > 0.05). A cutting height of 70 cm with a cutting intensity of 50% is recommended when handling this grass.

In northern Australia, beef cattle grazed extensively on tropical rangelands are responsible for 5% of the nation's total greenhouse gas emissions. Methane (CH4 ) is a potent greenhouse gas and in grazing ruminants might be mitigated by selecting forages that, when consumed, produce less CH4 when fermented by rumen microbes. This study examined variability in the in vitro fermentation patterns, including CH4 production of selected tropical grasses and legumes, to identify candidates for CH4 mitigation in grazing livestock in northern Australia.; Results: Nutritive values and fermentation parameters varied between plant species and across seasons. Grasses with a relatively low methanogenic potential were Urochloa mosambicensis (wet summer), Bothriochloa decipiens (autumn), Sorghum plumosum (winter) and Andropogon gayanus (spring), while the legumes were Calliandra calothyrsus (wet summer and autumn), Stylosanthes scabra (winter) and Desmanthus leptophyllus (spring). There was some correlation between CH4 production and overall fermentation (volatile fatty acid concentrations) in grasses (R2 = 0.67), but not in legumes (R2 = 0.01) and there were multiple plants that had lower CH4 not associated with reduction in microbial activity.; Conclusion: Differences in nutrient concentrations of tropical grasses and legumes may provide opportunities for productive grazing on these pastures, while offering some CH4 mitigation options in the context of northern Australian extensive beef farming systems. © 2017 Society of Chemical Industry.; © 2017 Society of Chemical Industry.

Erosion and sediment transport processes are strongly dependent on the spatial scale and land use. The objective of this study is to analyse the effects of slash and burn of vegetation followed by grass cultivation for grazing, on the hydrological and sedimentological behaviour at different spatial scales in a semiarid region in Brazil. Rainfall, runoff and soil loss were measured during three years (total of 116 rainfall-runoff events) at three spatial scales: 1 m2 and 20 m2 plots and 2.8 ha watershed. During the first year (2009) the native dry tropical forest/Caatinga vegetation was maintained, whereas on the following years (2010 and 2011) the original vegetation was cleared using slash and burn techniques to grow pasture (Andropogon gayanus Kunt). Annual runoff coefficient is highest at the 20 m2 plot among the investigated scales. Runoff presented the same trend in all years. Sediment yield was strongly influenced by the land cover. Slash, burn and pasture cultivation strongly impacted sediment yield: the first two events after the land cover change yielded roughly ten times more sediment than similar events in the years with native cover and after grass development. The change was most noticeable at the catchment scale due to erosion along the stream, redefining the drainage network. RESUMO Erosão e os processos de transporte de sedimentos são fortemente dependentes da escala espacial e uso do solo. O objetivo deste estudo é analisar os efeitos do desmatamento, seguido de queima e cultivo de capim para pastagem, sobre o comportamento hidrológico e sedimentológicos em diferentes escalas espaciais na região semiárida do Brasil. Precipitação, escoamento superficial e perda de solo foram mensurados durante três anos (total de 116 eventos chuva-vazão) em três escalas espaciais: parcelas de erosão de 1 m2, 20 m2; e microbacia de 2,8 ha. Durante o primeiro ano de estudo (2009) foi mantida a vegetação de caatinga nativa, enquanto que nos anos seguintes (2010 e 2011) a vegetação original foi alterada usando técnicas de desmatamento, queima e cultivo de capim (Andropogon gayanus Kunt). Os coeficientes de escoamento superficial anual foram mais altos nas parcelas de 20 m2, entre as escalas investigadas. Os coeficientes de escoamento superficial apresentaram a mesma tendência em todos os anos estudados. Já a produção de sedimentos foi fortemente influenciada pela cobertura da terra. Desmatamento, queimada e o cultivo de capim para pastagem impactaram fortemente a produção de sedimentos: os dois primeiros eventos, após a mudança da cobertura do solo, produziram cerca de dez vezes mais sedimentos do que em eventos semelhantes nos anos com cobertura nativa e/ou depois do desenvolvimento do capim. As mudanças foram mais perceptíveis na escala de bacia devido à erosão e redefinição da rede de drenagem.

BACKGROUND Plants from West Africa commonly used in both human and veterinary medicine contain various secondary metabolites. However, their potential in mitigating ruminal methane production has not been explored. This study examined the effects of seven essential oils (EOs) from plants acclimated to Benin at four dosages (100, 200, 300 and 400 mg L−1), on in vitro rumen microbial fermentation and methane production using Andropogon gayanus grass as a substrate. RESULTS Compared to control, Laurus nobilis (300–400 mg L−1), Citrus aurantifolia (300–400 mg L−1) and Ocimum gratissimum (200–400 mg L−1) decreased (P < 0.05) methane production (mL g−1 DM) by 8.1–11.8%, 11.9–17.8% and 7.9–30.6%, respectively. Relative to the control, reductions in methane (mL g−1 DM) of 11.4%, 13.5% and 14.2% were only observed at 400 mg L−1 for Eucalyptus citriodora, Ocimum basilicum and Cymbopogon citratus, respectively. These EOs lowered methane without reducing concentrations of total volatile fatty acids or causing a shift from acetate to propionate production. All EOs (except M. piperita) reduced (P < 0.05) apparent dry matter (DM) disappearance of A. gayanus. CONCLUSIONS The current study demonstrated that EOs from plants grown in Benin inhibited in vitro methane production mainly through a reduction in apparent DM digestibility. © 2014 Society of Chemical Industry

A utilização de forrageiras tolerantes ao sombreamento é fundamental para a sustentabilidade da integração lavoura-pecuária-floresta. Estudou-se o comportamento do Panicum maximum cv. 'Tanzânia' e do Andropogon gayanus cv. 'Planaltina' sob diferentes níveis de sombreamentos e épocas de entrada sob a sombra. Utilizou-se delineamento em blocos casualizados, com quatro repetições, em esquema fatorial com dois tipos de sombreamento: 30% e 50%; três épocas de entrada na sombra após transplante (07, 14 e 21 dias); e uma testemunha, mantida a pleno sol. Mudas com 8 a 12cm de altura das duas espécies, pré-cultivadas em bandejas de isopor, foram transplantadas para vasos e mantidas nos respectivos ambientes sombreados ou a pleno sol por 90 dias, em livre crescimento. A época de entrada na sombra não interferiu na produtividade e nos teores de clorofila foliar das cultivares, assim como na composição bromatológica. As massas seca e fresca das cultivares 'Tanzânia' e 'Planaltina' foram superiores em ambientes sombreados, quando comparadas ao pleno sol. As duas forrageiras, quando sombreadas, incrementaram os teores de clorofila a, porém não se observou alteração para clorofila b. A adaptação positiva em ambientes sombreados das cultivares torna-se promissora em sistemas de integração silvipastoris. The use of grasses tolerant to shade is essential to the sustainability of the Farming-Livestock-Forest Integration System. The performance of Panicum maximum cv. 'Tanzania' and Andropogon gayanus cv. 'Planaltina' under different levels of shading and times of entry under the shade were studied. We used designs in randomized blocks with four replications in a factorial scheme with two types of shading: 30% and 50%; three times of entry into the shade after transplantation (07, 14 and 21 days) and a witness, kept in full sun. Seedlings 8 to 12cm high of both species, pre-cultivated in styrofoam trays were transplanted to pots and maintained in their respective environments under the shade or full sun for 90 days in normal growth. The time of entry into the shade does not interfere with productivity and leaf chlorophyll content of cultivars, as well as in the bromatological composition. The fresh and dry matter of the cultivars of both 'Planaltina' and 'Tanzania' were higher in shaded environments rather than those in full sun. The two forage grasses when shaded increase the chlorophyll a content, but no change of chlorophyll b was thereof observed. The positive adaptation of cultivars in the shaded environments becomes promising in systems of integration of pastures with trees.

