Microbial succession and changes in carbon and nitrogen during decomposition of leaf litters of Tephrosia candida (Roxb.) DC. and Oryza sativa L. under shifting cultivation in Mizoram, northeast India

The present study aims to understand microbial succession and dynamics of dry matter, carbon and nitrogen during the decomposition of leaf litters of Tephrosia candida (Roxb.) DC. and Oryza sativa L. in two fallow lands (FL) of 3 years (FL-3) and 8 years (FL-8) following shifting cultivation in Mizoram. A total of 64 microorganisms were isolated from two leaf litters by serial dilution method, out of which 13 microbes were identified as decomposers as they exhibited a positive response towards the enzyme activity. Among these 13 microorganisms, 4 (SKT 02, SKT 05, SKT 09 and SKT 020) were bacteria (Streptobacillus sp. and Bacillus sp.), 5 (SKT 033, SKT 034, SKT 035, SKT 040 and SKT045) were fungi (Microsporum sp., Rhizopus sp. and Aspergillus sp.) and 4 (SKT 030, SKT 052, SKT 053 and SKT 060) were actinomycetes (Streptomycetes sp.). T. candida leaf litter possessed low initial Carbon/Nitrogen (8.77) and Lignin/Nitrogen ratio (2.29) and considered a high-quality resource exhibiting higher decomposition rate. Mass loss of carbon and nitrogen (~ 40-80%) was maximum during the initial two months, which slowed down in the later period of decomposition. It was concluded that the number of bacteria, fungi and actinomycetes regulate organic matter and nutrient dynamics in the soil through various enzymatic actions on high- and low-quality litters. The combination of O. sativa and T. candida litter is recommended to manage soil fertility in shifting cultivation of Mizoram,Northeast India.

Soil carbon stock in different land-use systems in the hilly terrain of Mizoram, Northeast India

Soil carbon is one of the most affected variables to land-use change in tropics. The soil carbon flux plays a major role in regulating microbial activities and nutrient distribution in soil. This study aimed to evaluate the soil carbon stock in various land uses at different depths in the hilly terrain of Mizoram, Northeast India. Soil samples at 0-10 cm, 10-20 cm and 20-30 cm soil depths were collected from Rubber plantation (RP), Oil palm plantation (OPP), Teak plantation (TP), Bamboo Forest (BF), 5 years fallow (5YF), 10 years fallow (10YF), Tephrosia candida plantation (TCP), Horticulture garden (HORT), Homegarden (HG) and Natural forest (NF). Soil carbon stock varied significantly (p <0.05) across the land uses and depths. The soil under Tephrosia candida stand had significantly (p <0.05) higher values of C stock (73.66 Mg ha-1) which may be due to high biomass, dense vegetative cover and high C in root exudates. The minimum C stock estimated in Horticulture garden (43.28 Mg ha-1) is probably due to reduced soil organic matter. Soil carbon stock in Homegarden, Teak plantation, Bamboo forest and Rubber plantation ranged from 46.82 Mg ha-1 to 59.34 Mg ha-1 whereas 5 years and 10 years fallow land, Natural forest and Oil palm plantation ranged from 61.35 Mg ha-1 to 73.35 Mg ha-1. The study indicated that the land use change in the mountainous region significantly affected the carbon stock in the soil. A proper land use management strategies to increase the soil organic matter is recommended to enhance the carbon stock in this region.

Tephrosia candida (white Tephrosia).

T. candida is a shrub 2-3 m tall, thought to be indigenous to Malaysia, and has been introduced and become naturalized in many parts of the tropics, including: Vietnam, Bhutan, Myanmar, India, Sri Lanka, Papua New Guinea, Indonesia, New Zealand, Philippines, Hawaii, and Puerto Rico. It is drought-tolerant, and commonly used in agroforestry systems. It grows well on acid and impoverished soils. Its soil improving characteristics have led to its use as a pioneer plant, in contour hedgerows to prevent soil erosion on steep slopes, as a shade tree in agroforestry systems (Nguyen and Thai, 1993), and as a nurse tree for commercial timber species (e.g. for Shorea robusta in India; Krishnaswany, 1956). It is one of the most common green manure species planted in Vietnam. Extracts from T. candida have insecticidal properties (Stoll, 1996). The flowers and fruits are susceptible to damage from Maruca vitrata (Chan Dang Dinh, 1982).

Growth, nutritive value and dry matter degradability of three Tephrosia species

Two trials were carried out to evaluate the potential of Tephrosia bracteolata (TB), Tephrosia candida (TC) and Tephrosia linearis (TL) for animal feed. In an 18-week growth experiment, Tephrosia species differed (P <0.05) in leaf number (LN) and stem height (SH). TB and TL had apparent (P<0.05) early and persistent growth than TC until weeks 12 - 18 when all retarded in growth at the commencement of flowering. TC however, increased geometrically in LN and SH. There were significant (P<0.05) differences among the species in dry matter (DM) and acid detergent fibre (ADF). The DM, CP, NDF, ADF, EE and ash range from 30.0, 41.8, 24-26.5, 62.3–68.5, 45.8 - 48.4, 2.3-2.6 and 5.6-6.2% respectively. Calcium and sodium were highest (P<0.05) in TB and TL. species but had similar composition in P, Mg and K. In the second trial, dry matter disappearance and CP release were determined. The Tephrosia species were not significantly (P>0.05) different in degradation characteristics. Lower amounts of crude protein (10-14.81%) was released in the three Tephrosia species. As a result of rapid growth, high nutritive value and easily rumen degradable dry matter of Tephrosia shrubs, ruminants could benefit immensely from the plants.

