No longer are people content just to be sustainable, but they are striving to create better soil conditions to pass on to the next generation.

Unfortunately, some of the management practices to improve soil health are not always based on good science. Here are some ways regenerative farming practices can be improved.

Rotationally graze but manage to keep the clover in the system – The rest periods are well known to favour the perennial grasses but at the expense of the shorter growing clovers. A compromise to keep clover in the system is to keep pastures grazed to about 5cm in height during winter. But if you want more sub-clover, graze frequently and down to 1000 kg DM/ha (about 3cm) This creates more leaves and more potential spots for flowers to form and set seed. Having pasture swards with 30% to 40% of clover not only results in good animal production but adds an important source of nitrogen to soil and helps create a stable pasture.

Maintain groundcover but not all the trash during autumn – Having above 70% groundcover, protects against soil loss, especially in summer when summer thunderstorms cause high impact raindrops. But having excessive trash, prevents sub-clover germination. Aim to achieve one to two handfuls of loose litter scraped up from a square foot area. Shading from trash also stops light interception at tiller bases which stimulates new plant tillering and prevents plants from being able to increase in size.

Use a fertiliser that works– whether this is a natural fertiliser or not, the nutrients that are sold off farm in livestock products must be replaced. Otherwise, the soil will become depleted of nutrients, plant growth will decline, and you will fail to achieve your objectives of improving soil condition. Soil nutrients not only drive pasture growth but support soil microbiology to carry out important functions such as organic matter breakdown.

Not all natural fertilisers will work. For example, reactive rock phosphate only releases phosphorus under high rainfall acidic soils. Green wastes can may cause microbes to draw down existing soil nitrogen stores when breaking down plant material and this can reduce crop or pasture growth. Plus, many “natural or alternative fertilisers” have shown few benefits when trialled by independent researchers. Therefore, farmers should trial these products first and compare to an adjacent control before adopting across the farm.

A common misbelief is that synthetic fertilisers cause acidification. This is true for products containing ammonium such as DAP or MAP and elemental sulphur. However, many do not, including  superphosphate in soils with pH values less than 7.7. It does however stimulate clover growth which fix nitrogen. This will increase the amount of nitrate nitrogen in the soil increasing the potential for leaching and this causes soil acidification.

Another misbelief is that synthetic fertilisers can have a negative effective on soil biology. It is true that excessive applications of phosphorus or even nitrogen may reduce the need for plants to form mutually beneficial associations with arbuscular mycorrhizal fungi which help increase phosphorus uptake or rhizobia which fix nitrogen. Most application rates used are not harmful and will increase plant growth and this means more organic matter and carbon can be recycled back into the soil.

Concentrate on available nutrients rather than total nutrients – It is true that there can be high stores of nutrients in the soil, but plants and soil biology can be locked out of using them. Phosphorus becomes tightly bonded to iron in acidic soil or calcium in alkaline soils and only slowly becomes available over time. More readily available nutrients like potassium and sulphur can be leached down the soil profile to 60 to 80 cm. If deep rooted plants species are available, they can take these up, but sometimes high clay contents, waterlogging and subsoil acidity means roots can’t access them.

Large numbers of different plant species are not needed to provided soil health – Phalaris and clover mixes have been reported to have good biological indicators (Stirling et al, 2016). Phalaris is deep rooted which helps improve soil structure at depth, clovers fix nitrogen and together they achieve high annual pasture yields which means more organic matter that can be returned to the soil. In well drained soils, cocksfoot and lucerne can be complementary and added to increase summer growth.

Focus on having quality species not quantity.  Pasture sowing is expensive and its not ideal to sow species that don’t persist because its wasted money and they leave gaps which weeds will fill. Select pasture species that have complementary growth, are well suited to conditions, provide a role in soil health and consider ease of management. Having herbicide options to intervene if weeds become an issue can be advantageous.

Photo: Black organic channels created from the deep roots of phalaris.

Reference: Stirling GR, Hayden H, Stirling M, Pattison T (2016) Soil Health, Soil Biology, Soilborne Diseases and Sustainable Agriculture: A Guide. CSIRO Publishing.

By Lisa Miller, SFS