O objetivo deste trabalho foi identificar ácaros na cultura de pinhão-manso e em espécies de plantas espontâneas associadas. Para isso, foram avaliadas a riqueza e a abundância de ácaros em plantas de pinhão-manso e em 14 espécies de plantas espontâneas associadas. As amostragens foram realizadas por meio de coletas mensais de folhas de plantas de pinhão-manso e de plantas espontâneas, nas entrelinhas do cultivo. Foram encontradas quatro espécies de ácaros predadores - Amblyseius tamatavensis, Paraphytoseius multidentatus, Typhlodromalus aripo e Typhlodromalus clavicus -, com potencial para uso no controle biológico de ácaros-praga na cultura do pinhão-manso, e duas importantes espécies de ácaros fitófagos - Brevipalpus phoenicis e Tarsonemus confusus - desconhecidas como praga da cultura. Entre as plantas espontâneas avaliadas, quatro espécies - Hyptis suaveolens, Peltaea riedelii, Urochloa mutica e Andropogon gayanus - abrigam grande riqueza e abundância de ácaros predadores, enquanto oito destacaram-se pela diversidade de ácaros fitófagos. The objective of this work was to identify mites in physic nut culture, and in associated spontaneous weed species. For this, mite richness and abundance on physic nut plants and on 14 species of associated spontaneous weeds were evaluated. Samplings were done with monthy collections of leaves from physic nut plants and from weeds, between planting lines. Four species of predatory mites - Amblyseius tamatavensis, Paraphytoseius multidentatus, Typhlodromalus aripo and Typhlodromalus clavicus -, with potential for biological control of pest mites on physic nut culture, and two species of phytophagous mites - Brevipalpus phoenicis and Tarsonemus confusus -, not yet known as pests of the culture were found. Among the evaluated spontaneous weeds, four species - Hyptis suaveolens, Peltaea riedelii, Urochloa mutica and Andropogon gayanus - harbor great richness and abundance of predatory mites, whereas eight harbored a high diversity of phytophagous mites.

Zeolites are hydrated crystalline aluminosilicate minerals of natural occurrence, structured in rigid third dimension net that can be used as slow release plant-nutrient source. The main objective of this study was to evaluate the effects of plant growth substrate under zeolite application, enriched with N, P and K, on dry matter yield and on nutrient contents in consecutive crops of lettuce, tomato, rice, and andropogon grass. The experiment was carried out in a greenhouse, with 3 kg pots with an inert substrate, evaluated in a randomized block design with three replications. Treatments consisted of four types of enrichment of concentrated natural zeolite: concentrated zeolite (Z) only, zeolite + KNO3 (ZNK), zeolite + K2HPO4 (ZPK) and zeolite + H3PO4 + apatite (ZP), and a control grown in substrate fertilized with a zeolite-free nutrient solution. Four levels of enriched zeolite were tested: 20, 40, 80, and 160 g/pot. Four successive crops were grown on the same substrate in each pot: lettuce, tomato, rice, and andropogon grass. Results indicated that N, P and K enriched zeolite was an adequate slow-release nutrient source for plants. The total dry matter production of above-ground biomass of four successive crops followed a descending order: ZP > ZPK > ZNK > Z.

Many tropical forage grasses and legumes grow well in acid soils, adapting to excess aluminum (Al) and phosphorus (P) starvation stresses by using mechanisms that are still unclear. To determine these mechanisms, responses to Al toxicity and P starvation in three tropical forages were studied: two grasses, Brachiaria hybrid cv. ‘Mulato’ (B. ruziziensis clone 44-06 × B. brizantha cv. ‘Marandu’) and Andropogon gayanus, and one legume, Arachis pintoi. The tropical grasses tolerated high levels of Al toxicity and P starvation, with the Brachiaria hybrid maintaining very low levels of Al concentration in shoots. 27Al Nuclear Magnetic Resonance spectroscopy (NMR) analysis revealed that, in the Brachiaria hybrid, Al makes complexes with some ligands such as organic-acid anions in the root symplast. The forages probably adapted to P starvation through high P-use efficiency. These experiments provide the first direct evidence we know of that organic acid anions within root tissue help detoxify Al in non-a...

Land use patterns affect soil nutrient transformation and availability. The study determined the distribution of phosphorus (P) fractions and sorption in five pasture fields composed of Andropogon gayanus, Brachiaria decumbens, Chloris gayana, Digitaria smutsii, and Stylosanthes guianensis. The objectives were to characterize P fractions in improved pastures and to determine the effect of forage species on soil P lability. Total P (Pt) across the pastures was not significantly different. Organic P (Po) accounted, on the average, for 64% of Pt. Resin‐P, considered the plant‐available P, ranged from 4 to 10 mg kg−1, suggesting acute P deficiency in the pastures. The sum of P fractions extracted by 0.5 M NaHCO3, 0.1 M NaOH, and 1.0 M HCl, together with the resin‐P, accounted for less than 35% of Pt. Factor analysis indicated that plant‐available P approximated by resin‐P was furnished by ‒HCO3‐Po mineralization and HCl‐P. The highest concentrations of ‒HCO3‐Po and ‒OH‐Po were maintained by Brachiari...

Este trabalho teve como objetivo avaliar a técnica de incorporação de 32P pelos eritrócitos de ovinos jovens, mantidos em pastejo de Andropogon gayanus, como método de diagnóstico da deficiência de fósforo. Vinte ovinos, com peso vivo inicial de 13,88±2,51 kg, foram divididos em dois tratamentos de dez animais cada; num dos tratamentos, os animais foram suplementados com 3 g de P por animal por dia e, no outro, os animais não receberam suplementação de P. Foram realizadas cinco pesagens dos animais, coletas de sangue e fezes nos 8º, 29º, 43º, 57º e 71º dias do experimento, para avaliar a incorporação de 32P pelos eritrócitos, determinar as concentrações de Ca, glicose e P no soro e a porcentagem de P nas fezes. Foi encontrada diferença significativa na concentração de Ca no 57º dia. Na concentração de glicose, porcentagem de P nas fezes e peso vivo não foram observadas diferenças significativas entre os tratamentos. A partir da segunda coleta, a concentração de P no soro foi mais elevada e a incorporação de 32P foi menor no grupo de animais suplementados com P. A incorporação de 32P pelos eritrócitos é uma técnica adicional para avaliar o status de P e identificar sua deficiência subclínica em ovinos jovens. This work had the objective of evaluating the method of 32P uptake by the erythrocytes of young sheep, supplemented with phosphorus and kept at pasture of Andropogon gayanus, as a tool for phosphorus deficiency diagnosis. Twenty lambs, initially weighing 13.88±2.51 kg, were divided in two treatments of ten animals each. In one of them, animals were supplemented with 3 g of phosphorus per animal per day and, in the other, animals did not receive supplementation of phosphorus. Weighing, and blood and faeces collection were carried out in the 8th, 29th, 43rd, 57th e 71st days of the experiment, to evaluate the incorporation of 32P by the erythrocytes, to determine calcium, glucose and phosphorus concentrations in the serum and percentage of P in the faeces. Significant difference for the concentration of Ca was found in the 57th day. For the glucose concentration, the percentage of phosphorus in faeces, and the weight, significant differences between the treatments were not observed. From the 29th to the 71st day, the concentration of phosphorus in the serum was higher, and the incorporation of 32P was lower in the group of animals supplemented with phosphorus. The analysis of 32P incorporation by the erythrocytes is an additional tool to evaluate the status of P, with identification of the subclinic deficiency in lambs.

