Fertilización nitrogenada y momento de cosecha en el rendimiento y la calidad de semillas del pasto guinea (Panicum maximum Jacq.)

An study was carried out during 1999 in Tejupilco, State of Mexico, Mexico (18ø 54' N, 100ø 08' W and 1320 m.a.s.I.), with aim of evaluate the effect of the application of nitrogen and harvest moments on seed yield and quality of guinea grass \{Panicum maximum Jacq.) cv. Tanzania. Treatments consisted in three N levels (50, 100, and 150 kg/ha) and six harvest moments (6, 10, 14, 18, 22, and 26 days after antesis, DAA) distributed in a randomized complete block design and arranged in split plots withthree replicates. Variables evaluate were: total yield (TSY) and pure seed yield (PSY), moisture content (MC), purity percentage (PP), 1000 seed weight (MSW), germination percentage (GP), and vigor percentage (VP) at 7 months of storing. Results showed that N application increased TSY and PSY (P 0.01). The highest yields of TSY and PSY occurred with the application of 150 kg/ha of N (146.9 and 104.6 kg/ha, respectively). The effect of N on MC, PP, GP, and VP was not significant (P 0.05). The harvest moments showed effect (P 0.01) on TSY, PSY, HC, pp, MSW, and VP. The highest TSY and PSY were obtained at 18 DM with 158.7 and 138.6 kg/ha, respectively. Vigor and germination percentage were 55.6% and 68.9%, respectively. The highest TSY and PSY were achieved when MC ranged between 44.6% and 51.2%. The interaction effects of N levels and harvest moments on TSY and PSY were significant (P 0.01). The highest TSY and PSY (210.4 and 187.1 kg/ha, respectively) occurred with the application of 150 kg of N/ha and 22 DAA. It is concluded that the highest total yield and pure seed yield was achieved using between 100 and 150 kg/ha of N and harvesting between 18 and 22 DM or when seed MC ranged of 45% to 51%