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 (δ 2H and δ 18O), 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 Ba？os, 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.
References
[1]
Maclean, J.L.; Dawe, D.C.; Hardy, B.; Hettel, G.P. Rice Almanac: Source Book for the Most Important Economic Activity on Earth, 3rd ed. ed.; CABI Pub: Oxon, UK, 2002.
[2]
Tuong, T.P.; Bouman, B.A.M. Rice Production in Water Scarce Environments. In Water Productivity in Agriculture: Limits and Opportunities for Improvement; Kijne, J.W., Barker, R., Molden, D.J., Eds.; CABI Pub: Oxon, UK/Cambridge, MA, USA, 2003; pp. 53–67.
[3]
Dobermann, A.; Witt, C.; Dawe, D.; Abdulrachman, S.; Gines, H.C.; Nagarajan, R.; Satawathananont, S.; Son, T.T.; Tan, P.S.; Wang, G.H.; et al. Site-specific nutrient management for intensive rice cropping systems in Asia. Field Crops Res. 2002, 74, 37–66.
Tuong, T.P.; Bhuiyan, S.I. Increasing water-use efficiency in rice production: Farm-level perspectives. Agric. Water Manag. 1999, 40, 117–122.
[6]
Bouman, B.A.M.; Peng, S.; Casta？eda, A.R.; Visperas, R.M. Yield and water use of irrigated tropical aerobic rice systems. Agric. Water Manag. 2005, 74, 87–105.
[7]
Timsina, J.; Buresh, R.J.; Dobermann, A.; Dixon, J. Rice-Maize Systems in Asia: Current Situation and Potential; IRRI: Metro Manila, Philippines, 2011.
[8]
Kirchner, J.W.; Feng, X.; Neal, C.; Robson, A.J. The fine structure of water-quality dynamics: The (high-frequency) wave of the future. Hydrol. Process. 2004, 18, 1353–1359.
[9]
McClain, M.E.; Boyer, E.W.; Dent, C.L.; Gergel, S.E.; Grimm, N.B.; Groffman, P.M.; Hart, S.C.; Harvey, J.W.; Johnston, C.A.; Mayorga, E.; et al. Biogeochemical hot spots and hot moments at the interface of terrestrial and aquatic ecosystems. Ecosystems 2003, 6, 301–312.
[10]
McGuire, K.J.; McDonnell, J.J. A review and evaluation of catchment transit time modeling. J. Hydrol. 2006, 330, 543–563.
Gat, J.R. Oxygen and hydrogen isotopes in the hydrologic cycle. Annu. Rev. Earth Planet Sci. 1996, 24, 225–262.
[13]
Butterbach-Bahl, K.; Gasche, R.; Breuer, L.; Papen, H. Fluxes of NO and N2O from temperate forest soils: Impact of forest type, N deposition and of liming on the NO and N2O emissions. Nutr. Cycingling Agroecosyst. 1997, 48, 79–90.
[14]
Breuer, L.; Papen, H.; Butterbach-Bahl, K. N2O emission from tropical forest soils of Australia. J. Geophys. Res. 2000, 105, 26353–26367.
[15]
Corton, T.M.; Bajita, J.B.; Grospe, F.S.; Pamplona, R.R.; Assis, C.A., Jr.; Wassmann, R.; Lantin, R.S.; Buendia, L.V. Methane emission from irrigated and intensively managed rice fields in Central Luzon (Philippines). Nutr. Cycling Agroecosyst. 2000, 58, 37–53.
[16]
Bai, M.; K？stler, M.; Kunstmann, J.; Wilske, B.; Gattinger, A.; Frede, H.-G.; Breuer, L. Biodegradability screening of soil amendments through coupling of wavelength-scanned cavity ring-down spectroscopy to multiple dynamic chambers. Rapid Commun. Mass Spectrom. 2011, 25, 3683–3689.
[17]
Berman, E.S.F.; Gupta, M.; Gabrielli, C.; Garland, T.; McDonnell, J.J. High-frequency field-deployable isotope analyzer for hydrological applications. Water Resour. Res. 2009, 45. 10.1029/2009WR008265.
[18]
Koehler, G.; Wassenaar, L.I. Realtime stable isotope monitoring of natural waters by parallel-flow laser spectroscopy. Anal. Chem. 2011, 83, 913–919.
[19]
Herbstritt, B.; Gralher, B.; Weiler, M. Continuous in situ measurements of stable isotopes in liquid water. Water Resour. Res 2012, 48. doi:10.1029/2011WR011369.
[20]
Munksgaard, N.C.; Wurster, C.M.; Bird, M.I. Continuous analysis of δ18O and δD values of water by diffusion sampling cavity ring-down spectrometry: A novel sampling device for unattended field monitoring of precipitation, ground and surface waters. Rapid Commun. Mass Spectrom. 2011, 25, 3706–3712.
[21]
Bende-Michl, U.; Hairsine, P.B. A systematic approach to choosing an automated nutrient analyser for river monitoring. J. Environ. Monit. 2010, 12, 127–134.
[22]
Chen, B.; Coops, N.C. Understanding of coupled terrestrial carbon, nitrogen and water dynamics—An overview. Sensors 2009, 9, 8624–8657.
[23]
Sandford, R.C.; Exenberger, A.; Worsfold, P.J. Nitrogen cycling in natural waters using in situ, reagentless UV spectrophotometry with simultaneous determination of nitrate and nitrite. Environ. Sci. Technol. 2007, 41, 8420–8425.
[24]
Koehler, A.-K.; Murphy, K.; Kiely, G.; Sottocornola, M. Seasonal variation of DOC concentration and annual loss of DOC from an Atlantic blanket bog in South Western Ireland. Biogeochemistry 2009, 95, 231–242.
[25]
Waterloo, M.J.; Oliveira, S.M.; Drucker, D.P.; Nobre, A.D.; Cuartas, L.A.; Hodnett, M.G.; Langedijk, I.; Jans, W.W.P.; Tomasella, J.; de Araújo, A.C.; et al. Export of organic carbon in run-off from an Amazonian rainforest blackwater catchment. Hydrol. Processes 2006, 20, 2581–2597.
[26]
Sandford, R.C.; Hawkins, J.M.B.; Bol, R.; Worsfold, P.J. Export of dissolved organic carbon and nitrate from grassland in winter using high temporal resolution, in situ UV sensing. Sci. Total Environ. 2013, 456–457, 384–391.
[27]
Underwood, A.J. On beyond BACI: Sampling designs that might reliably detect environmental disturbances. Ecol. Appl. 1994, 4, 3–15.
[28]
Witt, C.; Pasuquin, J.M.C.A.; Mutters, R.; Buresh, R.J. New leaf color chart for effective nitrogen management in rice. Better Crops 2005, 89, 36–39.
[29]
Brand, W.A.; Geilmann, H.; Crosson, E.R.; Rella, C.W. Cavity ring-down spectroscopy versus high-temperature conversion isotope ratio mass spectrometry; a case study on δ2H and δ18O of pure water samples and alcohol/water mixtures. Rapid Commun. Mass Spectrom. 2009, 23, 1879–1884.
[30]
PyPI-the Python Package Index. Available online: https://pypi.python.org/pypi (accessed on 10 October 2013).
