EXTRACTION, APPARENT N-RECOVERY AND MINERAL-COMPOSITION OF N-FERTILIZED SPECIES AND VARIETIES OF CYNODON IN A VERTISOL SOIL

The performance of five species and varieties of the Cynodon genus (C. dactylon cv. Coastal, C. dactylon cv. Coast cross 1, C. dactylon, cv. Coast cross 2, C. nlemfuensis cv. Panamanian and C. nlemfuensis cv. J amaican) was analysed in a vertisol soil, at increasing N dosages (0, 200 and 400 kg/ha/year) using a factorial arrangement (3 x 5) in a ran dom block design with 4 replications. There was no interaction for the factors studied. The N dosage differed (P < 0.001) for the N extracti on with 74, 258 and 420 kg/ha. The highest annual average extractions were for Coast cross 2 bermuda grass and Jamaican star grass with 260. 8 and 260.4 kg, while the lowest extractions were from Coast cross 1 b ermuda grass and Jamaican star grass with 240 and 241 kg, which differ ed (P < 0.001) from the rest of the pastures. There were differences ( P < 0.001) in the N recovery between the dosages, with the highest rec uperation in the lowest dosage (92%). Coast cross 2 bermuda grass pres ented the highest recovery (106.5%), followed by Coastal bermuda grass and Panamanian star grass (96.3 and 91.5%, respectively). not differi ng from Coast cross 1 bermuda grass and Jamaican star grass with 85.0 and 185.5%. The phosphorus content differed (P < 0.001) in all pasture s and the highest content was for Jamaican star grass with 0.50 and 0. 48% for the dry and rainy periods, respectively. Potassium was increas ed (P < 0.001) with the N level with average annual levels of 1.63, 1. 90 and 2.07%. Calcium and magnesium did not differ with N dosages, sur passing Coastal bermuda grass in calcium content in the dry period and Jamaican star grass showed poor variation in magnesium. The highest m ineral contents were achieved in the dry period. Results show that for the extractions obtained by the pastures, the apparent N recovery, as well as good mineral contents, N application is necessary.