Resumen

PEREIRA, A.; RODRIGUES, M. A.  y  ARROBAS, M.. Nitrogen release from organic amendments assessed by using anion exchange membranes and the SPAD-502 chlorophyll meter. Rev. de Ciências Agrárias [online]. 2009, vol.32, n.1, pp.27-39. ISSN 0871-018X.

Results from pot experiments where anion exchange membranes (MTA) were inserted into the soil to monitor soil nitrate levels over time, and the plant N nutritional status assessed with a SPAD-502 chlorophyll meter, are reported in this work. Maize was grown in the summer season and turnip and rye in the winter period. Maize was sown on June 5, 2004, and turnip and rye on September 23, 2004. The plants were subjected to the following treatments: Nutrisoil (Nut); Beiraadubo (Bei); Phenix (Phe); Vegethumus (Veg); cow manure (EB); chestnut fruit bark (CC); ammonium nitrate (NA); and control treatment, without N fertilization (T). Two weeks after the maize was sown, soil nitrate levels extracted by MTA ranged between 18.9 and 239.0 mg _L-1 in the CC and Bei treatments, respectively. In the first week of August mean soil nitrate values ranged between 12.9 and 52.3 mg L^-1 in the CC and Bei treatments. In September, the last sampling date, mean soil nitrate levels were found to be in the range of 9.7 and 67.9 mg L^-1 in the CC and Nut treatments. Relationships between MTA and SPAD results with dry matter yield and N uptake were established. The MTA were able to differentiate well as the organic amendments released their N during the season and this aspect influenced N uptake and plant growth. SPAD readings were also a good index of plant N nutritional status. SPAD values were linearly related with dry matter yield and N uptake. In this study, where the pots were managed to avoid nitrate leaching and denitrification, winter grown species recovered the residual N of maize fertilization. At the end of experiment the plants showed senescent leaves with deep N deficiency symptoms.

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