Construction, installation, and performance of two repacked weighing lysimeters (original) (raw)
Related papers
Measurement of evapotranspiration and its components in a corn (Zea Mays L.) field
Agricultural and Forest Meteorology, 1998
A ®eld experiment was conducted at Prosser, WA in 1993, to evaluate the consistency of ®eld techniques for measuring evapotranspiration (ET), transpiration (T), and soil evaporation (E) from a full-canopy corn ®eld, and to evaluate the ability of sap¯ow gauges to detect differences in water use of corn under two contrasting irrigation treatments: full irrigation (wet treatment) and irrigation stopped when full canopy was reached (dry treatment). Twenty-minute ET rates for the wet treatment were determined using the Bowen ratio energy balance (BREB) method. Transpiration (sap¯ow) rates under both irrigation treatments were measured at 20-min intervals using gauges placed on individual corn plants. Daily E rates for the wet treatment were measured using microlysimeters, and also estimated from the difference between BREB, ET and sap¯ow measurements. Soil±water content in both treatment areas was monitored using neutron probe and gravimetric samples. Considering the normal variation of ®eld measurements, the agreement and consistency among the different techniques used to determine ET and its components was adequate. Despite reductions in leaf area, dry matter production and grain yield, it was possible to differentiate transpiration rates (sap¯ow) between dry and wet irrigation treatments only at the end of the season. Microlysimeter measurements of daytime E were generally below 1 mm, with an average of 0.6 mm, representing 13.6% of daytime ET. Night time E values were lower, with an average of 0.2 mm. Large coef®cients of variation were observed. The use of microlysimeters under low soil evaporation conditions may not be practical, requiring a large number of replications to estimate the average with reasonable con®dence. Results also indicated, low agreement between E estimates obtained from the difference between BREB, ET and sap¯ow and E measured with microlysimeters. The variability of the measurements of sap¯ow per unit area was large for 20-min intervals, but decreased rapidly for daily to weekly intervals. Sap ow gauges seem capable of measuring weekly¯ow rates of ®eld corn within AE10% and 80±95% con®dence, and daily¯ow rates with 80% con®dence. For shorter time intervals or lower tolerable errors, the number of gauges required increases dramatically. #
DEVELOPMENT AND EVALUATION OF A WEIGHABLE LYSIMETER TO DETERMINE CROP EVAPOTRANSPIRATION
The development and evaluation of a weighable lysimeter to determine crop evapotranspiration is presented. A weighable lysimeter with a diameter of 31 cm and a depth of 37 cm was constructed. The lysimeter was evaluated by using it to estimate the crop evapotranspiration of waterleaf in Umudike in Southeastern Nigeria. The evapotranspiration (ETc) estimates by Pan Evapotranspiration, Blaney – Morin Nigeria, Blaney – Criddle and Modified Hargreaves – Samani methods were compared with the estimation of the weighable lysimeter which provides the most reasonable estimation of ETc and is one of the most reliable methods. The crop was irrigated daily and the daily data generated from the lysimeter were used to calculate the crop evapotranspiration (ETc Lysimeter) between the months of July/ August, 2013. Climatic data obtained for the same period were used to determine the crop evapotranspiration (ETc) using the Pan Evapotranspiration, Blaney – Morin Nigeria, Blaney – Criddle and Modified Hargreaves – Samani methods. The total crop evapotranspiration from the Lysimeter between July and August was 141.32 mm, while that of Pan Evapotranspiration (PE), Blaney – Morin Nigeria (BMN), Blaney – Criddle (BC) and Modified Hargreaves – Samani (MHS) were 147.72 mm, 136.81 mm, 131.61 mm and 132.52 mm, respectively. Test of hypothesis using z-Test indicates that there was no significant difference between the means of the ET by lysimeter and each of the other methods (Blaney-Criddle, Pan Evapotranspiration, Modified Hargreaves-Samani and Blaney-Morin Nigeria) for a 5% level of significance as z-cal < z-critical for the growth period of
Verification of Reference Evapotranspiration Estimated by Weighable Lysimeters and Its Applicability
Korean Journal of Soil Science and Fertilizer, 2019
The reference evapotranspiration (ET 0) is an essential indicator in explaining the water movement in the environment. In this study, we carried out to investigate the ET 0 , which were LYET (reference evapotranspiration calculated by the weighable lysimeter), PMET (reference evapotranspiration calculated by the FAO Penman-Monteith equation), and HSET (reference evapotranspiration calculated by the Hargreaves equation), respectively, and to estimate the relationship among the LYET, PMET, and HSET by regression analysis. Turfgrass was selected as the reference crop for calculating the ET 0 by the lysimeters. The experiment period was from 1st June to 31st December in 2015. The ET 0 in the lysimeter study area (National Institute of Agricultural Sciences, Wanju; WJ) was compared with that in the nearby Jeonju (JJ) location because of similar weather conditions. The relationship between PMET-WJ and PMET-JJ has the slope of 1.138, the coefficient of determination (R 2) of 0.972, and the relationship between HSET-WJ and HSET-JJ has a slope of 0.934 (R 2 =0.984); thus the fitness was high in both cases. The relationship between LYET and PMET in both soils (fine loamy, FL; coarse loamy, CL) showed a relatively high R 2 as higher than 0.9, whereas the relationship between LYET and HSET showed relatively low fitness (0.676-0.736 of R 2). According to the month, the fitness of PMET:LYET was higher than that of HSET:LYET, and in November and December, the R 2 of PMET:LYET was lowered to 0.7 or less as turfgrass entered into a dormant stage. The LYET, PMET, and HSET were found to have significantly high positive correlations with the minimum temperature, maximum temperature, mean temperature, and solar radiation (p < 0.01) and a significantly high negative correlation with mean humidity (p < 0.01). The estimated ET 0 by the lysimeter experiment was evaluated to be highly conformable with the ET 0 calculated by the FAO PM equations. Follow-up studies such as long-term monitoring are necessary to cope with the changing climate every year.
