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Metabolism of a sub-tropical low gradient black water river (1987)

EDWARDS, R. T. ; MEYER, J. L.

Oxford, UK : Blackwell Publishing Ltd

Freshwater biology 17 (1987), S. 0

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ISSN: 1365-2427

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: SUMMARY. 1. Single-station diel oxygen curves were used to monitor the oxygen metabolism of the Ogeechee River, a sixth-order blackwater river in the Coastal Plain of southeastern U.S.A., over a period of 4 years. Ecosystem production (P) and respiration (R) were estimated, and P/R ratios calculated to determine the extent of autotrophy characteristic of this type of river. The potential error in oxygen metabolism caused by photo-oxidation of dissolved organic carbon (DOC) in the water was measured and found to be minor.2. Rates of ecosystem primary production measured were intermediate compared to other rivers, ranging from 0.49 to 13.99g O2m−2 day −1.Primary production rates were highest during the summer when water levels were low. Regression analysis indicated that water depth and light absorption by DOM were significant predictors of primary production in this river. Incident light intensities were not significantly correlated with production rate.3. Respiration rates were unusually high, varying between 3.70 and 11.5 g O2 m−2 day − 1. System respiration also varied seasonally, but less than primary production. Rates were slightly higher in spring and summer.4. With one exception, P/R ratios were considerably lower than l throughout the study period, indicating that the Ogeechee River was highly heterotrophic. PIR ratios ranged from 0.09 to 1.3, and averaged 0.25.5. A carbon budget calculated for this river showed floodplain inputs were 7 times autochthonous production. Organic carbon turnover length was 690 km, considerably longer than has been reported for lower-order rivers.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1365-2427.1987.tb01046.x

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Irrigation water quality options for corn on saline, organic soils (1986)

Hoffman, G. J. ; Prichard, T. L. ; Maas, E. V. ; [et al.]

Springer

Irrigation science 7 (1986), S. 265-275

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ISSN: 1432-1319

Source: Springer Online Journal Archives 1860-2000

Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: Summary Corn production on the organic soils of the Sacramento-San Joaquin Delta of California was affected by the salinity of the irrigation water and the adequacy of salt leaching. Full production was achieved on soils that were saline the previous year, provided the electrical conductivity of the irrigation water (ECi) applied by sprinkling was less than about 2 dS/m and leaching was adequate from either winter rainfall or irrigation to reduce soil salinity (ECMSW) below the salt tolerance threshold for corn (3.7 dS/m). For subirrigation, an ECi up to 1.5 dS/m did not decrease yield if leaching had reduced ECMSW below the threshold. If leaching was not adequate, even nonsaline water did not permit full production. In agreement with previous results obtained in a greenhouse, surface irrigation with water of an electrical conductivity of up to 6 dS/m after mid-season (end of July) did not reduce yield below that of treatments where the salinity of the irrigation water was not increased at mid-season. Results also reconfirm the salt tolerance relationship established in the previous three years of the field trial. The earlier conclusion that the irrigation method (sprinkler or subirrigation) does not influence the salt tolerance relationship was also confirmed.