M. P. Palacios-Díaz, V. Mendoza-Grimón, J. R. Fernández-Vera and J. M. Hernández-Moreno

1In semiarid regions, the increasing cost of imported forage is encouraging its replacement by on-farm produced fodder crops. The aim of this study was to characterize the nutritive values of maralfalfa grass (Pennisetum sp.) in function of different harvest frequencies under subsurface drip irrigation. During 2009 a maralfalfa grass experiment was conducted in a field of 8000 m2 on allophanic soils in the island of Hierro (Canary Islands), under subtropical climate. In a randomized block design, one linear meter from three different rows was sampled of plants from 30 to 120 days. In a 50 m 2 subplot, biodegraded liquid pig manure was applied. Crude Protein (CP) in plants was determined with and without it. Another objective was to calculate N uptake which was added by manure and, the N depletion in soil in organic farming production. The results showed that the optimum age for harvesting was 55-60 days and also allowed to obtain relationships between CP and the age of the plant. Our results demonstrate that, in order to obtain high yields of maralfalfa by organic farming, the maximum animal residue use of 240 kg N ha-1 year -1 recommended by the European Community Directive 91/676/EEC should be increased.Granja Agrícola Experimental del Cabildo de Gran Canaria. Canary Islands. (Spain)

2Edafología y Geología. Univ. de La Laguna. Tenerife. Canary Islands. (Spain)