We can't do much about upgrading grazing management until the drought breaks. What has happened has happened. But we can reassess how we manage grazing when a decent break comes, as it will.
Changed grazing management can commonly far better protect soils following droughts; can result in faster feed recovery when rains occur; can produce more pasture, and can help improve pasture long-term persistence.
The biggest issue with overgrazed pastures is poor ability to capture rain when the break comes. For example, in our wider area, many properties received storm rains between 20-140 millimetres in March 2019. Even where good rains were received, where groundcover was very low, over half of it was lost as runoff. In some cases, water loss was even greater.
Soil water of 1mm can produce 30-40kg/ha of pasture dry matter. That means a storm/heavy rain event dropping 50mm can easily lose 25mm as runoff, equivalent to lost pasture production of 0.75 to 1.0t/ha dry matter.
In addition, poorer germination of annual grasses (or in winter, legumes) is likely because of lower soil moisture levels. Loss of further follow-up rain because of lack of groundcover can easily contribute to further big delays in feed growth.
Equally important is the loss of soil because of lack of groundcover, both from wind and water erosion. And as soil formation is so slow, soil loss is part of loss of property value with the majority of soil fertility being in the surface soil.
Retaining sufficient groundcover into droughts, or even common dry spells means sacrificing available feed for more future feed. While difficult, this is best addressed by feed budgeting, even if estimated measurements are rough and ready. Retaining as little as 0.5t/ha dry matter in a pasture or fodder crop can provide useful protection against erosion as well as improving capture of valuable rain in a heavy storm.
Feed budgeting means it is possible to pre-empt likely feed supply issues before groundcover reaches dangerously low levels. For example, if we can look forward at least two months in advance, we can make better decisions going into a dry spell or drought and preserve groundcover levels. In short, we want to avoid eating ourselves into a "drought" that is hard to recover from.
Conserving that last 0.5 t/ha of pasture dry matter is certainly a short-term cost, and is difficult when finances are tough. But this preserved groundcover ensures a quicker and more productive recovery. Also, decisions can be made ahead of crises situations including supplementary feeding, going into a feedlot or sacrifice area with full drought feeding, down selling, agistment, early weaning and the like.
Retention of reasonable groundcover can last indefinitely if not stocked until droughts or dry spells break and sufficient feed rebuilds. I have seen an example of paddocks in areas suffering three years of drought still with good levels of groundcover protecting these areas from wind and water erosion.
Research generally points to retaining sufficient groundcover as by far the most important grazing management consideration. Research also commonly supports some degree of rotational grazing as beneficial for many perennial species, including native grasses, lucerne and temperate perennials like phalaris and tropical grasses.
How intense rotational grazing needs to be, depends on many factors, including species, environment and seasonal conditions. The logic behind rotational grazing, especially in perennials, is to allow plants to replenish used-up root reserves after heaving grazing. For example, NSW DPI lucerne research has shown that after grazing in spring/summer, these stands need about 45 days to rebuild root reserves.
Another important aspect of grazing management is when the drought or dry spell breaks to recognise that plants will grow faster if allowed to develop reasonable leaf area before grazing. Some delay equals more final gain. Aspects like good soil fertility and selection of perennial species and variety are also important.
Next week: Silicon, a soil element that if not corrected can badly impact on some crops and pastures.
- Bob Freebairn is an agricultural consultant based at Coonabarabran. Email firstname.lastname@example.org or contact (0428) 752 149.