Effects of Leafy Biomass of Some Agroforestry Tree Species on Light Fraction Organic Matter Content of Soil

A study on light fraction organic matter was carried out on soil where leafy biomass of Enterolobium cyclocarpum (ENCY), Treculia africana (TRAF), Anogeissus leiocarpus (ANLE), Gliricidia sepium (GLSE), Leuceana leucocephala (LELE) were used as mulch. Soil samples were collected in each plot at two auger points 0-15 cm and 15-30 cm and then homogenized for laboratory analysis. ANLE was observed to have significant higher values (6.37, and 6.52) on soil pH, and at day 28 on soil pH respectively. Light fraction organic carbon (LFC) also experienced significant higher value (3.48 g/kg) at day 28 in ANLE leafy biomass. However, LELE had the significant highest values (0.37 g/kg, and 1.44 g/kg) on light fraction nitrogen (LFN), and at day 42 on LFN respectively, while, microbial population count (MP) was highest in ENCY (183516667 cfu/g), and (726666667 cfu/g) at day 14 respectively. It is therefore concluded that the leafy biomass investigated had improving positive effects on light fraction organic matter. Keywords: Organic matter, Soil content, Light fraction, Leafy biomass, Tree species

Évaluation de la qualité de composts à base de biomasses feuillées de deux espèces agroforestières à Cassou, Centre-Ouest, Burkina Faso

Albizia lebbeck (L.) Benth. and Gliricidia sepium (Jacq.) Kunth ex Walp. are species of the leguminosae group which are promoted in agroforestry. This study aimed at assessing the quality of leafy biomass composts of these two species in order to use them as green manure. For this, composts based on leafy biomasses of Albizia lebbeck and Gliricidia sepium have been characterized. The phytotoxicity tests of the composts was carried out using a germination test of Zea mays (L) and Arachis hypogaea (L). The effect of composts on the growth of Adansonia digitata L. and Sclerocarya birrea (A.Rich.) Hochst. subsp. Also evaluated. Comparison of means tests and repeated measures ANOVA were used to compare types of composts. The results show that these composts were not toxic. The average carbon, nitrogen, pHe and C / N ratios of the composts of Albizia lebbeck and Gliricidia sepium were in accordance with international standards. The effect of Gliricidia sepium compost on the growth of Adansonia digitata and Sclerocarya birrea was better than that of Albizia lebbeck and cow dung (P <0.05). The compost from the leafy biomass of Gliricidia sepium is of very good quality while that of Albizia lebbeck is of fairly good quality. The biomasses of these two species therefore constitute good material for composting. These results can be used to improve crop production in agroforestry. Albizia lebbeck (L.) Benth. et Gliricidia sepium (Jacq.) Kunth ex Walp. sont des espèces de légumineuses promues dans l’agroforesterie. Cette étude visait à évaluer la qualité des composts de biomasses feuillées de ces deux espèces afin de les utiliser comme engrais verts. Pour cela des composts à base de biomasses feuillées de Albizia lebbeck, de Gliricidia sepium ont été caractérisés. La phyto-toxicité des composts a été évaluée à l’aide d’un test de germination de Zea mays (L) et Arachis hypogaea (L). L’effet des composts sur la croissance de Adansonia digitata L. et Sclerocarya birrea (A.Rich.) Hochst.subsp. a également été évalué. Des tests de comparaisons de moyennes et une ANOVA à mesures répétées ont permis de comparer les types de composts. Les résultats montrent que les composts évalués n’étaient pas toxiques. Les teneurs moyennes en carbone, en azote, les pHe et les rapports C/N des composts de Albizia lebbeck et de Gliricidia sepium étaient conformes aux normes internationales. L’effet du compost de biomasse de Gliricidia sepium sur la croissance de Adansonia digitata et de Sclerocarya birrea était mieux que celui de Albizia lebbeck et la bouse de vache (P< 0,05). Le compost de biomasses feuillées de Gliricidia sepium est de très bonne qualité tandis que celui de Albizia lebbeck est d’assez bonne qualité. Les biomasses de ces deux légumineuses constituent donc un bon matériel pour le compostage. Ces résultats peuvent servir à améliorer la production végétale en agroforesterie.

