Evaluation of genotypes for a controlled traffic farming system : SRDC Final report BSS296

Abstract

The Sugar Yield Decline Joint Venture concluded that, in order to improve soil health, the sugar industry should break the monoculture using fallow legume crops, adopt controlled traffic and reduce soil cultivation. Controlled traffic can be achieved on any row configuration as it requires the matching of machinery and row spacing. Currently, however, the majority of harvesting machinery has a track/wheel spacing of 1.8 - 1.9 m. With many growers adopting these wide-row configurations there was a concern that the available cultivars would not be suitable. This was due to the majority of selection in the plant breeding program being conducted on a 1.5 m single-row configuration and recent evidence of a significant cultivar-by-row-configuration interaction.

BSS296 was undertaken to determine whether a cultivar’s performance did change significantly over different row configurations, understand the physiological mechanisms of the response, identify genotypes in the final stages of selection that performed well on wide row configurations, and ultimately further the adoption of controlled traffic. This was done by establishing two types of experiments. Firstly, the performance of current commercial cultivars was assessed over three row configurations at five sites throughout the sugar industry (Bundaberg, Mackay, Burdekin, Ingham and Meringa). Secondly, a large number of un-released genotypes were assessed over three row configurations at three sites with different environmental conditions (Meringa, Ingham and the Burdekin).

It was clear from all experiments that current cultivars are suitable for different row configurations. No cultivar-by-row configuration interaction was found in any experiment. This suggested that if you select a cultivar that performs well at a particular site, it will perform well on all row configurations. It also indicated that cultivars that perform well on wide-row configurations would make it through the selection system in the plant-breeding program. Clearly, a significant interaction effect reported previously does not always occur. In addition to this, the genotype term was shown to consistently account for substantially more variation than the genotype-by-row-configuration interaction term in all experiments. This indicated that there were large differences among genotypes but only a small difference as to how the genotypes performed over different row configurations. Genotypes that performed well at a site did so across row configurations. Therefore, selection of genotypes could be conducted on any row configuration.

Row-configuration effects were found at some sites. This was mostly attributed to low yield on the 1.8 m single-row configuration, associated with low stalk numbers when environmental conditions were limiting. While low stalk numbers were compensated for by increased stalk weight, in some cases the compensation was not sufficient to prevent a yield effect. Dual-row configurations maintained yield at wide row spacings. They consistently produced greater stalk populations than the two single-row configurations, particularly early in development, but this did not translate into increased yield. Low planting rates in experiments may have contributed to row-configuration effects, particularly when unfavourable environmental conditions were encountered during establishment. These issues need to be addressed in order to achieve greater adoption of controlled traffic.

Cultivars were shown to grow in different ways. Some were characterised by vigorous early growth, often associated with high stalk numbers, whereas others developed more slowly and consistently during the crop. No evidence was found to suggest that any one particular growth pathway (trait) would be best suited to a certain row configuration. It is likely that different growth pathways would be suited to different environments or harvesting times. Understanding how cultivars develop and what development pathways allow for better adaptation to particular environments may offer some gains to the industry.