Alfalfa Yield and Morphology of Three Fall‐Dormancy Categories Harvested at Two Phenological Stages in a Subtropical Climate

Abstract

Alfalfa (Medicago sativa L.) is the most important hay crop used in the dairy industry of the Po Valley, Italy, characterized by a subtropical climate with hot, humid summers and cool winters. Information is lacking as to selecting fall dormancy (FD) varieties adapted to the region and their response to intense harvest regimes. A 3-yr study was conducted to investigate the effect of two harvest regimes based on phenological stage (early bud and early flower) and three FD categories on productivity, canopy height, and leaf to stem proportion. Cultivars with FD ratings of 7.5 (less nondormant), 8.5 (nondormant), and 10.5 (very nondormant) were seeded in April 2005 at the experimental farm of Padova University in Legnaro, Italy. The experimental design was a randomized complete block in a split-plot arrangement. Canopy height and dry matter (DM) yield were measured at each harvest. Subsamples were collected to determine leaf area index (LAI), stem silhouette area index (SAI), and leaf dry matter to stem dry matter ratios (LSR). Nondormant cultivars had higher DM yield (18.2 Mg ha−1) than less nondormant (17.1 Mg ha−1) and very nondormant cultivars (16.9 Mg ha−1). Harvesting at early bud decreased DM yield by 11% compared to early flower. The FD categories had no effect on LAI/SAI and LSR ratios, however harvesting at early bud increased both ratios by 12.0 to 12.5%. Producers in subtropical climates may obtain alfalfa hay with a high portion of leaves at a reasonable yield from the three tested FD categories by cutting alfalfa at early bud stage

Agro-Morphological and Forage Quality Traits of Selected Alfalfa Populations and Their Application in Breeding

“…The average plant height ranged from 66.77 cm (MSP 14) to 79.39 cm (MSP 1), which was similar to the results of Rimi et al (2010) who obtained a range of plant heights from 65.9 cm to 75.0 cm. The fastest growth was recorded after cuts in population MSP 16 (26.56 cm), which was not significantly faster than the values determined regeneration in populations MSP 9 and 1 (Table 1).…”

Fall Dormancy and Harvest Stage Impact on Alfalfa Persistence in a Subtropical Climate

“…Besides environmental differences between the studies, this appears in agreement with Hall et al (2004), who found no measurable long‐term effects due to seeding rates on alfalfa stand density. Moreover, the forage yields recorded during this experiment (Rimi et al, 2010) were comparable to those reported in other studies that used a lower seeding rate and/or plant density (Kallenbach et al, 2002; Lauriault et al, 2009; Wang et al, 2009). In the previously mentioned reports, similar productivity by alfalfa with lower stand density may have been obtained via higher no.…”

“…Irrespective of FD rating and date (Table 2), the plots harvested at early flower had 11% more plants m −2 than those harvested at early bud, in the average of FD ratings and sampling dates (242 vs. 218 plants m −2 , data not shown). This difference in stand density between harvest regimes is consistent to the response of dry matter yield, since plots harvested at early bud also had low productivity (Rimi et al, 2010). Moreover, these results are similar to those of other studies where alfalfa harvested more frequently during the growing season had lower stand density (Sheaffer and Marten, 1990; Gramshaw et al, 1993; Ventroni et al, 2010).…”

“…However, the relationships occurring between FD and productivity and between FD and winter hardiness have been re‐examined in the recent past (Brummer et al, 2000; Weishaar et al, 2005; Wang et al, 2009). On one hand, several studies documented that alfalfa cultivars with high FD rating were less productive in comparison to more dormant cultivars (Lauriault et al, 2009; Wang et al, 2009; Rimi et al, 2010), contrary to what was commonly believed. On the other hand, it has been argued that FD rating and winter survival presented a limited genetic association or were not correlated in several alfalfa populations (Cunningham et al, 1998; Brummer et al, 2000; Weishaar et al, 2005).…”

“…There is not much information available on the influence of FD rating on alfalfa winter hardiness in areas with mild winters (Wang et al, 2009). Experiments conducted in temperate regions evinced that the choice of FD category is of secondary importance compared to that of harvest regime for forage yield (Rimi et al, 2010; Ventroni et al, 2010) and nutritive value (Rimi et al, 2012). However, there is equivocal information on how various FD categories differ in their response to harvest regime for plant survival and stand persistence.…”