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Table 4 The pH, total and ammonium nitrogen, as well as the amounts of acids in fresh and ensiled hemp, maize and faba bean

From: Evaluation of preservation methods for improving biogas production and enzymatic conversion yields of annual crops

Crop, year and treatment Months pH NH3, g/kg Percentage of dry matter
     Total N Oxalic acid Formic acid Malic acid Lactic acid Acetic acid VFA
Hemp 2008:           
Fresh 0 8.0 0.6 1.2 0.6 ND 1.3 ND 0.3 ND
No additives 4 5.5 0.6 1.2 ND ND 1.8 7.8 1.7 0.6
  8 6.4 1.8 1.3 ND ND 2.5 7.3 2.2 0.6
Formic acid 4 4.2 0.6 1.3 1.2 4.3 2.1 ND 0.9 0.4
  8 4.3 0.7 1.3 0.8 3.3 1.9 1.4 1.0 0.5
Hemp 2009:           
Fresh 0 7.0 ND 1.1 4.9 ND 0.7 ND 1.2 ND
No additives 4 7.5 1.1 1.1 3.0 ND 2.7 2.2 1.0 0.4
  8 8.1 0.9 1.0 2.7 ND 1.2 0.5 0.7 0.4
Urea 4 8.6 14.3 1.5 5.7 ND 0.8 ND 2.1 0.4
  8 8.7 8.4 1.6 5.1 ND 0.9 ND 2.1 0.4
Maize 2008:           
Fresh 0 5.5 0.3 1.7 9.2 ND 2.0 ND ND 1.0
No additives 4 4.3 0.7 1.7 9.6 0.9 0.7 8.2 3.0 1.2
  8 4.2 0.8 1.6 9.0 0.9 0.8 7.5 2.9 1.2
Formic acid 4 3.7 0.1 1.7 9.9 3.6 2.1 ND ND 1.6
  8 3.7 ND 1.7 6.8 2.4 1.4 ND ND 0.4
Faba bean 2008:           
Fresh 0 5.6 ND 3.0 0.1 ND 2.3 ND 0.7 1.1
No additives 4 4.6 0.8 3.0 0.1 ND 2.5 8.2 2.3 0.5
  8 4.6 1.4 3.0 0.1 ND 2.7 8.8 2.3 0.5
Formic acid 4 4.2 0.5 3.1 0.2 3.7 3.2 2.1 0.9 0.7
  8 4.1 1.4 3.1 0.4 4.0 3.6 2.7 1.0 0.6
  1. Acids and NH3 were determined from the filtrates of the blended crops.
  2. aPrewilted for urea ensiling.
  3. bExpressed as % of dry matter.
  4. ND = not detected; VFA = volatile fatty acids (propionic, butyric, valeric and isovaleric).