Agricultural Water Management
Evapotranspiration (ET) is the combination of soil water evaporation and plant transpiration. ET is a vital component of a field water balance; however, accurate determination of ET is difficult. Indirect methods and direct methods are used to measure ET at the field scale. Typical indirect methods estimate ET with energy balance or field water balance measurement. One possible direct method for determining ET involves the use of canopy chambers. The objectives of this study are to construct a portable canopy chamber; to quantify the diurnal and seasonal trends of ET in three cropping systems; and to compare reference evaporation (Priestley-Taylor method), ET estimated from field water balance components (i.e., rainfall, soil water storage and drainage), and portable canopy chamber measured ET. Three cropping systems, including corn and soybean in a corn-soybean rotation and reconstructed prairie, were studied at the Comparison of Bio-fuel Systems (COBS) research site in central Iowa. Portable canopy chambers were used to measure ET in the different cropping systems during the part of growing season in 2013, and the whole growing season in 2014. Three different chamber sizes were used to match different crop growth stages. Data were collected on 18 days (i.e., maximum ET flux measurements, average ET flux measurements, and diurnal measurements) during the part of 2013 crop growing season and 15 days (diurnal measurements) during the 2014 crop growing season. In 2013 (DOY 164-206 for corn and DOY 164-255 for prairie and soybean) the cumulative chamber measured ET values were less than half of the reference evaporation values, due to relatively dry soil conditions. In 2014 (DOY 156-261 for corn and DOY 156-277 for prairie and soybean), because of wet weather condition, cumulative chamber measured ET fluxes were 80% (corn), 70% (prairie), and 67% (soybean) of the reference evaporation, respectively. The cumulative chamber measured ET values were similar to the cumulative water balance estimated ET values for both growing seasons. The differences between chamber measured ET and reference evaporation were expected. However, the agreements between chamber measured ET and water balance estimated ET in both years provided strong evidence that the portable canopy chamber accurately measured field ET at the plot (m 2) scale. 1 CHAPTER 1. GENERAL INTRODUCTION This chapter includes a general introduction to evapotranspiration (ET), and it presents traditional analysis methods. The objectives of this study are stated. The final section of this chapter describes the organization of the thesis.
Field Measurement of Cotton Seedling Evapotranspiration
Agricultural Sciences, 2014
Information on cotton evapotranspiration (ET) during the seedling growth stage and under field conditions is scarce because ET is a difficult parameter to measure. Our objective was to use weighable lysimeters to measure daily values of cotton seedling ET. We designed and built plastic weighable micro-lysimeters (ML) that were 0.35 m deep with a soil volume of 6300 cm 3. The soil core was obtained in-situ by pushing the ML well casing into the soil using a commercial soil sampler. The soil core was weighed with tension and compression type load-cells, where a change in mass of 18 g•d −1 was equivalent to a water evaporation of 1 mm•d −1. We compared load-cell measurements of changes in mass to values measured with a portable field scale by linear regression analysis, and the slope was equal to 1, indicating no statistical difference (P = 0.05) between the two measurements. We measured and compared seedling height, root length and leaf area of cotton plants in the ML with cotton plants in the surrounding area and this comparison showed that the ML used was suitable to measure cotton seedling ET for the first 30 days after seed emergence. The root mean squared error for crop height was 0.09 cm, for leaf area index (LAI) was 0.03 m 2 •m −2 and 6.5 cm for root length. Also, soil temperature at a 0.1 m depth was statistically (P = 0.05) the same in and outside the ML's. For two planting dates, we measured daily values of soil water evaporation (E) and cotton seedling ET. The day following an irrigation event, E was ~ 9 mm * Corresponding author. # The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color, national origin, age, disability, and where applicable, sex, marital status, familial status, parental status, religion, sexual orientation, genetic information, political beliefs, reprisal, or because all or part of an individual's income is derived from any public assistance program. d −1 and quickly declined the following days. Results showed that ML's provide an accurate tool to measure water losses from the soil and cotton plants with a LAI of ≤0.2.
