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Title: FRESH VERSUS FIELD-CURED GRASS QUALITY, MINERAL, AND NITRATE CONCENTRATION AT DIFFERENT NITROGEN RATES

Author
item Singer, Jeremy

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/20/2002
Publication Date: 7/23/2002
Citation: SINGER, J.W. FRESH VERSUS FIELD-CURED GRASS QUALITY, MINERAL, AND NITRATE CONCENTRATION AT DIFFERENT NITROGEN RATES. CROP SCIENCE. 2002. V. 42. P. 1656-1661.

Interpretive Summary: Forage Scientists typically sample fresh forage to determine quality, mineral, and nitrate-nitrogen (N) concentrations regardless of the end use. This practice is common because research on conservation forage systems is resource-intensive. Our objectives were to determine if changes in grass quality, mineral, and nitrate-N occur under rain-free conditions between fresh and field-cured orchardgrass, smooth bromegrass, and timothy. Differences in quality, mineral, and nitrate-N concentration between fresh and field-cured forage were detected, with orchardgrass having the greatest consistency and smooth bromegrass the least. Consequently, forage scientists conducting research on grass hay quality indices and mineral content should sample subsequent to field-curing to provide accurate results.

Technical Abstract: Determining the extent of change in fresh versus field-cured grass hay quality, mineral, and NO-3-N concentrations under rain-free conditions provides valuable information to hay producers. The objectives of this research were to evaluate the effect of fresh vs. field-cured forage on crude protein (CP), neutral detergent fiber (NDF), total digestible nutrients (TDN), P, K, Ca, and NO-3-N concentrations of orchardgrass (Dactylis glomerata L.), smooth bromegrass (Bromus inermis Leyss.), and timothy (Phleum pratense L.), and to determine if interactions with N rate exist. At the low N rate in 1999 and 2000, orchardgrass CP in fresh and field-cured forage, NDF, and TDN concentrations were different. Orchardgrass P and K concentrations were lower in field-cured compared to fresh forage, but differences were inconsistent across N rates. In contrast, smooth bromegrass K (23 vs. 27 g kg**-1) and Ca (4.3 vs. 6.2 g kg**-1) concentrations were greater in field-cured compared to fresh forage in 1999 across N rates. Tissue NO-3-N concentration was greater in field-cured orchardgrass at all N rates and at the low N rate in smooth bromegrass in 1999. Interactions between N rate and fresh vs. field-cured smooth bromegrass were detected for all variables in 1999 and orchardgrass K concentration in 2000. Our results demonstrate that changes in grass quality, mineral, and tissue NO-3-N concentrations occur under rain-free field curing conditions. Consequently, forage scientists conducting research on grass hay quality indices and mineral content should sample subsequent to field-curing to provide accurate results.