Mulberry bush (Morus alba) response to nitrogen fertilization, sowing densities and to defoliation.

En la Estación Experimental de Ganado Lechero “Alfredo Volio Mata”, ubicada en una zona de bosque húmedo montano bajo, se evaluó una plantación de morera de dos años de edad, dividida en tres parcelas, con un distanciamiento entre plantas de 60, 90 y 120 cm entre hileras y plantas. Cada parcela se uniformó en una altura de poda de 60 cm. Las subparcelas se podaron en forma consecutiva a 56, 84 y 112 días durante 224 días. Se adicionaron cinco dosis de nitrógeno (0, 150, 300, 450 y 600 kg/ha). El rendimiento anual de materia seca de la planta entera de morera, sus tallos y hojas, resultó significativo (P = 0,0l) influido por la distancia de siembra y la frecuencia de corte. El rendimiento de hojas y tallos disminuyó conforme aumentó la distancia de siembra. La frecuencia de corte mostró una influencia marcada (P= 0,01) sobre la producción de biomasa en la planta entera y sus partes. El nitrógeno no mostró ningún efecto diferencial (P>0,05) sobre el rendimiento de biomasa total o sobre la producción de hojas o tallos.This experiment was carried out at the Alfredo Volio Mata Dairy Cattle Experimental Station in Costa Rica. A mulberry bush plantation was divided into three plots: with a distance of 60, 90 and 120 cm between rows and plants. All plots were uniformly pruned at 60 cm from the ground. During a 224-day period, these subplots were pruned consecutively every 56th, 84th and 112th day. The annual yield of dry matter of the whole mulberry bush (stems and leaves) was influenced (P = 0.01) by all the factors studied. The planting distance had a decreasing effect on the Yield of stems and leaves increased as the distance decreased. The cutting frequency had a marked influence (P = 0.01) on the production of biomass in the whole plant and its parts. A linear effect (P = 0.01) was observed on the stem yield, as well as the whole plant, when the cutting interval increased between the 56th and 112th days. Anegative effect (P <0.05) was observed in the leaf:stem ratio when the pruning interval was increased. The nitrogen dosage used in the experiment (0, 150, 300, 450 and 600 kg/ha) did not show a differential effect (P < 0.05) on the total biomass yield nor on the stem or leaf production. No significant effects were observed between the planting distance or the cutting frequency and the nitrogen dosage