By Alison Ballance
“We’ve an integrated research project using lysimeters to quantify how our management activities affect both the performance of crops and also how water and nutrients leach out the base.”
Sam Carrick, Soil Scientist, Landcare Research.
What do a 50-cm diameter barrel, a 2-metre diameter sewer pipe and a shipping container have in common? They are all being used to study stony soils in Canterbury, to see how water and animal urine move through the soil, affect plant growth and contribute to the emission of greenhouse gases such as nitrous oxide. They have been turned into lysimeters, which enclose an undisturbed plug of soil that can be fitted with scientific instruments so it can be studied in detail. The smaller lysimeters can even be dug up and moved to a new location, while keeping the soil structure intact.
Sam Carrick is a soil scientist from Landcare Research at Lincoln, and he is involved in a six-year research programme called ‘Forages for Reduced Nitrate Leaching’. The project, which is being run by a number of organisations at the Lincoln Hub, including Lincoln University, Dairy NZ, and Plant and Food as well as Landcare Research, aims to ‘reduce nitrate leaching losses by 20 percent by delivering proven, adoptable and profitable pasture and forage crop options.’
A number of lysimeters have been installed on research farms around Lincoln. One contains 24 of the smaller lysimeters, and has a moveable greenhouse that can slide over the lysimeters to keep them dry during a rain storm. This is because irrigation rates are being studied in this experiment, and natural rain would upset the calculations. Different kinds of irrigators deliver water at different rates, and even a centre pivot irrigator delivers differing amounts of water at different points along the irrigator. Sam says it’s important to know the best flow rate and the optimum interval to irrigate at to ensure that the greatest amount fo water stays in the soil and doesn’t flush straight through.
In other experiments lysimeters are variously treated with a nutrient-rich amount of water that mimics a natural urine patch left by a cow.
The 50-cm diameter barrels are the same size as an average urine patch, so some lysimeters can be treated while others are left as controls.
The exercise is being scaled up using the Christchurch rebuild-inspired lysimeters made from a piece of sewer pipe and the shipping container. These lysimeters are large enough to grow crops on, and a number of urine patches can be applied across the surface. Previous research has shown that in the course of a year about cows deposit urine on about half a paddock.