Environmental stimuli for sugarcane suckering in the wet tropics : SRDC final report BSS221

Abstract

The northern section of the industry has been in crisis for most of the years in the decade up to 2002 because of declining CCS. This decline has been due to increased extraneous matter levels due largely to increased sucker culm content of the crop. These have developed because of marked wet episodes during the harvest period in the majority of years in this period. This resulted in open canopy situations, because of sprawling and lodging, increased light penetration, and initiation and development of sucker culm populations.A hypothesis was proposed that excessive mature-crop moisture, combined with continued excessive nitrogen use, particularly early in the decade were initiating variables for the problem. Observations suggested that light, via an open canopy situation, also was a driver.The project tackled the problem with a preliminary series of experiments that allowed optimisation of management and data collection techniques for use in a main experiment proposed. The main experiment sought to establish the importance of levels of three environmental variables, light, nitrogen and moisture, on sucker initiation, and their interaction with each other and with two cultivars of known suckering propensity under commercial conditions.The preliminary experiments allowed us to make the following recommendations for the design and methods for the main experiment:1. The late nitrogen application of 70 kg N will be in late April early May if the weather is suitable and as soon as possible thereafter if the weather is too wet to allow the application at the desired time.2. That spectroradiometry measurements will be made in the core plots at a height of 10 cm and 1 m to determine the effect of plant spacing on the spectral composition received. Photosynthetically active radiation measurements will also be made.3. A similar soil sampling and nitrate measurement regime will be made in the main experiment as that in the preliminary experiment with the exception that more frequent smaller diameter cores will be taken to speed up sampling.4. Sucker counting and other trial management will continue as originally proposed.5. Applications of late N will be made in separate experiments on different cultivars and if possible to soils with low basal nitrate levels.