The objective of the study was to quantify the effect of nitrogen on the winter growth of the lowland pasture Pampa Deprimida) near Chascomús, Buenos Aires Province, Argentina. In the lowland pampa the forage growth, dominated by cool season species Lolium multiflorum, Bromus spp. and Stipa spp., is limited in winter by a severe deficiency of available nitrogen. Using a randomized block with three replicates, six fertilization treatments were evaluated: N0, N50, N100, N150, N200 and N250 kg N ha-1 with UREA (46% N), applied on 12/08/1997. The accumulation of forage was assessed on the dates 20/09, 29/09, 08/10, 20/10, 30/10 and 04/11 of 1997 by cutting 5 m2 of the plots. The statistical comparisons were made via variance analysis and the growth rates determined via linear regression. Nitrogen fertilization significantly (P > 0.05) increased the forage accumulation, achieving 7114 kg DM ha-1 with the N250 dosage at the end of the experimental period, a result that did not differ (P < 0.05) from N200 and N150. N0 showed the lowest forage yield (2433kg DM ha-1), a result that differed from the rest of the dosages utilized (p<0,05). The growth rates for N0 and N150 were 29.44 ± 5.29 and 81.36 ± 9.62 kg DM ha-1 d-1, respectively. The apparent response to the accumulation of forage was obtained using a decreasing return model, being maximal for N0 and minimal for N250 with 52.8 and 18.7 kg DM, respectively. The results showed that the N available in the soil was below the potential growth demands of the natural grassland. |
ChileanJAR
