HYPOXIA POLICE

Hypoxia in the Gulf

       What is Hypoxia? Hypoxia occurs when dissolved oxygen concentrations are below those necessary to sustain most animals life. 
Hypoxia in the Gulf is caused by excess nitrogen delivered from the Mississippi-Atchafalaya River Basin  in combination with stratification of Gulf waters. The reason for this is due to land alterations, river channelization for flood control and navigation, and major increases in fertilizer nitrogen.  Ever since the 1950’s the total nitrogen load has increased because of larger amounts of nitrate nitrogen. Also 90% of the nitrate load to the Gulf comes from non-point sources, this means this type of pollution is widely produced! The biggest effect nitrogen has is on the ecosystems and fisheries in the gulf, although nitrogen is a natural occurring element it is not safe in such high concentrations.  

Taking Action
     How we can mitigate this issue is by taking these two steps: (1) reduce nitrogen loads to streams and rivers in the basin and (2) restore and enhance denitrification and nitrogen retention within the Basin. 

     Although there are no single solutions to this problem there are many approaches we can take to reduce nitrogen and potentially safe our ecosystem in the Gulf. 

  

      

Fertilizer Application  
       There are many steps to fixing hypoxia, one of them is changing the rate of nitrgoen fertilizers. Using too little nitrogen with highly responsive crops like corn results in lower yields, pooreer grain quality, and reduced profits. When too much is applied it has many negative afffects for our environment. The extra nitrogent farmers usse is often called "insurance nitrogen." 
       There needs to be improved manure mangment, such as uniform application of know nurtient amounts and immediate incorperation. When the nutrient content of manure is known and best managment practices are used in land application it will not lead to excess nitrogen.   
       The timing of nitrogen application also plays an important role in the increase of nitrogen. Applying fertilizer in the spring is better than fall because less nitrogen is lost in the two to three month period between application and nitrogen uptake by the crop. Managing the rate and time of application, plays a key role in the loss of nitrate to surface waters. In a series of experiments, when nitrogen was applied in the fall and spring for continuous corn during a sic-year period. Nitrate losses from the crop lands were higher when fertilizers were applied in fall. Corn yields were 8% lower and annual losses of nitrates in the sub- surface drainage water were 36% higher with a late-fall application. At the end of the study, 65% of the nitrogen being lost in the drainage from high fall treatment was derived from the fertilizer, whereas only 15% of the nitrogen in the drainage water lost from a low spring treatment was derived from the fertilizer. 

Changing Cropping Systems 

One reason for nitrate concentrations in subsurface drainage is related to cropping systems.  The highest nitrate concentrations were found in soybean and corn crops, and lowest was alfalfa.  Row-crop soil was tested and the average nitrate – nitrogen was between 14 and 40 mg-N/L from 1990 to 1993. In comparison, perennial crops (alfalfa/ grass mix) had a nitrate concentration averaging between 0.3 to 4 mg-N/L.

Due to higher flow-volumes from the plots planted to row crops, nitrate losses from the row crops were 30-50 times higher than from the perennial crops.

How can control nitrate loss? If we change from row crops to perennial we are looking at a 75% nitrate reduction alone.

Crop System

Annual Nitrate–Nitrogen Concentration (mg-N/L) 1990 1991 1992 1993

Four-Year Total Nitrate Loss (kg-N/ha)

Continuous Corn Corn-Soybean Soybean–Corn

30           39 

22           29

                                            26           38

                                            40 20 217 26 14 204 27 13 202

                                           Alfalfa –4417 CRP1 – 4 1 0.3 4

                                        1CRP = Conservation Reserve Program (mixture of grass and alfalfa). Source: Randall et al. 1997.

Drainage Control 
       The things member 3 had to work on are drainage control, issues of edge of field interception, and drainage tile spacing. My solutions were drainage tile spacing, control drainage, and farm practices. Drainage tile spacing is when more drainage tiles there are, the more water will go out and faster it will be out of the field. Control Drainage is how big or small (size) the tile is and how much water is controlled coming through the tile. Farm Practices is how much fertilizer is applied when it is applied, how the soil is plowed and all the needs it has to have to have to farm.
Spacing off drainage tiles solution is how close or far the tiles are from each other and which one works the best. 5 meters of spacing is to close and puts more water out faster and more nitrogen escapes into the water. 10 meters is still a bit to close but has less nitrogen escaping into the water. 20 meters is a better spacing and puts less nitrogen in the water. So 15-20 meters pacing tiles is best for having les nitrogen escaping the fields. 15 meters is the recommended amount (not to close and not to far) but the 20 meters spacing tiles are better.
Controlling the drainage system solution is where and how you control the ways nitrogen gets into the water. Instead of letting nitrogen runoff into the streams that then go to the Mississippi river, the usage of more wetlands could hold more of the nitrogen. If you can’t use wetlands then wisely use a riparian butter on both sides of the steam with wile vegetation. It’s how to control the ways nitrogen gets into the streams/waters. It effects the run off because it helps prevents none or less nitrogen escaping into the water.
Crop rotation solution is using legumes to help get nitrogen into your field a safer way and not as much nitrogen escaping than liquid fertilizer or others farmers may use. Rotating crops each year with legumes could help prevent more nitrogen leaving the field and it’s a more natural and safer way to get the nitrogen a farmer needs for his fields. Properly discharge manure helps and it’s another natural way to get the fertilizer needed for farmers. Every other year changing your plants with legumes (plants that get nitrogen from the atmosphere and brings it into the soil) helps prevent runoff because it stays in the soil and helps other crops to grow.
Water control structure, the reduction of flow and nitrate concentrations could help overall 45% of nitrogen mass transport at the field edge. Controlled drainage has also been documented to reduce phosphorus transport by roughly 35%.