RESPONSE OF RICE TO DIFFERENT SOURCES AND DOSES OF NITROGEN IN THE PLAINS OF COCLE.

Abstract

The fertility of the soil of the Llanos de Cocle Experimental Station, classified as Aeric Tropaquept, was studied under laboratory and greenhouse conditions. The soils showed response to N, P, K and S according to biological test, while only showing response to N, P and K in the field. Considering previous results, the response of rice to different sources (urea, ammonium sulphate and ammonium nitrate) and doses of N (0, 40, 80, 120 and 160 kg N per ha) was studied under field conditions using the Cica 8 variety. A divided parcel design with 15 treatments was used. The combined analysis of the results of two years of study (1985 and 1986) show positive response of the Cica 8 variety to the application of N up to a dose of 120 kg of N per ha, with yields of over 4200 kg per ha of rice. Doses greater than 120 kg of N/ha reduce the yield. No differences were found among the sources of N. Neither was a significant effect of the interaction between doses and nitrogen source found, which established that the response of Cica 8 to different doses of nitrogen is independent of the nitrogen source. Economically, the best source is urea, because of its low cost and high nitrogen content.