Chronic Nitrogen Amendment Plots
Four treated plots were established within each stand: control, low N, low N plus sulfur (N+S) and high N. Each plot measured 30 x 30 meters (0.09 ha) and was divided into thirty-six 5 x 5 m subplots. Fertilizer additions of ammonium nitrate sodium sulfate began in 1988 as six equal applications over the growing season (May - Sept). Fertilizer was weighed, mixed with 20 liters of water (equivalent to 0.002 cm rainfall) and applied using a backpack sprayer.
Fertilizer Additions as g N or S m-2 yr-1
Study Period: 1988 - 2004
NOTE: Sulfur additions were terminated after 1998
|
Ammonium Nitrate (NH4NO3) |
Sodium Sulfate (Na2SO4) |
||||
| Treatment | Control | Low N | High N | Low N+S | Low N+S |
|---|---|---|---|---|---|
| 1988 | 0 | 3.8 | 11.3 | 3.8 | 7.4 |
| 1989 | 0 | 5 | 15 | 5 | 7.4 |
| 1990 | 0 | 5 | 15 | 5 | 7.4 |
| 1996 | 0 | 5 | 15 | 5 | 7.4 |
| 1996 | 0 | 5 | 15 | 5 | 7.4 |
| 1996 | 0 | 5 | 15 | 5 | 7.4 |
| 1996 | 0 | 5 | 15 | 5 | 7.4 |
| 1996 | 0 | 5 | 15 | 5 | 7.4 |
| 1996 | 0 | 5 | 15 | 5 | 7.4 |
| 1996 | 0 | 5 | 15 | 5 | 7.4 |
| 1996 | 0 | 5 | 15 | 5 | 7.4 |
| 1997 | 0 | 5 | 15 | 5 | 7.4 |
| 1998 | 0 | 5 | 15 | 5 | 7.4 |
| 1999 | 0 | 5 | 15 | 5 | 0 |
| 2000 | 0 | 5 | 15 | 5 | 0 |
| 2001 | 0 | 5 | 15 | 5 | 0 |
| 2002 | 0 | 5 | 15 | 5 | 0 |
| 2003 | 0 | 5 | 15 | 5 | 0 |
| 2004 | 0 | 5 | 15 | 5 | 0 |
| Total Additions 1988 - 2004 |
0 | 83.8 | 251.3 | 83.8 | 81.4 |
Beginning with the 2005 field season, ammonium nitrate fertilizer became very difficult to attain due to new homeland security transportation and shipping reastrictions. As a result, we received mislabeled material from our supplier for the first application in 2005; following the discovery of the above issues, we then were able to find only ammonium nitrate with potassium added. Fertilizer rates were not adjusted for the change in content; the same fertilizer quantities were applied. As a result, this changed the actual amounts of NH4NO3 applied to the plots. These amounts are listed in the table below.
Fertilizer Additions as g N or K m-2 yr-1
Study Period: 2005 - 2007
|
Ammonium Nitrate (NH4NO3) |
Potassium (as K)) |
|||||||
| Treatment | Control | Low N | High N | Low N+S | Control | Low N | High N | Low N+S |
|---|---|---|---|---|---|---|---|---|
| 2005 | 0 | tbd | tbd | tbd | 0 | tbd | tbd | tbd |
| 2006 | 0 | tbd | tbd | tbd | 0 | tbd | tbd | tbd |
| 2007 | 0 | tbd | tbd | tbd | 0 | tbd | tbd | tbd |
| Total Additions 2005 - 2007 |
0 | tbd | tbd | tbd | 0 | tbd | tbd | tbd |
Summary of all additions 1988 - 2007.
|
Ammonium Nitrate (NH4NO3) |
Potassium (as K)) |
Sodium Sulfate (Na2SO4) |
|||||||
| Treatment | Control | Low N | High N | Low N+S | Control | Low N | High N | Low N+S | Low N+S |
|---|---|---|---|---|---|---|---|---|---|
| Total Additions 1988 - 2007 |
0 | tbd | tbd | tbd | 0 | tbd | tbd | tbd | tbd |