1-23 Pasture renovation/renewal Pasture growth can decline over time due to a number of factors. Pasture renovation methods describe how to improve the long-term production and persistence of poor performing paddocks. The most successful approach is often complete pasture renewal. Benefits of pasture renovation: • • • • •

Increased total pasture yield (1.0 - 8.0 t DM/ha/yr) Increased milksolids production (if the extra growth is eaten) Improved pasture quality Can make pasture management easier by using late heading varieties to minimise the drop in pasture quality as seed heads appear in late spring Reduced animal health problems.

Should you renovate pasture? To get a return from investment in pasture renovation requires the identification of underperforming paddocks and estimating the potential extra pasture production. For example, where the yield can be increased by 2 t DM/ha the return is around 130 kg MS/ha. The return will be greater if the extra growth occurs at a time of the season when animal demand exceeds pasture growth.

Assessing pastures Estimating paddock pasture production can be done from grazing records or pasture cover assessments from farm walks. With grazing records you can calculate the performance of individual paddocks by adding up the number of cow grazing days over the year. This needs to be corrected for any silage made (extra growth) and silage fed out (if cows eat silage they eat less grass). A form and an example of how to calculate pasture eaten per paddock are given on page 8 of this Farm Fact. The best paddocks can show a farm's potential to grow pasture. The worst paddocks are identified for possible renovation. The difference between the best and worst paddocks gives an idea of the potential pasture production to be gained from renovation, provided these are similar in soil, drainage etc. The profile for your own farm will give quantitative information with which to develop an appropriate pasture renovation strategy. As a rule of thumb the breakeven return on investment is where renovation can improve pasture production by at least 1.5 t DM/year. The breakeven point will differ between farms depending on the cost of renovation and any other benefits from the renovation such as better stock health from selecting a new endophyte like AR1, or improved paddock contour.

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Reasons for poor pasture Once poor producing paddocks are identified, successful pasture renovation involves identifying reasons for poor pasture production and rectifying possible problems such as: • • • • •

Low soil fertility and/or incorrect soil pH? Poor drainage? Pasture pests (e.g. grass grubs, black beetle, clover root weevil, porina)? Excessive pugging, soil compaction and/or overgrazing? Weeds and unproductive grasses (lack of ryegrass)?

Treat the cause and not the symptoms (Table 1).

Table 1. Causes of poor pasture production and solutions Problem

Solution

Lack of ryegrass/clover

Implement a renovation program to establish strong ryegrass/clover pastures

Low soil fertility and / or incorrect pH

Test soil and apply fertiliser and lime

Poor drainage / compacted soil

Undertake suitable drainage (e.g. install plastic drains), sub-soil in spring, ripping

Pasture pests (black beetle, clover root weevil, grass grubs, porina)

Sow tolerant varieties, use specific endophyte types which provide resistance, use seed treated with pesticides, rotate summer crops with pastures

Excessive pugging and / or overgrazing

Use wintering pads, feed supplements, strategic destocking

Invasion of pastures by undesirable grasses / weeds

Improve drainage and fertility. Remove perennial weeds and undesirable grasses by spraying with a Glyphosate/Roundup herbicide before resowing. Double spray going from pasture to pasture or from crop to pasture to increase weed control. For many weeds and undesirable grasses going through a crop as part of the renovation program will be necessary to get a good pasture that will persist.

Choosing a Ryegrass cultivar (variety) Choose ryegrass cultivars that are adapted to the local climate, environment, and your farming system. There are a number of attributes to consider:

1. Heading dates Consider sowing cultivars with a range of heading dates (e.g. half the farm sown in early heading cultivars, the other half in late heading cultivars). This makes management easier as the whole farm is not losing quality as the same time. Sow cultivars with similar flowering dates in one paddock. 2. Aftermath heading (AMH) Aftermath heading refers to continued seed head production after the main spring heading. Choose cultivars that have reduced aftermath heading for improved summer pasture quality and animal productivity.

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3. Tetraploids and diploids Tetraploids (Table 2) are more upright clover-friendly plants. Tetraploid ryegrasses are highly palatable, tend to be grazed lower reducing litter levels and hence accumulation of facial eczema spores. Diploids produce more tillers and consequently are more persistent and tolerant of overgrazing than are tetraploids.

