Neutron Moisture Meter Calibration in Six Soils of Uzbekistan Affected by Carbonate Accumulation

Evett, Steven R.; Ibragimov, Nazirbay; Kamilov, Bakhtiyor S.; Esanbekov, Yusupbek; Sarimsakov, Maksudkhon; Shadmanov, Jamaliddin; Mirhashimov, Rahmonkul; Musaev, Ruzibay; Radjabov, T. F.; Muhammadiev, Bahram

doi:10.2136/vzj2006.0155

Cited by 20 publications

(24 citation statements)

References 9 publications

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“…1A). Th e larger slope for the deeper Bk horizon is the reverse of what is typically seen (Evett et al, 2007), however, probably partially due to the increased clay content below approximately 1-m depth (Table 1), and perhaps indicating that the carbonate or gypsum accumulation was weak and that the eff ect of soil textural diff erences exceeded the eff ect of carbonate or gypsum accumulation. Still, the depth of the separation between calibration slopes may indicate that the cambic horizon here extends to approximately 1.2 m, deeper than typical for the Panoche soil, probably due to intensive irrigation at the fi eld station.…”

Section: Resultsmentioning

confidence: 70%

Field Calibration Accuracy and Utility of Four Down‐Hole Water Content Sensors

Mazahrih¹,

Katbeh-Bader²,

Evett

et al. 2008

Vadose Zone Journal

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Soil water balance studies of profile water content, changes in stored water, crop water use, and spatial variability of water content and use require accurate soil water determinations that are representative across at least field‐sized areas. Several capacitance and other electromagnetic (EM) sensors are commercially available for use in access tubes to determine profile water content. Scientists and practitioners need to know if they are suitable replacements for the neutron moisture meter (NMM) in terms of accuracy and utility. In a field calibration of the NMM and three EM sensors in a Panoche clay loam soil in the San Joaquin Valley of California, three access tubes were installed in a site dried by plant water uptake and three were installed in an adjacent plot wetted to saturation and allowed to drain. Sensors were read and volumetric water content samples taken at several depths at each access tube; calibrations of water content vs. sensor reading were calculated for each depth and for appropriate combinations of depths by regression analysis. Calibrations for the EM sensors changed rapidly with depth, often requiring separate calibrations for every 10‐ or 20‐cm depth range, and were relatively inaccurate (RMSE of 0.015–0.063 m3 m−3). The NMM is the preferred choice for accurate profile water content and change in storage determination. In general, the EM sensors cannot be recommended for profile water content or change in storage determinations due to their relatively less accurate (larger RMSE values) calibrations, strong dependence of calibration slopes and exponents on depth, probable dependence of the calibrations on soil bulk electrical conductivity (BEC), and the likelihood of BEC changes in the field during the irrigation season.

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Section: Resultsmentioning

confidence: 70%

Field Calibration Accuracy and Utility of Four Down‐Hole Water Content Sensors

Mazahrih¹,

Katbeh-Bader²,

Evett

et al. 2008

Vadose Zone Journal

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“…Measurements of the volumetric water content of the soil profile were conducted twice a week and in two replicates during the experiments using a neutron probe to the 160‐cm depth in 20‐cm increments using the techniques described in Evett et al (2008). The neutron probe (Model 503DR1.5, CPN International, Concord, CA) was previously calibrated in polyvinyl chloride access tubes for each soil layer (Kamilov et al, 2003; Evett et al, 2007). Crop water use (evapotranspiration, ET) was established using the soil water balance approach on a weekly basis (Ibragimov et al, 2007) as ET = –Δ S + P + I + F + R , where Δ S is the change in water stored in the soil profile (decreases in stored water indicate positive ET), P is precipitation, I is irrigation, F is the flux across the lower boundary of the control volume (1.7‐m depth in this case and F positive into the control volume), and R is the sum of run‐on and runoff (assumed zero); all terms are in millimeters.…”

