DAIRY 101 SOIL MOISTURE
When the sky stays stubbornly blue.
Pasture management hacks for dry weather Story and photos by: Karen Trebilcock
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ournalists know as soon as we start writing about dry conditions or droughts it’s sure to rain, usually before publication date. So for any region of the country that is currently a bit on the dry side, fingers crossed, I hope this works for you. Knowing how to deal with dry periods is becoming more and more important as climate change occurs. However, we’ve had dry periods in the past as well. If you have been reading the ”50 Years Ago” in the Dairy Exporter each month you will know that at the start of 1970, drought affected the whole of the country causing many farmers to dry cows off early. Milk production was halved for the first few months of the year compared with the same time the year before. Imagine production taking a hit like that today. Now we have ways to mitigate dry periods that they didn’t have back then – pivot irrigation, balage, and the importation of cheap feeds such as palm 78
kernel – keep our cows fully fed and milking when the sky stays stubbornly blue. Decades ago we dried off cows and our income took a hit; now it’s the expense side of the balance sheet that shows the effect. Rain is free but unfortunately it never falls in regular amounts throughout the year. A nice 20mm soaking every Friday night would be great and make farming a breeze. But it’s not rainfall that necessarily keeps droughts at bay. Soil moisture is the more important measure because rain can be quickly evaporated away by sun and wind. There are some expensive gadgets out there that measure soil moisture but there is nothing wrong with a spade. Dig a hole in a paddock, away from fences and water troughs, and see how much moisture there is. At the same time, look at your soil structure and see how far the roots of your pasture go down. Knowing what you have to work with under your cows’ hooves can make sure
you ask the right questions to find the solutions. When it does rain, the soil stores the moisture but some types of soil, especially those high in organic matter, store moisture better than others and some plants can access that moisture better than others too. But it is also how you look after those soils. Whatever you think of regenerative farming, its principle of keeping covers high and pasture in a growing state as much as possible is hard to argue with. Plants shade soil from the sun and lessen moisture loss from the wind. They keep the moisture where it should be – trapped in their root zone, which is exactly where they need it. High covers also help to prevent soil compaction since animals are less likely to pug or compress the ground beneath them. All soils have pores that hold the water between the different aggregates. Compressing these pores lowers the soil’s moisture holding potential. A cushion of
Dairy Exporter | www.nzfarmlife.co.nz | November 2020