A strategy for rehabilitating degraded or unproductive native grassland is the establishment of improved pastures to sequester organic carbon (OC) in the soil. Microbial biomass C, N and P are the most biologically active fraction of soil OC, and are thus, useful indices for assessing the health of soil ecosystems. The impact of improved grass pastures and a legume pasture on microbial biomass C, N and P in a savanna soil at Shika (Lat. 11°11′ N and Long. 7°38′ E), in northern Nigeria, was studied. The objective was to determine the pasture plant that best improved the microbial properties of the soil. Five managed pasture fields, consisting of Andropogon gayanus Kunth., Brachiaria decumbens Stapf., Chloris gayana Kunth., Digitaria smutsii Stent. and Stylosanthes guianensis (Aubl.) Sw., were sampled for the study. The concentration of OC in the field under B. decumbens was nearly twice (23.9 g kg−1) the concentration in other fields (13.1–14.6 g kg−1). The field under D. smutsii had significantly higher microbial biomass C (MBC) than other fields as determined by fumigation–extraction method, and MBC accounted for between 1.5 and 3.9% of OC in the soil. Microbial biomass N (MBN), ranged from 41 to 119 mg kg−1 and microbial biomass P (MBP) from 22 to 113 mg kg−1. The fields under S. guianensis and D. smutsii had significantly greater MBN and MBP than the other fields. The MBN accounted for between 3 and 10% of total N, while MBP accounted for between 19 and 75% of organic P (Po). D. smutsii and S. guianenesis had the most significant impact on microbial C, N and P, whereas B. decumbens sequestered more OC in the soil. Thus, D. smutsii and B. decumbens are two promising grass pastures that can be established to rehabilitate degraded or unproductive savanna lands.

In an attempt to set up habitat management strategy against Eldana saccharina Walker, an economically important graminaceous stem and cob borer, two laboratory experiments were carried out. The first experiment was designed to assess oviposition preference of E. saccharina for growth stages, plant parts and freshness of different host plants and between host plants species. Zea mays L., Sorghum arundinaceum (Desv.) Stapf, Andropogon gayanus Kunth, Panicum maximum Jacq., Pennisetum polystachion (Linn.) and Cyperus papyrus L. were assessed. Results showed that E. saccharina preferred wild grasses to maize for oviposition. More than 94% eggs were laid on wild grasses. Of all tested grasses, P. polystachion was the most attractive with more than 30% of collected eggs. For all plant species, post-tasseling stage was more attractive than the tasseling and pre-tasseling ones. More than 90% of total eggs were laid on dry leaves and sheaths and less than 10% on fresh leaves. Different characteristics relating to population dynamics of E. saccharina were assessed in the second experiment. Larval survival rate was 10% on Z. mays, 0.50% on S. arundinaceum and around 0% on the other wild grasses. Larval development length was longer on S. arundinaceum than on Z. mays. Females reared on Z. mays were three times more fecund than those reared on S. arundinaceum. Complete life table of females from larvae reared on Z. mays was studied.

In West Africa policies for grazing, selective tree cutting and prescribed early fire in the savannah woodlands are rarely based on long-term experimental studies. The purpose of this study was to provide scientific evidence based on field data from two case studies for an informed discussion on the effects of various management options. The main findings were by and large specific for the species, the growth form and the location. This supports the argument for devolution of management responsibility to the local level where there is such site-specific ecological knowledge. Effects of selective tree cutting (50% of basal area), livestock (1–1.4 tropical livestock unit ha−1) and prescribed early annual fire on herbaceous biomass were studied in the state forests of Laba (shallow sandy soils) and Tiogo (deep clayey soils) in the savannah woodlands in the Sudanian Zone of Burkina Faso, from 1993 to 2001. The herbaceous biomass was analysed on three levels: total herbaceous biomass, per growth form (annual and perennial grasses and forbs) and for each of the four main species in the study areas (Andropogon pseudapricus, Loudetia togoensis, Andropogon ascinodis and Andropogon gayanus). At both sites, mean total biomass during the study period was reduced by the presence of livestock while it was not significantly affected by early prescribed fire or by selective cutting. There was interaction between the three treatments at both sites. Statistically significant treatment effects were found at each site when analysing each growth form and species individually. For instance, at the growth form level, grazing reduced the biomass of annual grasses in Tiogo, perennial grasses in Laba and forbs at both sites. Site and species-specific response to grazing was found for A. ascinodis with increased biomass in Tiogo and reduced biomass of A. gayanus in Laba. Although the effect of prescribed early fire was not statistically significant the trend was the same at both sites with increased biomass of annual grasses and decreased biomass of perennial grasses. This homogenising effect of fire was statistically significant at the species level with increased biomass of the annual grass L. togoensis and decreased biomass of the perennial grass A. gayanus at both sites. Selective cutting significantly increased mean biomass of annual grasses in Tiogo whereas there was no difference in Laba.

Carbon accumulation in soil under pasture is seen as a process of decreasing greenhouse gases concentration in the atmosphere. Thus, tropical areas such as the “Cerrado” region in Brazil, with an area of 204 million ha and of around 50 million ha of cultivated pastures, most of them with African grasses, are considered potential areas to sink carbon. Total carbon in soil profile was used to compare carbon accumulation among cultivated and native pastures on a Dark Red Latosol (Typic Haplortox) found in the “Cerrado” region, Brazil. Soil samples taken at 1.0 m deep were analyzed in seven different fields: native pasture (1), Panicum maximum (2), Brachiaria decumbens (3), Brachiaria brizantha+Stylosanthes guianensis (4), Andropogon gayanus+Neonotonia wightii+Centrosema brasilianum (5), two seed production fields, B. brizantha (6) and Paspalum atratum (7). Forage dry matter production was also evaluated at each field. All cultivated pastures were over three years old and grazed under different stocking rates, except for fields 6 and 7, which were not grazed. Dry matter production was higher in fields 6 and 7 and lower in fields 1, 3 and 5. An ongoing degradation process was detected in fields 3 and 5. Carbon storage amounted to 100 Mg ha−1 in 1 and ranged from 97 Mg ha−1 in 3 to 113 Mg ha−1 in 2, 6 and 7. Pastures in fields 3 and 5 (low shoot dry matter production and low fertility status), had less soil carbon than fields 6 and 7 (higher shoot dry matter production and better fertility status). Total soil carbon and forage dry matter production showed a high correlation (0.83, P

Pasture degradation is one of the greatest problems related to land use in the Amazon region, forcing farmers to open new forest areas. Many studies have identified the causes and the factors involved in this degradation process, in an attempt to reverse the situation. The purpose of this study was to examine the relationship between pasture degradation and some soil properties, to try to identify the most significant soil features in the degradation process. A cattle raising farm in the eastern Amazon region, with pastures of different ages and degrees of degradation, was used as the site for this study: a primary forest area, PN; three Guinea grass (Panicum maximum Jacq.) pastures in an increasingly degraded sequence—P1, P2 and P3; one Gamba grass (Andropogon gayanus Kunth) pasture following an extremely degraded Guinea grass pasture, P4. Aboveground phytomass data showed differences between the pastures, reflecting initially observed degradation levels. Grass biomass decreased sharply from P1 to P2 and disappeared at P3. Pasture recovery with Gamba grass at P4 was very successful, with grass biomass higher than P1 and weed biomass smaller than P2 and P3. Root biomass also decreased with pasture degradation. Soil bulk density increased with pasture decrease at the topsoil layer. Results from the soil chemical analysis showed that there were no signs of decrease in organic carbon and total nitrogen after the forest was transformed into pasture. In all pastures, degraded or not, the soil pH, the sum of bases and the saturation degree were higher than in the forest soil. The extractable phosphorus content, lower in forest soil, remained quite stable in pasture soils, but it could become a limiting factor for the maintenance of Guinea grass. Results indicated that pasture degradation does not seem to be directly related to the modification of the chemical features of soils.

