Research Reviews

by Ken Hough, OCPA Director of Research and Market Development

With the ink still not dry, let alone even put to page on significant portions of the pending provincial nutrient management legislation (Nutrient Management Act 2001), it is still much too early to predict exactly how and to what extent corn growers will be impacted by the regulations pertaining to nutrient management plans (NMPs). (Although many corn growers are also involved directly in livestock operations, the livestock aspects of the nutrient management legislation are not directly addressed here other than use of manure as a source of crop nutrients.) However, it is likely that the legislation and related regulations will impose some notable changes on crop producers, if only to formalize many of the best management practices (BMPs) that most cost-conscious growers have already adopted. In some situations, however, the changes brought on by the NM legislation may be more extensive, particularly for individuals who may not have paid as much attention to efficiency and stewardship in the past.

So, are the NM measures likely to be at odds with profitable farming? From a crop producer’s perspective, probably not (as long as record keeping and audit-trail documentation are kept at a reasonable level). The intent of a functional NMP will be to minimize off-site or unintended impacts of nutrients from any source. In essence, this should be the goal in profitable crop production as well – provide for the nutrient needs of the crop while minimizing excess nutrient availability and the potential loss to or impact on the surrounding environment (within the limitations imposed by weather variability). This, too, is exactly the target of OCPA’s research investment in nitrogen (N) management. OCPA views N as the nutrient that requires the greatest research effort and will provide the biggest economic and environmental dividends from appropriate, science-based NMPs/BMPs.

Unfortunately, the timelines for implementation of NMPs for crop producers are likely shorter than those required to obtain many of the research answers needed in order to ensure that NMPs are based on the best scientific understanding available. It is hoped, and will be OCPA’s message, that NMPs implemented in the meantime are allowed to be reasonable, practical and flexible, permitting improvements to be incorporated as a better understanding of the dynamics of N management is achieved.

So where does global warming fit into this picture? (Or is global warming merely a phenomenon caused by the elevated temperature of the political rhetoric and the friction of bureaucratic activity on ‘climate change’ issues?)

In fact, the best measures to address nutrient management planning (derived from the research efforts of OCPA and others), are likely, in large part, also the best measures for addressing agriculture’s global warming emissions.

Nitrous oxide (N2O) is one of three primary ‘greenhouse gases’. It is about 310 times more reactive in the atmosphere towards global warming than is carbon dioxide, and about 15 times more reactive than methane. Under certain conditions, particularly excessively moist or waterlogged soils, nitrous oxide can be emitted as an intermediary product of degradation of either inorganic or organic nitrogenous materials (i.e., respectively, commercial N fertilizers, and livestock manure or legume crop residues). However, high fluxes of emissions can be triggered by plough-down of legume green manure, or following significant rainfall events that release the store of N2O held by the population of soil micro-organisms.

Soil tillage management, crop rotation, crop fertility programs and inherent variability in soils all play a role, as does weather, in the level of N2O production and emissions (versus further conversion to plant accessible forms of N). Inter-related with this is the preservation and enhancement of soil organic matter, both for the crop productivity gains to be garnered but also as a potential ‘carbon sink’, against which farmers or others with net greenhouse gas can ‘buy’ credits. (This issue, deserving of a separate article, is exceedingly complex, with considerably more policy and practical development needed before OCPA can advise growers on the best course of action regarding carbon ‘credits’. In the meantime, buyer beware!)

A vast amount of study is required to more fully understand the implications of these crop production factors on N2O, and how these factors might be manipulated to reduce emissions and conserve the maximum amount of N for crop use. Over the past year or so, OCPA has invested considerable time in working with a myriad of government contacts and consultations in order to promote the realization that such research is needed in order to implement BMPs to effectively address agriculture’s global warming emissions for the longer term. By way of example, one strategy might be to maximize sequestration of atmospheric carbon dioxide as soil organic matter. However, in the conditions under which most of Eastern Canadian agriculture exists (warmer, moister climate than the Prairies), a strategy that focuses on management of N2O may be the more effective route to follow. In reality, the best path for Ontario and eastern Canada probably lies with a combination of the two aspects.

The challenge is to align everyone’s priorities (government, growers, society) on these issues in a manner that allows for practical and profitable, environmentally sound, science-based crop production methods across a diverse variety of production environments.