Multisensor capacitance probes (MCAP) are an alternative to gravimetric or nuclear soil water content (θ v , m 3 −3 ) measurements. Their θ measurements more convenient than gravimetric, and don't carry the regulatory burdens. Previous studies noted potential salinity temperature effects on MCAP determinations. Our objectives were calibrate verify measurement accuracy in two materials, salinities (1.3 11.3 dS −1 ), with diurnal fluctuations. The surface calcic horizons of Olton (fine, mixed,...

With any method for measuring soil water content it is useful to know the spatial sensitivity of measurement, i.e., what volume measured and distribution within that volume. We determined this information time-domain reflectometry (TDR), using a laboratory procedure in which surrounding waveguides was controlled give different arrangements around waveguides. The largely confined region with cross-sectional area approximately 1000 mm2 waveguides, although limited extends much farther,...

Abstract Dryland crops grown in semiarid environments often do not completely cover the soil, leaving a portion of soil surface exposed to condition rapid soil‐water evaporation. Quantitative separation evaporation and crop transpiration is important if cultural practices or cultivars are be evaluated. This study was designed evaluate combined energy water balance model, ENWATBAL, describe concurrent heat fluxes row crop. Inputs model include plant variables daily weather data. Measurements...

Abstract Experiments and calculations were performed to characterize the water relations of fritted clay, a material which has been found suitable for growing experimental plants. Its dry bulk density is 0.67 kg/liter, particle 2.50 total porosity 0.73, saturated hydraulic conductivity 9.5 × 10 −4 m/sec. The desorption relation was measured unsaturated as function content calculated. Much drains from by gravity. After drainage commonly used containers, holds 0.31 volume plant‐available...

The rapid decline in water availability for irrigation on the Texas High Plains (THP) is a significant problem affecting crop production and viability of large regional economy worth approximately USD 7 billion annually. This region largest continuous cotton-producing area United States, timely delivery efficient use are critical to sustainability profitability cotton this region. Current scheduling must be improved reduce consumption without compromising production. Presently, based...

Abstract It is estimated that 20% of cotton producers in the Texas High Plains use strip tillage practice planting ( Gossypium hirsutum L.) residues chemically terminated winter wheat Triticum aestivum L.). The effect residue on water partitioning between soil E s ) and crop c evaporation has not been reported. This study tested hypothesis cumulative evapotranspiration t ), ina system conventional are similar, modifies components total by reducing increasing . Winter was planted fall 1990...

Effects of factors influencing spatial and temporal variability crop yields are usually expressed in growth patterns. Consequently, monitoring can form the basis for managing site-specific farming (SSF). This experiment was conducted to determine whether patterns forecast grain yields. irrigation rates (50 80% evapotranspiration, ET), elevation, soil texture, NO3-N, arthropods, diseases on corn (Zea mays L.) yield were evaluated at Halfway, TX, 1998 1999. Data plant height, leaf area index,...

Abstract When crops are grown in a row configuration, heat and mass transfer within the soil‐canopy system influence energy water balance of crop. Field experiments were conducted near Lubbock, TX, to examine soil canopy separately, cotton ( Gossypium hirsutum L.) under variety aerial moisture conditions. Bowen ratio techniques used obtain field balance, including total latent flux (LE). Latent from crop (LE c was determined sap flow measurements transpiration. s ) computed as daerence...

Abstract A numerical model was used to simulate evaporation, water, and temperature profiles for a bare soil over drying cycles of 8, 9, 20 d using hydraulic characteristics meteorological data as input. The also evaluate the effect thickness surface layer in on simulated evaporation rates. values were compared actual measurements made same period time. predicted cumulative within 1 standard deviation (SD) measured values, 34 37 cases, daily rates SD means. water means measured. accuracy...

This study evaluated microbial communities of soil (0–10 cm) as affected by dryland cropping systems under different tillage practices after 5 years. The type was an Olton sandy loam with average 16.4% clay, 67.6% sand and 0.65 g kg−1 organic matter (OM). were grain sorghum (Sorghum bicolor L.)—cotton (Gossypium hirsutum) (Srg-Ct), cotton-winter rye (Secale cereale)-grain (Ct-Rye-Srg), a rotation forage (f) L. Sorghum sudanense) winter (Srf-Rye), which no-tillage (nt) conventional (ct)...

Radiometric data can be useful to determine the impact of field heterogeneity, irrigation, and fertilization on plant water N use. A 2‐yr (1998–1999) study was conducted South Texas High Plains investigate cotton ( Gossypium hirsutum L.) spectral agronomic responses irrigation simple cross correlation among reflectance, growth, uptake, lint yield, site elevation (SE), soil texture. The treatments were at 50 75% calculated evapotranspiration (ET) rates 0, 90, 135 kg ha −1 arranged in an...

The spatial variability of soil properties that affect the N budget and corn (Zea mays L.) grain yield were studied for 2 yr in south-central Texas to better assess potential variable-rate fertilization. Residual NO3–N with depth mineralization (Nmin) their relationships total N, organic C, clay content characterized. 60-cm was more related than at shallower depths. showed temporal variation structure existing first year when concentrations high, but this absent second low. opposite trend...

There is a need for an accurate method to calculate and measure crop water use on real‐time. We implemented system that combines knowledge of available technology control the timely application water. Our objective was test compare it empirical engineering approach uses coefficient relate reference evapotranspiration. Technologies involved are measurement plant with stem flow gauges, soil time domain reflectometry, weather variables. Measurements coupled calculated values obtained model...

Abstract Texas South Plains production systems for conserving rainfall and reducing wind erosion in cotton ( Gossypium hirsutum L.), a low‐residue crop, include the spring chemical termination of winter wheat Triticum aestivum L.) overseeded post‐harvest into cotton. This practice often increases lint yields under irrigation, but residues hinder weed control increase costs. study characterized infiltration response to (i) residue weathering soil consolidation with ridges, (ii) distribution...

Pre‐plant soil NO − 3 –N tests and petiole analysis are bases for Upland cotton ( Gossypium hirsutum L.) N management in the western USA. Alternative approaches include proximal multispectral reflectance sensing chlorophyll meter readings. Our objective was to determine if spectral measurements correlate with leaf biomass. Urea ammonium nitrate applied after emergence low energy precision (LEPA) center‐pivot, surface or subsurface drip irrigation water up peak bloom. Multispectral readings...

Irrigated agriculture in the Texas High Plains (THP) region faces severe challenges due to rapidly declining groundwater levels underlying Ogallala Aquifer, recurring droughts, and projected warmer drier future climatic conditions. Scheduling irrigation with appropriate deficits different crop growth stages could improve water use efficiency (IWUE), thereby enable additional savings valuable without severely compromising yield. Our objective was identify efficient growth-stage-based variable...

Nitrogen recommendations for Upland cotton ( Gossypium hirsutum L.) in the western USA are based on spring soil NO − 3 –N tests. In‐season monitoring of plant N status is another approach. Our primary objective was to test spectral reflectance and chlorophyll meter measurements as in‐season decision aids irrigated cotton, compare these with test‐based management. The secondary determine fate 15 affected by management irrigation modes. Urea ammonium nitrate applied low energy precision (LEPA)...

There are numerous published discussions on the water use and requirements of grapes (<i>Vitis vinifera</i>, L.), but data actual individual plants in an undisturbed field environment not available. We assessed applicability stem heat balance method, using commercially available gauges, to determine daily seasonal three-year-old Chardonnay New Deal, TX. first evaluated gauges by simultaneously measuring hourly a potted Cabernet Sauvignon plant gravimetrically with flow gauge. Second, we...