Irrigation Management

Competition for limited water supplies continues to restrict water available for irrigation. Irrigated agricultural must continually improve irrigation management to continue producing food, fiber and fuel for a growing world population. Precision irrigation is the process of applying the right amount of water at the right time and place to obtain the best use of available water. Precision irrigation management is needed on large irrigation projects so water delivery matches irrigation needs and on individual fields to apply the right amount of water at the right time and place. Technology is commercially available to precisely apply water when and where it is needed by crops, however, user-friendly decision tools are still needed to quantify specific irrigation needs and control water application within fields. Integrating information from various sensors and systems into a decision support program will be critical to highly managed, spatially varied irrigation

Planting geometries and the efficient use of water and nutrients

In nature and in the most primitive agricultural systems, seed distribution is broadcast across the landscape. Such a distribution results in nearly uniform spacial interaction of the developing phytomass. With the development of agrarian civilization has come an implement-dependent systemization of crop- planting patterns. This has brought about the planting of crops in uniform rows—from the drilling of small grains at inter-row spacings of 0.1 to 0.2 m and plant intra-row spacings of i to 5 cm, to the staking of horticultural and vine crops at 2- to 3—m inter-row spacings and typically 0.3- to l-m intra-row spacings. The implement dependence of agricultural cropping strategies has resulted in row cropping. The staple crops regarded as most suited to this approach are commonly called row crops, and this review will concentrate largely on how row crops interact with plant geometry, water, and nutrients to in?uence sustained productive capacity

Morphological, temporal, and nodal accumulation of nutrients by determinate soybean

Crop growth models that account for nutrient accumulation offer insight into soil fertility and plant nutrition interactions. This understanding provides opportunities to develop improved management practices. During the 1980s, several process-level growth models were developed for soybean [Glycine max (I..) Merr.). Model validation and application to different locations and weather require detailed, independent data sets. An extensive data set describing the nutrient status of a determinate soybean ('Bragg') was collected in 1979 on a Goldsboro (Aquic Paleudult) loamy sand near Florence, SC, USA. Because of its importance to subsequent model development, we concluded that providing this entire data set in a readily accessible form was a logical step in the course of this experiment. We report here, in tabular form, mean and standard deviation data for aerial accumulation of dry matter and eight nutrients (N, P, K, Ca, Mg, Mn, Fe, and Zn) for 10 dates, for four plant components (stems, leaves, petioles, pods, and total), and for each node (and whole plant). We will provide, upon arrangement, these same data on diskette for use in simulation models or other applications

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

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

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

Measurement of directional range components of nuclear recoil tracks in a fiducialised dark matter detector

We present results from the first measurement of axial range components of fiducialized neutron induced nuclear recoil tracks using the DRIFT directional dark matter detector. Nuclear recoil events are fiducialized in the DRIFT experiment using temporal charge carrier separations between different species of anions in 30:10:1 Torr of CS$_2$:CF$_4$:O$_2$ gas mixture. For this measurement, neutron-induced nuclear recoil tracks were generated by exposing the detector to $^{252}$Cf source from different directions. Using these events, the sensitivity of the detector to the expected axial directional signatures were investigated as the neutron source was moved from one detector axis to another. Results obtained from these measurements show clear sensitivity of the DRIFT detector to the axial directional signatures in this fiducialization gas mode

Heavy Quarks and Heavy Quarkonia as Tests of Thermalization

We present here a brief summary of new results on heavy quarks and heavy quarkonia from the PHENIX experiment as presented at the "Quark Gluon Plasma Thermalization" Workshop in Vienna, Austria in August 2005, directly following the International Quark Matter Conference in Hungary.Comment: 8 pages, 5 figures, Quark Gluon Plasma Thermalization Workshop (Vienna August 2005) Proceeding

Single Electrons from Heavy Flavor Decays in p+p Collisions at sqrt(s) = 200 GeV

The invariant differential cross section for inclusive electron production in p+p collisions at sqrt(s) = 200 GeV has been measured by the PHENIX experiment at the Relativistic Heavy Ion Collider over the transverse momentum range $0.4 <= p_T <= 5.0 GeV/c at midrapidity (eta <= 0.35). The contribution to the inclusive electron spectrum from semileptonic decays of hadrons carrying heavy flavor, i.e. charm quarks or, at high p_T, bottom quarks, is determined via three independent methods. The resulting electron spectrum from heavy flavor decays is compared to recent leading and next-to-leading order perturbative QCD calculations. The total cross section of charm quark-antiquark pair production is determined as sigma_(c c^bar) = 0.92 +/- 0.15 (stat.) +- 0.54 (sys.) mb.Comment: 329 authors, 6 pages text, 3 figures. Submitted to Phys. Rev. Lett. Plain text data tables for the points plotted in figures for this and previous PHENIX publications are (or will be) publicly available at http://www.phenix.bnl.gov/papers.htm

Nuclear Modification of Electron Spectra and Implications for Heavy Quark Energy Loss in Au+Au Collisions at sqrt(s_NN)=200 GeV

The PHENIX experiment has measured mid-rapidity transverse momentum spectra (0.4 < p_T < 5.0 GeV/c) of electrons as a function of centrality in Au+Au collisions at sqrt(s_NN)=200 GeV. Contributions from photon conversions and from light hadron decays, mainly Dalitz decays of pi^0 and eta mesons, were removed. The resulting non-photonic electron spectra are primarily due to the semi-leptonic decays of hadrons carrying heavy quarks. Nuclear modification factors were determined by comparison to non-photonic electrons in p+p collisions. A significant suppression of electrons at high p_T is observed in central Au+Au collisions, indicating substantial energy loss of heavy quarks.Comment: 330 authors, 6 pages text, 3 figures. Submitted to Phys. Rev. Lett. Plain text data tables for the points plotted in figures for this and previous PHENIX publications are (or will be) publicly available at http://www.phenix.bnl.gov/papers.htm