This volume consists of a collection of current studies on free electron lasers. Free
Electron Lasers covers the analysis of fundamentals and questions of design of these
devices functioning from the infrared to ultraviolet or xuv wavelength regimes. In
addition to the comparison with conventional lasers, analyses of some related topics
concerning near-field and cavity electrodynamics, compact and table-top
arrangements and strong radiation–induced exotic states of matter are presented.
Drainage of water through the soil proﬁle to
groundwater and surface water appears to be the
hydrologic pathway that most frequently leads to
problematic nitrate contamination of surface waters in
agricultural watersheds. This can occur in two ways: by
natural drainage where ground water contributes to stream
ﬂow and river ﬂow, and by artiﬁcial subsurface drainage,
where perforated pipes (sometimes called tile drains) have
been buried in the soil for the purpose of removing water
to reduce damage caused by saturated conditions and
thereby enhance crop production (Fig. 1).
In most agricultural settings, commercial fertilizer
provides only one source of N used for crop production.
Animal manure, biological N ﬁxation, mineralization from
soil organic N, and deposition of N from the atmosphere
can also contribute to soil fertility and surface water
contamination. Because there are multiple sources and
sinks of N in the soil, the relationship between N fertilizer
application rate and nitrogen loss in drainage water is not
always consistent across locations and across studies.
In many settings nitrogen enrichment of surface water
bodies has increased following the increased use of N
fertilizers. The precise contribution of nitrogen fertilizers
to surface water nitrogen has been difﬁcult to quantify
because there are multiple sources of nitrogen contributing
to most water bodies, and, depending on environmental
conditions, a certain portion of soil nitrogen may be
converted to gaseous or immobile forms.