Browsing by Author "RODRIGUEZ, J"

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    A SIMPLE-MODEL FOR ESTIMATING THE CONTRIBUTION OF NITROGEN MINERALIZATION TO THE NITROGEN SUPPLY OF CROPS FROM A STABILIZED POOL OF SOIL ORGANIC-MATTER AND RECENT ORGANIC INPUT
    (1994) MATUS, FJ; RODRIGUEZ, J
    A simple model was developed to estimate the contribution of nitrogen (N) mineralization to the N supply of crops. In this model the soil organic matter is divided into active and passive pools. Annual soil mineralization of N is derived from the active pool. The active pool comprises stabilized and labile soil organic N. The stabilized N is built up from accumulated inputs of fresh organic N during a crop rotation but the labile N is a fraction of total N added, which mineralizes faster than the stabilized N. The passive pool is considered to have no participation in the mineralization process. Mineralization rates of labile and stabilized soil organic N from different crop residues decomposing in soil were derived from the literature and were described by the first-order rate equation dN/dt = -K*N, where N is the mineralizable organic N from crop residues and K is a constant. The data were grouped K-1 by short-term (0-1 year) and K-2 by long-term (0-10 years) incubation. Because the range of variation in K-2 was smaller than in K-1 we felt justified in using an average value to derive N mineralization from the stabilized pool. The use of a constant rate of K-1 was avoided so net N mineralization during the first year after addition is derived directly from the labile N in the crop residues. The model was applied to four Chilean agro-ecosystems, using daily averages of soil temperature and moisture. The N losses by leaching were also calculated. The N mineralization varied between 30 and 130 kg N ha(-1) yr(-1) depending on organic N inputs. Nitrogen losses by leaching in a poorly structured soil were estimated to be about 10% of total N mineralized. The model could explain the large differences in N- mineralization as measured by the potential N mineralization at the four sites studied. However, when grassland was present in the crop rotation, the model underestimated the results obtained from potential mineralization.
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    CONGENITAL 11-BETA-HYDROXYSTEROID DEHYDROGENASE-DEFICIENCY ASSOCIATED WITH JUVENILE HYPERTENSION - CORTICOSTEROID METABOLITE PROFILES OF 4 PATIENTS AND THEIR FAMILIES
    (1985) SHACKLETON, CHL; RODRIGUEZ, J; ARTEAGA, E; LOPEZ, JM; WINTER, JSD
    Four children with 11 .beta.-hydroxysteroid dehydrogenase deficiency are described. All patients had severe hypertension, hypokalemia, and low plasma aldosterone and renin activities. Two of the patients were siblings and 2 were unrelated. The most noticable biochemical feature of these individuals was the extremely low excretion of cortisol metabolites containing on 11-carbonyl group compared to the excretion of the 11 .beta.-hydroxyl containing metabolites. Although this condition is readily diagnosed in affected individuals by urinary steroid analysis, carriers of the defect do not differ from normal in their urinary steroids. Both parents of the affected siblings had normal 11-oxo-steroid/11 .beta.-hydroxysteroid ratios under baseline conditions and the lesions could not be revealed by ACTH administration.
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    LIGNINASES FROM CHRYSONILIA-SITOPHILA (TFB-27441 STRAIN)
    (1987) DURAN, N; FERRER, I; RODRIGUEZ, J