Abstract
The objective of this study was to evaluate the effect of different defoliation frequencies on winter forage production and nutritive value of improved population of Agropyron cristatum (L.) Gaertn. Four entries, a) base population, b) selected plants from mass honeycomb selection (MHS), c) selected plants from pedigree honeycomb selection (PHS) and d) selected plants from pedigree honeycomb selection using the combined criterion CC = x¯2 (1 – CV) / CV [PHS (CC)] were tested under four defoliation frequencies: 1) frequent, 2) moderate, 3) infrequent and 4) control. Dry matter production under moderate defoliation treatment was 9% and 107% respectively higher than frequent and infrequent the first harvest year, while the second harvest year the corresponding percentages were 26% and 44%. The selected populations of A. cristatum consistently exceeded in herbage production the base population under all defoliation treatments during winter. Among the selected entries, [PHS (CC)] had consistently higher DM production compared to MHS and PHS for the two experimental years. The CP content was significantly higher, while NDF, ADF and ADL contents were lower in the increased defoliation frequency compared to the control in both harvest years. There were no significant differences of the nutritive value among the entries (P > 0.05). Generally, herbage production of the moderate defoliation frequency was more stable through the years with relatively high nutritive value.
Highlights
Low-elevation zone rangelands in Greece and generally in the Mediterranean region are characterized by relatively mild winters and hot, dry summers often with prolonged drought
On the other hand the frequent defoliation increased the dry matter (DM) production the first harvest year but it was detrimental to the productivity the second harvest year
These results are in agreement with several grazing and clipping studies (Malinowski et al, 2003; Turner et al, 2006b; Pontes et al, 2007), which reported A. cristatum and other perennial coolseason grasses stand deterioration over time due to frequent defoliation
Summary
Low-elevation zone (up to 800 m altitude) rangelands in Greece and generally in the Mediterranean region are characterized by relatively mild winters and hot, dry summers often with prolonged drought. In these environments, C4 perennial and C3 annual grasses are the dominant components (Papanastasis, 1999) and produce relatively high proportion of forage grazed by livestock during spring (C3 annual grasses) summer and fall (C4 perennial grasses). The gap in forage availability from October until late February may be filled by improved coolseason perennial grasses (Asay, 1991). Soil water- deficits and high temperatures during summer, reduce survival and limit the number of potentially adapted species, there are perennial coolseason grasses that have the ability to survive and recover rapidly once water becomes available in the fall (Kemp and Culvenor, 1990)
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