In the semiarid regions of sub-Saharan Africa, fertilizer recovery and nutrient release from organic sources are often moisture limited. Moreover, in these regions runoff brings about large nutrient losses from fertilizer or organic inputs. This study was conducted in the north sudanian climate zone of Burkina Faso (annual rainfall 800 mm, PET 2000 mm yr-1). We assessed the combined and interactive effects of two types of permeable barriers (stone rows and grass strips of Andropogon gayanus Kunth cv. Bisquamulatus (Hochst.) Hack.) and organic or mineral sources of nitrogen on erosion control and sorghum yield. The field experiment (Ferric Lixisol, 1.5% slope) was carried out during three rainy seasons and consisted of 2 replications of 9 treatments, in which the barriers were put along contours and combined with compost, manure and fertilizer nitrogen (N). Compared with the control plots, the average reduction in runoff was 59% in plots with barriers alone, but reached 67% in plots with barriers + mineral N and 84% in plots with barriers + organic N. On average, stone rows reduced soil erosion more than grass strips (66% versus 51%). Stone rows or grass strips without N input did not induce a significant increase of sorghum production. Supplying compost or manure in combination with stone rows or grass strips increased sorghum grain yield by about 142%, compared with a 65% increase due to mineral fertilizers. The sorghum grain yields at 1m upslope from the grass strips were less than those 17m from the grass strips. As stones do not compete with plants, the opposite trend was observed with stone rows. We conclude that for these nutrient depleted soils, permeable barriers improve nutrient use efficiency and therefore crop production. However, grass strips must be managed to alleviate shade and other negative effects of the bunds on adjacent crops.

The effect of tree species on the characteristics of the herbaceous stratum, during the first five years of a fallow, was evaluated in the North of Cameroon (average annual temperature 28.2 °C, total annual rainfall 1050 mm). Treatments included a natural grazed herbaceous fallow, a natural ungrazed herbaceous fallow and three planted tree fallows (Acacia polyacantha Willd. ssp. campylacantha (Hochst. ex A. Rich.), Senna siamea Lam. and Eucalyptus camaldulensis Dehnh.), which were protected against grazing. Because tree species influenced light interception in different ways, as well as having different root patterns, they had different effects on the herbaceous stratum in terms of species composition and biomass. The grazed herbaceous fallow maintained the greatest species richness. Protection against grazing or the introduction of tree species associated with the absence of grazing induced both a progressive evolution to a particular species composition. The ungrazed herbaceous fallow consisted mainly of Andropogon gayanus Kunth, which provided the greatest biomass (8 t dry matter ha–1 at the end of the fallow period). E. camaldulensis provided little shade and the lowest fine root mass in the top layer allowing the growth of A. gayanus and thus a greater herbaceous biomass (3.5 t DM ha–1) than that found under the other tree species. Under the heavy shade of A. polyacantha, the herbaceous stratum consisted mainly of annual Pennisetum spp. (2.2 t DM ha–1) and showed the greatest N concentration (1.3%), probably due to N2 fixation by the tree species. After the fourth year, despite the relatively open tree canopy, S. siamea, which showed the highest fine root mass, had a strong depressive effect on the herbaceous stratum.

Submitted by Guilherme Lemeszenski (guilherme@nead.unesp.br) on 2013-08-22T18:46:40Z No. of bitstreams: 1 S0100-204X2001001100012.pdf: 365339 bytes, checksum: 309be2e49302ff71d9993df0fa936e2a (MD5) Made available in DSpace on 2013-08-22T18:46:40Z (GMT). No. of bitstreams: 1 S0100-204X2001001100012.pdf: 365339 bytes, checksum: 309be2e49302ff71d9993df0fa936e2a (MD5) Previous issue date: 2001-11-01 Made available in DSpace on 2013-09-30T19:36:01Z (GMT). No. of bitstreams: 2 S0100-204X2001001100012.pdf: 365339 bytes, checksum: 309be2e49302ff71d9993df0fa936e2a (MD5) S0100-204X2001001100012.pdf.txt: 37808 bytes, checksum: f6c8ebe5140d82566c26897f23df5b97 (MD5) Previous issue date: 2001-11-01 Submitted by Vitor Silverio Rodrigues (vitorsrodrigues@reitoria.unesp.br) on 2014-05-20T15:09:41Z No. of bitstreams: 2 S0100-204X2001001100012.pdf: 365339 bytes, checksum: 309be2e49302ff71d9993df0fa936e2a (MD5) S0100-204X2001001100012.pdf.txt: 37808 bytes, checksum: f6c8ebe5140d82566c26897f23df5b97 (MD5) Made available in DSpace on 2014-05-20T15:09:41Z (GMT). No. of bitstreams: 2 S0100-204X2001001100012.pdf: 365339 bytes, checksum: 309be2e49302ff71d9993df0fa936e2a (MD5) S0100-204X2001001100012.pdf.txt: 37808 bytes, checksum: f6c8ebe5140d82566c26897f23df5b97 (MD5) Previous issue date: 2001-11-01 O objetivo deste trabalho foi avaliar: (i) a relação entre a degradação de pastagens de colonião manejadas com queima, e as modificações nas propriedades físicas e morfológicas de um Argissolo Vermelho-Amarelo da Amazônia; (ii) o crescimento radicular de pastagens com diferentes níveis de degradação; (iii) o potencial de recuperação de pastagens degradadas de colonião com a introdução de andropógon. Numa propriedade rural da Região de Marabá, PA, foram estudados quatro tipos de pastagem: pastagem produtiva de colonião (Panicum maximum Jacq.); pastagem de colonião em declínio produtivo; pastagem de colonião degradada (capoeira); pastagem de colonião degradada e recuperada com andropógon (Andropogon gayanus Kunth). Como referência das propriedades do solo antes do desmatamento, estudou-se, também, uma reserva de mata nativa. A queima das pastagens foi prática usual, e apesar disso, estas não foram adubadas. A degradação da pastagem diminuiu a cobertura do solo e o deixou exposto à chuva e ao pisoteio do gado, o que resultou em aumento da densidade do solo na camada superficial e diminuição do grau de floculação da argila e da porosidade total. A diminuição da produção da parte aérea na pastagem degradada foi acompanhada de diminuição do número de raízes no perfil do solo, e da concentração do sistema radicular próximo à superfície. O andropógon demonstrou bom potencial para recuperação das áreas de pastagens degradadas, na Região Amazônica. The objective of this study was to evaluate: (i) the relation between the degradation of burned Guinea grass pastures and the modifications of some physical and morphological properties of an Amazonian Ultisol; (ii) the root growth of pastures in different degradation stages; and (iii) the potential of rehabilitation of degraded Guinea grass pastures by introducing Gamba grass. on a farm at the eastern Amazon, region of Marabá, PA, Brazil, four pasture types were studied: productive Guinea grass (Panicum maximum Jacq.) pasture; Guinea grass pasture on yield decline; degraded Guinea grass pasture (fallow), and degraded Guinea grass pasture recovered with Gamba grass (Andropogon gayanus Kunth). As reference of the soil original characteristics before clearing, a native forest area was also studied. Burning was an usual practice; moreover, the pastures did not receive fertilizers. Pasture degradation decreased soil covering and exposed the soil surface to the direct impact of rain drops and cattle compaction, what resulted in soil bulk density increase in the superficial layer and decrease in clay flocculation and soil total porosity. Forage yield decline on degraded pasture was accompanied by a decrease on the number of roots on the soil profile, and there was a concentration of the root system close to the surface. Andropogon gayanus showed good potential for the rehabilitation of degraded pastures on the Amazon Region. Universidade Estadual Paulista Faculdade de Ciências Agronômicas Universidade Estadual de Viçosa Departamento de Agronomia Institut Français de Recherche Scientifique pour le Développment en Coopération Faculdade de Ciências Agrárias do Pará Núcleo de Estudos Integrados sobre Agricultura Familiar Universidade Estadual Paulista Faculdade de Ciências Agronômicas

