Holbrook Landcare Network researching the role of tropical grasses in southern NSW

Upgraded pastures not only add to improved profitability but generally also correlate with more organic matter and soil carbon as well as healthier soils.

An especially relevant project of theirs (staff and farm members) is researching the role of tropical grasses in southern NSW environments, something many might regard as odd. There are two main reasons that support this study. Many of the district's soils are acidic, including in the subsoil, hence less easily corrected via liming and limiting the use of lucerne. NSW DPI estimates 24 million hectares of agricultural land across the state is impacted by subsoil acidity, which is not a rare occasional situation.

Secondly, on average, even southern NSW areas like Holbrook receive quite a bit of late spring, summer and early autumn rain, often used poorly by temperate perennials and winter annuals. This can be especially the case if dry late winters/early springs cause the early shutdown of temperate perennials and annuals and if autumn breaks are late.

READ MORE: Past summer reveals effectiveness of strong pasture competition

Holbrook, for example, receives on average, around 300 millimetres of rain between November and April. It is this rainfall that tropical grasses can use effectively, sometimes being able to grow at 130kg/ha per day dry matter basis.

Apart from average summer rainfall being significant for pasture growth, as well as for fallow water storage (cropping), many climatologists believe rainfall pattern is changing. For example, Adapt NSW projects that summer and autumn rainfall will increase for Murray and Murrumbidgee regions and spring rainfall will decrease.

Several Holbrook farmers at field days I've attended report their rainfall over the last 20 years has seen far more summer than winter rain, different to long-term averages.

Holbrook and district landholders and Landcare staff have gone much further than just trying tropical grasses, with several already establishing viable stands. Holbrook Landcare staff, such as project officer sustainable agriculture Emma Smith, and executive officer Dr Alison Southwell, are involved, with their farmers, in a range of research to maximise tropical grass establishment success, its coexistence with legumes, how to ensure best feed quality, as well as management for quality soils.

On a recent field day held on Gary, Belinda and Tom Anderson's property, Cressy Park, Pulletop (40km north of Holbrook), we inspected excellent stands of Premier digit grass that had fattened a lot of weaner lambs over summer. The quality of such feed is an important issue for the Landcare group, both for cattle as well as sheep.

NSW DPI research in northern NSW has shown the difference between high nitrogen and low nitrogen stands is commonly large in quality as well as quantity. This is reflected in big differences in profitability, for example, 145kg/ha extra lamb weight over a 150-day trial comparison, from high nitrogen, compared to low, worth $1000 extra profit.

High nitrogen tropical grass can be achieved via growing with legumes and or added fertiliser nitrogen. Holbrook Landcare group are strongly focused on species, establishment and grazing management to ensure legumes coexist well with tropicals. They also are running a gibberellic acid and nitrogen trial on Andrew Hunter's Yerong Creek property to assess if the tropical grass growing season can be extended into winter and if it may affect clovers and subsequent tropicals next summer.

Summer sowing of hard-seeded species like serradella and biserrula with Alosca rhizobia-impregnated clay granules has shown great promise in research conducted by Belinda Hackney. Another critical aspect for good legumes with tropicals, discussed at the field day, is the need for adequate phosphorus and sulphur levels. Research conducted by Yass LLS agronomist Fiona Leech, documented how important this is.

Steven Scott, Scott's Angus Stud, Henty, host of last year's Holbrook tropical grass field day, is another strong supporter of tropical grasses. Tropicals compliment their other pastures, including temperate perennials like Phalaris, and are filling an especially valuable role in providing quality late spring, summer and autumn feed.

Next week: Not all bad news in the quest for carbon neutrality.