M. K. Hossain

Allelopathic effects of Mikania cordata on forest and agricultural crops in Bangladesh

Mikania cordata, an invasive weed is becoming a problem in the secondary degraded forests and plantations of Bangladesh, not only competing with but also releasing allelochemicals to cultivated crops. Allelopathic effects of the leaves of M. cordata were investigated through an experiment in the green house of the Institute of Forestry and Environmental Sciences, University of Chittagong, Bangladesh. Five economically important agricultural crops (Oryza sativa L., Triticum aestivum L., Vigna sinensis L., Abelmoschus esculentus L. and Amaranthus tricolor L.) and three forest crops (Acacia auriculiformis A. Cunn. ex Benth. & Hook, Albizia procera (Roxb.) Benth., and Paraserianthes falcataria (L.) Nielson) were used as bioassay species. Experiments were conducted on trays at an average room temperature 27xa0°C. The effects of different concentrations of leaf extracts were compared to controls. Water soluble allelochemicals of M. cordata inhibited the germination and initial growth of the tested agricultural and forest crops. Germination percent of forest crops declined with increasing concentration of extracts. The inhibitory effect on root elongation of forest crops was pronounced, whereas a stimulatory effect was found on P. falcataria up to a concentration of 25xa0%. Abelmoschus esculentus showed poor germination (%) and low shoot development (0.5xa0cm) and no development of taproot or lateral roots at treatment of 100xa0% concentration. The inhibitory effect was proportional to the concentrations of the extracts with higher concentrations producing stronger inhibitory effects. Lower concentrations showed some stimulatory effect. The inhibitory effect was pronounced in root and lateral root development rather than germination or shoot development of the crops. Mikania cordata should be eradicated for healthy growth and development of the forest and adjacent agricultural crops.

Improving Acacia auriculiformis seedlings using microbial inoculant (Beneficial Microorganisms)

A microbial inoculant, known as effective microorganisms (EM), was applied to determine its efficacy on seed germination and seedling growth in the nursery of Acacia auriculiformis A Cunn. ex Benth. The seedlings were grown in a mixture of sandy soil and cow dung (3:1) and kept in polybags; EM was poured at different concentrations (0.1%, 0.5%, 1%, 2%, 5% and 10%). Seed germination rate and growth parameters of seedlings — shoot and root lengths, fresh and dry weights of shoots and roots, vigor, volume, and quality indices and sturdiness — were measured. The nodulation status influenced by EM was also observed, along with the measurement of pigment contents in leaves. The highest germination rate (72%) was observed in 2% EM solution while the lowest (55%) was found in control treatment. The highest shoot and root lengths (30.6 cm and 31.2 cm respectively) were recorded in 2% EM and were significantly (p <0.05) different from control. Both fresh and dry weights of shoots were maximum (8.66 g and 2.99 g respectively) in 2% EM, whereas both fresh and dry weights of root were maximum (2.56 g and 1.23 g respectively) in 5% EM solution. Although the highest vigor index, volume index, and sturdiness (4450, 628 and 67.5 respectively) were found in 2% EM, the highest quality index (0.455) was found in 5% EM solution. The nodule number was higher at a very low (0.5%) concentration of EM but it normally decreased with the increase of concentration. The contents of chlorophyll a, chlorophyll b, and carotenoid were maximum (43.26 mg·L−1, 13.56 mg·L−1and 17.99 mg·L−1 respectively) in 2% EM. Therefore, low concentration of EM (up to 2%) can be recommended for getting maximum seed germination and seedling development of A. auriculiformis in the nursery.

Nursery practice on seed germination and seedling growth of Dalbergia sissoo using beneficial microbial inoculants

Nursery practice using microbial inoculants was performed to find out the efficacy of the inoculants on seed germination and seedling growth of sissoo (Dalbergia sissoo Roxb.). Microbial inoculants or effective microorganisms (EM) are a mixture of many different beneficial microorganisms in a solution. The seedlings were grown in a mixture of sandy soil and cowdung (3:1) kept in polybags with pouring EM solution at different concentrations (0.1%, 0.5%, 1%, 2%, 5% and 10%) before and after a week of sowing the seeds. Seed germination rate and growth parameters of seedlings were measured, such as, shoot and root length, vigor index, fresh and dry weight of shoot and root and total biomass increment. The nodulation status influenced by EM was also observed along with the measurement of pigment contents in leaves. The highest germination rate (69%) was observed in 2% EM treatment, followed by 67% and 65% in 1% and 5% EM. The highest shoot length (33.2 cm) was in 2% EM, whereas highest root length (26.3 cm) was in 1% EM. Both fresh and dry weights from shoot and root, were maximum (4.16 g and 1.57 g; 2.12 g and 0.83 g respectively) in 2% EM and were significantly (p ≤ 0.05) different from control. Vigor index was highest (4071) in 2% EM, which was significantly (p ≤ 0.05) different from control. Total dry weight increment was highest in 2% EM treatment, followed by 1% and 5% concentrations of EM. Nodulation number was higher at very low (0.1%) concentration of EM solution but it normally decreased with the increase of EM concentrations. The contents of chlorophyll a, chlorophyll b and carotenoid were highest (60.11, 17.05 and 42.48 mg·L−1 respectively) in 2% EM treatment and lowest (39.35, 13.55 and 27.29 mg·L−1 respectively) in control treatment. Therefore, low concentration of EM (up to 2%) can be used for getting maximum seed germination rate and seedling development of Dalbergia sissoo Roxb.