4. Winter productivity Generally annual and Italian ryegrasses produce more dry matter in the winter and early spring than other ryegrasses. Annuals persist for 6-8 months; Italians can persist from one year in summer dry areas and up to three years in summer wet conditions.

Table 2 Types

Features and examples of types of ryegrass cultivars Annual

Italian

Features

Live for 1-3 yrs Rapid establishment Faster growth in winter and spring More palatable More aftermath heading No endophyte

Examples

Progrow Archie*

Cordura Feast II* Crusader Tabu Warrior

Short rotation (Hybrid)

Long Rotation

Live for 2-5 yrs Cross between Italian and Perennial cultivars Available with or without endophyte

Live for 3-5+ yrs Slower establishment Less winter growth Less palatable Some seed heads Range of endophyte options

Maverick GII Delish* Harper

Impact Banquet II* Matrix Horizon* Ohau* SupremePlus Revolution Ultra Helix

Perennial

Quartet* Bronsyn Aries HD ONE50 Expo Samson Commando Bealey* Alto Arrow AlbertDart HSG AberMagic HSG

*Tetraploid cultivars

Use quality seed Seed quality is important and Certified Seed is recommended. This is seed produced under the NZ Seed Certification scheme, run by AssureQuality, that has met quality standards and is free of weed seeds. Major seed retailers stock certified seed. Cheap seed is sometimes available from a range of sources, and this is often of suspect quality or contains weed seeds. Germination, purity and endophyte certificates should be available, on request, to check seed quality. The germination should be 90%+, seed purity 99%+, and perennial ryegrass with endophyte should be 70%+ endophyte. Endophyte level declines over time, so it is preferable not to sow seed that is left-over from last year’s sowing; use seed harvested in the year of sowing for best endophyte viability.

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Endophyte selection With perennial ryegrass, endophyte option is very important. Ryegrass without endophyte can be used in summer moist areas such as Southland, South Otago and West Coast South Island, whereas endophyte-infected cultivars are needed for all of the North Island. • Most perennial ryegrass plants in New Zealand pastures contain a fungus called endophyte that grows inside the plant (Farm Fact 1-22). Endophyte protects the plant from insect attack but can also cause animal health problems. • New or “Novel” endophytes have been selected for special features. They provide a way of reducing animal health problems associated with ryegrass infected with the old “wild” endophyte, while maintaining positive effects on plant persistence. • Few varieties are now available with the old wild (also called Standard or High) endophyte and most contain novel endophytes. Choosing the right endophyte for your area will determine pasture persistence and animal productivity (e.g. AR1, AR37, Endo5, NEA2). See Farm Fact 1-24. • Talk to your DairyNZ Consulting Officer for local information. Research the benefits and costs of different cultivars and endophytes. Neighbouring farms, independent research trials and commercial seed companies are all sources of information.

Methods Different methods of establishing new pastures are compared below (Table 3).

Table 3. Comparison of methods of pasture renovation/ renewal

Pros

Undersowing into existing pasture

Spray and direct drilling for perennial pasture

Full cultivation for perennial pasture – grass to grass

• Simple • Little loss of

• Good control of

• Better establish-

production • Increases plant

density • Increased winter

competition through herbicide • Faster to first grazing

• Only short term • •

•

•

•

solution Doesn’t work in dense pastures Less opportunity to correct soil problems Annuals & Italian ryegrasses will not persist long and may attract insects as most do not contain an endophyte Results in open weedy pastures once ryegrasses have died May reduce clover content

• •

and spring growth if using annual or Italian cultivars Cons

•

•

ment of clovers Reduces compaction Improved weed control Can level paddock Can incorporate lime

Establishment after cropping • Best option to

establish new cultivars if done well • Reduces soil and plant pests • Best weed control

• Less opportunity

• Slower to first

• Expensive if

to correct soil problems • Pasture may not persist due to soil problems • Perennial weeds could return quickly

grazing • Release of carbon from soil

poor yielding crops • Requires planning to fit in with farm system • Requires good planning and timing of operations as well as attention to detail

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Undersowing Undersowing ryegrass cultivars, usually by direct drilling into existing pasture without applying herbicide provides a short-term solution in specific situations. Using annual, Italian or hybrid cultivars can provide more feed in the winter and early spring than using perennial ryegrass cultivars. To do this: • • •

Hard graze and drill into thin (open) pasture After emergence graze lightly and frequently to minimise shading of new seedlings by existing plants Do not pug in winter.

