Resumen

ALVAREZ-SANCHEZ, Edna; AMENDOLA-MASSIOTTI, Ricardo; CRISTOBAL-ACEVEDO, David  y  SOTO-BARAJAS, Milton C.. Nitrogen losses by leaching in a mixed grassland grazed in temperate climate. Rev. fitotec. mex [online]. 2014, vol.37, n.3, pp.271-278. ISSN 0187-7380.

Nitrogen losses by lixiviation in grazing grasslands are important because they may represent low N use efficiency in the production system and cause negative impact on underground water. Nitrogen lixiviation losses and the effect of excreta of grazing animals were estimated in a mixed grassland of alfalfa (Medicago sativa L. cv. 'Valenciana') and orchard grass (Dactylis glomerata L. cv. 'Potamac') in the east of the Valley of México. For assessment of the inorganic N (N-NO₃^- y N-NH₄⁺) present in drainage water, lysimeters receiving urine, feces and a control (without excreta) were utilized. Total N-content in excreta, net herbage production, the amounts of N ingested by the animals and inorganic N concentration (N-NO₃^- y N-NH₄⁺) in soil were estimated in this study. Inorganic N concentrations in the upper 60 cm of soil were high (70 to 80 mg kg^-1). During the rainy season, 10 rain events caused drainage below that soil layer, with high inorganic N concentrations in lixiviates (48 mg L^-1). As a consequence of both factors, 40 kg N ha^-1 year^-1 were lixiviated. Such an amount might be considered high, but within the range of values reported in the literature, and it only represented 7 % of the total N input of the system. The presence of animal excreta did not affect N losses.

Palabras llave : Medicago sativa; Dactylis glomerata; mixed grassland grazed; nitrogen leaching; dairy cows.

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