Over the last 25 years more than 70 million ha of the native vegetation in Brazil have been replaced by pastures for beef production planted to grasses of the genus Brachiaria, and to a lesser extent Andropogon gayanus, both of African origin. Some years after implantation, these pastures decline in productivity, probably due to low availability of P, and immobilisation of N in the soil due to the large quantities of senescent leaves (litter) of high C:N ratio deposited on the soil surface. In this paper we report the effects of the introduction of a forage legume (Desmodium ovalifolium) and different animal stocking rates on the deposition and decomposition of plant litter in pastures of Brachiaria humidicola at a site in the coastal Atlantic forest region of the south of Bahia State (Brazil). Litter existing on the ground, and that deposited in 14-day periods, was monitored at monthly intervals during 3 years of the study. Doubling the stocking rate from 2 to 4 animals ha-1 caused a highly significant decrease in litter deposition, but the presence of the legume in the sward had little effect. Calculations made directly from the quantities of litter deposited in the 14-day periods showed that between 15 and 18 tons of litter dry matter (dm) were deposited annually, but the relatively small quantities of existing litter (annual means of 0.8 to 1.5 t dm ha-1), showed that decomposition was rapid, showing values for half life of between 22 and 33 days. This technique was assumed to underestimate true litter disappearance rates, as with such rapid decomposition a significant proportion of the litter disappeared within the 14-day collection periods. An equation was developed to correct for this loss of litter during the collection periods and corrected litter decomposition constants of 0.037 to 0.097 g g-1 day-1 were recorded resulting in half lives of between 9 and 20 days. Using these data and adding them to estimates of animal consumption the net aerial primary productivity (NAPP) of the pastures ranged from 28 to 34 t dry matter ha-1 yr-1. Experiments with litter bags, and a "covered litter" system which allowed access of soil fauna to the litter, indicated that soil faunal activity had little impact on litter disappearance and such techniques underestimated true litter decomposition by at least an order of magnitude. We suggest that this underestimation is due to the fact, that in contrast to litter bags, in the open field situation fresh litter is being added continuously. As this material consists of both easily degradable ("active") and recalcitrant fractions, the easily degradable fraction fuels an active microbial biomass which continuously degrades the less decomposable material. It is concluded that the approach used in this study gives more realistic, and much higher estimates, of net primary aerial production of tropical grasslands and pastures than techniques heretofore utilised.

In an on-station agroforestry experiment conducted in south-west Niger, the effects of seven windbreak species and of a soil mulch made from crop residue on wind erosion and pearl millet (Pennisetum glaucum) production were monitored. Within a distance of 20 m, strips of the perennial grass, Andropogon gayanus, reduced total annual soil flux by 6–55% and hedges of Bauhinia rufescens 2 m in height reduced soil flux by 47–77% compared with unsheltered control plots. No significant overall windbreak effect on millet stover and grain yields was found. In contrast, erosion reduction and yield increases due to mulch application were highly significant. Soil mulch is a promising alternative to complex windbreak–millet cropping systems in regions where direct economic benefits for farmers are not ensured by windbreaks.

Guinea grass (Andropogon gayanus Kunth cv. Bisquamulatus) and Buffel grass (Cenchrus ciliaris L. cv. Biloela) are grown as temporary fodder crops in the Sahelo-Sudanese region of Africa. Differences in their responses to drought conditions may be important in optimizing cattle feeding programmes in integrated farming systems. An experiment conducted in a wind tunnel equipped with a tank forming a weighable lysimeter compared net photosynthesis (A), stomatal conductance (gs) and leaf water potential (Ψ leaf) of both species in a mixed sward during three simulated environmental conditions: (1) rainy season, (2) drought period within the rainy season and (3) dry season.With a soil water reserve (SWR in % volume) of 8% during the drought period and the dry season, the Ψ leaf and A parameters were significantly lower (Pgs values were significantly different during each environmental condition (PP>0·05) was found in gs and A between the two species during the rainy and the dry season or during a diurnal cycle, although a significant difference (PWhen the drought period was imposed during the rainy season (SWR declined from 25 to 5%), A was reduced from 19·8 to 7·7 μmol m−2 s−1 for Guinea grass and from 16·8 to 3·7 for Buffel grass. Ψ leaf in both species dropped below −2 MPa while gs declined slowly from 0·70–0·80 to 0·55–0·60 cm s−1. A was significantly higher (PIt is concluded that Guinea grass was as drought-resistant as Buffel grass and that no competition for water existed between the species in the mixed sward. The study also gives relationships between the physiological parameters of both species and the soil water content during a drying cycle.

The tree-shrub savanna ‘Foret Classee de Nazinon’ (Burkina Faso) is submitted to a management of grazing and rotational cutting of Detarium microcarpum. This species resprouts after cutting. In order to investigate whether this silvopastoral land use system is sustainable, aboveground herbaceous biomass was measured on subplots under uncut trees (‘uncut’), next to the stubs of cut trees (‘cut’) and on subplots not influenced by the (former) crowns of trees (‘open grassland’) in four lots. These lots were cut one, three, six and seven years before the study. Vegetation composition of the lots and the composition of the diet of cattle were also determined. Comparisons were made between treatments and lots. Herbaceous biomass was lower in the open grassland subplots than in uncut or cut subplots. We speculate that soil enrichment and more efficient precipitation input in (former) tree crown zones could have resulted in this pattern. Cutting and subsequent resprouting of trees did not lead to significant differences in herbaceous biomass between cut and uncut subplots. The most simple explanation for this is that the trees could extend their roots beyond the location of their neighbouring trees. Biomass and coverage of perennial grasses, mainly Andropogon ascinodis and Andropogon gayanus, did not change in lots cut one, three or six years before the study, but decreased dramatically in lots that were cut seven years before the study. When foraging, cattle spent more than 90% of their time feeding on these species. This indicates that, as a consequence of tree cutting, forage availability may be reduced to the point where local herdsmen are forced to take their cattle to another region.

