Development of improved fertilizer management practices has the potential to increase fertilizer use efficiency and improve environmental quality. The objectives of this study were (i) to ...characterize the within field spatial variability of N uptake across irrigated corn production fields, (ii) to quantify and compare N uptake and grain yield across three site specific management zones (SSMZs), and (iii) to compare grain yield response to applied N between management zones. This study was conducted on continuous corn (Zea mays L.) in irrigated fields in northeastern Colorado. Fields were classified into high, medium, and low site specific management zones. Treatments consisted of a control and two uniform N application rates over 2 site-years (one field over 2 consecutive yr and another field over 1 yr). Nitrogen fertilizer rates varied with site-year and ranged from 56 to 268 kg N ha(-1). Aboveground biomass samples were collected at physiological maturity and analyzed for total N. Between management zones, N uptake, grain yield, and grain yield response to applied N were found to be statistically different (p < 0.05). Management zones were found to be less spatially variable than the whole field. The SSMZs accurately characterized variability in N uptake as well as grain yield response to applied N. Thus, variation in N uptake and grain yield can potentially be managed using SSMZs.
Nitrogen (N) input is one of the most important factors in maximizing yields and economic returns to farmers. Of the essentials
nutrients, N is required in large quantities, and it is the most mobile ...and dynamic nutrient in soil systems. It is well-documented
that soil physical and chemical properties are spatially variable and affect N dynamics and the mechanisms for its losses.
For example, N dynamics could vary from high denitrification N 2 losses from ponded areas with low drainage to high NO 3 · leaching losses from coarse-gravelly areas of the field. Recent developments in new technologies are allowing us to identify,
measure, and map these changes across the field. We found that N management using site-specific management zones (SSMZ) that
account for soil variability and productivity provides the amounts of N needed to increase yields and maximize the agronomic
use efficiency of the applied N. The SSMZ-based N application outperformed treatments that used yield-goal-based and uniform
N application rates. Grid-based N application treatments performed as well as the SSMZ for yields but were more inefficient
as far as the unit of yields produced by unit of N fertilizer applied. The SSMZ can be used to improve N management and use
efficiency of the applied N to increase yields and reduce N losses to the environment.
The extreme energy densities generated by ultra-relativistic collisions between heavy atomic nuclei produce a state of matter that behaves surprisingly like a fluid, with exceptionally high ...temperature and low viscosity. Non-central collisions have angular momenta of the order of 1,000ћ, and the resulting fluid may have a strong vortical structure that must be understood to describe the fluid properly. The vortical structure is also of particular interest because the restoration of fundamental symmetries of quantum chromodynamics is expected to produce novel physical effects in the presence of strong vorticity. However, no experimental indications of fluid vorticity in heavy ion collisions have yet been found. Since vorticity represents a local rotational structure of the fluid, spin-orbit coupling can lead to preferential orientation of particle spins along the direction of rotation. Here we present measurements of an alignment between the global angular momentum of a non-central collision and the spin of emitted particles (in this case the collision occurs between gold nuclei and produces Λ baryons), revealing that the fluid produced in heavy ion collisions is the most vortical system so far observed. (At high energies, this fluid is a quark-gluon plasma.) We find that Λ and hyperons show a positive polarization of the order of a few per cent, consistent with some hydrodynamic predictions. (A hyperon is a particle composed of three quarks, at least one of which is a strange quark; the remainder are up and down quarks, found in protons and neutrons.) A previous measurement that reported a null result, that is, zero polarization, at higher collision energies is seen to be consistent with the trend of our observations, though with larger statistical uncertainties. These data provide experimental access to the vortical structure of the nearly ideal liquid created in a heavy ion collision and should prove valuable in the development of hydrodynamic models that quantitatively connect observations to the theory of the strong force.
Global polarization of Λ hyperons has been measured to be of the order of a few tenths of a percent in Au+Au collisions at √SNN = 200 GeV, with no significant difference between Λ and Λ¯. These new ...results reveal the collision energy dependence of the global polarization together with the results previously observed √SNN = 7.7 – 62.4 GeV and indicate noticeable vorticity of the medium created in non-central heavy-ion collisions at the highest RHIC collision energy.
Fluctuations of conserved quantities such as baryon number, charge, and strangeness are sensitive to the correlation length of the hot and dense matter created in relativistic heavy-ion collisions ...and can be used to search for the QCD critical point. We report the first measurements of the moments of net-kaon multiplicity distributions in Au+Au collisions at sNN=7.7, 11.5, 14.5, 19.6, 27, 39, 62.4, and 200 GeV. The collision centrality and energy dependence of the mean (M), variance (σ2), skewness (S), and kurtosis (κ) for net-kaon multiplicity distributions as well as the ratio σ2/M and the products Sσ and κσ2 are presented. Comparisons are made with Poisson and negative binomial baseline calculations as well as with UrQMD, a transport model (UrQMD) that does not include effects from the QCD critical point. Within current uncertainties, the net-kaon cumulant ratios appear to be monotonic as a function of collision energy.
