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Bottom racks are widely used in mountainous regions as intake structures for diverting water from the mainstream for different purposes. Most of the studies on bottom rack flow consider the concept of invariant specific energy. The present study experimentally investigates the specific energy loss in horizontal transverse bottom rack flow for Froude number varying from 0.1 to 1.5, discharge from 0.010 m3/s to 0.076 m3/s, spacing between bars varying from 0.004 m to 0.028 m and parameter (a/L) varying from 0.041 to 0.102. Experimental investigations suggest that the specific energy loss cannot be neglected in the bottom rack flow. Variation of specific energy loss with Froude number indicates its dependence on flow and rack geometry parameters. Based on the regression analysis of experimental data, the expressions developed for the discharge coefficient 'C1ʹ for the constant specific energy approach are evaluated. The study also developed expressions for the discharge coefficient 'C2ʹ, for variable specific energy. Significant agreement between observed and computed discharge based on developed 'C2ʹ establishes the efficacy of developed expressions. [ABSTRACT FROM AUTHOR]

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Field lysimetric experiments were conducted on Potato crop grown in a humid sub-tropical agro-climate during 2014–2017 cropping seasons. Reference evapotranspiration (ET0) methods based on limited climatic data were evaluated with the FAO-56 Penman-Monteith (P-M) method. The performance of temperature-based and radiation-based methods was reliable, but evaporation-based methods performed poorly. The best methods in each category viz. Hargreaves-Samani, FAO-24 Radiation, and Snyder along with FAO-56 P-M were considered to estimate the empirical crop evapotranspiration (ETc) using the crop coefficient approach. The empirical ETc was compared with the field ETc obtained through water balance approach. A root water uptake-based numerical model was utilized to simulate the soil moisture dynamics in the crop root zone, wherein ETc is an important input parameter. The model simulated soil moisture was compared with the field observed values. Results indicate that FAO-56 P-M and Hargreaves-Samani-based simulated values presented close agreement with field observed values. FAO-24 Radiation and Snyder-based simulations underestimated and overestimated the field observed soil moisture, respectively. The field soil moisture depletion of 30% corresponds to simulated depletion of 15% (Snyder), 25% (Hargreaves-Samani), 28% (FAO-56 P-M) and 40% (FAO-24 Radiation). [ABSTRACT FROM AUTHOR]

The article estimating crop water requirements for irrigation scheduling in different crops in humid subtropical agro-climate of Western Himalayas . Topics discussed include estimating crop water requirements for irrigation scheduling in different crops in humid subtropical agro-climate of Western Himalayas ; and the crop water requirement is generally crop evapotranspiration considering atmospheric water loss through plant transpiration and soil evaporation simultaneously.

The estimation of crop evapotranspiration (ETc) uses reference evapotranspiration (ET0) as a key variable. Physically based FAO-56 Penman–Monteith method provides accurate ET0 estimates; however, various methods are still used in different climatic regions worldwide, either due to simplicity of the methods or due to insufficiency of data required for Penman–Monteith method. The present study is conducted at sub-humid sub-tropical locations of western Himalayan agro-climate in the Indian state of Himachal Pradesh. Performance of 12 ET0 methods, representing combination type, pan evaporation, radiation and temperature based, is compared with Penman–Monteith method. Different ET0 methods are ranked on the basis of quantitative comparison performed on mean daily ET0 obtained for a period of 6 years. The temperature-based methods performed better than radiation and pan evaporation-based methods. Linear regression equations are developed between Penman–Monteith ET0 (dependent variable) and ET0 estimates from alternate method (independent variable). Relative significance of meteorological factors essential for accurate ET0 estimation in the climate considered is investigated using sensitivity analysis. Solar radiation is identified as the most sensitive parameter for ET0 estimation in the climate of the study area, followed by maximum temperature and relative humidity. [ABSTRACT FROM AUTHOR]

Further, the original study mainly focuses on the objective of predicting the HT ht of Indian mustard using these techniques without focusing on their mathematical details. • The HT ht value during the validation stage of the MLR model is different in Table 3 and Fig. Further, the discussers pointed out a mistake in the HT ht calculation for the MLR models during the validation stage. The original study employed Kohonen self-organizing map (KSOM), feed-forward neural network (FFNN), and multiple linear regression (MLR) for estimating the well-watered canopy temperature ( HT ht ) of Indian mustard grown in a humid subtropical agro-climate. [Extracted from the article]

Water shortage is the prominent limiting factor for agricultural sector in developing countries. The efficient water use is required which helps to obtain effective irrigation schedule for various crops. The present study aims at establishing optimized irrigation schedule for potato, which is a major cash crop in Northern India. Study is conducted in open field plot of Agricultural Experimental Station at National Institute of Technology Hamirpur (India) for Potato during 2013-2016. Irrigation scheduling models based on root water uptake and growing degree days concept are used to workout irrigation schedule for potato in the study. Comparison of field observed and modelled values of percentage moisture depletion in different depths and soil moisture variation at various depths is performed to evaluate the models efficacy in estimating soil moisture extraction by the potato crop for the crop period and replications during study period. Root uptake-based model is found to have better agreement with observed values. The irrigation schedule developed helps in optimal use of irrigation water in water scarce areas. [ABSTRACT FROM AUTHOR]

The study was conducted to determine the feasibility of canopy temperature based crop water stress index (CWSI) for scheduling irrigation of Indian mustard (Brassica juncea). Field crop experiments were conducted in Hamirpur, Himachal Pradesh (India) during three consecutive cropping seasons (2015, 2016 and 2017). The experimental field was divided into five plots with different levels of irrigation treatments based on depletion of total available soil water (TASW) in the crop root zone. The maximum soil moisture depletion (SMD) of TASW at 10%, 30% and 50%, full irrigated (non‐stressed) and extremely dry (full stressed) conditions were maintained in respective plots. Relationships were developed between canopy‐air temperature differential (TC‐TA) and vapour pressure deficit (VPD) for non‐stressed and fully stressed conditions to generate non‐water‐stressed baseline (NWSB) and maximum water‐stressed baseline (MWSB) baselines for Indian mustard crop. The CWSI was computed for different SMD of TASW by using a proven empirical approach based on the baselines. The irrigation treatment corresponding to 30% SMD with a mean CWSI of 0.4 resulted in optimal yield and maximum water use efficiency. Results of the study suggest that established CWSI value can be used to detect stress and schedule irrigations for Indian mustard. [ABSTRACT FROM AUTHOR]