An irrigation experiment with sweet sorghum was carried out in La Rinconada (Sevilla), as a part of a series of experiments being performed in Andalucia to study the possibilities of this promising crop in the area. 2 different regimes of water application, normal and restrictive during the season of maximum growth were assayed. 2 different dates to stop irrigation, September 1st., and October 1st., were considered in each treatment. The amount of water applied ranged between 749,5 mm and 1.064,5 m. Three varieties, "Dale", "Keller" and "Wray" were used. The standard regime of irrigation was clearly better than the restrictive one, however, no significant difference could be found between the 2 dates in which irrigation was no longer applied. (Each treatment, or combination of treatments, was harvested in different date, according with its maturity). "Keller" variety was better, specially when dry matter was considered. The best results, 10,29 t/ha of sugars (juice and bagasse) and 18,19 t/ha of dry fiber, were obtained by irrigating the "Keller" variety with 864,9 mm of water until September 1st.

<abstract language="eng">A pre-concenvration method for extracting organochlorines from seawater was employed to analyse &#931;DDTs and PCBs. The sampling device and the conditions for optimal adsortion performance are described. Recovery tests with spiked solutions were made before applying the method on real samples. Working up of the samples prior to gas chromatographic analysis, precautions and advantages of the procedure are also discussed. The application of the method for seawater, containing very low levels of organochlorines, is shown by data from equatorial surface waters. The average level for &#931;DDT and PCBs was 0.21 ng/l and 0.37 ng/l. The overall precision of the method is about ± 15% with a lower limit of detection of 0.1 ng/l-1 for PCBs and 0.05 ng/l-1 for ZDDT.

Se estudió la composición del agua de lluvia en la localidad de A. Korn, unos kilómetros al sur de Buenos Aires, y su relación con suelos circundantes. La composición media del agua pluvial fue la siguiente, en mmolc L-1 Ca: 0,20; Mg: 0,13; Na: 0,14; K: 0,03, Cl: 0,15; CO3H: 0,31; SO4 : vest. El pH fue 5,95 y la conductividad eléctrica 0,046 dS m-1. El aporte iónico estuvo determinado por aerosoles marinos y-o polvos terrestres, según los iones. La composición de la solución del horizonte Al del Argiudol se asemejó a la composición química de la lluvia. En cambio, la composición de los horizontes Al del Natralbol, del Natracuol y del Natracualfe fue similar a la de sus correspondientes capas freáticas. Se concluyó que la precipitación pluvial no aporta sales en cantidades significativas a los suelos del área. El aporte de nutrimentos vegetales fue, por otro lado, de 0,39 kg ha-1 año de P (como PO4H2) y 7,6 kg ha-1 año de N (total). | tbls.