Section: Methodsmentioning

confidence: 99%

Permanent Beds vs. Conventional Tillage in Irrigated Arid Central Asia

Ibragimov¹,

Evett

Esenbekov³

et al. 2011

Agronomy Journal

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Limited or no tillage with residue retention on the soil surface has had mixed success in irrigated agricultural systems. The effects of tillage and crop residue management on soil properties and crop yields were studied on a silt loam soil using a rotation of winter wheat (Triticum aestivum L.) and maize (Zea mays L.) for 2 yr, followed by cotton (Gossypium hirsutum L.) for 2 yr. Permanent beds (PB) with limited reshaping and conventional tillage (CT) were compared, each with both 25% residue retention on a mass basis (R25) and 100% residue retention (R100). There was greater soil compaction and consolidation in the 0.2‐ to 0.3‐m depth with the PB system regardless of residue retention practice. Compared with the CT system and the PB+R25 treatment combination, the PB+R100 treatment combination increased the amount of water‐stable macroaggregates, however only in the fourth year. The soil organic C in the 0‐ to 0.4‐m depth increased at 0.70 Mg ha−1 yr−1 in PB+R100 vs. 0.48 Mg ha−1 yr−1 in CT+R100. Poor early plant growth and reduced plant population in PB caused decreased water use efficiency (WUE) and irrigation water use efficiency (IWUE) of maize and cotton grown consecutively in 2006 and 2007. Generally, R100 improved IWUE and WUE, except for cotton in 2007. For PB+R100, cotton seed‐lint IWUE in 2008 increased to 0.59 kg m−3 from 0.41 earlier. Smaller maize and cotton plant populations and cooler soil temperatures at cotton emergence in PB+R100 decreased crop productivity during the first 3 yr.

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“…Because dynamic hydrogen in soil is mainly in the form of H 2 O, a linear relationship exists between thermalized neutron counts and soil water for a given soil type (Evett et al. ). The Jornada LTER uses two NMMs, both are Campbell Pacific Nuclear Corporation (Concord, California, USA) model 503DR with 50mci Americium‐241/Beryllium neutron source.…”

Section: Methodsmentioning

confidence: 99%

Soil water dynamics at 15 locations distributed across a desert landscape: insights from a 27‐yr dataset

et al. 2018

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Abstract. Desert ecosystems are primarily limited by water availability. Within a climatic regime, topography, soil characteristics, and vegetation are expected to determine how the combined effects of precipitation, temperature, and evaporative demand of the atmosphere shape the spatial and temporal patterns of water within the soil profile and across a landscape. To forecast how desert landscapes may respond to future climatic conditions, it is imperative to improve our understanding of these ecohydrologic processes. Here, we report on 27 yr of monthly soil volumetric water content (VWC) measurements and associated soils data from a site in the northern Chihuahuan Desert of North America. The dataset includes VWC and soil properties measured to 3 m in depth across 15 locations that encompass a range of Chihuahuan Desert vegetation types. We use this unique dataset (1) to generate insights into general temporal and depth patterns in VWC, (2) to analyze how VWC corresponds to measures of climatic conditions, and (3) to qualitatively evaluate the relative importance of soils, topographic setting, and vegetation type in mediating temporal patterns in VWC. Analyses of this unique dataset emphasize the importance of soil and topographic setting in determining depth and temporal patterns in VWC across time. Results emphasize the episodic nature of deep wetting events in our study system-essentially limited to three large events over the 27-yr record driven primarily by wetter than normal winters. Comparison of soil water dynamics between mesquite shrub coppice dunes and interspace soils suggests the "island of fertility" concept does not extend to soil water. Median VWC was strongly coupled to climatic conditions over surprisingly long windows at most locations (6-18 months), suggesting that soil water at depth is decoupled from short climatic pulses. However, VWC dynamics and VWC-climate relationships varied among locations, depths, and seasons, with unexpected similarities in ecohydrologic dynamics observed among very different vegetation types (e.g., an eroded creosote shrubland and a playa grassland). These results further underscore the importance of ecohydrological investigations in these ecosystems, given forecasts for a warmer and more variable climate in deserts globally.

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Neutron Moisture Meter Calibration in Six Soils of Uzbekistan Affected by Carbonate Accumulation

Cited by 20 publications

References 9 publications

Field Calibration Accuracy and Utility of Four Down‐Hole Water Content Sensors

Field Calibration Accuracy and Utility of Four Down‐Hole Water Content Sensors

Permanent Beds vs. Conventional Tillage in Irrigated Arid Central Asia

Soil water dynamics at 15 locations distributed across a desert landscape: insights from a 27‐yr dataset

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