Abstract
We have developed a high-resolution automatic sampling system for continuous in situ measurements of stable water isotopic composition and nitrogen solutes along with hydrological information. The system facilitates concurrent monitoring of a large number of water and nutrient fluxes (ground, surface, irrigation and rain water) in irrigated agriculture. For this purpose we couple an automatic sampling system with a Wavelength-Scanned Cavity Ring Down Spectrometry System (WS-CRDS) for stable water isotope analysis (δ2H and δ18O), a reagentless hyperspectral UV photometer (ProPS) for monitoring nitrate content and various water level sensors for hydrometric information. The automatic sampling system consists of different sampling stations equipped with pumps, a switch cabinet for valve and pump control and a computer operating the system. The complete system is operated via internet-based control software, allowing supervision from nearly anywhere. The system is currently set up at the International Rice Research Institute (Los Baños, The Philippines) in a diversified rice growing system to continuously monitor water and nutrient fluxes. Here we present the system's technical set-up and provide initial proof-of-concept with results for the isotopic composition of different water sources and nitrate values from the 2012 dry season.
Highlights
Rice (Oryza sativa L.) is the primary food source for nearly half of the World’s population, including most of the poor, and is the only cereal that can grow under wetland conditions
We constructed a sampling system consisting of 18 sampling points for groundwater (GW) and surface water (SW), additional sampling points for irrigation water (IW) and rain water (RW), a water transport and distribution system including a remote-control computer, a switch cabinet and several analytical devices
We have shown that automatic measurements of water from various sources are possible
Summary
Rice (Oryza sativa L.) is the primary food source for nearly half of the World’s population, including most of the poor, and is the only cereal that can grow under wetland conditions. A more detailed understanding of water and nutrient cycling in rice-based cropping systems is needed, and requires the investigation of hydrological and biochemical processes as well as transport dynamics at the field scale. New developments in analytical devices permit monitoring parameters at temporal resolutions recently impossible/cost prohibitive These new systems facilitate high-resolution data acquisition without much necessary maintenance or analysis over longer periods. Developments in new hyperspectral UV photometers have resulted in small and reagent-free systems for water analysis at low detection limits With these new instruments it is possible to observe the closely related hydrological and biogeochemical fluxes of water, C and N as proposed by Chen and Coops [22]. We present a new type of automatic sampling set-up that facilitates in situ analysis of hydrometric information, stable water isotopes and nitrate concentrations in spatially differentiated agricultural fields.
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