Pasture improvement, an exercise in planning

Consider species such as native grass, tropical or temperate perennial grasses.

Year after year, including this year, it has been near impossible to acquire seed of many sought-after annual winter legume species and varieties at the time they were most needed, for early autumn sowing. 

Many desirable winter legumes, like serradella and biserrula, are to a large degree sourced from WA.

Commonly their seed arrival is late, for a variety of reasons, including late harvest (a wet summer such as earlier this year), cleaning, grading, testing, transport and distribution.

Now is a good time to secure seed for next year, as there is commonly seed available of most species left over from this year’s requirements, including good supplies from some local producers.

This includes various serradella varieties as well as species such as rose clover, biserrula, sub clover medics, gland and bladder clover.

Adding winter legumes before the autumn break means they will germinate at the same time as existing winter annual species, such as annual grasses, existing naturalised or introduced legumes, weeds and other herbage.

Adding them after the autumn break means greater competition for them from these existing species.

Competition is for moisture, sunlight, nutrients and space, all important factors likely to affect their successful introduction.

Should winter and spring be tough, early adding of winter legumes before the autumn break is commonly a big advantage for them.

Where possible direct drilling them into the pasture is an advantage, as it places seed in a better germination environment should the season be on the dry side.

However, adding them via topdressing, commonly with fertiliser, tends to work well in an average to above average year.

Stock also can help with trampling seed into the soil when seed is added early.   

Choosing annual legumes to add to pastures is a very important aspect and depends on many factors such as soil pH (including that of the sub soil), environment, pasture type and likely grazing management.

It is commonly wasteful and more expensive to choose propriety mixtures that often have species not suited to a given soil type or range of soil types over the paddock. Earlier-maturing varieties within a species often better suit than more-common, later-maturing ones for given areas.

While later-maturing varieties commonly have greater production capability in a good season, they often set far less seed in drier spring years, an important consideration for long-term persistence.

Hard seed content of a species and variety is also important for long-term persistence.

Varieties with significant hard seed content means once a good soil seed bank has been set up, a good proportion of seed will be available should seasonal conditions (droughts) prevent or largely restrict seed set in one or more consecutive years. Good hard seed content can also allow persistence after a moderate cropping phase.

Sowing of pasture legumes ahead of the autumn break also requires careful consideration with ensuring adequate survival of rhizobia bacteria.

Newer technology such as appropriate clay impregnated with rhizobia has long survival.

Assessing and correcting soil deficiencies if they exist is also important for good legume content. 

Next week. “Winter habit” important for early sown grazing, dual purpose or grain only crops.