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An evaluation of the effects of rate of nitrogen fertilization of grassland on silage fermentation, in‐silo losses, effluent production and aerobic stability
Author(s) -
KEADY T. W. J.,
O'KIELY P.
Publication year - 1996
Publication title -
grass and forage science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.716
H-Index - 56
eISSN - 1365-2494
pISSN - 0142-5242
DOI - 10.1111/j.1365-2494.1996.tb02070.x
Subject(s) - silage , zoology , dry matter , chemistry , agronomy , perennial plant , fertilizer , formic acid , effluent , forage , nitrogen , biology , environmental science , organic chemistry , chromatography , environmental engineering
Abstract A factorial experiment was carried out to evaluate the effects of level of nitrogen (N) application to grassland and subsequent treatment of the herbage at ensiling with formic acid on the rate of silage fermentation, dry‐matter (DM) recovery, aerobic stability and effluent production. Herbage from the primary regrowth of predominantly perennial ryegrass swards received either 72 (LN), 126 (MN) or 180 (HN) kg N ha −1 . The herbages were harvested and yield estimated after a 50‐day regrowth interval. After storage for 24 h in polythene bags, the herbages were ensiled, unwilled, in laboratory silos (6 kg capacity) either untreated (UT) or treated with formic acid (F) at 3 ml (kg herbage) −1 . Three silos per treatment were opened and sampled on days 1, 3, 6, 15, 50 and 105 after ensiling. The mean herbage yields for the LN, MN and HN swards were 5.2, 6.3 and 6.2 (s.e. = 0.27) t DM ha −1 and there was no carryover effect of nitrogen treatment on the yield of a subsequent 22‐day regrowth harvested on 2 September. As level of fertilizer N application increased, concentrations in the herbage at mowing of crude protein, nitrate and ash increased, DM decreased and water‐soluble carbohydrate and in vitro DM digestibility remained unchanged. Increasing the rate of N fertilizer to the sward resulted in higher silage pH ( P < 0.001) and ammonia N concentrations ( P <0.001) at each time of sampling. Increasing the rate of fertilizer N increased effluent output ( P < 0.001) and DM recovery ( P < 0.001). Aerobic stability was improved ( P <0.001) by use of high rates of N fertilizer application. Formic acid treatment restricted fermentation and increased effluent output ( P <0.001) but had no effect ( P > 0.05) on DM recovery. It is concluded that the rate and extent of pH decline was reduced with increasing N application, associated with increased buffering capacity and decreased DM concentrations of the herbage at ensiling. However, increasing the level of N fertilizer applied increased DM recovery and effluent output, and improved aerobic stability of the resulting silages.