Choice of cultivar
The ‘traditional’, though now superseded, cultivar Hunter River (a semi-dormant) produced eight hay cuts per year under irrigation in south-eastern Queensland. By comparison, a winter-active cultivar will produce another one or two cuts per year and these occur in the cool season. Conversely, winter-dormant types produce up to four cuts less than Hunter River.
High winter production by winter-active types is greatest under irrigation. Winter-active lucernes are then equally as productive as the more winter-dormant classes in the warmer months. Thus, high winter activity does not imply lighter or fewer cuts during the warmer months. Winter hay attracts a premium price. However, it is no use growing a winter-active type in areas where winter haymaking is difficult or impossible.
Conversely, it is not worth growing a winter-dormant type for haymaking in Queensland (unless haymaking is difficult or impossible) as dormancy in winter is not compensated for by higher production at other times of the year. Thus, winter conditions and the market requirements should dictate cultivar choice.
Haymaking potential and quality
Winter-active germplasm and cultivars have been bred mainly for the hot, dry summer environment on the west coast of North America where high humidity is rarely experienced during the summer months. In these conditions, leaf diseases are rarely a severe problem, and no leaf disease resistance has been incorporated into this germplasm. In Queensland, humidity is often high and leaf diseases cause considerable loss of quality in hay. Breeding has improved the resistance for some leaf diseases in winter semi-dormant and winter-active cultivars but little progress has been made in highly winter-active cultivars.
The lucerne plant appears to use the dormant (or slow-growth) period in winter to build up reserves in the roots. Because the winter-active cultivars grow continuously, their reserves can be run down more quickly than with the semi-dormant or dormant types. Irrespective of disease resistance, then, winter-active cultivars as a group are more likely to have a shorter stand life, particularly if cut very frequently (fewer than four weeks between cuts).
Although there is currently no standard method of rating lucernes for their hay quality, stem thickness and leafiness are commonly used indicators. The highly winter-active cultivars seldom meet the criteria for prime quality hay. They have smaller crowns with fewer basal shoots. Over time, this tends to produce a less dense stand. The lengths between stem internodes are longer, the foliage is ‘thinner’, and the cultivars are susceptible to leaf diseases which cause leaf bleaching and leaf fall.
Semi-dormant cultivars, on the other hand, form larger crowns with thicker, semi-prostrate foliage, and they make better hay, particularly in the cooler months. They recover more slowly after cutting, and the timing of the hay cut is less critical than with the winter-active cultivars.
Grazing
The reasons for good persistence under grazing are not clear. In southern Australia, lucernes with a low crown producing many tillers are more persistent, particularly when grazed by sheep, than those with a high crown and poor tillering ability. Thus, the highly winter-active types are not planted as grazing lucernes, especially if long stand life is the major requirement.
However, in Queensland, where more winter growth is made by the winter-active cultivars, the provision of high quality forage is more important than persistence. Additionally, it seems that with the current varieties, susceptibility to disease limits the persistence of both those cultivars with low and high crowns. In Queensland, a winter-active lucerne with good levels of disease resistance is an ideal choice as a grazing lucerne. For example, the variety Sequel has performed well as a grazing lucerne in dairying, beef cattle and prime lamb enterprises for the dual purpose of haymaking and grazing.
Cutting management
Cultivars from the various dormancy categories have different regrowth and recovery rates after cutting. Thus, they reach the next cutting stage at different times. Cutting a stand too early results in premature stand loss.
Each cultivar should be cut when the crown buds begin to grow. The old axiom ‘cut at one-tenth bloom’, used in the management of the superseded cultivar Hunter River is not appropriate for the winter-active types. Stands can reach the cutting stage in midwinter without flowering.
Selecting the right cultivar depends on selecting for the disease, and insect, resistance required, and matching the dormancy type to meet enterprise requirements. Choosing a dormant or semi-dormant type may result in slightly lower annual hay yields (10-15% less) than from active types. However, the less active types allow a greater degree of management flexibility for making prime quality hay. High yields of quality hay from the very active types are possible when management is finely tuned. For haymaking, the very active cultivars are less forgiving. For grazing, selection for both disease and insect resistance, and for winter activity is advised.
With the cultivars now available, ranging in winter activity from 3 to 10, it is possible to choose disease and insect-resistant cultivars that perform well in a range of enterprises and environments.
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