Under current (2020) autumn conditions the window for more production without compromising calving targets is fast closing, so continuing milking is very risky, and will require careful monitoring of pasture cover, cow BCS, supplement inventory, and secure winter grazing arrangements.
- Focus on leaving consistent post-grazing residuals
- Body condition score the herd for proactive feed management
- Complete an autumn feed budget to identify feed shortages
- Ensure any pasture renewal is a quality job, target autumn pests where possible
- Build APC by increasing rotation length.
Pasture Management (March to May)
Good grazing management through early autumn is maximising the pasture you grow and utilise, balanced with allowing pastures to recover following any dry periods in the summer.
The secret to achieving this good grazing management is leaving consistent post-grazing residuals and graze pastures at the right time (2.5-3 leaves). Grazing ryegrass pastures too early reduces autumn growth and too late reduces quality.
Good management: improved persistence
- Grazing at the 2½ - to 3-leaf stage. During May, the rotation length may be extended beyond this to start building feed for winter.
- Preventing grazing below 7 clicks/1500 kg DM/ha.
- If residuals are less than 7 clicks/1500 kg DM/ha, feed supplement to maintain herd intake and protect pasture. If there is no supplement available then stand cows off pasture once they reach the target residual
Poor management: reduced persistence
- Allocating too much pasture area (fast rotation) immediately after rain
- Frequent intense grazing before plants reach the three leaf stage reduces recovery of tiller numbers during autumn.
Successful autumn grazing involves knowledge of likely winter pasture growth rates for the farm from mid-May to mid-July, relative to the likely feed demand over this period. To plan autumn rotation targets correctly you need to determine if winter feed demand is likely to be greater than or less than winter pasture growth. Using this knowledge as a basis for an end of May target, along with growth rates and leaf stage over autumn will help to set the most appropriate rotation lengths for your farm.
It is important to determine the leaf stage of your own pastures. Leaf appearance rates mainly depend on temperature and water availability with leaves taking longer to appear in colder temperatures or where water is limited.
The following table shows the approximate leaf appearance rates for different regions in autumn; this can be used as a guide to determine rotation length.
Minimum rotation length (e.g. two leaf stage): Time taken for one leaf to fully grow x 2
Maximum rotation length: Time taken for one leaf to grow x3
To determine the leaf stage of your own pasture, collect 10 tillers and compare the leaf stages with the grazing pocket guide pages 10 & 11.
Autumn guideline to regional leaf appearance rates based on average monthly temperatures
Region North land Nth Waikato Sth Waikato BOP Taranaki Lower NI Top of South/ WC Canterbury / N. Otago Southland / S. Otago Average Autumn temp 14-20°C 12-20°C 10-18°C 11-20°C 10-18°C 10-18°C 10-18°C 6-16°C 6-15°C Time taken for one leaf to fully grow 8-12 days 8-14 Days 10-17 days 8-16 days 10-17 days 10-17 days 10-17 days 11-28 days 12-28 days
Adapted from Julia Lee et al., DNZ Technical Series Issue 3. Assumes that available soil moisture is at minimum 40%, if less than 40% time taken for a leaf to fully grow will increase dramatically. This is a guide actual rate will vary with temperature and water.
If farm cover is below where is should be (in order to meet target cover at calving) N fertiliser can be a great ‘circuit breaker’ to get growth back on track. Use a large part of the farm for best effect.
Feed management and BCS
Whole herd body condition score (BCS) assessment is a powerful tool to assist proactive feed management during autumn and to sort mobs of cows for differential feeding during winter.
To manage calving BCS targets, the herd must be assessed in early March. There are a number of strategies managers can use to get every cow close to her ideal BCS at calving.
Early calving cows
From early March, OAD milking and feeding milker’s supplements are not effective ways to gain BCS in early-calving cows. To hit targets, cows need to be dried-off based on their individual BCS, their approximate calving date, and the amount of supplementary feed available for autumn feeding.
For later-calving cows, OAD milking and supplementary feeds can form a part of the strategy for BCS management. But the time taken to gain the necessary BCS must be considered. Particular attention must be paid to R2s and heifers finishing their first lactation.
Autumn feed budget
An autumn feed budget can be used to reflect on the current feed supply and demand situation, and plan ahead to reach cow condition and pasture cover targets.
Autumn feed budget considerations
- Meeting pasture cover targets
- Using N to boost autumn pasture growth.
