Parmodh Sharma

Coupled Liquid Water, Water Vapor, and Heat Transport Simulations in an Unsaturated Zone of a Sandy Loam Field

Information on the coupled liquid water, water vapor, and heat transport under arable field conditions is still limited, particularly for unsaturated soils of semi-arid and arid regions such as New Mexico. HYDRUS-1D model was applied to evaluate various transport mechanisms associated with temporal variations in water content and soil temperature in the unsaturated zone of a sandy loam furrow-irrigated field located at Leyendecker Plant Science Research Center, Las Cruces, New Mexico. The model was calibrated using measured soil water content and soil temperature at 5-, 10-, 20-, and 50-cm depths during a 19-day period (day of the year [DOY] 85 to DOY 103, 2009) and validated for a 31-day period (DOY 104 to DOY 134, 2009). Measured and optimized soil hydraulic and thermal properties and hourly meteorological data were used in model simulations. HYDRUS-1D simulated water contents and soil temperatures correlated well with the measured data at each depth. The total liquid water flux, composed of isothermal and thermal liquid water flux, dominated the soil water movement during early periods after irrigation, whereas the contribution of total water vapor flux, composed of primarily thermal and much smaller isothermal water vapor flux, increased with increasing soil drying. During the soil drying process, the total liquid flux within 15-cm depth eventually changed to water vapor flux near the surface. The upward total liquid and vapor fluxes decreased from 5 cm, indicating that vapor flux was much higher in the layer near the soil surface. The total vapor flux in this unsaturated soil layer was approximately 10.4% of the total liquid and vapor fluxes during the simulation period.

Spatial Variability of Soil Properties in Agricultural Fields of Southern New Mexico

Estimating the spatial variability of soil physical and chemical properties is a prerequisite for soil and crop-specific management. The objectives of this study were to determine the degree of spatial variability and variance structure of soil physical and chemical properties on a 40-ha agricultural field in Las Cruces, New Mexico, to observe any change in the variance structure caused by the cropping system and to suggest future sampling designs to make efficient management decisions. Soil samples were collected at the center of a regular grid of 50 m × 50 m and on the grid line during November 2008 and 2009 from 0 to 15 cm of depth. The software package GS+ was used to model the variance structure of sand, silt, clay, soil bulk density, saturated hydraulic conductivity (Ks), pH, electrical conductivity (EC), nitrate-nitrogen (NO3-N), chloride, and volumetric water content at six different matric potentials (−33, −100, −300, −500, −1,000, and −1,500 kPa). The coefficient of variation ranged from 4% (pH) to 141% (Ks). The semivariograms showed that the range of spatial dependence varied from 86 m (pH, 2008) to 563 m (Ks) for all measured soil properties. Cross-semivariograms showed that NO3-N and EC were spatially correlated; therefore, kriging or cokriging can be used to estimate NO3-N values throughout the growing season from easily available EC data. Correlograms with Moran I indicated that a distance of 140 m was sufficient to yield independent samples for measured soil physical and chemical properties. The kriged contour maps showed positional similarities. These contour maps of soil properties, along with their spatial structures, can be used in making better future sampling designs and management decisions.

Assessment of the Soil Physical and Chemical Properties of Desert Soils Irrigated With Treated Wastewater Using Principal Component Analysis

The knowledge of soil heterogeneity is useful for designing site-specific soil management practices especially for those affected by anthropogenic activities. The objectives of this study were to identify and select the dominating soil factors and attributes caused by wastewater application for the management decisions of West Mesa land application site using the principle component analysis. Variability in soil properties was identified by coefficient of variation (CV) as the indicator. A property was ranked as least (CV < 0.15), moderate (0.15 < CV < 0.35) or most (CV > 0.35) variable using the criteria proposed by Wilding. Nitrate (NO3−), chloride (Cl−), sodium adsorption ratio, saturated hydraulic conductivity, sodium (Na+), and electrical conductivity were most variable in the irrigated plots at the 0- to 20-cm depth. The principle component analysis, which is widely used to reduce the dimensions of data, grouped 15 soil physical and chemical properties into four components (eigenvalue >1) soil sodicity, water transport, soil texture, and organic matter at the 0- to 20-cm depth and soil sodicity, soil texture, water retentiona and organic matter at 20- to 40-cm depth. Redundancy analysis showed that soil sodicity factor and Na+ as the most dominantly measured soil properties at both depths. Therefore, Na+ should be monitored over time in the West Mesa land application site. The mean sodium adsorption ratio for study site was 19.17 ± 2.92 in the irrigated plots, which is above the threshold limit for many plant species and may threaten the survival of woody and perennial herbaceous vegetation in the study area. Therefore, it is necessary to initiate management strategies for controlling soil sodicity in the West Mesa land application site.