Variable rate fertilizer application technology (VRT) can provide an opportunity to more efficiently utilize fertilizer inputs; however, accurate prescription maps are essential. Researchers and ...farmers have understood the value of dividing whole fields into smaller, homogeneous regions or management zones for fertility management. Management zones can be defined as spatially homogeneous subregions within a field that have similar crop input needs. Delineating management zones that characterize the spatial variability within a field may provide effective prescription maps for VRT. The objective of this research was to compare and evaluate management zones developed from soil color (SC) and farmer experience with management zones developed from apparent electrical conductivity (ECa). These two methods of developing management zones were compared with soil nutrient levels, texture, and crop yields collected on two fields in 1997. The soil and yield parameters followed the trends indicated by both management zone methods at Field 1 with the highest values found in the high productivity zones and the lowest the low productivity zones. Significant differences were found among the management zones. However, at Field 2 the high and medium productivity zones were generally not significantly different using the SC approach, whereas the ECa approach was effective in identifying three distinct management zones. Both methods of developing management zones seem to be identifying homogeneous subregions within fields.
Precision manure management is a relatively new concept that merges the best agronomic and manure management practices along with precision agricultural techniques, such as site‐specific management ...zones (MZs), for agricultural productivity and environmental quality. The objective of the study was to assess the influence and compare the economic efficiency of variable‐rate applications of animal manure on grain yield in maize (Zea mays L.) fields across MZs in limited irrigation cropping systems. The study was conducted on furrow‐irrigated maize fields in northeastern Colorado, USA. Fields were classified into low, medium, and high yielding MZs, based on soil color, elevation, and yield history. Experimental strips were 4.5 m wide and 540 m long spanning across all MZs with manure and N fertilizer management strategies nested within MZs. Variable‐rate manure applications of 22, 44, and 67 Mg ha–1 were considered for variable yield goal (VYG) and constant yield goal (CYG) manure management strategies. The results of this study indicates that maize grain yield was significantly different across MZs a majority of times, however, not always consistent with the MZ productivity level. For instance, the low MZ showed a significantly (P ≤ 0.05) higher grain yield under a CYG manure management strategy. The enterprise budget analysis indicated that application of animal manure alone was economically inefficient for maize grain production. The study suggests that variable‐rates of manure can be used in conjunction with synthetic N fertilizer to ensure that crop N requirements are met at early growth stages of maize.
The Λ (Λ¯) hyperon polarization along the beam direction has been measured in Au+Au collisions at sNN=200 GeV, for the first time in heavy-ion collisions. The polarization dependence on the ...hyperons' emission angle relative to the elliptic flow plane exhibits a second harmonic sine modulation, indicating a quadrupole pattern of the vorticity component along the beam direction, expected due to elliptic flow. The polarization is found to increase in more peripheral collisions, and shows no strong transverse momentum (pT) dependence at pT greater than 1 GeV/c. The magnitude of the signal is about 5 times smaller than those predicted by hydrodynamic and multiphase transport models; the observed phase of the emission angle dependence is also opposite to these model predictions. In contrast, the kinematic vorticity calculations in the blast-wave model tuned to reproduce particle spectra, elliptic flow, and the azimuthal dependence of the Gaussian source radii measured with the Hanbury Brown–Twiss intensity interferometry technique reproduce well the modulation phase measured in the data and capture the centrality and transverse momentum dependence of the polarization signal.
Nonmonotonic variation with collision energy (sqrts_{NN}) of the moments of the net-baryon number distribution in heavy-ion collisions, related to the correlation length and the susceptibilities of ...the system, is suggested as a signature for the quantum chromodynamics critical point. We report the first evidence of a nonmonotonic variation in the kurtosis times variance of the net-proton number (proxy for net-baryon number) distribution as a function of sqrts_{NN} with 3.1 σ significance for head-on (central) gold-on-gold (Au+Au) collisions measured solenoidal tracker at Relativistic Heavy Ion Collider. Data in noncentral Au+Au collisions and models of heavy-ion collisions without a critical point show a monotonic variation as a function of sqrts_{NN}.
Maintenance and improvement of soil quality across spatially variable soils in continuous cropping systems are critical to sustaining agricultural productivity and environmental quality. The ...objectives of this project were (i) to study the effects of variable-rate application of animal manure on selected topsoil quality parameters across site-specific management zones (MZs) and (ii) to evaluate the variable-rate applications of manure using risk-assessment tools of nitrogen (N) leaching and phosphorus (P) runoff indices to understand its impact on environmental quality. This study was conducted in northeastern Colorado on continuous and furrow-irrigated maize fields. Experimental strips, 4.5 m wide and 540 m long, spanned across all MZs with treatments nested within MZs in the field. Variable rates of dairy and beef feedlot manure applied on irrigated and dryland fields respectively ranged from 0 to 67 Mg ha
−1
. Surface soil quality parameters evaluated before and after this study included bulk density, organic matter, water-holding capacity, electrical conductivity, and particle-size analysis. Results indicate that animal manure applications of 44 and 67 Mg ha
−1
significantly (P ≤ 0.05) increased soil organic matter and decreased bulk density of low- and medium-productivity-level MZs and had no significant impact on surface soil organic matter and bulk density of the high-productivity-level MZs. Animal manure significantly (P ≤ 0.05) increased surface soil water-holding capacity and soil electrical conductivity across zones; however, the maximum manure-induced soil EC was 1.0 dS m
−1
, which was below levels regarded as potentially harmful for maize production. Soil texture was not affected by animal manure applications. Colorado N leaching and P index indicated no environmental hazard associated with variable rate application of animal manure across MZs. This study indicates that variable-rate application of animal manure across MZs has potential to improve or maintain soil quality parameters over time without impairing the environment.
PDF
