15 research outputs found
Economic and risk considerations of nitrogen fertilizer use in the Brown Soil Zone
Non-Peer ReviewedOptimum use of nitrogen fertilizer requires consideration of factors that influence plant response and those that govern the decisions of producers. The response of spring wheat to soil moisture and N fertilizer was assessed in a 9-yr zero tillage study conducted on a medium texture soil at Swift Current, Saskatchewan. These data were used to assess the economic merit and risk considerations of alternate N fertilizer management systems when combined with snow-trapping to enhance soil moisture reserves. The N fertilizer system included rates from 0 to 100 kg ha-1, spring versus fall applications and deep-banding versus surface broadcasting. The results showed that the optimum rates of fertilizer N
(FN) varied directly with spring soil moisture reserves (SM) and the probability distribution for 1 May to 31 July precipitation, and inversely with soil N (SN), the ratio of FN cost to wheat price, and the level of risk aversion held by producers. The optimum FN rates were highest for spring- and fall-banding; they were 3 to 14 kg ha-1 lower for spring broadcasting and 7 to 22 kg ha-1 lower with fall broadcasting. The
optimum rates increased 3.7 to 5.7 kg N ha-1 for each 10 mm increase in SM, with the higher rates associated with high SN. The FN rates declined 5 kg ha-1 for each additional year that the land was cropped continuously. For producers seeking to maximize expected profit or those with low risk aversion, the optimum FN rates were considerably higher than those recommended by the Saskatchewan Soil Testing Laboratory (SSTL) . In contrast, the FN rates for producers with high risk aversion were generally lower than those of the SSTL. The SSTL recommended rates were most appropriate for producers with medium risk aversion. The study found no single combination of timing and method of N fertilizer placement to be superior in all cases. Spring- and fall-banding provided higher net margins than broadcasting N fertilizer when SM or wheat prices were high, or if banding fertilizer can be combined with a tillage operation for weed control. The economic benefit from snow-trapping averaged 32 ha-1
depending on FN rate and wheat price; however, little benefit or a small loss was incurred in some years when infiltration of melt water was low or winter snowfall was minimal
Measurement of the Bottom-Strange Meson Mixing Phase in the Full CDF Data Set
We report a measurement of the bottom-strange meson mixing phase \beta_s
using the time evolution of B0_s -> J/\psi (->\mu+\mu-) \phi (-> K+ K-) decays
in which the quark-flavor content of the bottom-strange meson is identified at
production. This measurement uses the full data set of proton-antiproton
collisions at sqrt(s)= 1.96 TeV collected by the Collider Detector experiment
at the Fermilab Tevatron, corresponding to 9.6 fb-1 of integrated luminosity.
We report confidence regions in the two-dimensional space of \beta_s and the
B0_s decay-width difference \Delta\Gamma_s, and measure \beta_s in [-\pi/2,
-1.51] U [-0.06, 0.30] U [1.26, \pi/2] at the 68% confidence level, in
agreement with the standard model expectation. Assuming the standard model
value of \beta_s, we also determine \Delta\Gamma_s = 0.068 +- 0.026 (stat) +-
0.009 (syst) ps-1 and the mean B0_s lifetime, \tau_s = 1.528 +- 0.019 (stat) +-
0.009 (syst) ps, which are consistent and competitive with determinations by
other experiments.Comment: 8 pages, 2 figures, Phys. Rev. Lett 109, 171802 (2012
Seed dispersal in changing landscapes
10.1016/j.biocon.2011.09.018Biological Conservation14611-13BICO