Silicon soil amendments for enhancing disease resistance while improving overall crop health for cucurbits in organic farming systems

Project Overview

Project Type: Research and Education
Funds awarded in 2006: $180,000.00
Projected End Date: 12/31/2010
Region: Southern
State: Florida
Principal Investigator:
Amanda Gevens
University of Florida

Annual Reports


  • Agronomic: sorghum (milo)
  • Vegetables: cucurbits


  • Crop Production: cover crops, organic fertilizers, tissue analysis
  • Education and Training: demonstration, display, farmer to farmer, on-farm/ranch research
  • Farm Business Management: budgets/cost and returns
  • Pest Management: cultural control, integrated pest management, prevention
  • Production Systems: organic agriculture
  • Soil Management: soil analysis, soil chemistry
  • Sustainable Communities: local and regional food systems, partnerships


    The purpose of this project was to address plant diseases in organic farming systems by targeting soil health as the fundamental principle towards achieving a healthy cucumber crop. The effect of Si [Ca2SiO4; wollastonite (Vansil W-50)] incorporation into soil at 200-600 kg Si/ ha on cucumber ‘Straight Eight’ diseases, fruit yield and quality, and Si content in root and above ground plant tissues was evaluated in multiple seasons at two organic field locations in north central Florida. Silicon application did not limit the incidence and severity of downy mildew, caused by the fungus-like pathogen Pseudoperonospora cubensis, melon worm and leaf miner, caused by Diaphania hyalinata and Lyriomyza sativae, respectively, or root knot nematode, caused by Meloidogyne spp. Yield and fruit quality were also not affected by Si soil amendment. Plant tissues tested from the field indicated no elevation in Si content in cucumber plants or cover crops (sorghum x sudangrass in spring and rye in winter) across all Si treatments and this may account for the lack of disease reduction observed. Other elements and micro-elements were also not impacted by Si amendments.

    The effect of amending soil with a high rate of Si (Vansil W-50, equivalent to 600 kg Si/ha) on anthracnose (Colletotrichum orbiculare) and Si uptake was also evaluated in multiple greenhouse experiments with 2-week-old ‘Straight Eight’ cucumber plants. Soil amendment with Si significantly reduced anthracnose severity in the leaves and increased Si uptake compared with the non-amended control. The results of this research indicate that Si may play a significant role in disease control of cucumber in a greenhouse setting where high pressure from multiple pathogens may be absent and arthropod pests and environmental factors can be better controlled.

    We established protocols for testing the role of plant-generated phytoalexins (low molecular weight antifungal compounds produced by plants) as a mechanism for disease resistance in cucumber. Implementation of the protocol was carried out on greenhouse-generated and plants inoculated with C. orbiculare. HPLC analyses of methanolic extracts of leaves showed that specific UV-positive peaks defined by their elution pattern induced following pathogen infection were also induced by silicon and plants exposed to a combination of silicon and the pathogen had the greatest levels of them.

    Project objectives:

    1.Survey natural organic farm ecosystems for diseases infecting cucurbits amended without and with Si.

    2.Determine the fate of Si as a soil amendment in the agricultural system without and with cover crops.

    3.Quantitatively assess the role of Si in suppressing diseases of cucumber in greenhouse evaluations and determine whether any flavonoid phytoalexin is involved in Si-induced resistance.

    4.Determine the potential economic impact of Si soil amendment on cucumber diseases through partial budgeting.

    Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.