Modelling regional level spatial distribution of aphid (Lipaphis erysimi) growth in Indian mustard using satellite-based remote sensing data

Abstract

We developed a procedure for preparing a model for mapping spatially distributed zones of aphid pest (Lipaphis erysimi) outbreaks at a regional level. This study employed near-surface meteorological parameters derived from National Oceanic and Atmospheric Administration (NOAA) Television and Infra-Red Operational Satellites (TIROS) Operational Vertical Sounder (TOVS) data and field observations of disease infestation. The study area comprised three sites representing semi-arid and sub-humid regions of dominant Indian mustard (Brassica juncea L.)-growing regions of India. A model based on TOVS-derived cumulative surface air temperature and minimum specific humidity (SpH) was developed to estimate the date of ‘aphid onset’ (first appearance), date of peak infestation and location of severity with respect to aphid population density. Aphid population growth rate during the linear growth phase between aphid onset to peak was computed using SpH-weighted temperature and dates of sowing of the crop (crop age). Sowing dates of mustard crop, of northwest India, were obtained from spectral growth profiles derived from time series remote sensing (RS) products of the SPOT-4 VEGETATION sensor. Estimated dates of peak aphid infestation and peak population showed a strong match with the observed data. The location of peak aphid population density was depicted in each spatial grid of 25×25 km² for parts of northwest India. The simulated aphid population build-up and date of peak population density was validated with observed data for an unknown site in the Sriganganager district, Rajasthan state, India. Comparison of predicted dates of attaining peak aphid population with observations showed a deviation of ±7 days. After validation, the regional level model was applied over a large area of a mustard-growing region for varying dates of sowing, surface air temperature and specific humidity, to show the spatial distribution of aphid growing severity zones (population density) and to predict dates of severe aphid infestation (peak population) at each grid level in the region.     

Spatial distribution of soil physical properties of alluvial soils: a geostatistical approach

Knowledge of spatial variation of soil is important in site-specific farming and environmental modeling. Soil particles size and water distribution are most important soil physical properties that governing nearly all of the other attributes of soils. The objectives of this study were to determine the degree of spatial variability of sand, silt and clay contents, and water content at field capacity (FC), permanent wilting point (PWP), and available water content (AWC) of alluvial floodplain soils. Data were analyzed both statistically and geostatistically to describe the spatial distribution of soil physical properties. Soil physical properties showed large variability with greatest variation was observed in sand content (68%). Exponential and spherical models were fit well for the soil physical properties. The nugget/sill ratio indicates except clay all other soil physical properties were moderate spatially dependent (37–70%). Cross-validation of the kriged map shows that prediction of the soil physical properties using semivariogram parameters is better than assuming mean of observed value for any unsampled location. The spatial distribution of water retention properties closely followed the distribution pattern of sand and clay contents. These maps will help to planner to develop the variable rate of irrigation (VRI) for the study area.     

Determination of critical limits of soil nutrients for use in optimizing fertilizer rates for fish ponds in red, lateritic soil zones

Mesocosms containing lateritic soil from West Bengal, India and de-ionized water were treated with different amounts of nitrogen (N), phosphorus (P), and potassium (K) fertilizers. Concentrations of available N, P, and K in soils and gross primary productivity were measured for the mesocosms. Critical concentrations of the three nutrients were estimated by the graphical method of Cate and Nelson that has been used widely for establishing critical soil nutrient concentrations in fertilization research on terrestrial crop plants. Critical concentrations of the three nutrients were: available N, 200 mg kg⁻¹; available P, 13 mg kg⁻¹; available K, 80 mg kg⁻¹. Ponds sited in red, lateritic soil in West Bengal were treated monthly with 20, 15, and 3 kg ha⁻¹ application⁻¹ of N, P, and K, respectively. There was an increase in gross primary productivity when the critical concentrations of available N, P, and K established in the mesocosm study were attained in the pond soils. Fish production in fertilized ponds is positively correlated with gross primary productivity. Thus, the concept of critical nutrient concentrations in soils could be a valuable tool in pond fertilization research.     

Uptake of nutrients by banana at the 8th- and 19th-leaf stage

Uniform 2-leaved suckers of dwarf banana ‘Cavendish’ (Musa cavendishii) were treated with 2 doses and 2 frequencies of irrigation as main treatments, and 5 combinations of NPK as sub-treatments. Observations of the plants' response to these treatments were made at the 8th- and 19th-leaf stage. Irrigation at fortnightly or monthly intervals in combination with applications of NPK improved plant morphology. P uptake increased with frequent high irrigation and a high level of P application. With low but frequent irrigation, K and Ca uptake increased with high K application and balanced NPK application, respectively. N uptake with a high application of NPK or N increased at the 8th-leaf stage with frequent irrigation at both levels, and increased at the 19th-leaf stage at low level, less frequent irrigation. The leaves contained the highest quantity of N, followed by the petiole.     

