Em4885 irrigation management practices to protect ground water

4 CHAPTER
Possible Effects on Water Diversions
It would not be expected that achieving this Objective would have a large effect on required water
diversions. However, depending on the existing situation, improved nutrient management could
increase crop yields to the point where crop evapotranspiration increases and more water is required
for irrigation.
Possible Effects on Crop Yields
Depending on the situation, improved fertilizer management could improve yields, quality,
or both. Again, it is not the intent of this Objective to reduce crop yields by reducing fertilizer
applications. However, note IP 3.02.07 which seeks to set realistic yield goals. In some cases,
maximum economic yields (i.e., most profitable yields) are less than the maximum obtainable yields.
Possible Effects on Ground Water Quality
Especially when considering nitrogen sources, achieving this Objective should reduce adverse
impacts on ground water quality. Leaching of nitrogen in the form of nitrate-N is a major problem.
Note that achieving Objective 2.00, improved irrigation performance, is also essential since deep
percolation from excess irrigations is a prime factor in the transport process.
Possible Effects on Surface Water Quality
The direct pollution of surface water by fertilizers is due to both the availability of the fertilizer
and the detachment/transport of the fertilizer through surface runoff. Although reducing available
fertilizer is important, reducing surface runoff by achieving Objective 2.00 will probably have more
of an effect.
Note also that ground water can return to surface water supplies. Thus, by improving ground
water quality as previously discussed, there may be beneficial effects on surface water quality as well.
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