Dynamics in tropical lowland soil nutrients as influenced by leafy biomass of some agroforestry trees

One of the major challenges of the developing countries is the production of sufficient food for the rapidly increasing population, and over cultivation of land resulting to soil infertility. Hence, transfer of nutrients through tree biomass contribute to micro variability in soil fertility and plant growth. A field research was conducted in the forest nursery of the Federal University of Agriculture, Abeokuta (FUNAAB), Nigeria to investigate the response of tropical lowland soil to the application of leafy biomass of some agroforestry tree species; Anogeissus leiocarpus, Enterolobium cyclocarpum, Gliricidia sepium, Leuceana leucocephala and Treculia africana at the rate of 5 tons per hectare (5t ha-1 or 5000 kg ha-1). The soil samples were collected at 2, 4, 6, 8 and 10 weeks after application (WAP). Split plot experimental design was used with the time of soil sampling as main plots, mulch type as sub-plots. Data were statistically analysed using Analysis of Variance (ANOVA) at p =0.05 on pH, organic carbon, total N, P, K, Ca, Mg and Na. L. leucocephala had highest nutrient release values on; total nitrogen (0.019±0.002), calcium (41.07±3.75), sodium (139.0±36.927). Control plots was high in organic carbon (3.12±0.067), as well as pH (6.45±0.029). However, E. cyclocarpus also had highest nutrient contents in potassium (90.0±4.79) and magnesium (152.50±24.575). It is concluded that L. leucocephala had fast decomposition rate and its rapid nutrient release is a good alternative to improving soil nutrients in lowland tropical soil and therefore recommended as a better choice soil improvement agroforestry tree leafy biomass among other species as investigated from the study.

Developing Allometric Equations for Estimating Shrub Biomass in a Boreal Fen

Allometric equations for estimating aboveground biomass (AGB) from easily measured plant attributes are unavailable for most species common to mid-continental boreal peatlands, where shrubs comprise a large component of the vegetation community. Our study develops allometric equations for three dominant genera found in boreal fens: Alnus spp. (alder), Salix spp. (willow) and Betula pumila (bog birch). Two different types of local equations were developed: (1) individual equations based on genus/phylogeny, and (2) a general equation that pooled all individuals regardless of genera. The general equation had a R2 = 0.97 (n = 82), and was not significantly different (p > 0.05) than any of the phylogenetic equations. This indicated that a single generalized equation is sufficient in estimating AGB for all three genera occurring in our study area. A closer look at the performance of the general equation revealed that smaller stems were predicted less accurately than larger stems because of the higher variability of leafy biomass found in small individuals. Previously published equations developed in other ecoregions did not perform as well as our local equations.

Lignocellulosic Fermentation of Wild Grass Employing Recombinant Hydrolytic Enzymes and Fermentative Microbes with Effective Bioethanol Recovery

Simultaneous saccharification and fermentation (SSF) studies of steam exploded and alkali pretreated different leafy biomass were accomplished by recombinantClostridium thermocellumhydrolytic enzymes and fermentative microbes for bioethanol production. The recombinantC. thermocellumGH5 cellulase and GH43 hemicellulase genes expressed inEscherichia colicells were grown in repetitive batch mode, with the aim of enhancing the cell biomass production and enzyme activity. In batch mode, the cell biomass (A600 nm) ofE. colicells and enzyme activities of GH5 cellulase and GH43 hemicellulase were 1.4 and 1.6 with 2.8 and 2.2 U·mg−1, which were augmented to 2.8 and 2.9 with 5.6 and 3.8 U·mg−1in repetitive batch mode, respectively. Steam exploded wild grass (Achnatherum hymenoides) provided the best ethanol titres as compared to other biomasses. Mixed enzyme (GH5 cellulase, GH43 hemicellulase) mixed culture (Saccharomyces cerevisiae, Candida shehatae) system gave 2-fold higher ethanol titre than single enzyme (GH5 cellulase) single culture (Saccharomyces cerevisiae) system employing 1% (w/v) pretreated substrate. 5% (w/v) substrate gave 11.2 g·L−1of ethanol at shake flask level which on scaling up to 2 L bioreactor resulted in 23 g·L−1ethanol. 91.6% (v/v) ethanol was recovered by rotary evaporator with 21.2% purification efficiency.