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Time for cotton to uptake water of a known isotopic signature as measured in leaf petioles

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Agricultural Sciences 2014年第2期5卷 170-177页

作者： Timothy S. Goebel robert j. lascano Wind Erosion and Water Conservation Research Unit Cropping Systems Research Laboratory USDA-ARS Lubbock USA

While stable isotopes of water have been used to study water movement through the environment, they generally have not been used to examine shorter, more transient events, e.g., rainfall of j.ctive of this study was to measure the time required by a plant to transpire water from a source of water with a different isotopic signature than the water that the plant was irrigated. To this end, cotton (Gossypium hirsutum (L.)) plants were grown in a greenhouse and the time required for the enriched water added the soil to show up in the meristematic petioles of cotton leaves was measured. The initial divergence from the irrigation water signature occurred as quickly as 4 hours. The water from the sampled petioles then reached equilibrium with the new source water within 12 hours.

关键词： Cotton Stable Isotopes Water Use

Test of the Rosetta Pedotransfer Function for Saturated Hydraulic Conductivity

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Open j.urnal of Soil Science 2012年第3期2卷 203-212页

作者： Carlos Alvarez-Acosta robert j. lascano Leo Stroosnij.er Cropping System Research Laboratory Wind Erosion and Water Conservation Research Unit 3810 4th St Lubbock TX 79415 USA Wageningen University Land Degradation and Development Group Soil Science Centre P. O. Box 47 6700 AA Wageningen The Netherlands

Simulation models are tools that can be used to explore, for example, effects of cultural practices on soil erosion and irrigation on crop yield. However, often these models require many soil related input data of which the saturated hydraulic conductivity (Ks) is one of the most important ones. These data are usually not available and experimental determination is both expensive and time consuming. Therefore, pedotransfer functions are often used, which make use of simple and often readily available soil information to calculate required input values for models, such as soil hydraulic values. Our obj.ctive was to test the Rosetta pedotransfer function to calculate Ks. Research was conducted in a 64-ha field near Lamesa, Texas, USA. Field measurements of soil texture and bulk density, and laboratory measurements of soil water retention at field capacity (–33 kPa) and permanent wilting point (–1500 kPa), were taken to implement Rosetta. Calculated values of Ks were then compared to measured Ks on undisturbed soil samples. Results showed that Rosetta could be used to obtain values of Ks for a field with different textures. The Root Mean Square Difference (RMSD) of Ks at 0.15 m soil depth was 7.81 × 10–7 m·s–1. Further, for a given soil texture the variability, from 2.30 × 10–7 to 2.66 × 10–6 m·s-1, of measured Ks was larger than the corresponding RMSD. We conclude that Rosetta is a tool that can be used to calculate Ks in the absence of measured values, for this particular soil. Level H5 of Rosetta yielded the best results when using the measured input data and thus calculated values of Ks can be used as input in simulation models.

关键词： Rosetta Saturated Hydraulic Conductivity Ks Pedotransfer Function

A Technical Note: Orientation of Cracks and Hydrology in a Shrink-Swell Soil

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Open j.urnal of Soil Science 2012年第2期2卷 91-94页

Crack orientations are an important soil physical property that affects water flow, particularly in vertic soils. However, the spatial and temporal variability of crack orientations across different land uses and gilgai features is not well-documented and addressed in hydrology models. Thus;there is a need to quantify crack orientations for different land uses and to incorporate their spatial and temporal dynamics into hydrological models. Our obj.ctives were to document the spatial variability of cracks orientations across two land uses and to demonstrate the potential importance of crack orientation related to the hydrology of Vertisols. The exploratory field measurements of the spatial distribution of crack orientations across two Vertisol catenae of two land uses and gilgai features are presented. The field survey showed the complexity of crack geometry in a field, the potential impact of crack orientation on Vertisol hydrology and the challenges associated with measurement of crack orientations.