African Journal of Biotechnology, 2010
Lysimeters are considered the standard for evapotranspiration (ET) measurements. However, these units are often not replicated and are few in number at any given location. The Bowen ratio-energy balance (BREB) is a micrometeorological method often used to estimate ET because of its simplicity, robustness, and cost. In this paper, ET of irrigated soybean (Glycine max L.) was directly measured by weighing lysimeter and estimated by BREB method over a growing season in a semi-arid climate of eastern Mediterranean region. The study was conducted in Adana-Turkey du ring the summer of 2009 on a 0.12 ha area with a weighing lysimeter (2.0 × 2.0 × 2.5 m) located in the center of the field completely covered by well watered soybean where the prevailing direction of the wind and the upwind fetch was about 60 m. Cumulative evapotranspiration totals from the lysimeter and BREB methods were 354 and 405 mm, respectively. The BREB method showed a good performance for daily ET estimation when compa...
Irrigation and Drainage, 2016
Weighing lysimeters differ in shape and size and are well established in measuring soil water balance components, such as evaporation, transpiration and drainage. This study addresses the development, calibration and testing of low-cost small lysimeters for measuring evaporation and transpiration of barley in a glasshouse for three consecutive winter seasons (2011-2013). Forty-one small lysimeters were developed and used during the study. The lysimeters were made from plastic materials mounted on Tedea-Huntleigh model 1260 load cells. The temperature effect on the final mass reading from the load cells was corrected by deducing temperature correction factors for all the lysimeters. During calibration, the lysimeters had high linearity and no hysteresis. Sensitivities of the lysimeters ranged between 0.1 and 0.35 mm. The small lysimeters developed, installed and calibrated were able to measure evaporation and transpiration separately at high accuracy, sensitivity and precision. These lysimeters measured on hourly and daily bases, and were able to measure all the soil water balance components. Apart from the simplicity of these lysimeters, the water content of the whole soil profile could be easily monitored due to the deeper depth of the lysimeter. These small lysimeters were cheap to construct, and installation was easy compared to other lysimeters.
Agricultural Water Management, 2004
An enclosed portable chamber was constructed and calibrated to measure actual evapotranspiration (ET) from crop and pasture and then evaluated against established methods that are used to determine evapotranspiration. The chamber was equipped with variable speed electric fans to mix the air within the chamber during each ET measurement. The most appropriate fan speed was investigated. Pasture ET measured using the enclosed portable chamber compared well with predicted water loss using the water balance method for a six day period during winter 1997 in Armidale (NSW, Australia). Mean cumulative pasture ET for the six day period was 5.75 mm and 5.89 mm measured with the enclosed portable chamber and soil profile water loss respectively. Wheat ET measured using the enclosed portable chamber was compared with that estimated by the Bowen Ratio (BR) method for a two day period in the early growth stages of the crop. Mean ET using the enclosed portable chamber was 2.4 mm/day compared with 2.3 mm/day using the BR method. Results from the enclosed portable chamber method showed sensitivity to the choice of fan speed. A slow fan speed that produced an air velocity of 2.7 km/hr, gave the closest agreement with the Bowen Ratio method (2.3 versus 2.2 mm/day) for the wheat crop. The main attractions of the enclosed portable chamber method include: (1) its suitability for ET measurement within small areas (<1m 2), which enables ET measurement from individual plant communities within small areas; (2) its main principles of measuring the actual water flux from transpiring vegetation rather than inferring it from climatic parameters; (3) the speed by which an instantaneous ET rate is obtained (less than one minute); (4) instantaneous ET measurement can be repeated throughout the day from the same plant communities; and (5) the portability of the enclosed portable chamber. ET measurement using the enclosed portable chamber method may be combined with the existing soil water balance models for comparing alternative crop and pasture systems in terms of their water balance.
Actual Evapotranspiration of Unirrigated Grass in a Smart Field Lysimeter
Vadose Zone Journal
Lysimeters are basic instruments for evapotranspiration measurement. This study characterized the actual evapotranspiration of unirrigated and unfertilized grass in a warm region of the Czech Republic on a Chernozem loamy soil. An SFL-300 weighing lysimeter (diameter 0.3 m, depth 0.3 m) was used for this purpose. The suction at its bottom was maintained at the same level as in the native soil nearby. We selected 585 rainless days with regular records for the analysis of daily differences. On most days, the lysimeter-measured actual evapotranspiration, ET a , was smaller than the Penman-Monteith FAO 56 reference crop evapotranspiration, ET 0. The FAO 56 procedure was found to be a reasonable estimator of the unstressed evapotranspiration in a moderately stressed environment. The ET a /ET 0 ratio and the canopy surface resistance, r s , depend on the soil water content and suction measured at 5 cm. These graphs break down into horizontal unstressed parts and declining (for ET a /ET 0) or inclining (for r s) water-stressed parts. The ratio ET a /ET 0 is about 85% and r s is about 250 s m −1 when the grass is not under water stress. The annual curve of the unstressed crop coefficient has a sine shape. An energy balance criterion suggests that advection of heat is important in winter but not so much in summer. The study provides parameters of evapotranspiration for a canopy that can be found on many standard weather stations and demonstrates that high-quality research into evapotranspiration of low, dense, and shallow-rooting crops is possible with small lysimeters of this type.