Spray and direct drilling for establishment of perennial pasture Pastures dominated by unsown grasses (e.g. paspalum, fog, browntop, Kikuyu, wild fescue) or weeds must be sprayed with an appropriate herbicide before sowing. This eliminates competition between new seedlings and established plants, resulting in improved seedling growth and survival. Best results for summer dry farms will be achieved by spraying in the autumn (as described below). For South Island farms under irrigation and farms that are not under moisture stress, new pasture can be sown in spring or autumn. Spring is often the preferred time as paddocks can be renovated when there is surplus feed. Spray/cultivation or a cropping regime will control perennial weed problems better than will spray/drilling.

Management for successful direct drilling with herbicide (no tillage) • • •

• •

•

•

•

Hard graze to 7-8 clicks on the rising plate meter to remove excess plant residue Allow 1-2 weeks or up to 5-6 cm growth Spray with Glyphosate/Roundup herbicide to actively growing plants, following recommended spraying rates. Reducing spraying rates will result is inferior results. For a paddock cleanup use 4-6 litres/ha (360 formulation). Graze pasture 3-4 days after spraying, before pasture browns off. Delay grazing for 7 days for other Glyphosate formulations. New pasture can be established with just one Glyphosate/Roundup spray. However, when hard to kill perennial weeds (e.g. Californian thistle, Kikuyu, dock, browntop, Poa pratensis) are present, use multiple sprays, in particular, two autumn sprays. Some weeds (e.g. Kikuyu and Mercer grass) require special treatment to prepare them for a successful kill with Roundup. Kikuyu pastures should be “mulched” 1-2 times over the summer, to remove stolons and produce a leafy pasture before spraying in autumn. After the second mulching, DO NOT graze until after the Roundup has been applied, to ensure no Kikuyu is “hidden” by cow dung. Check for slugs before and after sowing. Slugs are a major cause of failure with spray/drilling, as the decaying vegetation is a perfect habitat for them. To monitor slug numbers put wet sacks out over night, if 6+ slugs/sack are present seek advice on slug bait control. If in doubt apply slug bait. Apply 25-50kg N/ha 2-4 weeks after seedling emergence to stimulate growth (tillering).

Drilling Drill ryegrass NO deeper than 2cm using appropriate equipment. Ensure seed is covered using a press wheel on the drill or by dragging a chain or brush harrow. •

•

For good clover establishment DO NOT drill clover seed in the same rows and at the same depth as ryegrass seed, as this reduces clover establishment as ryegrass will always beat the white clover. This will require purchasing clover seed separate to ryegrass rather than buying a mix of clovers and grasses.

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One method of establishment is to use a direct drill with a separate small seeds box on the front that can sow the clover in front of the drills sowing the ryegrass; use a bar or brush harrow to cover the clover seed. If broadcasting the seed into a cultivated seedbed, clover and ryegrass can be mixed Cross drilling at half the desired seeding rate each way may appear to give the best result but may be less economic than a single pass at the full rate. Cross drilling gives faster canopy development, resulting in less weed pressure. Using drills with 10 or 7.5 cm drill spacing (rather than the traditional 15 cm spacing) will give a better result through better ground coverage by ryegrass and better long-term weed control. Seeding Rates: 16-25 kg/ha ryegrass (Table 4 below) 3-4 kg/ha white clover 3-4 kg Chicory – optional 3-4 kg/ha red clover – optional. The above rates are dependant on the following: a good consolidated seedbed seed is drilled evenly (tractor speed slow) drill has good depth control there is adequate moisture after sowing.

Research has shown that increasing seeding rate results in many weak plants that die in the first summer. With excellent seedbed preparation rates as low as 10 kg ryegrass/ha or 16 kg/ha cross-drilled are adequate. With attention to detail, excellent seedbed preparation and good sowing technique (not too deep, not sown too fast) the cost of establishment can be considerably less as lower seeding rate is required.

Table 4.

Suggested ryegrass seeding rates (kg/ha)

Diploid Tetraploid

Treated seed

Untreated (bare) seed

16 1/

20

20 – 30

25 – 30 2/

Note 1/

Higher seeding rates are often recommended as a cover for poor seedbed preparation. High seeding rates do result in good coverage in early establishment and provide competition for weed species. However, high seeding rates also result in smaller, weaker individual plants that do not survive the first summer.