关键词： Crack Orientation Hydrology

System for High Throughput Water Extraction from Soil Material for Stable Isotope Analysis of Water

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j.urnal of Analytical Sciences, Methods and Instrumentation 2012年第4期2卷 203-207页

作者： Timothy S. Goebel robert j. lascano Wind Erosion and Water Conservation Research Unit Cropping Systems Research Laboratory USDA-ARS# Lubbock USA.

A maj.r limitation in the use of stable isotope of water in ecological studies is the time that is required to extract water from soil and plant samples. Using vacuum distillation the extraction time can be less than one hour per sample. Therefore, assembling a distillation system that can process multiple samples simultaneously is advantageous and necessary for ecological or hydrological investigations. Presented here is a vacuum distillation apparatus, having six ports, that can process up to 30 samples per day. The distillation system coupled with the Los Gatos Research DLT-100 Liquid Water Isotope Analyzer is capable of analyzing all of the samples that are generated by vacuum distillation. These two systems allow larger sampling rates making investigations into water movement through an ecological system possible at higher temporal and spatial resolution.

关键词： Isotope Vacuum Distillation Soil

Evaluation of Stable Isotopes of Water to Determine Rainwater Infiltration in Soils under Conservation Reserve Program

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j.urnal of Agricultural Chemistry and Environment 2016年第4期5卷 179-190页

作者： Timothy S. Goebel robert j. lascano Veronica Acosta-Martinez USDA-ARS Wind Erosion and Water Conservation Unit Lubbock TX USA

The Conservation Reserve Program (CRP) is a USDA program introduced in 1985 to reduce soil erosion by increasing vegetative cover of highly erodible land. Participation in the CRP is done via contracts (10 - 15 years in length) and currently the total area of land under contract is set to decline as per the 2014 Farm Bill. The Texas High Plains (THP) leads the US with >900,000 ha enrolled in CRP. A potential long- term benefit of CRP is to increase soil organic matter and to improve soil structure leading to increased water infiltration. Our obj.ctive was to evaluate the feasibility of using stable isotopes of water to measure and compare infiltration of rain in land under CRP management to land under continuous dryland cotton in the THP. For this purpose we selected two sites, with soils in the Amarillo series, enrolled in CRP, one for 25 years and the second site for 22 years. Results from several rain events showed that stable isotopes of water are a method that can be used to evaluate the depth of rainwater infiltration for soils under CRP and dryland management.

关键词： Conservation Reserve Program Rain Infiltration Stable Isotopes Dryland Cotton

Phosphate Sorption in Water by Several Cationic Polymer Flocculants

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j.urnal of Agricultural Chemistry and Environment 2016年第1期5卷 45-51页

作者： Timothy S. Goebel robert j. lascano Todd A. Davis Cropping Systems Research Laboratory USDA-ARS Lubbock TX USA Department of Chemistry United States Air Force Academy Colorado Springs CO USA

Although inorganic phosphate is an essential plant nutrient, elevated levels in surface waters lead to adverse effects in the environment. These effects are attributed to runoff from rain or irrigation events that may cause the sorbed phosphate to be transported from the application sites and to move into neighboring watersheds. Increased phosphate concentration in watersheds may lead to a variety of environmental problems including increased algal blooms, bacterial contamination, and in some cases eutrophication. To overcome these effects, polymer flocculants have been shown to reduce the phosphate concentration in water by removing suspended solids and thereby removing the phosphate sorbed to the solids. The purpose of this study is to determine the amount, if any, of phosphate removed by several commercial polymers. The polymers chosen include the polyacrylamides Magnifloc 494C, Magnifloc 985N and Poly (diallyldimethyl ammonium chloride) (Poly (DADMAC)). Using these polymers, it is discovered that the positive charge density of the polymers affects the amount of phosphate removed from solution with Poly (DADMAC) (having 100% positive charge density) removing 40% of the phosphate from a solution containing 10 ppm phosphate.

