UVM Theses and Dissertations
Format:
Print
Author:
Jimenez-Serrano, Felix R.
Dept./Program:
Plant and Soil Science
Year:
2005
Degree:
MS
Abstract:
Methods for predicting forage quality of cool-season grasses are limited by accuracy, affordability and ease of use in the field. This study was conducted to assess the relationship of chronological age (CA), accumulative growing degree days (GDD) and mean stage (MS) of development to forage quality in monoculture during the spring growth. The effects of CA, GDD and MS on the changes of acid detergent fiber (ADF) and neutral detergent fiber (NDF) of 'Pizza', 'Barindana' and 'Pennlate' orchardgrass [Dactylis glomerata (L.)], 'Sunrise' and 'Sunset' Timothy [Phleum pratense (L.)] and 'Palaton' reed canarygrass [Phalaris arundinacea (L.)] were investigated in East Montpelier, VT on a Glover-Vershire complex soil and in South Burlington, VT on a Vergennes clay soil over a two year period (2002 and 2003). The date in which each grass treatment reached a target ADF and NDF of 30g kg⁻¹ and 50g kg⁻¹, respectively, varied by year, location, specie and cultivar. However, ADF and NDF increased with CA and GDD at a linear rate that was consistent across grass specie and cultivar treatments.
When pooled among grass treatments, the slopes of the linear response of ADF to CA, NDF to CA, and NDF to GDD were significantly different (P <0.05) among years and locations. However, the slopes of the linear response of ADF to GDD were not significantly different (P <0.05) among all site-year assessments indicating a consistent spatial and temporal response for this variable. Generally, mean stage by count (MSC) and weight (MSW) were numerically lower with the non-jointed orchardgrass (NJG) cultivars as compared to the jointed grasses (JG). MSW was more superior in showing greater numerical differentiation and lower standard deviation (SD). Only the MSW of the pooled JG treatments showed a consistent linear response to GDD when assessed across time and location. Also, only the linear response of ADF and NDF to MSW of NJG treatments had spatial and temporal consistency. Based on these results, the GDD method for predicting ADF in grass monocultures'has potential to be used as a harvest decision making tool for predicting high quality first cut forage.
When pooled among grass treatments, the slopes of the linear response of ADF to CA, NDF to CA, and NDF to GDD were significantly different (P <0.05) among years and locations. However, the slopes of the linear response of ADF to GDD were not significantly different (P <0.05) among all site-year assessments indicating a consistent spatial and temporal response for this variable. Generally, mean stage by count (MSC) and weight (MSW) were numerically lower with the non-jointed orchardgrass (NJG) cultivars as compared to the jointed grasses (JG). MSW was more superior in showing greater numerical differentiation and lower standard deviation (SD). Only the MSW of the pooled JG treatments showed a consistent linear response to GDD when assessed across time and location. Also, only the linear response of ADF and NDF to MSW of NJG treatments had spatial and temporal consistency. Based on these results, the GDD method for predicting ADF in grass monocultures'has potential to be used as a harvest decision making tool for predicting high quality first cut forage.