Note 2/

As tetraploid seed varies in size check with the seed company as to recommended rate e.g. sowing rate for Bealey is 25-30 kg/ha as it twice the normal seed size.

Seed Treatments •

• •

When sowing new ryegrass seed always use treated seed to control insect attack on seedlings. Note: endophyte in ryegrass seed is not active against insects during the first few weeks after germination, so the use of treated seed is essential in insect-prone areas The effects on seedlings of black beetle, grass grub, porina, Argentine stem weevil and other pasture pests can be devastating There are three main seed treatments: “SuperStrike” and Agricote contain insecticides for Argentine stem weevil and black beetle control and fungicides (also rhizobia in the case of clover). “Gaucho” contains an insecticide (no fungicide) and controls grass grub and black beetle. “Ultrastrike” controls Argentine stem weevil, grass grub and black beetle

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Use of summer crop or full cultivation for establishment of perennial pasture Outline of method Where there is a major problem with the current species, weed infestation or wanting to establish a new endophyte the best results are through at least one crop and for Kikuyu may require 18 months of cropping before establishing permanent pastures. 1.

This system begins with a Roundup spray in autumn, before sowing a winter ryegrass. This is a more effective at killing perennial weeds than spraying in spring.

2.

In October a second Roundup spray is applied in preparation for the summer crop.

3.

After the summer crop a third and final Roundup spray is applied to ensure all Kikuyu, browntop, or ryegrass with wild endophyte, for example, are completely killed.

Cultivation • •

•

Must result in a fine, firm, clod-free seedbed to provide new pasture seeds with the best opportunity for long-term establishment. Roll the seedbed before and after sowing. Incorporating lime into the soil at cultivation is recommended, particularly if you are using high rates of nitrogen fertiliser and have a low soil pH (See Farm Fact 6-2). If applying urea, 1.5 kg lime is required to be applied annually per kg urea, to adjust for soil acidification from the urea. Acidification from urea applied at 400 kg /ha/year (184 kg N/ha), will be neutralised with 600 kg lime/ha/year. If using DAP, apply twice this rate, i.e. 3.0 kg lime per kg DAP/annum.

Timing •

•

A general rule: In warmer winter regions, where summer grasses are a problem, sow seed just before or at the start of autumn rain. Sowing early when still warm results in better pasture establishment and early autumn production. In colder winter regions, sow seed in the spring.

Good management is a must to profit from your dollars invested in new pasture •

Ideally a light grazing (e.g. with calves) about six weeks after emergence, when plants snap off and don’t pull out when plucked by hand, will encourage tillering and clover establishment. Cows can be used in dry conditions, but only for 2-3 hrs. Be prepared to move them. Light applications of nitrogen fertiliser (e.g. 50 kg urea/ha) at establishment and again after the first grazing will aid seedling establishment.

To prolong the life of your pasture: • • • •

DO NOT pug - instead consider standing off on races/feed pad, or grazing off-farm DO NOT overgraze in summer - instead use supplements to allow the cows to leave adequate residuals (i.e. a height of 7-8 clicks on the rising plate meter) DO NOT cut for silage or hay in the first spring after sowing DO use adequate fertiliser, especially nitrogen considering the extra production from the new pasture. It takes 12-18 months for nitrogen from clover to become available.

Talk to your DairyNZ Consulting Officer for advice specific to your farm. Updated: March 2010

©DairyNZ 2010

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Form to Calculate Pasture Eaten Per Paddock No. of Milker Grazings

Average no. milking cows per grazing

Average Intake of Milkers Kg DM/cow

Total kg DM Eaten by Milkers

No. Dry cows grazed

Average Intake Dry Cows

Total Kg DM Eaten by Dry Cows

Plus Silage /hay Made Total kg DM

Less Supplement Fed out Kg DM

Total Kg Pasture Eaten Per Paddock

Kg DM Eaten Per Ha

Paddock No. Name

Paddock Area Ha

Example

A

B

C

D

BxCxD=E

F

G

FXG=H

I

J

E+ H + I – J=K

K÷A

1

3.3 ha

9

250

16

36,000

200

10

2000

5000

5000

38,000

11,500