Nutrient availability of composted and noncomposted residues in a Patagonian Xeric Mollisol |
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| Authors: | F Laos Patricia Satti Ingrid Walter María Julia Mazzarino Susana Moyano |
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| Institution: | (1) Centro Regional Universitario Bariloche, Universidad Nacional Comahue, Quintral 1250 (8400), Bariloche R.N., Argentina e-mail: suelos@crub.uncoma.edu.ar Fax: 54-2944-422111, AR;(2) Instituto Nacional de Investigaciones Agrarias, Madrid, Spain, ES;(3) CONICET, Consejo Nacional de Investigaciones Cientificas y Técnicas, Argentina, AR |
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| Abstract: | The main objectives of this study were to determine: (1) the agronomic value of composted and noncomposted residues originated
in the Andean-Patagonian region (APR), and (2) whether aerobic incubations provide a reliable index of nutrient availability
to estimate application rates. A Xeric Mollisol of the transitional zone between the APR and the Patagonian steppe, amended
with composted and noncomposted residues, was employed in laboratory incubations without plants and in a 5-month greenhouse
trial with ryegrass. Noncomposted residues were biosolids and fish wastes (FW) collected under farming cages. Composts were
obtained from fish offal and biosolids mixed with sawdust, woodshavings and yard trimmings. A commercial compost was also
included. In laboratory incubations at similar rates of application (10 g kg–1), net N mineralization (Nmin) was about two-fold higher with the noncomposted (17–23%) than with the composted residues (0–12%) and P release was very
high with the FW. Ryegrass yields were closely related to the total Kjeldahl N and mineralized N of the organic residues and
weakly related to their P contents (total or extractable). Yields were increased even in the case of composts which exhibited
very low values of Nmin (and slight N immobilization) during laboratory incubation, suggesting that the presence of plants enhanced Nmin at rates of 10–20 g kg–1. Soil residual extractable P after ryegrass removal was high for fish-derived amendments and the commercial product, suggesting
a potential risk of P pollution when these are applied according to N requirements. Aerobic incubations provided a relatively
good index with which to assess adequate rates of application.
Received: 17 July 1999 |
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| Keywords: | Organic residues Aerobic incubations Nutrient availability Ryegrass growth uptake Xeric Mollisol |
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