Nutsedge Time of Removal in Ratoon Sugarcane

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Nutsedge Time of Removal in Ratoon Sugarcane

• C. Rainbolt and S. Chandramohan
• Everglades REC, University of Florida

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Introduction

• Sugarcane is a large subtropical grass
• A perennial crop that is harvested annually in
  Florida
• Typically 1 plant crop and 2-3 ratoon crops
• Intra-row cultivation is limited in ratoon crops
• Weed pressure tends to increase as the crop ages

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Nutsedge and Sugarcane

• Purple and yellow nutsedge are common in
  Everglades Agricultural Area sugarcane fields
• In containers, Shine and Duchrow (2000) found
  that purple nutsedge densities as low as 50/m2
  reduced sugarcane tiller number and stalk weight
• Etheredge et al. (2006)reported that low initial
  tuber densities reduced sugarcane biomass in pot
  studies

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Objectives

• To determine if purple nutsedge interferes with
  ratoon sugarcane growth and yield
• If interference does occur, when should nutsedge
  be removed

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Materials and Methods

• Experimental design was a randomized complete
  block with four replications
• Plots were 4 rows (20 ft) by 70 ft long
• Sugarcane cultivar was CP72-2086
• Treatments included purple nutsedge removal 3, 6,
  and 9 weeks after harvest (WAH) and one control
  treatment (no nutsedge removal)
• Nutsedge was removed by treating with
  halosulfuron at 0.047 lb/A at the initial removal
  date and a sequential treatment 3 weeks later

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Materials and Methods

• Initial nutsedge plant and tuber number and
  biomass were collected in a 0.4 m2 quadrat
• Sugarcane stalk population (early season and
  millable) were counted
• 10 stalk samples were collected and weighed to
  determine stalk weight and sugar analysis
• Leaf area index was measured using a SunScan leaf
  area meter

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Nutsedge density

• Initial tuber density was 165 m2
• Tuber density was 244 m2 9 WAH
• Herbicide applications provided 99 to 100 control

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2 weeks after initial removal treatment
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Untreated Control - 9 WAH
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LSD (0.05) 0.94
AB
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AB
B
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Summary

• Initial results indicate that ratoon sugarcane
  stalk populations, stalk weight, and sugar yield
  were not significantly affected by nutsedge time
  of removal
• Trials will be repeated at multiple locations in
  2008

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Why does ratoon sugarcane appear to be more
competitive than other crops?

• Plant cane is often harvested late when
  temperatures are warm and cane is growing quickly
• Ratoon cane is likely more competitive than plant
  cane
• Sugarcane grand growth period occurs in summer
  months following canopy closure
• Purple nutsedge is sensitive to shading