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

Abstract

Persistence of alfalfa (Medicago sativa L.) is a critical component of productivity and can be influenced by genetics and management; however the responses of fall dormancy (FD) level to harvest regimes are unclear. This study was conducted to investigate the effect of three FD categories and two phenologically based harvest regimes on stand persistence and characteristics of taproot and crown in a humid subtropical climate. Cultivars with FD ratings of 7.5 (less non-dormant), 8.5 (non-dormant), and 10.5 (very non-dormant) were seeded in April 2005 at the experimental farm density, mass of taproot (to a 15-cm depth) and crown, water soluble carbohydrate (WSC) concentration of taproots and crowns, and taproot diameter at 3-, 5-, and 15-cm depth were measured. Changing the cutting stage from early flower to early bud reduced the average stand density from 242 to 218 plants m -2 , irrespective of FD category and date. In November, plants harvested at early bud had smaller taproots and crowns compared to those harvested at early flower but generally had higher concentrations of WSC. The implications of FD category appeared secondary in comparison to harvest regime to maintain alfalfa persistence in an environment characterized by temperate winters.

Contrasting Strategies of Alfalfa Stem Elongation in Response to Fall Dormancy in Early Growth Stage: The Tradeoff between Internode Length and Internode Number

“…Fall dormancy (FD), a useful trait that defines alfalfa adaptation to distinct climate conditions [ 9 ], is defined as the reduction in shoot growth in the autumn due to decreasing day-length and temperatures [ 10 ]. Alfalfa cultivars can be grouped into eleven FD ratings (from one to eleven) based on regrowth height in the autumn, with FD = one representing those going dormant earliest and having the smallest plant height in the fall, and FD = eleven representing those having the tallest plant height in the fall and being the least dormant [ 10 , 11 ]. Cultivars can be further described as fall dormant (FDT, with FD ratings from one to three), semi-fall dormant (SDT, with FD ratings from four to six), non-fall dormant (NDT, with FD ratings from seven to nine), and extremely non-fall dormant (EDT, with FD ratings from ten to eleven [ 12 , 13 ].…”

Evaluation of Different Fall Dormancy-Rating Alfalfa Cultivars for Forage Yield in a Semiarid Environment

“…Photoperiodism and air temperature in fall and throughout winter determine alfalfa fall dormancy which is related to plant growth, biomass accumulation and abiotic stresses tolerance of the alfalfa plant [7,[12][13][14][15]. Fall dormant alfalfa cultivars go dormant the earliest, have reduced shoot elongation in the fall and survive better throughout winter, whereas extremely non-fall dormant cultivars continue to grow, have the tallest plant height in the fall, and generally do not have good survival over the winter [16,17].Alfalfa forage productivity is impacted by its fall dormancy-rating that has correlation with forage nutritive value, plant survival, root characteristics, and persistence [8,[18][19][20][21][22][23][24]. Efforts have been made to improve alfalfa forage yield with improvement in the first/second harvests of newly released varieties and yield improvement is dependent on identification of the genes controlling yield and yield components such as canopy height, herbage, stubble, stem population, which is quite complex due to the involvement of several genes in the agronomic traits like forage yield [25,26].…”

“…Alfalfa forage productivity is impacted by its fall dormancy-rating that has correlation with forage nutritive value, plant survival, root characteristics, and persistence [8,[18][19][20][21][22][23][24]. Efforts have been made to improve alfalfa forage yield with improvement in the first/second harvests of newly released varieties and yield improvement is dependent on identification of the genes controlling yield and yield components such as canopy height, herbage, stubble, stem population, which is quite complex due to the involvement of several genes in the agronomic traits like forage yield [25,26].…”

Variety selection in intensive alfalfa cutting management

“…Hovewer, a less intensive cutting regime could contribute to the longer life of alfalfa stands and reduced harvesting costs (Lloveras et al, 1998;Lamb et al, 2007). Choice of the most appropriate cutting schedule for each variety it is of great importance (Kallenbach et al, 2002;Orloff & Putnam, 2010;Rimi et al, 2014). Time of cutting is the most powerful tool under the alfalfa grower's control to affect yield and quality and fundamentally increase economic production potential; more than the variety selection, fertilization and other management factors (Orloff & Putnam, 2006).…”

“…Time of cutting is the most powerful tool under the alfalfa grower's control to affect yield and quality and fundamentally increase economic production potential; more than the variety selection, fertilization and other management factors (Orloff & Putnam, 2006). Therefore, the selection of variety (its dormancy rating) should be considered in compliance with harvest regime choice in order to improve the yield performance and persistence of alfalfa in environments with temperate climates (Rimi et al, 2014). The cutting regime, or more precisely how frequently the alfalfa is cut, has a greater influence on forage quality than any other factor under the farmer's control (Putnam et al, 2005;Putnam, 2010).…”