关键词： Polymer Flocculants Phosphate Sorption Polyacrylamides Poly (DADMAC) Smectite

Stable Carbon Isotope Discrimination (δ¹³C) of Cotton Burrs and Seeds as a Season-Long Integrator of Crop Water Stress

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American j.urnal of Plant Sciences 2022年第12期13卷 1448-1459页

作者： Dennis C. Gitz III j.ffrey T. Baker robert j. lascano Cropping Systems Research Laboratory ARS-USDA1 Lubbock USA

Plant-based irrigation management schemes typically use surrogates such as canopy temperature, alone, or in conj.nction with environmental variables, to infer the degree of “crop stress” (biological strain) induced by drought. Few systematic studies of the relationship between “crop stress”, as defined by such surrogates, and physiological estimates of water use efficiency (WUE) exist over both daily and seasonal time scales relevant to agronomic irrigation control. The systematic application of stable carbon isotope discrimination (δ13C) might allow post hoc evaluation of irrigation scheduling schemes and might also be a useful germplasm screening tool if the source(s) of variability can be uncovered and/or controlled. Results from preliminary efforts comparing leaf and cotton seed δ13C to season-long water deficits showed that seeds are more useful indicators of season-long water stress and water use efficiency during crop development.

关键词： Irrigation-Scheduling Germplasm Screen Water Management

Scaling Leaf Measurements to Estimate Whole Canopy Gas Exchanges of Cotton

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American j.urnal of Plant Sciences 2016年第14期7卷 1952-1963页

作者： Dennis C. Gitz III j.ffrey T. Baker robert j. lascano Wind Erosion and Water Conservation Unit Cropping Systems Research Laboratory USDA-ARS1 Lubbock TX USA

Diurnal leaf and canopy gas exchanges of well-watered field grown cotton were measured. Our obj.ctive was to scale leaf-level values of transpiration and net assimilation to the whole canopy level using estimates of canopy leaf area. Single leaf gas exchange measurements were made with two portable photosynthesis systems and canopy measurements with four open Canopy Evapo-Transpiration and Assimilation (CETA) chamber systems. Canopy leaf area was measured at the end of the experiment and estimated during gas exchange by fitting values to a growth curve. Leaf level measurements were arithmetically scaled to estimate canopy level gas exchange based on canopy leaf area and then compared to the measured values. Scaled values of single leaf transpiration were very similar to canopy transpiration measurements, although both whole canopy transpiration and assimilation were overestimated around mid-day. We conclude that canopy cotton transpiration of well-watered field grown plants could be estimated within 5% throughout the day by scaling leaf level measurements to the whole canopy using measured canopy leaf area. Estimating canopy assimilation from leaf level measurements remains problematic.

关键词： Cotton Gossypium hirsutum Scaling Assimilation Transpiration Drought Stress

Relating Xylem Cavitation to Gas Exchange in Cotton

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American j.urnal of Plant Sciences 2015年第11期6卷 1742-1751页

作者： Dennis C. Gitz III j.ffrey T. Baker robert j. lascano Cropping Systems Research Laboratory USDA-ARS# Lubbock USA

Acoustic emissions (AEs) from xylem cavitation events are characteristic of transpiration processes. Though a body of work exists describing AEs and limited stem hydraulic conductivity under water stress, there is limited information about the effects of AEs on stomatal aperture and limitation on carbon assimilation. The obj.ctive of this work was to relate AEs to drought stress in cotton. Cotton was grown in mini-lysimeters in the greenhouse and instrumented with a portable photosynthesis system and ultrasonic transducers connected to a digital signal-processing unit. Whole plant transpiration, leaf level gas exchange and ultrasonic AEs were measured. Xylem cavitation events temporally associated with the onset of drought stress. The results are consistent with stomatal closure in response to reduced hydraulic conductance from xylem cavitation events. Clear direct empirical evidence of a reduction in carbon assimilation associated with xylem cavitation resulting from water stress is presented.

关键词： Xylem Cavitation Drought Stress Stomatal Control Irrigation Scheduling