R. G. V. Bramley

Patterns of within-vineyard spatial variation in the ‘pepper’ compound rotundone are temporally stable from year to year

Background and Aims Within-vineyard variation in the concentration of grape berry rotundone has been shown to be spatially structured and related to variation in the land (soil, topography) underlying the vineyard, although its temporal stability has not been evaluated. Our aim here was therefore to ascertain whether patterns of rotundone variation were stable from year to year. This is an important aspect in understanding and exploiting terroir on a vineyard-scale as it informs how targeted management might take advantage of the variation to the benefit of both grapegrowers and winemakers. It also facilitates targeted research into the biophysical factors that may be critical to the formation of rotundone in grapes. Methods and Results Immediately prior to the commercial harvest of a 6.1 ha vineyard block in the Grampians region of Victoria, 177 geo-referenced samples of grapes were collected in each of three seasons (2012, 2013 and 2015) and analysed for their rotundone concentration. The mean berry rotundone concentration varied 40-fold between seasons, yet spatial analysis of maps of rotundone variation produced for each year indicated that the patterns of spatial variation were stable across seasons. Conclusions Irrespective of the seasonal factors which affect the mean concentration of berry rotundone, variation in the land (soil, topography) underlying the vineyard is a consistent driver of within-vineyard variation in this important grape-derived flavour and aroma compound. Significance of the Study This work suggests that targeted vineyard management strategies, including selective harvesting, may be used to manipulate wine style – in this case, the pepperiness of cool climate Shiraz wines. It also suggests that further study of the relationships between the environment and berry composition is warranted in pursuit of a more robust understanding of terroir.

Regional scale application of the precision agriculture thought process to promote improved fertilizer management in the Australian sugar industry

Nitrogen (N) fertilizer management in the Australian sugar industry is guided by the ‘SIX EASY STEPS’ (6ES) advisory program, for which the potential yield and amount of N that is potentially mineralizable from the soil are key input parameters; the latter is estimated from soil carbon (C) content. Whilst 6ES is not prescriptive about the scale at which it is used to deliver advice to sugarcane growers, common practice is to use the ‘district yield potential’ (DYP) to guide N fertilizer recommendations at the farm and block scales. Analysis of yield variation at the block scale, using sugar mill records over 7 seasons (2009–2015) from the Herbert River district, showed yield to be markedly spatially variable, with the patterns of this variation stable across seasons and crop class. Accordingly, DYP is sub-optimal as an input to 6ES. A block yield potential (BYP), derived from a map of the estimated maximum block-scale yield of first ratoon cane achieved over the 7 seasons, is suggested as a better alternative which can be readily updated as more data become available. Further refinement of the application of 6ES is possible with access to soil C data, derived from either regional soil survey or local soil testing. The present study suggests that use of BYP rather than DYP could lead to a total annual reduction in N applied of approximately 1700 t N over the Herbert River district without negatively impacting yield. Whilst the value of this to growers (A

Farmer attitudes to the use of sensors and automation in fertilizer decision-making: nitrogen fertilization in the Australian grains sector

23/ha) is a minimal proportion of the costs of production, a reduction in the risk of N loss to receiving waters of this magnitude could be of significant benefit to the protection of the Great Barrier Reef. Since data similar to those used here are collected by all sugar mills, similar analyses could be conducted in other sugarcane growing areas. The approach may also be of value in other cropping systems which use central points of delivery (e.g., grain silos).

Understanding variability in winegrape production systems

A survey of Australian grain growers was conducted to gauge grower attitudes to crop and soil sensing and their role in nitrogen fertilizer management. The technologies considered were yield monitors, remote and proximal crop sensing, high resolution soil survey, soil moisture sensing and digital elevation models (DEM). Whereas Australian grain growers have readily adopted machine guidance and autosteer, and a majority have access to yield monitoring, the rate of use of many crop and soil sensors remains comparatively low. However, the survey results suggest a positive effect on sensor adoption through present use of yield mapping. Access to yield maps was significantly associated with the use of remotely sensed imagery, high resolution soil survey, soil moisture sensing, DEM and variable rate application of fertilizers and/or soil amendments. There is some support for proximal crop sensing, albeit with low present rates of use; the use of soil water sensors and DEM is presently very low. For the further development of precision agriculture (PA), the results make clear that expending effort in enhancing the adoption and use of yield maps would be valuable as a lever to gain ‘buy-in’ from growers to sensing and PA more broadly. Since growers use many sources of information to support fertilizer decision-making, any new fertilizer decision aid needs to establish a point of difference from, but be complementary to, existing tools. One way of achieving this would be to use sensors, supported by locally derived algorithms, as a key input to fertilizer decision support.