An ongoing political wrangle around the type of plastic which can be used in the EU was one of the reasons behind a move by Samco to consider single-row application plastic laying machines, used here for maize.
The uncertainty around legislation which governs the type of plastic that might be used in future could increase the cost of plastic by around €60 per roll.
This could challenge the cost-effectiveness of maize under plastic, which already costs €100 to €120/ac.
I recently asked Robert and Sam Shine of Samco why they are looking at a single-row application system. They said they had already developed a machine to apply plastic on single rows for the Canadian market.
The Canada experience
Growers in that country predominantly use min-till establishment systems which did not have adequate soil to provide anchorage for the double-row system. So Samco developed a machine some years ago that could work in min-till situations.
Large fields and lack of shelter were added pressures on the double-row system in Canada. Also, it was common to drill the maize initially using their very large drills and then come back with a specific plastic laying machine as a second pass to lay the plastic cover.
Given the size of the farms and the fields, Samco developed the single-row plastic laying machines for that market. This brought two distinct advantages:
Soil coverage differences
Conventional double-row plastic came in 1.4m rolls and this left 1m of plastic exposed to sunlight. The oxo-biodegradable plastic is denser than the conventional plastic but with less than half the working width per row, these new rolls have 6,200m per roll compared with 3,100m in the double-row rolls, so there is only half the down time to load plastic.
Robert said the average plastic ground cover in a field of double-row maize is 66% compared to 30% using the single-row system. This means fields of plastic-covered maize would be far less visible than heretofore.
The Gen 3 machines leave about 26cm of exposed plastic per row at 75cm spacings compared to 1m in double-row systems.
They also use less plastic per metre length and this results in a saving in overall plastic use. Sam said this saving in plastic would offset the additional cost of Oxo-biodegradable plastic if necessary and help the viability of the system.
Cover and yield
One of my immediate concerns for this system was the impact of about a 50% reduction in plastic cover on its ability to heat the ground and bring the same yield and maturity benefits.
This was also a concern for the Samco team but evaluation over the past three years has shown similar field performance from the single versus double-row systems.
“The heat is still trapped around the plant and the area of its roots without having to heat the inter-row space,” Robert said. This is also important in terms of nutrient availability in the warmer soil close to the young roots.
These results mean this system could be used to help offset the obligation to use the more expensive fully biodegradable plastic sometime in the future. However, this may not happen at all.
The Gen 3 machines provide the same herbicide application flexibility as existing machines. Herbicide can be applied under the plastic and on the exposed soil between the rows. Or the latter can be left for overall spraying post planting.