Chemical characterization of an aqueous extract and the essential oil of Tithonia diversifolia and their biocontrol activity against seed-borne pathogens of rice

Journal of Plant Diseases and Protection - The high cost of chemical pesticides and their negative impact on the environment prompted the search for natural pesticides from plants. The objective of...     

Bioactive Chromodorolide Diterpenes from an Aplysillid Sponge

The known chromodorolides A (1) and B (2), and a new derivative chromodorolide C (3) have been isolated from an Australian sponge and characterized by 1D and 2D NMR experiments. The chromodorolides exhibited significant cytotoxicity against the P388 mouse leukaemia cell line, and also showed activity against the free-living larval stages of the parasitic nematodes Haemonchus contortus and Trichostrongylus colubriformis.     

Evaluation of environmental impact of the raised-bed-dike (Rong Chin) system along the Tha Chin river in Suphan Buri-Nakhon Pathom Provinces,Thailand

Vegetable cultivation on an embankment surrounded by water (raised-bed-dike system, Thai name rong chin) along the Tha Chin (Suphan Buri) river in the Suphan Buri and Nakhon Pathom Provinces was surveyed. The system was introduced by Chinese immigrants to produce vegetables in the river delta. The rong chin system in this area produced mainly Chinese kale, chili, bitter gourd, yard-long bean, taro, and sweet potato, while fruit trees and flowers were seldom cultivated, because of the flooding of the river in the rainy season. The amounts of nitrogen and phosphorus applied into field soils as fertilizers were far higher than those recovered in the harvested vegetables, indicating that only a limited portion of the nutrients was taken up by the crops and that part of the nutrients remained in the soils and in the dike water. Periodical flooding promoted leaching of the accumulated nutrients in the fields. Analyses of the soils and river waters revealed that phosphorus had started to accumulate in the environment, whereas only a small amount of nitrogen was detected in the river, canal, and dike waters, presumably because of the active uptake of nitrogen by biomass and denitrification.     

Soil organic carbon,nitrogen, and phosphorus distribution in stable aggregates of an Ultisol under contrasting land use and management history

Different land‐use affects the organization of mineral soil particles and soil organic components into aggregates and the consequent arrangement of the aggregates will influence essential ecosystem functions. We investigated a continuous rubber plantation (forested), land fallowed for 10 y (fallow), 10‐y continuous arable cropping land and cropped land with top soil removed (TSR) for concentrations of C, N, and P in bulk soil and dry aggregates. Results showed that a high level of soil disturbance decreased the proportion of surface (0–15 cm) soil aggregate stability (low mean weight diameter) in TSR by 149% and arable cropping by 125% compared with the forested. Aggregate associated SOC was higher in aggregate‐size fractions of forested land‐use when compared with that in 10‐y fallow, continuous arable cropping, and TSR. For aggregate associated N, fallow and forested land‐use types concentrated higher proportion across aggregate sizes than the arable cropping and TSR. Macro aggregate fractions generally contained higher concentrations of C, N, and P compared with the micro‐aggregates. Water transmission indicators like total porosity and saturated hydraulic conductivity recorded higher values with forested and fallow land‐use than the others. We can thus conclude that long‐term soil disturbance due to cultivation and removal of top soil reduces the accumulation of soil C, N, and P in bulk soil and decreases water transmission properties. On the other hand, aggregate‐associated C, N and P accumulations are dependent on the level of soil surface disturbance and aggregate sizes.     

Soil penetrating quality in cultivated and forested coastal plain sands of Southern Nigeria

Conversion of natural forest to intensive cultivation makes to soil susceptible to flooding, declining fertility and loss of organic matter (OM) and reduced water movement into and within the soil. We studied infiltration rates and related soil penetrating indicators of forested and cultivated soils in humid tropical coastal plain sands in Southern Nigeria. Results showed that mean-weight diameter (MWD) and water stability of aggregates were higher in forested than cultivated soils. Stable aggregates > 1.00 mm were 16.5% and 31.1% respectively, for cultivated and forested soils at 0–15 cm depth, indicating formation of more macro-aggregates in forested soil. Soil disturbance through cultivation decreased hydraulic conductivity and increased bulk density of the soil. Infiltration rate attained after 2 hours was higher in forested soil. Temporary infiltration rate of 178 mm hr^?1 at initial time in cultivated soil was followed by very low infiltration rate of 7 mm hr^?1 after 2 hours. Soil organic matter (SOM), saturated hydraulic conductivity, MWD and total sand correlated positively with infiltration rates are r = 0.76, 0.61, 0.57 and 0.51 respectively. Changes in these parameters are dependent on surface soil disturbance by cultivation. Cultivation of forest decreased infiltration rates and water transmission properties of the soil.