26 November 2024. Paul McIntosh, Pulse Australia and WeedSmart.
No matter where you are in rural Queensland, the humble rain gauge has been an important piece of property on posts or fence lines for many decades.
It measures our rainfall events and does a pretty effective job at delivering the good or bad news to its owners.
Now, a rain gauge has some peculiarities attached to it compared to our soil surfaces. For instance, a rain gauge holds all or most of the rain events and it certainly can give spirits a lift on viewing next day when measuring an inch or two of rain.
However, our soils can tell a different story after rain. Certainly, I have walked around paddocks 24 hours after a heavy two or three inch fall of rain and it was still too dry to plant any crop.
With the efficiency of water entry being very important to future cropping or pasture growth endeavours, key factors like stubble cover, rate or heaviness of the rainfall pattern, soil compaction, tillage system, surface sealing restrictions or surface roughness and are there any of those massive cracks in soil types like can occur in our heavy black clays.
These cracks can be a metre deep and are very effective at channelling excess surface water straight down into our sub soil areas for future plant needs.
Stubble cover is a huge positive for improving water infiltration and I do prefer standing stubble myself for extra erosion control and less movement or blockage issues when going through the paddock by various planter types.
Unfortunately, there is stubble and there is stubble, with crops like wheat, barley and even millets providing the best quality stubble for moisture infiltration and evaporation reduction. So, whilst stubble from grain sorghum or maize is useful, our winter cereal crops are top of the pops.
Notice I said evaporation reduction and not total elimination of moisture loss amounts despite big stubble loads, where fallow efficiency can be down to 20% or 30% levels. Seems fairly incredibly low efficiency numbers, however, you still need those consecutive rain events plus your stored sub soil moisture, to go the right way for cropping success. It is well acknowledged that mid summer evaporation events can reach down to at least 20cm in heavy soil to down to 50cm in lighter or sandy soils.
Soil water losses can occur from deep drainage in some lighter soils as well, however, when all said and done, infiltration is the key to building soil moisture during our heavy summer storm events.
How could I forget dratted weed burdens in paddocks and I include pasture paddocks here as well. I know it is hard to get the chipping hoe out and get rid of a few pesky weeds in a fodder block, however, some of these useless annual weeds can shed a few thousand seeds each generation or year.
All we need now is to have even rainfall events from one end of paddock or strip to the other end … .. correct ?? Unfortunately, that does not always happen, so perhaps you may need more than one or two gauges to judge rain events for an entire paddock planting possibility or pasture growth response. Certainly I have witnessed in the space of a few hundred yards soil that is saturated on one end and nearly bone dry on the other.
Yes, I will agree that the fancy indoor battery operated rainfall measuring devices are easy and handy, however for myself there is no better feeling than to make the wet trek to the rain gauge post in the middle of the day or night, to see how much glorious rain you have received.
That’s all folks.
Regards
Paul McIntosh (JP Qual)
Macca's long term rain gauge