Tips to grow winter legumes longer into spring and early summer

On our farm in central west NSW, we endeavour to achieve green feed all year, given available soil water.

For some time, research has focused on winter legumes that can grow longer into spring and early summer, even as conditions warm and soil moisture commonly declines.

Species like serradella, arrow leaf clover, and biserrula often do grow several weeks longer than traditional species like sub clover and medics.

This is partly because these species root deeper and can be inherently more drought tolerance.

In our case, serradella has performed this role.

In drought years, like 2019, serradella grew into spring, providing useful feed and did set seed.

In contrast, sub clover, even early maturing varieties, died off early and failed to seed.

A wet year like 2022 saw all suitable winter legumes seed down, but serradella provided green feed into early January, months after subs had dried off.

Read more: What the research says on conventional fertilisers

Tropical and native summer grasses are capable of providing quality green feed while ever soil moisture is available, after winter legumes have dried off.

In a year with a dry early spring when winter legumes hay off early (such as 2019), these summer grasses provide feed from September onwards when rain occurs.

In years with a good spring, like this past year, with ample growth of winter legumes and grasses, their growth often doesn't get away till much later, often October or November onwards.

Lucerne is an "all-year grower" and commonly highly valued by mixed farmers using it as part of a cropping rotation.

It has a restricted market because of aspects like not liking acid soils, especially where it is hard to correct sub soil acidity.

Lucerne is also poor at tolerating waterlogging, has a limited life and creates issues like bloat.

White clover is another "all-year grower" but in many areas is not that drought tolerant.

Hard seeded varieties have often regenerated well since the drought broke in 2020.

Grazing management is important when combining winter legumes with summer growing natives or tropical grasses.

A criticism is that good winter legume growth can smother summer growing perennial grasses and greatly impede their growth or even lead to their death.

This should not occur with appropriate grazing management.

It is important to avoid winter legumes and other herbage, such as winter annual grasses, smothering summer grass growth at the time the summer species begin to refire after winter.

For example, this past spring it was not uncommon to have winter species dry matter levels above 4 tonnes per hectare by mid-spring.

We endeavoured to graze these (legumes and annual grasses like ryegrass and bromes), below 4t/ha, generally sufficient so that perennial grasses can capture some sunlight.

Through October and November in a good season, summer perennials, for example natives or tropical species, are competing with the end of the growth cycle of winter annuals, hence their production will be restricted by this competition.

However, that generally means there is lots of feed, much of it high quality.

Once the winter species dry off, strong perennials are then best able to return to maximum growth rate.

It is helpful, where possible, to allow perennials recovery time to build up root reserves once they refire after winter.

Continual grazing where all green feed is constantly eaten can lead to poor vigour, less growth, and even plant loss if conditions return to prolonged dry.

At least a degree of rotational grazing is desirable.

Good soil fertility is important for legume growth as well as that of companion perennials.

Good legume growth helps ensure high soil nitrogen for the grasses - an important part of high feed quality.

Come this autumn and a reverse situation can occur if it has been wet and summer grass growth has been profuse.

By autumn break time, it is important for this to be reasonably grazed down for winter legume to successfully germinate.

Next week: New winter crop varieties for 2023.