Irrigation management for double-cropped fresh-market tomatoes on a high-water-table soil

Two tomato (Lycopersicon esculentum, Mill.) experiments were conducted for two years on a southeastern Coastal Plain soil that has a high, fluctuating water table. In one experiment, two methods for managing microirrigation were compared to a treatment that received only rainfall by measuring marketable fruit yields for spring and fall cropping seasons. Irrigation increased yields for both seasons in the second year because of low rainfall. Measurements among seven shallow wells on the site showed no consistent differences for either water table depth or gradient between adjacent wells. Two cultivars were evaluated in the second year, primarily because frost severely damaged the tomato plants about three weeks after transplanting. In the second experiment, two excessively irrigated treatments were evaluated in an effort to induce a "soft-fruit" storage and shipping problem experienced by many growers in this region. Although extremely large quantities of irrigation water were applied, these symptoms were not observed in this study. There were no differences in fruit yield between the two water management treatments in either spring or fall. Fruit quality measurements showed no significant differences. The 'Sunny' cultivar performed better than 'Walter' during the fall season for the extremely wet soil condition. A double-crop, microirrigation management system has higher input costs but provides increased profitability for fresh-market tomato production, particularly where markets are available for both spring and fall crops

Correction of cone index for soil water content differences in a coastal plain soil

Soil penetration resistance (cone index) varies with water content. The field variation of water content could mask treatment differences. The correction of cone index data to a single water content would help prevent this. We used equations from TableCurve software and from the literature to correct cone indices for differences in soil water contents. Data were taken from two field experiments where cotton (Gossypium hirsutum L.) was grown using conventional and conservation tillage without irrigation, and beans (Phaseolus vulgaris L.) were grown using conventional tillage with microirrigation. Boundary conditions based on hard, dry and soft. wet soils were imposed on the equations. Equations fit the data with coefficients of determination ranging from 0.55 to 0.92 and error mean squares from 1.37 to 6.35. After correction, cone index dependence on water content was reduced. A single-equation correction did not always fit the data across all treatments. Separate corrections, based on treatment, might be required. When corrections required multiple equations, differences may be real or may be a manifestation of the correction differences. In this case, the correction may not be feasible (unless some future work can coordinate different equations and assure a uniform correction)

A comparison of pressure chamber, leaf-press, and canopy temperature for four species under humid conditions

Numerous techniques are currently available for measurement of plant water status in field environments, including pressure chambers and indices based upon infrared-determined canopy temperatures. The Campbell-Brewster (J-14) leaf press has been promoted as a compact alternative to the pressure chamber for plant water potential determination. In-depth comparisons of the J-14 (?J) with the pressure chamber (?x) or with canopy temperatures (Tc) and crop water stress index (CWSI) have been limited, and an evaluation of the technique in a humid environment was needed. All three J-14 end points [exudation from cut (?Jc) or uncut leaf edges (?Ju) or darkening of interveinal areas (?Jd)] were highly correlated among themselves for the four species studied. Correlations of J-14 end points with other stress indicators from unstable diurnal periods were poor. None of the water status indicators correlated well with leaf diffusive resistance. Our data showed a species-related reliability of the J-14. The J-14 produced r2 values above 0.7 for soybean [Glycine max. (L.) Merr.] for all but comparisons with CWSI or Tc, minus air temperature (?T), and for corn (Zea mays L.) for ?x only. The J-14 did not perform well for tomato (Lypersician esculentum Mill.) or rapeseed (Brassica napes L.), and is probably best regarded only as a relative indication of plant water status in the absence of calibration with other techniques. Failure of ?x or J-14 to correlate well with CWSI underscores difficulty with CWSI measurement under humid conditions

Comparison of Campbell-leaf press with standard plant water stress measurements for four species

The Campbell-Brewster (J-14) leaf press is a compact alternative to the pressure chamber for plant water potential determination. Data comparing the J-14 with the pressure chamber (?x) or with canopy temperatures (Tc) and crop water stress index (CWSI) are limited. All three J-14 end points (exudation from cut or uncut leaf edges or darkening of interveinal areas) were highly correlated among themselves for the four species studied. Correlations of J-14 end points with other stress indicators from unstable diurnal periods were poor. Our data shoved a species-related reliability of the J-14. The J-14 produced r2 values above 0.7 for soybean for all but comparisons with CWSI or Tc minus air temperature (?T), and for corn for ?x only. The J-14 did not perform well for tomato or rapeseed. Failure of J-14 or ?x, to correlate well with CWSI suggests difficulty with CWSI measurement under humid southeastern conditions

