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Soil Nitrate-N Levels

Pre-plant soil nitrate-N

Eleven farms had complete soil nutrient testing prior to the growing season. Results and interpretations were distributed to the farms. None of the results were unusual for organic farms with compost-based nutrient management.soilprobe.JPG

Nitrate-N in Spring Collected Soil    
  2006a   2007b  
Farm NO3-N mg kg-1 Std Error NO3-N mg kg-1 Std Error
1 1 (0.4) 11 (1.9)
2 12 (0.8) 7 (0.4)
3 4 (0.4) 13 (0.5)
4 8 (2.3) 11 (1.1)
5 11 (0.2) 10 (0.6)
6 10 (1.7) 20 (1.4)
7 2 (0.1)    
8 23 (0.9)    
9 23 (1.1)    
10 6 (0.1) 9 (1.0)
11 3 (0.1) 10 (0.4)
median 8 (0.4) 11 (0.8)
         
asamples collected between 3/28/06 and 4/27/06    
bSamples collected between 19 March and 29 March 2007.  

In-season soil nitrate-N

Soil was sampled from the potato hills during the growing season.  Samples were taken from plots where no current season compost or fertilizer was applied (Zero-N plots), and from the larger potato field that received typical inputs by the grower collaborators (+N). 

Levels of nitrate-N in the top 30 cm of soil during the 2007 growing season
Farm # DAP Zero-N +N
    mg/kg or ppm mg/kg or ppm
       
1 45 14 25
1 60 12 24
1 75 10 10
1 90 6 7
1 105 12 8
2 45 16 38
2 60 11 21
2 75 9 16
2 90 7 8
2 105 10 10
3 45 52 71
3 60 42 42
3 75 27 28
3 90 20 9
3 105 14 35
4 45 11 9
4 60 4 4
4 75 4 2
4 90 5 5
4 105 4 5
5 45 37 46
5 60 18 19
5 75 6 8
5 90 9 10
5 105 13 15
6 45 24 42
6 60 17 31
6 75 4 8
6 90 9 12
6 105 10 14
11 45 30 19
11 60 22 21
11 75 30 38
11 90 29 36
11 105 18 23
       
DAP = Days after planting