Investigation of Shade Tree Species Used in Tea Garden in Bangladesh

The shade trees are an integral component of tea cultivation in Bangladesh. The shade trees are essential for modulating the environment of the tea ecosystem, enriching the soil fertility, reducing temperature and the evaporative capacity, conserve soil moisture and helps in the control of certain pests and diseases which are positively thermotropic in nature. The shade trees provide partial shade to the tea plants, which is important for improving the quality of the tea leaf. The right type of shade trees and their proper management is a prerequisite for successful tea crop growing. For this persists, a floristic exploration of shade trees was carried out at fifteen tea gardens in Chattogram and Moulvibazar District of Bangladesh from November 2017 to December 2018. During the investigation, a total of 44 species of Angiosperm representing 31 genera of 9 families was enlisted. For every species, scientific name, vernacular name, status, and necessary photographs are mentioned. In the assessment, the Fabaceae family shows the highest number of shade trees comprising 19 genera and 31 species. The most common permanent shade tree species among the tea gardens are Albizia odoratissima, A. chinensis, A. lebbeck, A. lucidior, A. procera, and Derris robusta. Indigofera teysmannii is frequently using as a temporary shade species in all investigated tea gardens. Cajanus cajan, Tephrosia candida, Tephrosia candida, Gliricidia sepium, Erythrina lithosperma and Desmodium gyroides species are also used as temporary shade trees in many tea gardens. Further investigations, however,are required to find out the right type of shade tree species on the growth and yield of tea plants in tea cultivation areas of Bangladesh. SAARC J. Agri., 18(1): 219-237 (2020)

Effectiveness of Tephrosia vogelii and Tephrosia candida Extracts against Common Bean Aphid (Aphis fabae) in Malawi

Common beans (Phaseolus vulgaris) remain an important dietary protein source in Malawi. However, its production is highly hindered by insect pest and disease attack. The study aimed at evaluating the effectiveness of Tephrosia vogelii and Tephrosia candida extracts against bean aphid (Aphis fabae). The evaluation involved two botanical extracts at three different concentrations (0.5%, 2%, and 5% w/v) against bean aphid. Plant extracts (leaves) were air-dried and milled. Powders were then soaked in a 2-litre plastic bucket of cold water. Results indicated that there was significant difference (P<0.05) among treatments. The effectiveness of the treatments was based on reduction in aphid population per plant, pod length, and bean yield. Pod length and bean yield were higher in T. vogelii and Karate as compared to untreated and T. candida. There was a high mortality rate of aphid on the plots treated with T. vogelii compared to plots treated with T. candida at the same concentration. Though these two plant extracts were not as effective as the synthetic insecticide in reducing aphid population, they were considerably and significantly found to be effective; hence, its use by poor-resource farmers is recommended in the protection of bean against aphid.

Effect of density of Tephrosia candida stands on soil characteristics

With one-year-old Tephrosia candida trees as experimental material, influence of stand density on soil nutrient content and enzyme activity was studied. The results showed that density had little influenced on pH value in 2, 4 and 8 trees m2 stands. The contents of soil organic matter, effective nitrogen and effective phosphorus significantly increased in 2 trees m2 stands. The contents of soil organic matter and effective nitrogen significantly increased, whereas total N, total P, total K, effective N, effective P and effective K significantly decreased in 4 trees/m2 stand. Soil organic matter and nutrients except for total P significantly decreased in 8 trees m2 stand. Among the three density stands, the activities of urease, catalase and phosphatase were the lowest in 8 trees m2 stand.

Impact of fishing with Tephrosia candida (Fabaceae) on diversity and abundance of fish in the streams at the boundary of Sinharaja Man and Biosphere Forest Reserve, Sri Lanka

Local communities in some Asian, African and American countries, use plant toxins in fish poisoning for fishing activities; however, the effects of this practice on the particular wild fish assemblages is unknown. This study was conducted with the aim to investigate the effects of fish poisoning using Tephrosia candida, on freshwater fish diversity and abundance in streams at the boundary of the World Natural Heritage site, Sinharaja Forest Reserve, Sri Lanka. A total of seven field trips were undertaken on a bimonthly basis, from May 2013 to June 2014. We surveyed five streams with similar environmental and climatological conditions at the boundary of Sinharaja forest. We selected three streams with active fish poisoning practices as treatments, and two streams with no fish poisoning as controls. Physico-chemical parameters and flow rate of water in selected streams were also measured at bimonthly intervals. Fish were sampled by electrofishing and nets in three randomly selected confined locations (6 x 2 m stretch) along every stream. Fish species were identified, their abundances were recorded, and Shannon-Weiner diversity index was calculated for each stream. Streams were clustered based on the Bray-Curtis similarity matrix for fish composition and abundance. Physico-chemical parameters of water were not significantly different among streams (P > 0.05). A total of 15 fish species belonging to four different orders Cypriniformes, Cyprinodontiformes, Perciformes and Siluriformes were collected; nine species (60 %) were endemic, and six (40 %) were native species. From these, 13 fish species were recorded in streams with no poisoning, while five species were recorded in streams where poisoning was practiced. Four endemic and one native fish species were locally extinct in streams where fish poisoning was active. Fish abundance was significantly higher in control streams (32-39/m2) when compared to treatment streams (5-9/m2) (P < 0.05). We concluded that fish poisoning with T. candida may have resulted in a significant reduction in species richness, total abundance and Shannon-Weiner diversity index of fish species in the studied streams at the boundary of Sinharaja forest. We recommend that this fishing practice should be strictly regulated, and to inform local communities about the legal status of fish poisoning, its consequences and the importance of fish diversity for local livelihoods and conservation purposes.