The use of tropical grass–legume mixtures containing the grasses Brachiaria decumbens or Andropogon gayanus associated with a mixture of several herbaceous legumes was tested on farms in the rainforest area of Pucallpa, Peru. Pastures were established by farmers using manual labour and without fertilizer in previously deforested areas covered with secondary growth. The pastures, together with their grass-alone control, were incorporated by farmers into the normal paddock rotation, and were grazed by dual-purpose cattle of mixed breeding. Cows were milked once daily by hand and with their calves at foot. Following a training period, farmers kept records of milk yields. Frequent and unannounced visits at milking time by the research team were used to verify milk yields and to annotate events such as calving, drying out, sales and others. Across farms and years, grass–legume mixtures significantly outyielded grass-alone pastures by 9%. Milk yields on the mixed pastures were examined further by stepwise regression. A positive and significant effect of the proportion of crossbred cows in the herd was established, whereas soil quality (evaluated by the percentage of aluminium saturation) had a negative impact on milk yields. Two of the farms, which for different circumstances had poorer than average animal and pasture management, also had a significantly negative effect on milk yield. The interactions between animal and pasture management, and regional infrastructure are discussed. It is concluded that grass–legume mixtures increased milk yields on farms. Nevertheless, it is also hypothesized that they may have a more restricted niche than anticipated and that their adoption may be highly sensitive to the overall economic context of the region.

An experiment was conducted in a semi‐arid region located in the State of Zulia, western part of Venezuela (10°32'N and 71°42'W, 600 mm average annual rainfall), to evaluate dry matter (DM) yield and in vitro organic matter digestibility (IVOMD), and crude protein (CP) content of Andropogon gayanus Kunth as affected by three frequencies of defoliation (every 42, 63, and 84 days) and fertilization with three levels of nitrogen (N) (0, 100, and 200 kg N ha‐1‐year‐1) and two levels of phosphorus (P) (0 and 75 kg P2O5 ha‐1.year‐1) in a factorial array using a split‐split‐plot experimental design with frequencies in the main plots, N in the sub‐plots, and P in the sub‐subplots with three replications. Soil was a sandy loam Aridisol with a pH of 5.5. Average soil calcium (Ca), magnesium (Mg), sodium (Na), potassium (K), and P contents were 0.6, 0.3, 0.1 and 0.17 meq‐100g‐1 soil, and 6 ppm, respectively. Data from six, four, and three cuttings for the frequencies of 42, 63, and 84 days were analyzed ove...

An experiment was conducted in a semi‐arid region located in the State of Zulia, western part of Venezuela (10°32'N and 71°42'W, and 600 mm average annual rainfall), to evaluate ash and macroelement concentrations of Andropogon gayanus Kunth as affected by two frequencies of defoliation (every 42 and 63 days) and fertilization with three levels of nitrogen (N) (0, 100, and 200 kg N ha‐1‐year‐1) and two levels of phosphorus (P) (0 and 75 kg P2O5 ha‐1#lbyear‐1) in a factorial array using a split‐split‐plot experimental design with frequencies in the main plots, N in the sub‐plots, P in the sub‐sub‐plots, and two replications. Soil was a sandy‐loam Andisol with pH 5.5. Average soil calcium (Ca), magnesium (Mg), sodium (Na), potassium (K), and P contents were 0.6, 0.3, 0.1, and 0.17 meq#lb100 g‐1 soil and 6 ppm, respectively. Data from six and four cuttings for the frequencies of 42 and 63 days were analyzed over the total duration of the study (252 days) as well as separately for periods with “high”...

SUMMARYThe possible use of tropical forage legumes in pastures based on Brachiaria decumbens and Andropogon gayanus pastures was tested on farms in the humid tropics region of Pucallpa, Perú. The pastures were established by farmers using manual labour. They were associated with maize in some cases and were normally grown without fertilizers. The pastures were established in areas where fallow regrowth was felled and burnt. These pastures, with grass-alone controls, were incorporated by farmers into their normal paddock rotation and were grazed by dual-purpose cows. Despite the variable terrain and soil conditions, all the pastures established and persisted well. Over a four year period under grazing, the legume contribution to the forage averaged 21% and ranged between 1 and 66%. Desmodium ovalifolium was the dominant legume in paddocks that were not burnt, whereas in pastures regularly burnt to control weeds it tended to disappear and Stylosanthes guianensis was the main legume present. It is concluded that where farmers ensure the maintenance of adequate levels of forage, grass-legume mixtures are a viable and persistent option even if the pasture is occasionally burnt.

A greenhouse experiment was conducted to determine the critical deficiency levels of potassium (K) in the subhumid zone soils for predicting response of a mixture of Andropogon gayanus and Stylosanthes hamata cv. Verano to K application. Twenty coarse textured soils, having loamy sand to sandy loam textures and with exchangeable K contents ranging from 0.08 to 0.97 cmol/kg, were used. Two rates of K applied were 0 and 80 mg K/kg. Application of K on soils testing less than 0.18 cmol/kg significantly increased the dry matter yields of both Andropogon and stylo tops. Soil K was significantly related to relative yields of Sole Andropogon (r = 0.60∗∗), sole stylo (r = 0.78∗∗∗), and Andropogon/stylo mixture (r = 0.77∗∗∗). There was a high correlation between the K concentration in plant tissue and the relative yields of sole Andropogon (r = 0.68∗∗), sole stylo (r = 0.67∗∗), Andropogon in mixture (r = 0.65∗∗), and stylo in mixture (r = 0.64∗∗). The graphical model of Gate and Nelson indicated the criti...

Tree and windbreak species considered for the Southern Sahelian Zone (SSZ) of West Africa have to be evaluated following multiple criteria such as fast establishment, shelter efficiency, production of feed for livestock, and firewood. An on-station experiment was conducted on a sandy soil in southwest Niger between 1988 and 1993 to assess the establishment, growth, nutritive, and calorific values of seven species considered for windbreaks:Andropogon gayanus, Bauhinia rufescens, Acacia holosericea, Acacia nilotica, Acacia senegal, Faidherbia albida, andAzadirachta indica. Mortality and stem diameter were monitored twice a year. From 20 months after planting (MAP) onwards, species were annually trimmed to 2 m height and to 1 m sidewards of the main stem. Fresh and dry weight of leaves, twigs, wood, and fruits were recorded. Leaves were analyzed for crude protein (CP) and metabolizable energy (ME) content. Wood was analyzed for its gross calorific value and its ash content. At 56 MAP, all species had less than 5% morality, except forA. holosericea, which had a mortality rate of 15.9%.A. indica andA. holosericea showed the highest stem diameter among species with 12.2 and 11.8 cm, respectively, at 56 MAP.A. senegal had the highest dry matter production with 22.3 t ha−1 at 56 MAP, followed byA. indica (12.0 t ha−1),A. holosericea (11.7 t ha−1) andB. rufescens (11.2 t ha−1), butA. holosericea was most productive at earlier harvests. OnlyA. senegal (6.4 t ha−1) andA. indica (5.1 t ha−1) had a significant wood production, whereasA. holosericea (5.7 t ha−1) had the highest phyllodes production. Leaves ofA. senegal andA. indica had highest CP contents of 258 and 214 g kg−1, respectively. The leaves of all species exceptA. gayanus had a higher CP:ME ratio than natural pasture in the region. The calorific values of firewood did not differ significantly among the species.A. nilotica, the species with one of the lowest firewood production, had the highest Fuelwood Value Index of 6.6. The choice of species for planting trees and windbreaks in the SSZ must be oriented along these criteria. Further research should be directed towards cost-benefit analyses, land tenure and property rights in combination with surveys on local knowledge of rural people.

