Know Your Plants for Changing Times

Allister Moorhead – Product Development Manager, Agricom ([email protected])

Setting the scene of the current system

Since 2008, pastures in northern New Zealand have faced significant challenges to their reliability of dry matter production and the most resilient of these have often been those pastures that are least desired. In setting the scene for this paper, it is important to acknowledge that using a perennial ryegrass/white clover pasture remains the most desirable feed system for in situ (in paddock) grazing. There is no other grass/legume pasture that combines so many desirable characteristics which most dairy environments in New Zealand can and regularly do benefit from so much. Only where you cannot grow perennial ryegrass/white clover successfully, should alternatives be considered.

A perennial ryegrass based pasture system can offer:

  • ease and speed of establishment (time to first grazing),
  • great spring growth potential with high quality maintained under basic management,
  • vegetative summer productivity (with summer moisture),
  • cool season growth both in the autumn and late winter/ early spring,
  • full winter activity (especially NZ bred material),
  • potential to be fully perennial both via reseeding and vegetative survival,
  • tolerance to a level of pasture wear (not heavy pugging), and
  • a natural relationship with seed borne endophyte that can provide a range of pest control options.

Perennial plants can tolerate certain levels of stress but the risk of collapse increases as more types of stress are added to the recipe. Among these stresses the impact of the southerly shift of sub-tropical environmental conditions on this temperate pasture system can’t be ignored. Farm systems which don’t allow for natural reseeding take away one element of natural resilience for perennial ryegrass /white clover pastures to be truly perennial.

Further, the climatic changes which bring about warmer, drier conditions influence the seasonality and survival of pasture pest species, and because of this some pests are maintaining populations at constantly high levels, while others are achieving multiple life cycles. Climate extremes, with more intense weather events, particularly severe, prolonged, dry conditions, once the domain of just summer, are now not uncommon in autumn and even late spring.

More intense cropping can contribute to challenges of pasture survival post cropping. Periods of critical soil disturbance, combined with both wet and serve dry periods, can have a detrimental effect on the soil environment of some soil types, which can negatively impact pasture survival.

Perennial ryegrass based pastures are coming under severe strain with these building pressures.

What are the roles of other grass species in addressing this change? To answer this question, we need to know our plants.

Perennial Grasses

Tall Fescue

  • Continental plant of deep fertile flood plains – prefers high fertility.
  • Thick, fibrous root system than can be significantly deeper than ryegrass.
  • Tolerant to hot summer conditions and when moisture is present can have higher growth rates at higher temperatures than perennial ryegrass.
  • Tolerant to a range of pests at low to moderate levels and can have novel endophyte to extend pest tolerance.
  • Has extremely high spring growth and therefore can be harder to manage within a normal ryegrass rotation.
  • Is slow to establish and establishment can often be compromised if sown late in cooler conditions, but conversely can host a high legume content.

Cocksfoot

  • A grass species of low to medium fertility that responds well to higher fertility levels.
  • Has a distinctive crown and a highly fibrous root structure. It is suited to free draining soils but is not tolerant to long periods of wet conditions or wet weather pasture damage.
  • On average, a green cocksfoot leaf does not have the quality of a perennial ryegrass leaf equivalent. However, cocksfoot maintains its quality a lot longer than ryegrass under summer moisture stress.
  • Does not have a natural relationship with an endophyte for insect tolerance and while the plant is tolerant to several pasture pests, it is still severely damaged by insects, such as black beetle (particularly their larvae).
  • Highly suited to mixtures with ryegrass where it is slow to establish, becoming more obvious when climate conditions allow it to express its natural advantages.

Timothy

  • A slow tillering grass of cooler environments that is suited to fertile and heavy country.
  • Has a very small seed and no endophyte protection. It’s generally believed to be vulnerable to insect pests, although it can be surprisingly persistent.
  • Not suited to intensive rotations.

