Data set ID:
An ion exchange resin bag technique (Binkley 1984, Lajtha 1988) was used to determine N availability in the rhizosphere of fluffgrass. Ion exchange resin bags were used to determine NH4.
Twenty 6 x 6 m plots were established with a 3 m buffer between plots. Five plots were randomly assigned to one of four treatments: (1) chlordane amendment 100ml AI (active ingredients) per 10,000 ml) to exclude microarthropods, (2) sprinkler irrigation (6 mm per week), (3) sprinkler irrigation (6 mm/week) plus chlordate amendment (as above), (4) control (no treatment). Two CA-bags were placed in the rhizosphere of a fluffgrass in each plot. Bags were left in the field 3 months, collected, brought to the lab and analyzed for NO3.
A 50 cm2 area of undyed nylon stocking material was sewn into a bag containing 10 g (wet weight) of Dowex 50 W-X8 cation exchange resin, 20-50 mesh. Cation resins already in the H+ form, were rinsed three successive times with dilute HCl. Bags were rinsed with deionized water and spun dry in an open-basket hand centrifuge before being taken to the field. Two bags of cation exhange resin were placed in each plot (total of 20 plots), directly in the rhizosphere of a plant (12 plants per plot) at approximatley 10 cm depth. Bags were replaced every 12 weeks for 9 months. Bags were rinsed thoroughly in deionized water and spun dry upon collection from the field. Cation bags were desorbed in 2.0 M KCl + PMA (to avoid bacterial and fungal growth). Samples were shaken 30 times, let set overnight and filtered. The solution was analyzed for NH4 -N using an automated salicylate procedure (Wall and Gehrke 1975; Nelson 1983).
This study was conducted in the Jornada del Muerto Basin on the NSF Long-Term Ecological Research (LTER) site, located on the New Mexico State University College Ranch 40 km NNE of Las Cruces, Dona Ana County, New Mexico. The site lies on an alluvial piedmont (bajada) sloping from west to the east and north. The non-arroyo areas of the upper bajada where this study was conducted have an essentially monospecific shrub cover of creosotebush and support a veriety of annuals and the small perennial grass Erioneuron pulchellum (fluff grass). Study plots were established in an area that is downslope from the LTER Upper Trailer and immediately downslope from the road running from the NMSU College Ranch headquarters SSE past the LTER Weather Station and exiting the College Ranch at the south boundary on the same powerline road that runs on along the north side of Mt. Summerford in the Dona Ana Mountains.
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