Effects of Green Manure Mixed Cropping Patterns on Physical and Chemical Properties of Soil and Economic Characters of Flue-cured Tobacco

[Objective] The aim was to clear the suitable green manure cropping pat- terns in Xiangxi tobacco-planting areas. [Method] 8 treatments were set to study the effects of the monoculture and mixed cropping of common vetch （Vicia gigantea Bge.）, perennial ryegrass （Lofium） and rapeseed （Brassica campestris L.） on physi- cal and chemical properties of soil and economic characters of flue-cured tobacco. [Result] （1） Green manure turnover can reduce soil bulk density by 1.08%-8.62%, and the effect of green manure mixed cropping pattern was the best. （2） Green manure turnover also can increase the soil nutrient, soil organic matter, total nitro- gen （N）, total phosphorus （P）, total potassium （K）, alkali-hydrolyzale N, rapidly available P and rapidly available K by 1.44%-6.10%, 0.01-0.12 g/kg, 1.89%- 11.32%, 0.12%-3.56%, 1.06%-11.76%, 0.04%-18.93% and 0.98%-23.12%, respec- tively, and the effect of the monoculture of common vetch was the best.（3） The overall change of soil pH was not obvious.（4）Green manure turnover can increase the yield and output of flue-cured tobacco, and the effect of the monoculture of common vetch was the best. [Conclusion] The monoculture of common vetch can be generalized in the dry land of Xiangxi tobacco-planting areas.

The Removal and Remediation of Phenanthrene and Pyrene in Soil by Mixed Cropping of Alfalfa and Rape

The mechanisms and efficiencies of the removal and remediation of polycyclic aromatic hydrocarbons （PAHs） in soils by different planting patterns with rape （Brassica campestris） and alfalfa （Medicago sativa） were studied by pot experiments in a greenhouse. Results showed that the remediation efficiencies under mixed cropping of alfalfa and rape significantly exceeded those under single cropping when the initial concentrations of phenanthrene and pyrene were at 20.05-322.06 mg kg^-1 and 20.24-321.42 mg kg^-1, respectively. After 70 days plantation of crops, the contents of extractable PAHs in soils under mixed cropping were much lower than those under single cropping. About 65.17-83.52% of phenanthrene and 60.09%- 75.34% ofpyrene was removed from the soils under mixed cropping, respectively, which were averagely 43.26 and 40.38% for phenanthrene, and 11.03 and 16.29% for pyren higher than those under single cropping. Alfalfa or rape did absorb and accumulate PAHs from the soils apparently; the PAHs concentrations in plants monotonically increased with the increase of initial PAHs concentrations in soil; the accumulations of PAHs in plants showed following sequence as roots 〉 above parts, phenanthrene 〉 pyrene and single cropping 〉 mixed cropping at same contamination level. Despite the presence of vegetation significantly enhanced the remediation of PAHs in soils, contributions of abiotic loss, plant uptake, accumulation and microbial degradation was much lower than those of plant-microbial interactions in the process of phytoremediation. Thus plant-microbial interactions are the main mechanisms for the remediation enhancement of soil PAHs pollution under mixed cropping models. Results suggested a feasibility of the establishment of multi-species phytoremediation for the improvement of remediation efficiencies of PAHs, which may decrease accumulations of PAHs in crops and thus reduce their risks.

Effect of mixed-cropping and water-stress on macro-nutrients and biochemical constituents of rhizomatous medicinal plants in Central Himalaya,India

Plants in the alpine zone mainly depend on the reserved food materials stored in their rhizomes for the next growing season. We investigated the effect of mixed cropping （Phaseolus vulgaris L. var. Pinto） with four rhizomatous medicinal plants, i.e., Angelica glauca, Arnebia benthamii, Rheum emodi and Pleurospermum angelicoides as well as three levels of water stress treatment under two conditions （shade net and open field） on macronutrients （NPK） and biochemicals （carbohydrates and protein）. The experiment was conducted by completely randomized design （CDR）. The data were analyzed with ANOVA as well as CDR. The experimental results show that in all the species shade conditions with sever water stress （SSWS） increased the level of macronutrients （NPK）. However, （N） concentration was highest under shade with mixed cropping （SMIX）. Under SMIX, carbohydrate content was highest than open field control conditions （CONT）. This investigation results demon- strate that mixed cropping of medicinal plants with Phaseolus vulgaris could be a good livelihood option in the mountainous regions of Indian Central Himalaya. And the water-stress conditions along with mixed cropping could improve the biochemical constituents in the rhizome of these species.

