1. Abreu Z, Sarmiento L, Bottner P (2007) Destino del nitrógeno agregado por fertilización en un cultivo de papa en los Andes de Venezuela. Rev Fac Agron LUZ 24(2):203–228
2. Allen R, Pereira L, Raes D, Smith M (1998) Crop evapotranspiration (guidelines for computing crop water requirements). Paper no. 56 FAO irrigation and drainage, Rome
3. Appel T, Mengel K (1993) Nitrogen fractions in sandy soils in relation to plant nitrogen uptake and organic matter incorporation. Soil Biol Biochem 25:685–691
4. Arauzo M, Martínez-Bastida J, Valladolid M, Díez J (2010) Field evaluation of Gee passive capillary lysimeter for monitoring drainage in non-gravelly and gravelly alluvial soils: a useful tool to estimate nitrogen leaching from agriculture. Agric Water Manage 97:465–474
5. Axmann H, Sebastianelli A, Arrillaga JL (1990) Sample preparation techniques of biological material for isotopes analysis. In: IAEA (ed) Use of nuclear techniques in studies of soil–plant relationships. Vienna, Austria