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2010 - 20182
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Subject: Soil and Water Engineering × Author: Mahesh Chand Singh × Start date: 1971 ×
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    ThesisItemOpen Access
    Modeling Microclimate of Naturally Ventilated Greenhouse under Cropped Conditions in Soilless Media
    (Punjab Agricultural University, Ludhiana, 2018) Mahesh Chand Singh; Singh, J.P.
    A study was undertaken to develop mathematical models for simulating microclimate of a naturally ventilated greenhouse under cropped conditions and develop the optimal operating microclimatic conditions for drip fertigated cucumber crop in soilless media. Cucumber crop was grown in coco-peat in a split plot design in three replicates during two successive growing seasons of 2016-17. The treatments included three levels of fertigation in main plots viz. F1=100.0%, F2=85.0% and F3=70.0% of complete nutrient solution under optimal microclimatic conditions. Sub-plots included cultivars viz. V1 (Kafka), V2 (Multistar) and V3 (PBRK-4). Mathematical models for standardizing the temperature of greenhouse cover, air, plant and growing media were developed, calibrated and validated in Simulink MATLAB with a mean model efficiency and coefficient of determination values of 94.7% and 0.96 respectively. Mathematical models of sensible and latent heat balance were developed to predict vertical air temperature profile and vapour pressure and solved analytically. Models for predicting saturation vapour pressure (SVP), actual vapour pressure (AVP) and vapour pressure deficit (VPD) from internal and external climates were developed and solved in Simulink MATLAB. Further, models for predicting temperature of air, leaf, plant root-zone and relative humidity were also developed from external climate. The average fruit yield was obtained in the range of 2.4-3.5 kg plant-1 and 3.3-4.4 kg plant-1 with and without fruit thinning having lowest and highest yield under treatments F3V3 and F1V2. Crop water use efficiency (CWUE) was found in the range of 60.4-86.3 kg m-3 and 84.5-108.9 kg m-3 with and without fruit thinning respectively. The average benefit cost ratio (BCR) was computed to be 1.91 and 1.54 with and without subsidy respectively without fruit thinning. However, BCR decreased by 23.7% and 23.8% with and without subsidy respectively with fruit thinning. The developed models were calibrated and validated separately for both growing seasons and a good agreement was observed between the model predictions and observed data. Thus, the developed models successfully simulated the greenhouse microclimate. Based on microclimate modeling, the desirable range of Tapc, TL, Trz, Eapc, Irad and VPD were worked out to be 22.0-27.0°C, 20.5-25.1°C, 16.9-22.9°C, 60.0-85.0%, 100.0-169 Wm-2 and 0.53-1.10 kPa respectively for optimal plant growth and development.
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    ThesisItemOpen Access
    SIMULATION OF SOIL MOISTURE MOVEMENT UNDER RICE FIELD
    (2010) Mahesh Chand Singh
    Soil moisture is a key variable in controlling the exchange of water and heat energy between the land surface and the atmosphere through evaporation and plant transpiration. A field study was conducted at Punjab Agricultural University, Ludhiana, in the year 2009, to simulate the soil moisture movement under rice field using numerical model Hydrus-2D. The treatments included two dates of transplanting (June 5 (D1) and June 20 (D2)), two varieties (PAU-201 (V1) of 120 days duration and hybrid RH-257 (V2) of 90 days duration (from transplanting to harvest)) and two irrigation regimes (intermittent irrigation at 2-days drainage period (I1) and irrigation based on soil water suction (SWS) of 16 k Pa (I2)). During calibration, for both varieties the parameters Ks (saturated hydraulic conductivity) and n (fitting parameter) were found to be most sensitive in respect of the model output. The validation of model was done by comparing observed and simulated values of soil moisture content at different depths. The model performance in simulating soil moisture profiles was evaluated by comparing observed and simulated values using four parameters namely, RMSE, Absolute percentage error, correlation coefficient and model efficiency. The distribution of the soil moisture under field experiment and by model simulation at different growth stages agreed closely. In case of PAU-201 (V1), it was observed that the irrigation water applied in the treatment D1V1I1 was 44 mm higher than the treatment D2V1I1 and the irrigation water applied in the treatment D1V1I2 was also 44 mm higher than the treatment D2V1I2. In case of RH-257 (V2), the irrigation water applied in the treatment D1V2I1 was 44 mm higher than the treatment D2V2I1 and the irrigation water applied in the treatment D1V2I2 was 124 mm higher than the treatment D2V2I2. In case of PAU-201 (V1), the deep drainage loss in treatment D1V1I1 was 133 mm less than the treatment D2V1I1 and in treatment D1V1I2 it was 75 mm less than the treatment D2V1I2. In case of RH-257 (V2), the deep drainage loss in treatment D1V2I1 was 120 mm less than the treatment D2V2I1 and in the treatment D1V2I2 it was 46 mm less than treatment D2V2I2. During validation the absolute error varied from 2.19 to 13.21 percent, Root Mean Square Error varied from 0.006 to 0.032 cm, correlation coefficient varied from 0.773 to 0.996 and the average model efficiency was 98.6 percent. Thus, Hydrus-2D model can be successfully adopted for simulating soil moisture profiles under rice crop.