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					                Limiting Nutrient Leaks


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                By Dr. Tom Bruulsema, CCA

       atural ecosystems are           Best management practices             Going further in limiting
       often nutrient-limited.      limit the leaks. Applying the         leaks requires further research
They support flora and fauna        right source at the right rate,       and technology. Current
adapted to specific nutrient        time and place ensures that           technologies            include
limitations. With a diversity       crops take up the largest             inhibitors and coatings that
of species competing for a          possible portion, limiting the        control     release.     Future
limited supply of nutrients,        amount available to be                technologies may include
little leaks out of the system.     leaked.                               nutrient-need         forecasts
                                                                          related to weather. All
Cropping systems are                                                      technologies require on-farm
                                                                          testing to validate their
different                           Best management
Agricultural      management                                              effectiveness.
                                    practices are specific to
adds nutrients to boost
                                    the soil and cropping
productivity. While higher
                                    system
                                    They often include:
                                                                          Are some crops leakier
yields save land for natural
                                    • Soil and plant analysis.
                                                                          than others?
ecosystems, nutrient leaks can                                            Some consider corn to be
perturb them by altering their      • Placement for maximum               particularly so, and worry that
species composition.                  plant availability.                 the biofuel-demand-driven
   Nitrogen is a nutrient that      • Nutrient budgeting to               increase in corn production
leaks in many ways. It can            match crop removal.                 will lead to larger leaks.
leach away as nitrate, causing                                            However, nutrient leaks can
                                    • Mapping and managing
issues for water immediately                                              occur before, during and after
                                      soil variability among and
below the field and as far                                                the growth period of any
                                      within fields.
away as the ocean. It can leak                                            particular crop. It is important
                                    • Timing applications and
to the air in the form of                                                 to consider the management
                                      controlling release to
nitrous oxide, depleting the                                              of the full crop rotation.
                                      synchronize with plant
ozone      layer     in     the                                           Extensive research in the
                                      demand.
stratosphere and warming the                                              Chesapeake Bay watershed
climate       through       the     • Selecting genetics and              has shown that cover crops
greenhouse effect. Or it can          managing for higher yield           following corn is one way of
leak to the air as ammonia,           and nutrient uptake.                reducing nitrate leaks.
possibly affecting air quality      • Maintaining a buffer zone              Increasing global demand
and smog, and potentially             between the fertilized field        for food, fiber and fuel
disturbing nearby natural             and watercourses.                   increases expectations for
ecosystems.                         • Growing cover crops to              crop     productivity.     Best
   The nutrient phosphorus            retain nutrients for the next       management of both cropping
leaks in small amounts. But           growing season.                     systems and nutrients gives
even the small concentrations       • Conservation tillage to             the best chance of preserving
in surface runoff or tile drain       minimize runoff and                 natural ecosystems, and
water can stimulate blooms of         erosion.                            limiting the nutrient leaks that
algae in rivers and lakes.                                                might affect them.




                Tom Bruulsema is a Certified Crop Adviser employed by the International Plant Nutrition
                Institute as their Northeast Director located in Guelph.
                There are over 500 Certified Crop Advisers (CCA) in Ontario. Each CCA has demonstrated their
                knowledge about Ontario crop production by passing the required exams. In addition, they
                have the crop advisory experience, the education, the commitment to continuing education and
                have signed a comprehensive code of ethics, which places the grower’s interests first.

This industry driven program helps ensure that Ontario crop producers are well served by those
providing their crop production advice. This article was written by one of those CCA’s.