Potential of low ground pressure for harvesting machinery in a controlled traffic farming system in organic agriculture

Seasonal controlled traffic farming (SCTF), i.e. CTF without using the permanent traffic lanes for harvesting and primary soil tillage, leads to improved soil structure, higher crop yields, significant reduction of the emission of nitrous oxide and increased uptake of methane. Improved timeliness of operations, easier mechanical weed control and favourable returns on investments are considered practical advantages of SCTF. Further improvements, including reduced tillage, seem possible by avoiding overcompaction of the soil in the cropping beds during harvesting. The objective of the research was to find out what ground pressures can be applied without compromising soil structure and subsequent growth of a green manure crop, i.e. without tilling the topsoil after compression. No driving over the beds (ground pressure = 0) and simulation of harvesting with equipment requiring tyre inflation pressures of respectively 40, 60 and 80 kPa were investigated. Under dry or moist (field capacity) soil conditions support of harvesting machinery on the planting bed with tyres inflated to 0.4 bar did not lead to severe compaction and subsequent yield reductions.