Allelopathic effects of leaf litters of Eucalyptus camaldulensis on some forest and agricultural crops

Allelopathic effects of different doses of Eucalyptus camaldulensis leaf litters were investigated through an experiment in the green house of Institute of Forestry and Environmental Sciences, Chittagong, Bangladesh. Three popular agricultural crops： Falen （Vigna unguiculata）, Chickpea （Cicer arietinum）, Arhor （Cajanus cajan） and two widely used plantation trees： Sada koroi （Albizia procera） and Ipil ipil （Leucaena leucocephala） were selected as bioassay species. Experiment was set on tray at room temperature 27℃. The effects of different doses of leaf litter extracts were compared to the control. Results suggest that leaf litters of E, camaldulesis induced inhibitory effects, It was also found that the effect depend on concentration of extract and litterfall, type of receiver species. Higher concentration of the materials had the higher effect and vice versa. Though all the bioassay species were suppressed some of them showed better performance. Vigna unguiculata, Cicer arietinum are recommended in agroforestry based on this present Experiment output. In mixed plantation, Leucaena leucochephala is a better choice while compared to Albizia procera.

Allelopathic effects of Leucaena leucocephala leaf litter on some forest and agricultural crops grown in nursery

An experiment was conducted to assess the effect of leaf litter of Leucaena leucocephala on two forest crops Sada koroi （Albizia procera）, Ipil ipil （L. leucocephala） and three agricultural crops Falen （Vigna unguiculata）, Chickpea （Citer arietinum） and Arhor （Cajanus cajan） in the nursery of the Institute of Forestry and Environmental Sciences, Chittagong University, Bangladesh, in a Randomized Block Design. Results suggested that leaf litters ofL. leucocephala induced inhibitory effects on germination and growth of bioassay. It was also found that the effect depended on concentration of extract and litterfall, type of receptor species. Higher concentration of the materials had the higher effect and vice versa. Growth response of receptor crops varied with the variation of leaf litter application. The study revealed that application of low-dose leaf litter specially litter of 10 g·m^-2 had stimulating effect on shoot growth of C. arietinum, Vunguiculata and A. procera. While in all other cases significant inhibitory effect was observed and it was significantly increased with the increase of leaf litter application. However, the trend of inhibition was uneven with treatments. Root growth was found to be more affected than shoot growth.

Diversity and endophytic fungal composition in Ananas comosus(L.)Merr.var queen cultivar isolated from three different growing conditions

Present study deals with the isolation of endophytic fungi from leaf and root explants of Ananus comosus var queen from three growing conditions i.e.wild,cultivated as monoculture and cultivated as mixed cropping system with rubber plants.A total of twenty-nine endophytic fungal strains along with two nonsporulating forms were isolated from the host plant from three experimental plots.The maximum numbers of fungal strains were found belong to family Aspergillaceae and order Eurotiales.The highest rates of colonization and isolation(p<0.05)of endophytic fungi have been reported in wild foliar explants(95.53±0.53)and monoculture(1.02±0.01),respectively.The highest relative frequency was observed among isolated fungal strains in the case of Lasiodiplodia theobromae isolated from the leaf and root of wild(26.22%)and monoculture(29.62%)explants.In L.theobromae and Aspergillus flavus,isolated from the leaf and roots of wild(21.66%)and monoculture(14.66%)explants showed the highest colonization frequency.Current findings showed that the distribution of fungal endophytes and their relative frequency in host plants vary in three different growing conditions.