Search

Variably saturated flow models that simulate soil–water–plant interactions within the rhizosphere largely ignore the effect of plant health. This makes it difficult for them to effectively simulate root water uptake (RWU) and implement alternate management practices for diseased trees. This research was aimed at understanding the hydrological and plant controls on RWU simulations dominated by the health of the tree using experimental and numerical frameworks. Two research plots, one around a healthy mature and the other around a diseased mature (Phytophthora spp. affected) orange tree (Citrus reticulate Blanco), in the Vidarbha region of India were considered for our analysis. Three-dimensional electrical resistivity tomography (ERT) performed at the two locations revealed that the soil moisture profiles following irrigation are different between the two plots. A two-dimensional axisym-metric form of Richards’ equation was then solved using HYDRUS (2D/3D) by incorporating a root distribution function. A global sensitivity analysis was performed to identify the root distribution parameters that influence soil moisture simulations. These parameters were then optimized using a genetic algorithm for healthy and diseased conditions. We observed that the diseased orange tree had consumed less water, leaving high soil moisture in the rhizosphere, a condition favorable for the further growth of disease-causing fungi. Hence, managing irrigation water in accordance with RWU patterns is essential for diseased trees. To understand the error propagation in RWU estimation, we simulated RWU from a diseased tree with the optimal parameters derived for a healthy case. Results show that the error in estimating RWU from the model cells progressively increases with radial distance and soil depth. © Soil Science Society of America.

Fixed plot survey was undertaken to plot correlation between environmental factors with population of Phytophthora spp. in soil and the disease intensity during June 2015 to May 2016. Agro-meteorological data was recorded by using wireless sensors (for air temperature 107 Temperature probe, for relative humidity HC2S3 and for rainfall measurement Texas Electronic rain gauge) in selected plots. All four orchards were found infected with Phytophthora in the range of 3.2–43.6 cfu/g of soil. There was consistent increase in pathogen population in all plots with increase in rainfall, relative humidity with decrease in temperature and vice versa. At high rainfall condition intensity of root rot was increased to 35.81 per cent in the month of August and gummosis (41.01%) was also increased in the month of October with average propagules of 25.84 cfu/g of soil. Increase in temperature decreased intensity of gummosis (26.29%) and root rot (20.09%) in the month of May, with the average propagules, i.e., 4.56 cfu/g of soil. Present findings suggest that, humidity and rainfall were significantly correlates with population dynamics of Phytophthora spp. and disease intensity, while temperature was found inversely proportional.

Epidemics caused by Phytophthora spp. were monitored in four commercial citrus orchards to plot correlation between environmental and soil factors with root rot disease caused by Phytophthora spp. in citrus. Agro - meteorological d ata was recorded by using wireless sensors (for air temperature 107 Temperature probe, for relative humidity HC2S3 with 30 minutes time interval for both the sensors and for rainfall measurement Texas Electronic rain gauge) in selected plots. The soil mois ture, soil pH and soil EC was recorded at fortnightly interval. The observations recorded in order to characterise the progression of the symptoms expression over the time and to provide evidence for the possible correlation of inoculum dynamics with root rot and environmental factors. The relationship of rainfall, temperature, relative humidity, soil moisture, soil pH and soil EC on disease development was investigated. Sensor based data was recorded for rainfall, temperature, relative humidity and convert ed to forth nightly interval. The disease progress and inoculum potential recorded at forth nightly interval from June 2016 to May 2017. There was significant progression in the disease development with the increase in the rainfall and soil moisture. There was significant increase in the disease at second fort night of August (38.53%) and progression continued up to October (87.58%). Progress in disease was attributed to increase in soil moisture, relative humidity and decrease in the air temperature. A ten dency of spreading the disease at adjoining trees was observed. Drainage of water, possibly containing propagules of the pathogen may have been responsible for disease progression. The disease initially low but gradually increases with time. There was posi tive correlation between rainfalls, soil moisture, relative humidity, soil EC with disease progression and inverse correlation with air temperature

Vidarbha region in Maharashtra, India is witnessing a continuous decrease in orange crop due to the propagation of `Phytopthora root rot', a water mold disease. Under favorable conditions, the disease causing bacteria can attack the plant root system and propagates to the surface (where first visual impression is made), making difficult to regain the plant health. This research aims at co-relating eco-hydrological fluxes with disease sensing parameters of orange trees. Two experimental plots around a healthy-young and declined-young orange trees were selected for our analysis. A 3-dimentional electrical resistivity tomography (ERT) (Figure) was carried at each plot to quantify the soil moisture distribution at a vadose zone. Pedo-electric relations were obtained considering modified Archie's law parameters. ERT derived moisture data was validated with time domain reflectometry (TDR) point observations. Soil moisture profiles derived from ERT were observed to be differ marginally between the two plots. Disease quantification was done by estimating the density of Phytopthora spp. inoculum in soils sampled along the root zone. Identification of Phytopthora spp. was done in the laboratory using taxonomic and morphologic criteria of the colonies. Spatio-temporal profiles of soil moisture and inoculum density were then co-related to comment on the eco-hydrological fluxes contributing to the health propagation of root rot in orange tree for implementing effective water management practices.

An evolutionary algorithm is presented for the automated calibration of the continuous cellular automaton for the simulation of isotropic and anisotropic wet chemical etching of silicon in as many as 31 widely different and technologically relevant etchants, including KOH, KOH+IPA, TMAH and TMAH+Triton, in various concentrations and temperatures. Based on state-of-the-art evolutionary operators, we implement a robust algorithm for the simultaneous optimization of roughly 150 microscopic removal rates based on the minimization of a cost function with four quantitative error measures, including (i) the error between simulated and experimental macroscopic etch rates for numerous surface orientations all over the unit sphere, (ii) the error due to underetching asymmetries and floor corrugation features observed in simulated silicon samples masked using a circular pattern, (iii) the error associated with departures from a step-flow-based hierarchy in the values of the microscopic removal rates, and (iv) the error associated with deviations from a step-flow-based clustering of the microscopic removal rates. For the first time, we present the calibration and successful simulation of two technologically relevant CMOS compatible etchants, namely TMAH and, especially, TMAH+Triton, providing several comparisons between simulated and experimental MEMS structures based on multi-step etching in these etchants.