It’s been a successful spring at Bonavaree! Early spring had been fairly wet and so early spring growth was relatively slow. Although soil conditions are now perfection for Lucerne, and Fraser had seen a notable shift in gear in the lucerne stands, with a flush of feed evident. See photos below of Jeffries Front Flat (taken in November), with several large cracks evident on the soil surface it shows how the soil has undergone wetting and drying cycles in the last month.
Within this lucerne paddock the top 1 cm of soil moisture has been removed by evaporation only, and not evapotranspiration, i.e.
evaporation = sun + wind
evapotranspiration = sun + wind + plant transpiration.
There is no evapotranspiration of surface soil moisture because the majority of the lucerne roots (hair roots and tap roots) are located much further down in the soil profile. This makes lucerne a perfect plant within a dryland situation because the location of the root mass means the plants are less reactive to soil wet + dry cycles, as well as being able to acquire moisture at deep subsoil depths making it more drought tolerant. So as we look further into the soil depth to 3-5cm the soil moisture is more than adequate for continued growth, and so would be even better further down where the majority of the lucerne roots are located (see photos above).
However the dry is edging ever closer, although Bonavaree is geared to cope with the dry with a system that booms when moisture conditions are limited.
Tailing was completed late September with a record 158.8% lambs tailed to ewes mated. This is a figure that Fraser is keen to increase, with his triplet mobs being the focus. Strategies are being planned to increase lamb survival of triplets during lambing.
Fraser manages spring rotation length by lucerne height, rather than time. Planning grazing rotation length based on lucerne height during peak growth is much more effective than a strict routine of paddock rotation. This means that individual paddocks are grazed at their optimum pasture mass and means lucerne quality is at its best. Fraser has found that the optimum height for grazing pure lucerne paddocks during spring is an average height of 30cm. This normally equates to 4 weeks at Bonavaree in spring, but would be different in other regions, lucerne height is therefore a better measure to use. At peak growth lucerne paddocks that are left to grow higher than 30cm have a higher stalk content, and the sheep tend to trample the lucerne thereby increasing wastage and decreasing utilisation. Fraser has observed that the pure lucerne stands have zero growth in the first week the ewes are off the paddock, with ever increasing plant growth in the subsequent weeks, with the stand growing the fastest in the last 10 days of the rotation. This growth process is initiated from the basal buds in the crown of the plant.
Aphid numbers are still being closely monitored, with none being observed as yet. Lucerne will be sprayed if aphids reach large numbers. The negative effects of aphid infestations on lucerne is shown in the grazing animals where sheep will start to scour and not thrive. Fraser anticipates that there will be pest challenges this year due to the mild winter with the possibility that pests have carried through from autumn having survived the winter. Young lucerne paddocks will be the most vulnerable.
Lucerne growth rates:
We are now reporting lucerne growth data from this paddock on a regular basis with herbage cuts taken from pasture exclusion cages. We have kindly been given access to facilities at Plant and Food – Marlborough in order to pass this information to our blog readers. Thanks to Richard Hunter at Plant and Food, for sorting this out for us!
Photo below of the pasture exclusion cage behind the herbage about to be harvested.
…and the results:
October-November 2013 Lucerne growth data Jeffries Front Flat, Bonavaree
|Number days growth
|Yield (kg DM/ha)
|Growth rate(kg DM/ha/day)
Key Bonavaree messages:
· Use lucerne height rather than time when planning spring grazing rotation length. Means you can get in and graze a paddock when it’s at its optimum, rather than when it fits the schedule.
· Closely monitor for aphid infestations, particularly young lucerne paddocks. Pest challenges predicted due to mild winter.