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The dual-purpose livestock systems in the tropics milk production is reduced during the dry season due to the decrease in the quantity and quality of forage on offer. The impact can be reduced by using forage crops as supplements generated with the use of green fertilizers. The objective of this research was to determinate the nitrogencontribution of legumes in corn forage production. During the years 2013 to 2014, in the Colombian Dry Caribbean three experiments were established with seven levels of nitrogen (N) (0, 25, 50, 75, 100, 150 and 200 kg/ha) and the incorporation of Canavalia brasiliensis (CIAT 17009), Vigna unguiculata (CIAT 4294), Clitoria ternatea (CIAT 21815), Canavalia ensiformis (CIAT 21826) and Lablab purpureus (CIAT 22656) in a random block design. C. ensiformis showed the highest contribution of N (151 kg/ha) and V. unguiculata the lowest (35 kg/ha). The application of 200 kg of N and the incorporation of C. ensiformis and C. brasiliensis did not show a difference in the yield of maize biomass. N use efficiency by corn crop was 31 - 84%, reduced with increased in the dose of N. Levels of NO3 in the soil ranged from 20 to 41 mg/kg at the time of harvest, suggesting that a high proportion of N coming from the legume was not assimilated by the crop. The C:N ratio was 11·63 in legumes and 23·94 in weeds. Organic soil C increased by 22% due to legume green manure, with the highest content (0·70%) in L. purpureus. The legumes C. ensiformis, C. brasiliensis and L. purpureus showed high potential to provide N, C, and to conserve soil moisture. [ABSTRACT FROM AUTHOR]

Legume cover crops are planted to control weed, to prevent soil erosion, and to increase nitrogen in soil. The objective of this study was to evaluate the response to phosphorus fertilization of the legumes Mucuna pruriens cv. cinza, Mucuna pruriens cv. preta, Crotalaria spectabilis, Vigna radiata, and Pueraria phaseoloides, during two seasons of the year. The experiment was carried out in a greenhouse at the Agricultural Experiment Station Fabio Baudrit Moreno (EEAFBM, in Spanish), of the University of Costa Rica, Alajuela, Costa Rica, from November 2012 to January 2013, and it was replicated from April to May 2013. Doses of 0, 30, 60, and 90 kg P2O5/ha were applied on steam sterilized soil, an then it was used to fill 2 kg capacity pots. The variables assessed were plant height, number of true leaves, and dry weight 18-26 days after planting, depending on legume species. Crotalaria spectabilis, V. radiata, and P. phaseoloides achieved the highest growth when fertilized at the rate of 60 kg P2O5/ha, whereas both M. pruriens cultivars did not increase growth as a response to phosphoric fertilization. Due to the positive effect of phosphorus fertilization on growth of small seeded legumes, it is important to validate the use of this fertilizer to achieve rapid soil cover, which could decrease weed competition. [ABSTRACT FROM AUTHOR]