Meadow fescue

  • A Northern European grass of fertile conditions. High quality and highly palatable fescue species.
  • Mostly winter dormant, although from the Waikato north this dormancy is broken. It shows considerable winter activity, more similar to tall fescue, in the north of New Zealand.
  • Has a natural endophyte that produces large amounts of loline alkaloids. These can circulate into the roots and are enough to potentially provide resilience to grass grub and black beetle larvae.

Prairie grass

  • A free seeding, medium-term grass that is suited to fertile free draining soils.
  • Has a strong all-season growth pattern, but is not suited to fast rotations.
  • Is most similar to hybrid ryegrass in its seasonal growth habit, but has fewer tillers and a significantly wider seeding pattern. Prairie grass seed head is highly palatable to cattle.

Hybrid ryegrass

In circumstances where the longevity of perennial ryegrass is not meeting economic thresholds, short term hybrid ryegrass (a natural cross between perennial ryegrass and Italian ryegrass) with an appropriate endophyte could fit into standard dairy systems. Hybrid ryegrasses can have strong winter and spring growth, and they show intermediate dry matter production in summer and early autumn relative to perennial ryegrass. They are not long-lived but are significantly more reliable than an Italian ryegrass for second, and at times possible third, year productivity.

Italian ryegrass

Italian ryegrass, and true annual ryegrass, have been the standard in many subtropical pasture systems, especially those based around the C4 sub-tropical grass, kikuyu. Sown in autumn, Italian ryegrass maximises winter and spring growth before being overwhelmed by sub-tropical weather conditions and the invasion of C4 summer grasses. In New Zealand there are Italian ryegrasses with endophyte that typically extend their persistence, often supporting them to get through a second winter. However, in the north of New Zealand even Italian ryegrass with endophyte struggles to reliably get through a second summer.

In summary, there are a number of alternative grass species that are relevant for the New Zealand dairy industry. However, the key point is to understand the characteristics of the grass and to know the grass well before placing it on your farm. No grasses described here are perfect or they would already be implemented as a standard in the industry. Each of these grasses have a fit in different environmental conditions from an ecological perspective. There are strategic ways these grasses can be mixed together but sowing rates have to be well thought out as they all have significantly different establishment vigour and tillering characteristics which may lead to different outcomes than initially desired.

An example of mixing alternative species is a 50:50 mix of tall fescue and meadow fescue. These species establish at very similar rates. Three years of experience in extremely difficult seasons has the Agricom product development team believing this mix could be a major step forward in fescue pastures for difficult conditions in dairy environments. Tall fescue provides the yield and productivity potential, while meadow fescue is improves the palatability and ease utilisation of this fescue pasture, while also providing some resilience to pasture pests, such as black beetle and grass grub. Using cocksfoot in a ryegrass mix has been mentioned earlier.

The natural future of nitrogen cycling on dairy farms

Legumes’ importance to dairy systems in the presence of nitrogen caps can’t be understated. The natural ability to fix atmospheric nitrogen through rhizobia, and their symbiotic relationship with the roots of legumes, is a significant advantage to the New Zealand temperate dairy system. Legumes, in general, also improve the palatability and utilisation of pasture during periods of pasture quality decline. White clover has also been shown to provide significant increases in milk solids production with just small increases in pasture clover content.

White clover is a free seeding, clonally spreading, pasture legume that has formed an incredibly strong place in New Zealand farming systems. When searching for other legumes there are only a few that compete with white clover in general dairy pasture.

Red clover was historically a short term tap rooted legume well adapted for hay and silage production but modern New Zealand-bred red clovers have focussed on persistence under grazing within typical pasture rotations. The intensive late winter and spring grazing rotations found on most dairy farms often don’t suit red clover, leading to it not contributing as much as it can. If rotation lengths change in dairy systems New Zealand-bred red clover will have a role in maintaining consistent legume content in dairy pasture. It is important to note that nearly all dairy environments are wet for considerable time frames and this is not always ideal for red clover. Red clover is a logical addition to any pasture on a runoff or silage area where it can add significant dry matter production at lower nitrogen inputs.