Effects of industrial and residential sludge on seed germination and growth parameters of Acacia auriculiformis seedlings

A study was conducted to evaluate the effects of sludge (industrial and residential) on seed germination and growth performance of Acacia auriculiformis seedlings at the nursery of Institute of Forestry and Environmental Sciences, Chittagong University (IFESCU), Bangladesh. Before sowing of the seeds, different combinations of sludge were incorporated with the nutrient-deficient natural forest soils. Seed germination and growth parameters of the seedlings (shoot and root length, collar diameter, fresh and dry weight of shoot, and root and total dry biomass) were recorded after one, two and three months of seed sowing. Physio-chemical parameters (pH, organic carbon, nitrogen, phosphorus, and potassium) and heavy metals (chromium, nickel, manganese, cadmium and zinc) of each treatment were also analyzed before sowing of seeds and after harvesting of seedlings. Results show that the seed germination percentage and the seedling growth parameters varied significantly in the soil added with sludge in comparison to control. The highest germination percentage (90%) was observed in the treatment of soil with residential sludge of 2:1 compared to control. The highest growth and biomass of the seedlings as well as the maximum percentage of organic carbon and nutrients (N, P and K) were also recorded in the same combination. Soil added with industrial sludge had a higher concentration of heavy metal than that of residential sludge. The highest concentrations of heavy metals were found in soil added with industrial sludge of 1:1. It is recommended that soil added with residential sludge of 2:1 provide good condition for better seed germination and growth of A. auriculiformis seedlings in degraded forest soil.

Pre-sowing treatments for improved germination and growth of two rare native species of Bangladesh

Pre-sowing treatments are expected to increase seed germination. This evaluates response to pre-sowing treatments and the growth performance of two native and rare tree species, Garuga pinnata Roxb. and Vitex glabrata R. Br. The hard seed coats were treated by rubbing with sand paper, nail clipping, and immersion in water and acid (H2SO4). Results indicate that G. pinnata showed a 90% germination rate and 30% germination energy when seed coats were nicked with a nail clipper. Rubbing with sand paper was the best pre-sowing treatment for V. glabrata, resulting a 80% germination rate and 30% germination energy. G. pinnata and V. glabrata seedlings from seeds soaked 24xa0h in water resulted in maximum heights and collar diameters. These were significantly higher (at pxa0<xa00.05) than those of other treatments. The results indicate that scarification or nicking of seeds may have some negative impacts on seedling growth. Therefore, it is difficult to recommend a pre-sowing treatment of seeds for achieving both maximum germination and good early seedling growth.

Assaying the allelopathic effects of Eucalyptus camaldulensis in a nursery bed incorporated with leaf litter

Allelopathic effects of Eucalyptus camaldulensis Dehnh. were confirmed in Petri dish and pot experiments in our previous studies. However, the degree to which such effects under controlled experiments exist in more complex ecological settings remains to be tested. Thus, the present study was carried out by incorporating different proportions of ground litter of E. camaldulensis in soil. The growth of three agricultural crops: falen (Vigna unguiculata (L.) Walp.), chickpea (Cicer arietinum L.), and arhor (Cajanus cajan (L.) Millsp.), and two tree species, kala koroi (Albizia procera (Roxb.) Benth.) and ipil ipil (Leucaena leucocephala (Lam.) de Wit) were tested. There were inhibitory effects of leaf litter on germination, shoot and root growth, leaf number, and collar diameter as well as a reduction of nodulation by legume crops (25–80% reduction). The extent of the effects was dependent on the proportion of leaf litter, the species and the type of traits. In contrast to shoot growth, the effect on root growth was more severe. No effect on germination was found with the agriculture crops while the two tree species showed reduced germination. The effect was greater in the presence of higher proportions of leaf litter mixed in soil while in some cases lower proportions stimulated growth. Not all species were suppressed; A. procera, C. cajan, V. unguiculata showed compatible growth while C. arietinum and L. leucocephala were found incompatible. This study provides evidence that E. camaldulensis has allelopathic potential under field conditions and a careful selection of associated crops in agroforestry systems is highly recommended.