IOSR-JAVS   Volume-4 ~ Issue-4 ~ JULY-AUG-2013

ABSTRACT: Shifting cultivation is the major cultivation in hilly region of North-Eastern India. Shifting cultivation cycles and landuses practices of shifting cultivated area of are considerably related. Fertility status of owing to the shrunk of jhum cycle (2-3 years); resulted deterioration of in soil health and ecological imbalance. So to keep shifting cultivation a sustainable farming system, we examine the relationship between fallow cycles (0-1, 3-5years, 5-7 years, 8-10 years and 12 years) and improved/alternated landuses (intermittent agriculture, agroforestry, abandoned jhum land) in relation to fertility status in shifting cultivated area of Chandel district of Manipur, India. In all landuses short term fallow cycle (3-5 years) deteriorated soil fertility attributes by significant reduction in soil pH, organic carbon and available and total major nutrients. With the increased of fallow cycles (>8 years) its fertility status in all the landuses were significantly restored except intermittent agriculture due to irregular crop fallow rotation. Among the landuses, abandoned jhum land were relatively stable in restoring soil in 5-7 years fallow cycle onwards due to sufficient surface coverage, lack of anthropogenic intervention and internal regulation. Soil restoration starts from 8-10 years onwards in agroforestry system dominated with soil enriching pulse crops and deep rooted nitrogen fixing trees and was remarkable improved from 25 years old pine dominated undisturbed secondary forest ecosystem. Therefore, adoption of improved appropriate landuses in combination with optimum fallow cycles 5-7 years more and proper combination of soil enriching crops and tress have the significant potential in restoring soil fertility status and sustain production in degraded jhum land of northeastern India.

Keywords - Fallow cycles, Improved landuses, Shifting cultivation, Soil fertility

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ABSTRACT: The objective of this study was to predict soil erodibility using soil properties of upper and lower tributary river (Enyong Creek and Ikpa river) basins wetland, comprising different soil groups or series. Mathematical formulation used for the nomograph of Wischmeier et al was used for the evaluation. Investigated soil properties included soil organic matter (SOM); granulometry of silt and clay; soil structure and permeability. The predicted K-factors, hence soil erodibility potentials, were high and significantly different (p<.05) from each catchment soil, and ranged between 0.0073 and 0.0827 for Ikpa River wetland, and between 0.0827 and 0.121 for Enyong Creek wetland. Percentage SOM was significantly different (P<0.01) between the wetlands, with Ikpa river wetland registering higher values. Percentage clay in Ikpa was generally higher than its values in Enyong Creek; other properties were not significantly different. Significant correlation was observed between silt percentage and erodibility factor. Further investigation is required between K-factor and influence of saturated hydraulic conductivity. However, the study provided baseline information on wetland erodibility for the reduction of soil susceptibility to erosion when considering any appropriate wetland development projects. Keywords: Soil erodibility, K-factor, river basin development, granulometry, wetland erosion.

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ABSTRACT: Reliable and sensitive quantification of Phytophthorainfestansin potato plant is of crucial importance in managing the multiple syndromes caused by this pathogen. A Real-Time polymerase chain reaction (PCR) assay was developed for the determination of P.infestans in host tissues. DNA levels of a highly virulent isolate were measured in different potato cultivars with varying degrees of resistance. Using SYBR Green and specific primers for P.infestans the minimal amount of pathogen DNA quantified was 0.0005ng/μl. Pathogen DNA was recorded at 24 hours postinoculation. Thereafter, the increase was rapid in susceptible cultivars and slower in resistant ones. The amount of pathogen DNA quantified in each potato cultivars correlated with susceptibility to late blight. Likewise, there was a relationship between the virulence of the pathogen and the degree of colonization. Differences also were found in pathogen amount among host tissues, with maximal pathogen biomass occurring in susceptible one. The real-time PCR technique developed in this study was sensitive and robust enough to assess both pathogen development and resistance to Late blight in different potato genotypes. Keywords: Phytophtohorainfestans, resistance, potato, cultivars, Real Time PCR

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