The distribution of chemical constituents in the plant parts of six tropical forage grasses at early anthesis was studied. The forage grasses were guinea grass Panicum maximum (Jacq.); angleton grass Dichanthium aristatum (Poir.); gamba grass Andropogon gayanus (Kunth); buffel grass Cenchrus ciliaris (L.); birdwood grass Cenchrus setigerus (Vahl.); and rhodes grass Chloris gayana (Kunth.). Apart from ether extract, which generally decreased from the inflorescence down to the basal culm, and crude fibre, which increased from the inflorescence down to the basal culm, no clear gradient of constituents within the plants could be established for any of the forage grass species.

International audience; In the soudano–sahelian zone of Burkina Faso, the short-term fallow effect on the soil chemical and microbial properties was evaluated. In four farm experiments, two types of fallows were compared with cultivated fields: a natural vegetation fallow and a fallow enriched with Andropogon gayanus. After 5 to 7 years of experiments, soil chemical and microbial characteristics were determined in laboratory for 0–10 cm soil depth. Soil organic carbon (+64%), nitrogen (+35%), microbial biomass (+76%), basal respiration (+141%), and β-glucosidase activity (+86%) were significantly higher in fallows plots than in cultivated fields. The metabolic quotient was not significantly different on fallows compared to the cropped plots. Also, no significant difference was highlighted between natural vegetation fallows and the A. gayanus-enriched one.

The effects of vegetation barriers and tillage on runoff and soil loss were evaluated in an alley crop system at a research station in central Burkina Faso. On a 2% slope of a sandy loam various local species (grasses, woody species and a succulent) were planted as conservation barriers in order to examine their influence on sediment transport. After each erosive storm, runoff and sediment yield was determined. The dense effective barriers (Andropogon gayanus and dense natural vegetation) slow down flow velocity, build up backwater and promote sedimentation uphill. The through flow in the less effective barriers with woody species and succulents (Ziziphus mauritania and Agave sisalana) was slightly hampered and flow velocity was not reduced enough, resulting in a higher soil transport. Under degraded conditions soil loss diminished 50% with less effective and 70–90% with effective barriers. During the initial cropping phase (light tillage; sowing) erosion was reduced 40–60% with effective barriers and showed an increase of 45% with less effective barriers. In the full tillage (weeding) period erosion decreased by 80–90% for effective and 70% for less effective barriers, aided by the development of the barrier and the crop on the alley. Barriers of natural vegetation and A. gayanus are preferred for diminishing soil loss. Sediment yield could best be predicted by the erosivity index (AIm), second best by runoff amount (mm), closely followed by maximum peak intensity. All these parameters are related to the volume of overland flow needed to transport soil particles. Correlation of soil loss with small rain showers was poor and correlation with big showers was good. Sediment transport with no barrier had the highest correlation, closely followed by less effective barriers. Due to the heterogeneity in development of the effective barrier, correlations were much lower. The bulk of soil loss was only dependent on a few extreme events during the observation period.

Efficient use of external inputs and water conservation are a prerequisite of sustainable agricultural productivity in semiarid West Africa. A field experiment was carried out during 3 years (2000-2002) at Saria in semiarid Burkina Faso (800 mm of annual rainfall, PET of 2000 mm per year) to assess the effects of stone rows or grass strips of Andropogon gayanus Kunth cv. Bisquamulatus (Hochst. Hack.) as soil and water conservation (SWC) measures, the sole application of an organic (compost-N) or mineral (urea-N) nitrogen and the combined use of SWC and compost-N or urea-N on N flows and balances. The trial was conducted on a Ferric Lixisol with 1.5% slope and comprised nine treatments in two replications. The SWC measures were put along contours lines. During the three consecutive years, all treatments induced negative annual N balances (-75 to -24 kg N ha-1). The main factors explaining these negative balances were N exports by sorghum biomass and soil erosion-induced N losses. Large amounts of N (7 kg N ha-1 per year in 2000 and 44 kg N ha-1 per year in 2002) were lost in the control treatment through runoff and eroded sediments, which corresponds respectively to about 10 and 43% of the total outflow of N. Sole stone rows and grass strips reduced erosion N losses to 8 and 12%, respectively, of the total annual loss. The combined application of SWC measures and nutrients inputs reduced erosion N losses to only 2-7% of the annual N loss. The application of urea-N or compost-N led to the lowest soil N mining over the 3 years, whereas the highest N mining was observed in plots without added N. We conclude that N mining in poor fertile soils of West Africa can be mitigated through an integration of local water and nutrient management practices. (Resume d'auteur)

Nutrient limitation is the main cause of per capita decline in crop production in the Sahel, where water shortage also limits an efficient use of available nutrients. Combining soil and water conservation measures with locally available nutrient inputs may optimize crop production and economic benefit in cereal-based farming systems. A study conducted in 2001 and 2002 at Saria, Burkina Faso (annual rainfall 800 mm, PET of 2000 mm yr–1) assessed the combined effects of two types of semi-permeable barriers (stone rows and grass strips of Andropogon gayanus Kunth cv. Bisquamulatus (Hochst.) Hack.) and the application of compost or urea on sorghum performance and economic benefits. The field experiment was carried out on a Ferric Lixisol, 1.5% slope and comprised 9 treatments in which the barriers were put along contours and combined with compost-N or urea-N. Installation of stone rows or grass strips without addition of nutrient inputs was not cost effective, although it induced sorghum yield increase (12–58%) particularly under poor rainfall conditions. Combining compost with stone rows or grass strips significantly increased sorghum yield that induced positive interaction effects (mean added effects of 185 kg ha–1 for stone rows combined with compost-N and 300 kg ha–1 for grass strips combined with compost-N). Economic benefits were substantial (109 480 to 138 180 FCFA ha–1) when compost-N was added to both stone rows and grass strips, whereas limited economic benefits were observed with the application of urea-N (1120 to 22 120 FCFA ha–1). This may provide farmers with capital to invest in soil management and may also contribute to poverty alleviation in sub-Saharan Africa.

The comparative decomposition of tropical leaf litters (e.g. Andropogon gayanus, Casuarina equisetifolia, Faidherbia albida) of different qualities was investigated under laboratory conditions during a 60-day incubation period conducted with a typical oxisol. Total CO2-C, soil inorganic N, microbial biomass (fumigation-extraction), β-glucosidase and dehydrogenase activities were determined over the incubation to assess how they responded to the addition of inorganic N (+N). Cumulative CO2-C evolved from the litter-amended soils was higher than that recorded for the unamended control soil. For the unfertilized treatment (0 N), correlation coefficients calculated between initial chemical data and CO2 flux during the first day of incubation were r =0.963 for water soluble-C and 0.869 for soluble carbohydrates (P

The objective of this study was to assess the agronomic, morphogenic and structural characteristics of tropical forage grasses during the establishment phase and throughout the second year in northeast Brazil. The treatments included 9 grasses: Brachiaria humidicola (koronivia grass), Brachiaria hybrid cv. Mulato, Brachiaria brizantha cvv. Piatã, Xaraés and Marandu, Brachiaria ruziziensis (ruzi grass), Brachiaria decumbens (signal grass), Panicum hybrid cv. Massai and Andropogon gayanus (gamba grass). The grasses were planted in a randomized complete block design with 4 replications. The following parameters were measured: total forage production, leaf:stem ratio, tiller population density, number of dead tillers, leaf emergence rate, phyllochron, leaf elongation rate, stem elongation rate, rate of leaf senescence, final length of leaf blade and life-span of leaves. In the establishment year, cv. Mulato produced the highest forage yields, followed by cvv. Xaraés and Massai, with gamba grass and koronivia grass worst. In the second year, cvv. Mulato, Xaraés and Marandu, and gamba grass showed highest forage production, while cvv. Massai and Piatã produced the least. All grasses showed a marked drop in production during the dry season. Cultivar Massai consistently had the highest leaf:stem ratio. The morphogenic and structural characteristics differed according to cultivar and season of the year. In general, leaf emergence rate, leaf elongation rate, stem elongation rate, rate of leaf senescence, final length of the leaf blade, number of live leaves per tiller and density of living tillers were higher in the rainy season, while the phyllochron and life-span of leaves were higher in the dry season. The results of this research highlight the potential of the Brachiaria cultivars Mulato and Xaraés, gamba grass and Panicum cv. Massai in subhumid Maranhão, northeast Brazil.

