Long-Term Residual Effects of Nitrogen Fertilization on Western Wheatgrass
1985; University of Arizona; Volume: 38; Issue: 5 Linguagem: Inglês
10.2307/3899723
ISSN2162-2728
Autores Tópico(s)Crop Yield and Soil Fertility
ResumoNitrogen (N) fertilization can be an effective way of increasing forage production. The question is how much does N fertilization increase forage yield of western wheatgrass (Agropyron mnithti)when there is not a shift in species composition as occurs when N is applied to a native range site.The objectives of this research were to determine the residual effects of a single application of ( 1) 6 geometric rates of N and phosphorus (P) on forage yield, in vitro dry matter digestibility (IVDMD), crude protein (CP), and phosphorus (P) concentration (cone) of western wheatgrass grown near Sidney, Mont.during a lO-year period.Ammonium nitrate was applied at 0,40,80,160,320, and 640 kg N/ha in March 1973 and triple super phosphate at 45 kg P/ha on split plots during August 1975.A single application of N increased forage yield by 0.0, 0.0, 0.95, 0.35,0.0,1.16, 0.52, and 1.41 kg/ha per kg of N applied the lst, 2nd, 3rd, 4th, Sth, 6th, 7th, and 10th year sampled, respectively, regardless of N rate.Nitrogen fertilization increased the accumulative forage (IYO.01) and CP (X0.01) yield over the 8 harvest-years by 4.35 and 0.87 kg/ha per kg of N applied.Nitrogen fertilization increased the average forage IVDMD by 0.1 percentage units (KO.05) and decreased P cone by 0.03 percentage units per 100 kg N/ha applied (KO.01).Application of 45 kg P/ha in 1975 increased the P cone of the forage an average of 0.04 percentage units each year, increased forage yield only the 10th year by 150 kg/ha, and had no effect on IVDMD or CP.This study also showed that long-term observations are necessary to measure the residual effects of fertilization.Nitrogen(N) fertilization can effectively increase forage production in the northern Great Plains.Annual applications of 35 to 55 kg N/ha have doubled forage production of native range plant communities (Wight 1976).Read (1969), Wight and Black (1979) and Power (1981) found that a single application of N to native range in the Northern Great Plains increased forage yields for 4 to 6 years.However, they did not know what proportion of the forage increase was due to residual N per se or to a shift in species composition.Nitrogen fertilization has generally increased the composition of cool-season species such as western wheatgrass (Agropyron smithii) and decreased warm-season species such as blue grama (Bouteloua gracilis)( Rogler and Lorenz 1965).Forage yield increases from N fertilization on native range are probably largely due to a species shift.No literature was found on the long-term effects of a single application of N fertilizer on a monoculture of western wheatgrass.Nitrogen fertilization has had variable effects on forage quality.No literature was found on the effects of N fertilization on digestibility of western wheatgrass forage.Studies have shown that N fertilization increased the in vitro dry matter digestibility (IVDMD) of bermudagrass (Cynodon dactylon) (Fribourg et al. 197 1, Taliaferro et al. 1975), weeping lovegrass (Erugrostis curvulu), and old world bluestem (Bothriochloa ischaemum var.ischoemum)(Taliaferro et al. 1975).However, other studies have shown that N fertilization had no effect on the IVDMD of reed canarygrass (Phuluris arundinaceu) (Niehaus, 1971), bromegrass (Bromus inermis), orchardgrass (Dactylisglomerata), and timothy (Phleum
Referência(s)