Forecasting of Lipaphis erysimi on oilseed Brassicas in India—a case study

Experiments at Bharatpur, Pantnagar, Berhampur, Mohanpur, New Delhi, S.K. Nagar, Kangra and Sriganganagar, India were sown with oilseed Brassica cultivars Varuna and an important cultivar for the area on 10 dates at weekly intervals. Data of experiments conducted previously at Hisar and Ludhiana as available in reports were also used for the study. Mustard aphid (Lipaphis erysimi) appearance on inflorescences of the plants was positively correlated to a maximum temperature between 20–29 °C in the preceding week and also to a morning relative humidity (RH) >92% and daily mean RH of >75%. Long hours of leaf wetness and minimum temperature >5 °C also favoured aphid infestation. Regional and cultivar specific models were developed to predict the crop age at which the mustard aphid first appears on the crop, the peak number of aphids and the crop age at peak number at least 1 week ahead of first appearance of the pest on the crop. These will allow growers to apply insecticides in a more timely and effective manner. Here we report only the models that were found effective based on validation in the 2 years.     

Antioxidant activity of piper betel leaf extract and its constituents

The 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay of the ethanol extracts of three varieties (Bangla, sweet, and Mysore) of Piper betel (pan) revealed the Bangla variety to possess the best antioxidant activity that can be correlated with the total phenolic content and reducing powers of the respective extracts. Column chromatography of the extract of the Bangla variety led to the isolation of chevibetol (CHV), allylpyrocatechol (APC), and their respective glucosides. The HPTLC analyses of the extracts revealed similar chemical profiles in all three P. betel varieties, although the concentrations of CHV and APC were significantly less in the sweet and Mysore varieties. Among the isolated compounds, APC showed the best results in all the in vitro experiments. It could prevent Fe(II)-induced lipid peroxidation (LPO) of liposomes and rat brain homogenates as well as gamma-ray-induced damage of pBR322 plasmid DNA more efficiently than CHV. The superior anti-LPO and radioprotective activities of APC vis-à-vis those of CHV could not be explained by their respective Fe(II) chelation and .OH radical scavenging capacities. The better ability of APC to scavenge O2-. radicals and H2O2 might account for the results.     

Antioxidant activity of Myristica malabarica extracts and their constituents

The 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay of the ether, methanol, and aqueous extracts of the spice Myristica malabarica (rampatri) revealed the methanol extract to possess the best antioxidant activity. Column chromatography of the methanol extract led to the isolation of a new 2-acylresorcinol and four known diarylnonanoids of which the diarylnonanoid, malabaricone C, showed the maximum DPPH scavenging activity. Malabaricone C could prevent both Fe(II)- and 2,2'-azobis(2-amidinopropane)dihydrochloride-induced lipid peroxidation (LPO) of rat liver mitochondria more efficiently than curcumin. The anti-LPO activity of malabaricone C was attributed to its better radical scavenging and Fe(II) chelation capacities. The superior activity of malabaricone C was rationalized by a systematic structure-activity correlation of the results obtained with the structurally related diarylnonanoids and curcumin. Malabaricone C also prevented the gamma-ray-induced damage of pBR322 plasmid DNA in a concentration-dependent manner. The radioprotective activity was found to correlate with its (*)OH radical scavenging property, which matched well with that of d-mannitol.     

Distribution of forms of potassium in relation to different agroecological regions of North-Eastern India

Distribution of potassium (K) in soils is governed by the agroecological region (AERs), as the operational intensity of factors and processes of soil formation vary with AER. Therefore, we aimed at finding out the relationship between the forms of K(K forms) with AER and the association of K forms with soil properties in the North-Eastern region of India. For this, horizon-wise soil samples were collected from pedons, three each from three AERs (15 (hot sub-humid to humid), 16 (warm per-humid) and 17 (warm per-humid with less cool winter)) in the North-Eastern India. The water balance diagram for AER shows that precipitation (P) exceeds the potential evapo-transpiration (PET) from June to October, AER 16 shows almost no period when the PET is more than the P and AER 17 shows that the region experiences only a short water deficit of 100–150 mm during post-monsoon period. Soil samples were analysed for physical and chemical properties and K forms. The soils were acidic to neutral with low cation exchange capacity (CEC). The water-soluble K ranged between 0.006 and 0.144 cmol kg^?1, exchangeable K between 0.07 and 0.54 cmol kg^?1, fixed K from 16.7 to 61.3 cmol kg^?1 and total K from 17.4 to 63.6 cmol kg^?1 in soils of different horizons. Further, the results revealed that all the K forms followed the trend of AER 16 > AER 17 >AER 15. Exchangeable K showed higher correlation with clay (r = 0.519**), while fixed K with organic carbon (r = 0.390*).