Lucerne is a “right plant in the right place” legume in dairy systems. It is a very deep rooted, highly perennial legume for often very dry environments. In wetter environments persistence is greatly reduced although its reliability for spring, summer and autumn forage production, especially in potential extended dry conditions, is outstanding. It is best suited for use as a supplementary feed but is becoming strategically used as a summer crop alternative in more extensive dairy systems. It has little winter growth, but when it does grow in the cool season and/or is winter grazed with cattle, particularly in wet conditions, this can be very detrimental to stand longevity.

Annual clovers include Persian clover, Balansa clover, Arrow leaf, Sub clover and Crimson Clover. These are all true annuals that are dead by summer but can add a short term kick to new pasture, especially in spring. These types are potentially useful in short term pastures, such as annual and Italian ryegrass; they can be dominated by fast ryegrass establishment in warmer conditions, and often ryegrass will need to be sown at lower rates to get the most out of these short-term legumes. Annual clovers are best suited to silaging systems on runoffs.

Getting legumes off to a great start

To get the most successful and uniform establishment, legumes should be sown no deeper than 1 cm when in a mix with any grass.

If the legumes are going to be the champion of the pasture, another major strategy is to manage the sowing rate of the grass species depending on their vigour and tillering ability. It must be fully acknowledged that in reducing grass sowing rates you will give up early dry matter production, possibly delaying first grazing and may also encourage a higher than expected weed burden.

Functional herbs

Chicory is a summer-active, mineral-rich herb widely used as a cropping option for multiple summer grazings before being direct drilled with perennial ryegrass in the autumn. It can also be sown as part of pasture mix where it is especially useful in free draining soils, lasting in pasture for greater than two years. Chicory is not tolerant of wet soils, particularly when grazed in wet conditions with dairy cows. Chicory has few herbicide options, and care must be taken to understand the weed burden of individual paddocks before including it in mixes.

Plantain is a functional herb that is traditionally a winter-dormant weed. Some New Zealand-bred cultivars show significant winter activity making it a useful part of a pasture mix. It can also be used as a summer crop that may survive for more than two summers. Over the last five years, research has shown that Ecotain® Environmental Plantain can significantly reduce the loss of nitrogen from the urine patch to the environment and as of 2021 this is being acknowledged in the Overseer nutrient management model. Ecotain can be incorporated in pasture mixes, broadcasted or direct drilled into open or damaged pasture. Plantain has few herbicide options that are complementary to mixed legume pastures.

Pasture diversity

There is an emerging interest in pasture species diversity and its role in resilient pastures. At present, Agricom is running a project looking at the productivity of diverse pastures in five beef farmlets. These are being measured for animal performance, pasture botanicals, and soil characteristics. The Diverse Pasture Project, aiming to run for at least five years, is looking at:

  • A 50-year-old diverse, naturalised pasture.
  • Complex diversity pasture, initially made up of around 28 different species.
  • Fescue pasture made up of tall fescue, meadow fescue, white clover, red clover, chicory and Ecotain.
  • Perennial ryegrass and cocksfoot, white clover, red clover, chicory and Ecotain.
  • A five-year-old cocksfoot pasture with lucerne and red clover.

Initial learnings show the need to understand the cultivars used in the mix. Some choices of species could damage a paddock with undesirable reseeding of annual plants so thought needs to go into what is in mixes so this is avoided.

Further, not all plants are safe for animals and although these may have benefits to soil health they may not be entirely compatible with animal grazing. Typically, there is a cost to animal production with slow establishing diverse pastures. To date, the perennial ryegrass cocksfoot diverse and the fescue diverse pastures have shown the highest levels of animal performance.

The Diverse Pasture Project will provide a good insight into the role of diverse pasture in a beef system and this could help provide more information to help with decision making in the future.

More information:

Allister’s comprehensive presentation Forage Choices for Changing Times contains more information about each of the pasture species mentioned above.

 

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