The Conservation Reserve Program (CRP) is a U.S. federal land conservation program that incentivizes grassland reestablishment on marginal lands. Although this program has many environmental benefits, two critical questions remain: does reestablishing grasslands via CRP also result in soil health recovery, and what parts of restored fields (i.e., topographic positions) recover the fastest? We hypothesized that soil health will recover over time after converting cropland to CRP grassland and that recovery will be greatest at higher topographic positions. To test this, we sampled 241 midwestern U.S. soils along a grassland chronosequence (0-40 yr, including native grasslands) and at four topographic positions (i.e., a chronotoposequence). Soils were measured for bulk density, maximum water holding capacity (MWHC), soil organic C (SOC), extractable inorganic N, potentially mineralizable C (PMC), and N. Native grasslands had superior soil health compared with cropland and most CRP soils, and even 40 yr since grassland reestablishment was not adequate for full soil health recovery. Topographic position strongly influenced soil health indicators and often masked any CRP effect, especially with MWHC and SOC. However, PMC (a measure of active C) responded most rapidly to CRP and consistently across the landscape and was 26-34% greater 19-40 yr after grassland reestablishment. Reestablishing grasslands through CRP can improve soil health, although topographic position regulates the recovery, with greatest improvements at shoulder slope positions. Patience is needed to observe changes in soil health, even in response to a drastic management change like conversion of cropland to CRP grassland.
The
practical impact of analytical probes that transduce in the
near-infrared (nIR) has been dampened by the lack of cost-effective
and portable nIR fluorimeters. Herein, we demonstrate straightforward
designs for an inexpensive microplate reader and a portable fluorimeter.
These instruments require minimally complex machining and fabrication
and operate with an open-source programming language (Python). Complete
wiring diagrams, assembly diagrams, and scripts are provided. To demonstrate
the utility of these two instruments, we performed high-throughput
and field-side measurements of soil samples to evaluate the effect
of soil management strategies on extracellular proteolytic, cellulolytic,
and lignin-modifying activities. This was accomplished with fluorescent
enzyme probes that utilized uniquely sensitive transducers exclusive
to the nIR spectrum, single-walled carbon nanotubes. We also used
the portable fluorimeter to evaluate spatial variations of proteolytic
activity within individual field plots, while minimizing the effects
of soil storage and handling. These demonstrations indicate the utility
of these fluorimeters for translating analytical probes that operate
in the nIR beyond the laboratory and into actual use.
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