FINAL8 AG Flashcards
Are pelleted organic nitrogen fertilizers slow-release fertilizers?
60 to 66% of organic N in feather meal, seabird guano, fish powder, and blood meal was mineralized in 8 weeks (Hartz and Johnston, 2006)
Suggest that its better to reduce rate of pre-plant pelleted fertilizers
“Where has all the N gone?”
surface runoff, leaching, immobilization, and denitrification
N loss by runoff is the major problem in this site with a thick claypan ~45 cm below the soil surface
New waiver – proposed for 2011
Divides irrigated ag operations into 3 “tiers” dependant upon the severity of the risk for pollution of surface or groundwater
Rates high risk crops based on likelihood of leaching to groundwater –
Conclusions
Organic strawberry yields were relatively good and consistent but amounts of N loss during the winter varied greatly year by year.
“High input organic farming” can lose significant amount of N to the environment.
Polynomial regression used to find best fit model to predict N loss over the winter rainy season
Can use this equation to determine best preplant fertility amendment rates depending on residual N in soil after previous crop harvest
N Management in Organic Broccoli
Optimize fertility inputs and cover crop use
Compare soil NO3-N test, leaf-blade TN tissue test, and petiole NO3-N tissue test as tools to aid growers
Modeling NO3-N leaching and N2O emission from organic broccoli systems (biogeochemical simulation model DNDC
Monitoring
Soil NO3-N (0-30cm deep weekly) Tissue test (TN in leaf blades, NO3-N in mid ribs and petioles at first buds)
Summary
At first bud, petiole NO3-N correlated with floret yield.
However, first bud stage might be too late for deciding supplemental N needs of broccoli in organic systems
Soil NO3-N level at ~3 weeks after pre-plant fertilizer application may be used in deciding supplemental N application in organic broccoli (PSNT)—need further studies