Nitrate-Nitrogen Leaching from Onion Bed under Furrow and Drip Irrigation Systems

Water is a limited resource for crop production in arid areas of Southern New Mexico. The objectives of this study were to estimate the amount and depth of water and nitrate-nitrogen (NO3-N) fronts, water and NO3-N balances, and irrigation efficiencies for two onion (Allium cepa L.) fields under furrow and drip irrigation systems. Monthly soil samples were analyzed for NO3-N and chloride concentration for two onion growing seasons starting September 2006 to August 2009. The average amount of NO3-N in the soil water estimated by chloride tracer technique varied from 97.4 to 105.2 mg L-1 for furrow and 65.2 to 66.8 mg L-1 for drip-irrigated fields for the 60- to 200-cm depth. The NO3-N loadings below the rooting zone ranged from 145 to 150 kg ha-1 for furrow- and 76 to 79 kg ha-1 for drip-irrigated fields. The irrigation efficiencies varied from 78 to 80% for furrow- and 83% for drip- and N application efficiencies (NAEs) were 35 to 36% for furrow- and 38 to 39% for drip-irrigated fields. Small N fertilizer applications, delayed until onion bulbing starts, and water applications, preferably through drip irrigation, are recommended to reduce deep percolation and increase nitrogen and water efficiencies.

Numerical Evaluation of Nitrate Distributions in the Onion Root Zone under Conventional Furrow Fertigation

AbstractHYDRUS (2D/3D) model was used to simulate spatial and temporal distributions of nitrate-nitrogen (NO3-N) within and below the onion root zone under conventional furrow fertigation with the urea-ammonium-nitrate (UAN) liquid fertilizer. The simulated water contents in the furrow irrigated onion field agreed well with the measurements. Simulations produced similar patterns of the measured NO3-N concentration profiles throughout the growing season. NO3-N concentrations remained higher and accumulation of NO3-N was observed within the root zone. Higher NO3-N within the root zone was dependent on the rate of the UAN fertilizer application, quantity of NO3-N removed by root uptake, and NO3-N drainage fluxes below the root zone. Simulations also suggested that NO3-N below the root zone during different growth stages remained much higher than a recommended (for drinking water) standard concentration level (10  mg L−1). This resulted in higher NO3-N drainage fluxes, particularly during the fertigation even...

Cluster and Principle Component Analysis of Soybean Grown at Various Row Spacings, Planting Dates and Plant Populations

Abstract Increased light interception (LI), along with concomitant increases in crop growth rate (CGR), is the main factor explaining how cultural factors such as row spacing, plant population, and planting date affect soybean yield. Leaf area index (LAI), LI, and CGR are interrelated in a “virtuous spiral” where increased LAI leads to greater LI resulting in a higher CGR and more total dry matter per area (TDM). This increases LAI, thus accelerating the entire physiological process to a higher level. A greater understanding of this complex growth dynamic process could be achieved through use of cluster analysis and principle components analysis (PCA). Cluster analysis involves grouping of similar objects in such way that objects in same cluster are similar to each other and dissimilar to objects in other cluster. PCA is a technique used to reduce a large set of variables to a few meaningful ones. Seasonal relative leaf area index (RLAI), relative light interception (RLI), and relative total dry matter (RTDM) response curves were determined from the data by a stepwise regression analysis in which these parameters were regressed against relative days after emergence (RDAE). Greatest levels of RLAI, RLI and RTDM were observed in soybean planted early on narrow row spacings and recorded greater plant population. In contrast, lower levels of these parameters occurred on plants with wide row spacings at late planting dates. For farmers, these results are useful in terms of adopting certain cultural practices which can help in the management of stress in soybean.

A water balance trickle irrigation scheduling model

In order to conserve water, some form of irrigation scheduling should be used by the farming community. Most irrigation scheduling computer models in the U.S. are 1 dimensional (1 D) water balance models which may not be appropriate for a two dimensional flow (2 D) regime under trickle irrigation. However, the 1 D water balance models have been applied to all forms of irrigation systems from flood, to sprinkler to trickle irrigation. The objective of the research was to develop an irrigation scheduling model that simulates two dimensional water infiltration, drainage, and uptake for a surface line source trickle irrigation system and to compare the results to the simpler 1 D model for a shallow rooted onion crop and a deep rooted chile crop. Two experiments were conducted to evaluate the models. One experiment was conducted during 2006-2007 growing season for a shallow rooted onion crop and the other experiment was conducted for a deep rooted chile crop grown in 1995 and 1996. The 1 D model over estimates seasonal evapotranspiration (Et) compared to the measured values for onions by 20% and for chile by 12%. The 2 D model over estimates seasonal Et compared to the measured values for onion by 5% and for chile by 8%. Therefore, the 2 D model is recommended for scheduling irrigation for trickle irrigated shallow rooted crops. For deep rooted crops both the 1D and 2D models give reasonable results but the 2 D model simulates the seasonal water balance better than the 1 D model.