SummaryThe persistence under a close intermittent grazing regime of eight accessions of Stylosanthes guianensis, Stylosanthes macrocephala and Stylosanthes capitata in combination with Andropogon gayanus (cv. Planaltina) and Brachiaria decumbens (cv. Basilisk) was evaluated in small plots on a low fertility acid oxisol in the tropical savannah region of Brazil. Five accessions persisted for four seasons with both grasses, although legume yields were lower in the B. decumbens associations.S. macrocephala CIAT 1582 (CPAC 139), S. capitata CIAT 1019 (CPAC 704) and CIAT 1097 (CPAC 706) were the most productive accessions at the end of the experiment. The three accessions S. guianensis cv. Cook, S. capitata CIAT 1315 (CPAC 707) and CIAT 1405 (CPAC 846), which failed to persist, were destroyed by anthracnose (Colletotrichum gloeosporioides). This disease remains the primary factor limiting the use of Stylosanthes in the region. The value of small-plot grazing experiments is briefly discussed.

SUMMARYThe persistence and productivity under grazing of seven accessions of Stylosanthes macrocephala, Zornia latifolia and Zornia brasiliensis in combination with Andropogon gayanus (cv. Planaltina) were investigated in small plots at two stocking rates on a low fertility, acid oxisol in the tropical savannah of the centre-west region of Brazil.Two new accessions of S. macrocephala CIAT 2039 (CPAC 1033) and CIAT 2053 (CPAC 1034) were more productive and persistent than the control cultivar Pioneiro. After 4 years there were no differences in dry-matter yield between the two accessions. No anthracnose (Colletotrichum gloeosporioides) problems were noted in these accessions. Animals refused to graze Z. brasiliensis accessions at any time during the trial. Stocking rate effects became pronounced over time and legume contents were highest in the treatment grazed at 3·0 animals/ha. The advantages of the small-plot grazing method used in the experiment are discussed.

SUMMARYExperiments made at Shika, Nigeria, over a period of 3 years showed that the drymatter response of Andropogon gayanus to applied N was curvilinear over the range 0–896 kg N/ha, with maximum yields being obtained at an application rate of about 500 kg N/ha. However, the highest return of dry matter per unit of fertilizer applied (14·4 kg D.M./kg N) occurred at 28 kg N/ha and there was only a modest increase in crude-protein content as N was increased, reaching a maximum of 10·5% at the highest level of N. Also, at both high and intermediate levels of N, A. gayanus was replaced by less desirable grasses.May, the beginning of the rainy season, was found to be the most efficient time to apply N, although reasonable dry-matter responses were obtained by applying N in the dry season. ‘Nitro-chalk’ and calcium nitrate were more efficient sources of N than urea, sodium nitrate and, in the long term, ammonium sulphate.

Andropogon gayanus Kunth var. bisquamulatus Hack, is a polymorphic bunch grass, widely distributed throughout most of the tropical and subtropical savannahs of Africa, south of the Sahara in areas with a long dry season. This grass was introduced into the Colombian Llanos from the Shika Agricultural Research Station, northern Nigeria, in 1974. Subsequent to its introduction, a series of agronomic trials were initiated by Centro Internacional de Agricultura Tropical (CIAT) at the Carimagua Research Centre and various national research institutions in Latin America to evaluate the potential of A. gayanus, primarily in the vast Ultisol and Oxisol savannah regions of the continent. As a result of further evaluation at a number of locations, accession A. gayanus var. bisquamulatus CIAT 621 was released in 1980 in Brazil as cv. Flanaltina and in Colombia as cv. Carimagua 1. During 1982–3 Peru, Venezuela and Panama subsequently released the same accession under the cultivar names of San Martin, Sabanero and Veranero, respectively. It is estimated that 168000 ha have been sown with A. gayanus in Brazil since 1982 (J. E. Ferguson, C. Sere and R. de Andrade, personal communication). Smaller areas have been established in other countries.

SUMMARYThe forage potential of Andropogon gayanus (gamba grass) was assessed in cutting experiments on a low fertility, acid Ultisol in Colombia. This grass recently introduced from Africa outyielded Hyparrhenia rufa, Panicum maximum, Brachiaria decumbens and Digitaria decumbena in various mixtures made up of a single grass and a single legume. A. gayanua performed well as a companion grass with the legumes Styloaanthes guianensis, Stylosanthes capitata and Centroaema sp., while B. decumbena suppressed the legumes planted in these trials during the 2nd year following establishment.

SUMMARYChanges in yield and quality of an Andropogon gayanus sward were traced throughout the 1964 wet season and part of the following dry season.Quality, in terms of crude-protein content, was highest at the beginning of the wet season, but yield increased to a maximum at the beginning of the dry season. Once flowering was completed in October, herbage quality fell to a very low level. It was concluded that the best time to cut for hay was in early October, at which time the crude-protein content showed a small but significant increase. Regrowth measurements taken in mid-November indicated the benefit of taking an early hay cut in July as a means of producing better quality hay at the end of the rains.During the early vegetative phase of growth leaf production was greater than stem production. Quality was high because the leaves contained a higher content of crudeprotein, calcium, phosphorus and carotene than the stems. During the reproductive stage of growth, comprising stem elongation in September culminating in anthesis in early October, quality was lower due to the high fibre content of the stems. The increase in crude-protein in early October, coincided with the expansion of new leaves on the flowering stems.It was concluded that throughout most of the latter part of the growing season A. gayanus did not provide adequate supplies of crude-protein, calcium and particularly phosphorus for normal cattle growth, especially after flowering was completed in late October.

SummaryHerbage production from twelve perennial grasses was analysed under two frequencies of defoliation. There were differences in the speed of establishment from seed, Heteropogon contortus, Pennisetum pedicellatum and P. polystachyon being most rapid. Once the grasses were established, the highest yields were obtained from Andropogon gayanus and Brachiaria brizantha and the lowest from Paspalum notatum. Yields were higher at the lower frequency of cutting. There were large differences in production throughout each year, with yields during winter and the dry season (November to April) only about one-tenth of those obtained in the rainy season. A. gayanus, B. brizantha, Chloris gayana and Dichanthium caricosum gave higher yields than other species during winter. Variations in yield between species could generally be ascribed to variations in the extension of leaf area, although some species maintained high net assimilation rates during unfavourable growth periods.

Investigations of isolating barriers which may be operating within the perennial grass species Andropogon gayanus are described and their significance to the selection programme discussed. The taxonomy and cytological variation, the degree of crossfertilization and the effect of variation in time of flowering are considered.