- Utilising home-grown feed
- Strategically using supplement and grazed crops,
- Off farm grazing
Matching feed demand
- Culling low producing cows
- Demand of returning replacements
- Length of time at off farm grazing
- Drying off
- Feed requirements for BCS targets (and time!)
Autumn pasture renewal
If you are planning to renew poor performing pastures firstly identify the poor performing paddocks for renewal and address the underlining problems behind pasture deterioration. Consider soil fertility and pH, over-grazing, pugging, drainage, soil compaction, weeds and pests.
Right sowing date
- For areas north of Taupo, the recommended renewal date is March 31 and for the lower North Island around March 20.
- If permanent pasture is following crop consider the time for full crop utilisation and the renewal process.
- Buy quality seed and select the right pasture species and/or cultivar for your farm
- Sowing a small area well is less risky than sowing a large area poorly.
- Consolidate your seed bed
- Take-care sowing clover, clover should be sown at a shallower depth than ryegrass
- Attention to weed control, contouring and levelling if avoiding cultivation after forage crops.
After sowing and first grazing
New pastures should first be grazed when the plants break off rather than pulled out when plucked by hand. Use the pluck test to test when to graze. The first grazing should be a quick nip off with (top 2-3cm) with young stock or 2-3 hours grazing with cows.
- New grass often becomes nitrogen deficient 2-3months after sowing, particularity after a wet spell. Look out for yellow leaf tips, the most obvious symptom of this occurring. Small applications of nitrogen (20-30 kg N/ha) from 6-8 weeks after sowing will increase seedling size before summer
- Before 1st grazing it may pay to test a sample for nitrate toxicity – Nitrate poisoning is not uncommon when grazing resown pastures especially annuals.
- Weed control - spray new pastures. Monitor your new pasture for weeds, seedlings weeds can be sprayed before or after 1st grazing. Spraying should be delayed if there is more than 50% bare ground. Waiting for all clover plants to be big enough to spray means that weeds are often to advance to control.
Autumn Pests Location Host plant/ forage affected Autumn Management Considerations
Adult black beetle
Cause of autumn damage, yellowing tillers that pull easily from the pasture.
Northern North Island Annual and perennial ryegrass, tall fescue, paspalum, kikuyu
Summer grasses are a good host. Eliminating summer grasses where possible through good renewal practice. When consider break crops and when renewing use the right endophyte and treated seed
Further information: Black Beetle Farmfact
Brassica aphid, cabbage aphid, grey cabbage aphid
Stunt plant growth Transmit plant viruses.
Throughout NZ All brassica types
Autumn sprays as directed by your consultant or industry representative. Removal of weeds that can act as host.
Further information: AgPest website
Clover root weevil
Adults notching in clover leaves, larvae feed on roots/ root nodules. Can result in total clover loss. More info
Throughout NZ Clover Pasture establishment application of insecticide can be used close to seedling emergence to control adults, provides a window in which clover plants may establish before re-invasion .
Grass-grub, brown beetle larvae
Feed on roots. Densities greater than an average of 8 larvae per spade square (200/m2) will cause damage.
Throughout NZ Pasture species Digging - from mid-February to measure damage AgPest. Early warning strips in Autumn. Chemical control after sampling based on density
Seedling stands can be attacked in autumn. Adults attack foliage. Larval feeding on root
Throughout NZ Lucerne
Insecticidal control against adult weevils returning to Lucerne at the end of autumn. Insecticidal control should only be used when damage is severe.
Further information: AgPest website
Caterpillars and the damage they cause are most noticeable from April until September. At high densities plants are destroyed allowing inferior plant species to establish
Throughout NZ, damaging populations uncommon in northern North Island Porina occurs in most pastures. Whether or not they attain pest status is largely governed by weather at key times of their life cycle No of different species require different assessment - Agpest for appropriate autumn management and control.
Tasmanian Grass Grub
Autumn sown brassica crops and legume seedlings can be severely damaged as larvae sever plant stems and the plants will die.
Northern North Island, Hawkes Bay, coastal Taranaki, Marlborough and the Canterbury plains Most pasture plants, pasture weeds and brassica seedlings. Favour legumes incl. clovers and Lucerne.
Larvae in the soil in autumn. When larvae are present at damaging levels insecticide may be the only recourse to limit damage and save pasture. Maintaining good pasture cover during January/February reduces the availability of egg laying sites.
Further information: AgPest website
For more information on identification and control check out AgPest.
Feed management tools
Completing the simple will identify any shortage in home-grown feed and therefore determine if supplementary feed is needed.
This calculator can be used to help make decisions on purchasing supplement to feed to dry cows for live weight gain.