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Drought Mitigation Strategies

Direct drilling

Is direct drilling suitable in dry conditions? There are differences in opinion about this, with some people saying it works and others getting poor results. There are plenty of examples of direct drilling not working in dry conditions, however, there are techniques that can be used to minimise this risk and produce good results even in dry conditions.

With the correct preparation, direct drilling consistently produces better results in dry conditions than conventional seeding does.

1. Double spray/fallow

If moisture retention is a problem, using the double spray/fallow technique improves moisture availability. Trials have shown that up to 12 times more moisture is retained to 20 cm depth compared to unsprayed sites.

Double spray fallow involves killing the old pasture with herbicide then leaving the paddock fallow for at least 6 weeks. Over this time, roots break down, and because the plants are not transpiring, less moisture is lost.

Double spray/fallow retains moisture due to reduced evapo-transpiration rates.

2. Choice of drill

Different drills are suited to different conditions. If drilling can be done when moisture conditions are good, any type of drill should give good results. If conditions are dry, different drills will perform differently.

The best results will be obtained by using cross-slot drills, or a drill that uses press wheels to close the slot and retain moisture and good soil/seed contact. Hoe coulters will give the next best results followed by older triple disk designs. New triple disk designs with small press wheels give better results than older designs.

In dry conditions, use the double spray fallow technique when using triple disk drills. Triple disk drills perform best when moisture conditions are good, or in sandy or stony soils.

If you have your own direct drill, you can quickly capitalise on any rain and get in and drill while there is moisture around.

Drought strategy using poplars and willows

The prevalence of drought highlights the importance of low cost, readily available supplementary feeds in summer-dry and drought-prone regions. Common supplements such as silage, lucerne, feed grains (such as barley), and summer feed crops tend to be in short supply and can be very expensive in drought times. This has led to recent research into the effectiveness of feeding poplar and willow to livestock in dry summer and drought conditions.

Poplars and willows have been planted as a multipurpose resource, with reasons for planting including:

• As an erosion control measure for soil conservation
• Shelter and shade effect against wind, rain and sun
• For aesthetics to enhance the general look of the property
• As a potential timber resource
• As a food source during summer dry or drought periods

1. Potential feed production

Cost/benefit analysis shows that farms can regain almost half the cost of a drought by supplementing ewes with tree fodder during mating.

Poplars and willows are equal to lucerne hay and silage in terms of their food value per kg of dry matter. The table below provides a comparison of various foods.

Measurements during the 1988 drought in Otago confirmed that poplar and willow species could produce large quantities of nutritious fodder. Prunings from 9 year old planted for soil conservation produced 20‑50 kg of leaf DM per tree (equivalent to 1‑2 bales of lucerne hay). Once pruned, trees should produce 30-40 kg DM fodder every 3-4 years.

2. Management regimes for fodder production

Harvesting method will vary according to individual needs or objectives. Available tools, previous treatment, timber potential and tree location all form part of the equation.

Suggested regimes include the following:

• Form pruning and side trimming– this is appropriate where there is possible timber potential
• Thinning where there has been substantial over-planting– this is an easy option, but may be appropriate in many cases

Pruning can be done with a long handled pruning saw, from a ladder using a hand saw, or from a mobile platform where there is easy contoured country. Pruning may be time consuming, but offers the advantage of improving timber potential on poplars.

Benefits from alternative fodder

Some of the benefints from using alternative fodder are:

• Drought feed (late summer)
• Pre-tupping supplementary feed
• Better balanced diet (trace elements)
• Reduced stock drench uses
• May relieve grazing pressure on other pastures
• Shelter and shade provisions

Benefits from using poplars and willows

Some of the benefits from using poplars and willows are:

• More frost tolerant
• Less shading in winter (less impact on pasture)
• A deep root system (so minimal impact on pasture)
• Rapid breakdown of litter (minimal impact on soil pH)
• Relatively fast growth rates
• Aesthetically suited with colours in autumn and early spring

Benefits of feeding poplar foliage on lambing ewes.

The following table is based on trials at Massey University.

Notes:

• Ewes were fed poplar foliage under drought conditions during mating.
• The trial was based on ewes (57 kg) split into 3 groups fed on typical pasture for 10 weeks, in weekly breaks, starting on 1 February 2001.
• Low rates to one group was 0.75 kg of fresh poplar/ewe/day.
• High rates to other group was 1.5 kg of fresh poplar/ewe/day.
• Pre and post grazing pasture cover was similar for all three groups at 1040 and 525 kg/DM/ha.
• The high and low treatments gave a gross margin/ewe of $13.36 and $9.13 respectively, higher than the control group (on pasture only).
• Cartage and labour costs to cut and carry the poplar foliage were not considered.

Examples of some stock fodder plants suitable for farms:Tree Fodder- Veronese poplar, Flevo poplar, Tasman poplar, Argyle poplar, Matsudana willow, Moutere willow and Tangoio willow. Shrub Fodder- Kinuyanagi willow (high DM yields – graze in situ), other shrub willows and Mediterranean saltbush (Atriplex halimus).

Harvesting and feeding of poplars and willows.

The method of harvest chosen will depend on your farm management, topography of the fodder area, staff availability and location of site to the grazing animals.

1. Grazing in-situ

• Best on easy rolling fertile land so one can maximise production
• Low growing shrub species preferred e.g. Kinuyanagi willow, which can be break fed
• Can apply dairy effluent to maximise production (if the site is suitable)

2. Pruning selective branches

• Feed directly on-site where branches fall (small branches)
• Cut and carry to another feed area (labour intensive)

3. Pollarding

• Cut tree down at about 1.3-1.5 m height (below shoulder height) and feed set amount per day (use hot wire and break fence)
• Best after 6-8 years growth from the initial stake or seedling
• Ensure stem is not too large in diameter as large volume of wood will remain on-site
• Care in post management so stock especially cattle do not debark stem
• Paint cut surfaces to stop any fungal pathogens entering
• Pollard again after 3 years or depending on growth rates
• Alternatively can cut some of the re-growth shoots every second year

4. Coppicing

• Cutting stem as above at approximately 30 cm height above ground
• Feeding sheep is preferred on-site as cattle may damage the remaining stool
• Use hot wire
• Paint cut stems with a fungicide
• Exclude stock for some time to ensure new shoot re-growth

Contact Land Sustainability Officers at Environment Southland for free on-site advice.

Environment Southland
Private Bag 90116, Invercargill
P: +64 3 211-5115
P: 0800 76 88 45 (within Southland only)
F: +64 3 211-5252
E: service@es.govt.nz