Experiences with microirrigation for agronomic crops in the southeastern USA

Microirrigation offers several advantages over sprinkler irrigation in humid areas, including ease of automation; lower water pressure and flow rate; improved management of water and nutrients; and easy seasonal start-up, especially for subsurface placement. Microirrigation system cost could be reduced and made more profitable for agronomic crops by using wider spacing and subsurface placement of microirrigation laterals. Results are reviewed from five experiments involving microirrigation of agronomic crops (corn, soybean, and cotton) and including 14 site-years of data. Agronomic crops can be effectively and efficiently irrigated in the southeastern Coastal Plain with microirrigation systems. In three experiments involving nine site-years of data, both normal (0.76 - 1.0 m) and wide (1.5 - 2.0 m) lateral spacings were used to irrigate corn and cotton; yields were equal except in one year when corn yield was reduced by about 10% for the wide spacing. With corn, there was no yield difference between surface and subsurface placement of laterals at the normal spacing (every row). Other data indicate that wider spacing of laterals in subsurface installations produces cotton lint yields similar to those for the same spacing in surface placements. Consequently, it appears that surface or subsurface placement of laterals at wider spacings (alternate furrow, 1.5 - 2.0 m) has significant potential for profitable irrigation of agronomic crops such as corn, cotton, and soybean in the southeastern USA

Velocity-space sensitivity of the time-of-flight neutron spectrometer at JET

The velocity-space sensitivities of fast-ion diagnostics are often described by so-called weight functions. Recently, we formulated weight functions showing the velocity-space sensitivity of the often dominant beam-target part of neutron energy spectra. These weight functions for neutron emission spectrometry (NES) are independent of the particular NES diagnostic. Here we apply these NES weight functions to the time-of-flight spectrometer TOFOR at JET. By taking the instrumental response function of TOFOR into account, we calculate time-of-flight NES weight functions that enable us to directly determine the velocity-space sensitivity of a given part of a measured time-of-flight spectrum from TOFOR

Relationship of edge localized mode burst times with divertor flux loop signal phase in JET

A phase relationship is identified between sequential edge localized modes (ELMs) occurrence times in a set of H-mode tokamak plasmas to the voltage measured in full flux azimuthal loops in the divertor region. We focus on plasmas in the Joint European Torus where a steady H-mode is sustained over several seconds, during which ELMs are observed in the Be II emission at the divertor. The ELMs analysed arise from intrinsic ELMing, in that there is no deliberate intent to control the ELMing process by external means. We use ELM timings derived from the Be II signal to perform direct time domain analysis of the full flux loop VLD2 and VLD3 signals, which provide a high cadence global measurement proportional to the voltage induced by changes in poloidal magnetic flux. Specifically, we examine how the time interval between pairs of successive ELMs is linked to the time-evolving phase of the full flux loop signals. Each ELM produces a clear early pulse in the full flux loop signals, whose peak time is used to condition our analysis. The arrival time of the following ELM, relative to this pulse, is found to fall into one of two categories: (i) prompt ELMs, which are directly paced by the initial response seen in the flux loop signals; and (ii) all other ELMs, which occur after the initial response of the full flux loop signals has decayed in amplitude. The times at which ELMs in category (ii) occur, relative to the first ELM of the pair, are clustered at times when the instantaneous phase of the full flux loop signal is close to its value at the time of the first ELM

Search for Tensor, Vector, and Scalar Polarizations in the Stochastic Gravitational-Wave Background

The detection of gravitational waves with Advanced LIGO and Advanced Virgo has enabled novel tests of general relativity, including direct study of the polarization of gravitational waves. While general relativity allows for only two tensor gravitational-wave polarizations, general metric theories can additionally predict two vector and two scalar polarizations. The polarization of gravitational waves is encoded in the spectral shape of the stochastic gravitational-wave background, formed by the superposition of cosmological and individually unresolved astrophysical sources. Using data recorded by Advanced LIGO during its first observing run, we search for a stochastic background of generically polarized gravitational waves. We find no evidence for a background of any polarization, and place the first direct bounds on the contributions of vector and scalar polarizations to the stochastic background. Under log-uniform priors for the energy in each polarization, we limit the energy densities of tensor, vector, and scalar modes at 95% credibility to Ω0T<5.58×10-8, Ω0V<6.35×10-8, and Ω0S<1.08×10-7 at a reference frequency f0=25 Hz. © 2018 American Physical Society