Developing a Sustainable Soil Management Model to Increase Farm Gate Returns in Tasmania
A large number of physical, chemical and biological soil properties together with management practices were analysed against carrot and potato crop performance over a three year period.
Soil organic carbon, aggregate stability and soil type were found to have an influence on potato quality. On average, potatoes performed better when produced in red ferrosol soils compared with other soil types. Soils other than ferrosols produced higher quality potatoes with higher organic carbon and aggregate stability levels. Sampling of paddocks using PCR testing revealed a good correlation between disease expression on washed tubers and the levels of soil DNA for black dot (Colletotrichum coccodes) and powdery scab (Spongospora subterranea). The results for other diseases, such as rhizoctonia and common scab (Streptomyces scabies) were less conclusive.
None of the soil or management measures which were collected were found to have a consistent influence on carrot quality over the three seasons. Relationships between carrot quality, sap nitrate and soil compaction were found in the first two seasons but not in year three. Other factors found to have an impact on carrot quality in the first two seasons such as day degrees also failed to occur in 2010/11. This was thought to be due to the extreme weather events that characterised 2010/11 which probably masked other factors. The relationships between carrot quality and plant sap nitrate and soil compaction found in the first two years require further research over longer time frames in order to establish their significance.