FINAL11 Strawberry and vegetable production Flashcards
Incremental Approach
Non-chemical alternatives to soil fumigant use
Fertility management optimization
Sustainability issues ?
Production level? Very high yielding system Ecological? Use of controversial soil fumigants Water use and runoff issues Soil erosion Nutrient losses Pesticide use Social? Heavy use of manual labor – farmworker welfare Economic? High production costs high risk/high return or loss!
Transformative
organic system
Development of disease suppressive and nutrient use efficient rotation systems for organic production
Nutrient cycling and carbon sequestration in organic systems
Life Cycle and economic analysis of different organic rotations
Strawberries
California is the nation’s leading producer of strawberries.
In 2011, more than 2.1 billion pounds of strawberries were harvested.
That amounts to 88 percent of the country’s total fresh and frozen strawberries.
California’s unique coastal environment provides moderate temperatures year round.
Warm sunny days and cool foggy nights are the perfect combination for growing strawberries.
Why fumigants?
Verticillium wilt and other diseases
Fumigant situation
MeBr + chloropicrin combination most effective at disease/weed control and gives highest yields
Methyl bromide set to be phased out by 2015 under Montreal protocol
Strawberry industry continuing to get Critical Use Exemptions for some application – amount declining every year
What else can be used?
Other fumigants
Major emphasis over last 20 years has been looking for other fumigants that work as well as MeBr
Chloropicrin, 1-3 Dichloropropene (telone) reasonably effective, used alone or often in combination
Great anticipation for methyl iodide (or iodomethane) – but faced opposition
Approved by USEPA, but would reconsider based on CA decision
CA EPA and CA DPR approved registration despite negative review from independent scientific committee
Major outcry – lawsuit filed
Arysta - company that produces MeI withdrew from production for US market
Nov 2012 - Arysta requested voluntary cancellation of all of the company’s product registrations
ASD Potential mechanisms
Production of organic acids toxic to some pathogens
Production of volatiles toxic to some pathogens
Reduction of iron and manganese – Fe2+ and Mn2+ toxic to some pathogens
Shifts in microbial communities to create competition or antagonism that suppress pathogens
Lack of oxygen, low pH,
Combination of the above – all interrelated!
Need to accumulate enough depth/time of anaerobic conditions – 50,000 mVhr below 200mV
Soil temperature also has to be warm enough - above 20oC (68oF) for at least first week of ASD treatment
asd
(Premises of current work:)
Biologically-based control methods are inevitably affected by environmental conditions (temperature, moisture, oxygen level) and by the microbial and pathogen communities present in the soil.
These methods are seen as less reliable and more risky than traditional fumigants, which can limit their adoption.
Improved understanding of mechanisms of disease suppression and how they are affected by environmental/biotic conditions will enable optimization of recommendations for managing specific pathogens in different situations.
Potential mechanisms
Production of organic acids toxic to some pathogens
Production of volatiles toxic to some pathogens
Reduction of iron and manganese – Fe2+ and Mn2+ toxic to some pathogens
Shifts in microbial communities to create competition or antagonism that suppress pathogens
Lack of oxygen, low pH,
Combination of the above – all interrelated!
How are each of these processes related to suppression of specific pathogens?
How are processes affected by C source used, soil moisture and temperature, and initial microbial community?
Still need systematic work to understand…..
Which C sources best for specific pathogens?
What are the soil temperature/cumulative Eh thresholds for suppression of specific pathogens?
Do shifts in microbial communities impact longer term suppression of key pathogens?
experiments underway to examine these questions
Other practical challenges
Cost of carbon source – need to find more options than work as well as RB, less costly
Nitrogen dynamics – 9t/ac RB adds more than 300lb/ac N, may lead to excessive losses either through leaching or as N2O gas (greenhouse gas)
Possible options being tested:
Grape pumice
Summer cover crops +/- supplemental RB
glycerol
