Kiwi inventiveness is alive and well in Lincoln where these objects are playing a leading role in experiments being carried out by soil scientist Dr Sam Carrick of Landcare Research.
Sam is part of a team of scientists working in the DairyNZ-led Forages for Reduced Nitrate Leaching programme. The goal of the programme is to develop profitable pasture and forage crops to reduce nitrate leaching losses. This will help to reduce farming’s environmental footprint by improving nutrient efficiency and water quality.
As part of his research, Sam is developing and field testing large area lysimeters to accurately quantify field scale drainage and nitrate leaching losses from large forage plot trials. Small barrel lysimeters have proven very useful for studying individual urine patch processes, but Sam says he had to consider how to carry out experiments on a larger scale and whether it was possible to build something big enough to contain an ecosystem of multiple plants and urine patches in proportion to non-urine areas.
“I started thinking about what large scale devices we could use. Being near Christchurch was handy because there are shipping containers everywhere. I first looked at larger pipes at an Irrigation New Zealand conference field trip about three years ago. At that stage they were about 1.5 metres in diameter, but after the earthquake when the infrastructure started to be replaced in Christchurch, larger sewer pipes, two metres in diameter, were brought in, so that made me think they might be useful for these experiments,” says Sam.
Using the sewer pipes, Sam has installed three barrel lysimeters that contain undisturbed 1.2m deep columns of soil. These will be compared against the efficiency of a shipping container lysimeter (6x2.4m) that has a repacked soil profile. After the installation, the excavated soil around the lysimeters was reinstated and the pasture sown with Italian ryegrass because it was late in the season.
The objective of the experiment is to compare the drainage and leaching behaviour of the two different lysimeter designs. The research is in its early stages, but preliminary results will be available by spring 2015.
During this winter, the same pattern of multiple urine patches will be applied to the surface of each lysimeter. Drainage behaviour between the lysimeters will be monitored and calibrated and the difference in total drainage and leaching compared.
Sam says that DairyNZ, AgResearch, Plant & Food Research and Lincoln University have already done a lot of work on distribution of urine on paddocks as part of the Pastoral 21 programme.
“We are picking up their data about the form, size and frequency of urine patches and deciding how we can measure that in the field. This is critical for large plot trial studies.
“We are focusing on these large plots and we have decisions to make around how we sample them. Do we use just one type of lysimeter and how many do we use? Then there are the practical considerations like how we sow the crop, how we graze it and how we collect the leachate. There’s a lot of information that feeds together, and it’s a complex problem.”
Sam says the major opportunity of the Forages for Reduced Nitrate Leaching programme is that it’s bringing together the whole spectrum of researchers.
“I’m working on these large area lysimeters which show promise, but other research within the programme will help to decide how best to use them in the large plot trials. It’s a great opportunity, because although we’re all working in different areas individually on one piece of the puzzle, the interaction with other researchers is really positive as we’re all focused on the same outcome which is finding ways to reduce nitrate leaching losses.”