Greenhouse Gas Mitigation
Greg Stewart, OMAFRA Corn Specialist

Recent efforts to highlight the importance of minimizing greenhouse gases in agriculture, have resulted in projects being eastablished across the province todemonstrate appropriate technologies. In most of these situations, greenhouse gasses (such as nitrous oxide) are not actually measured. However, the main principle behind the project is that if nitrogen use efficiency in the crop production system is improved, then less nitrogen will be available to contribute to atmospheric gases. Improving nitrogen use efficiency has meant a focus on three main areas:

1) cover crops,

2) strategic placement and timing of nitrogen fertilizer and

3) soil nitrate testing to enhance N management on livestock farms.

Cover Crops

The ability of various cover crop species to sequester soil nitrogen present following cereal harvest, was evaluated on six sites located in Perth and Oxford counties. On five of the sites, manure was applied during the last week of August and the various fall seeded cover crop species were established during the first week of September. The cover crop species evaluated were: Oats, Annual Ryegrass, Oilseed Radish, Peas and Red Clover. (See Figure 1). The red clover was present only at one of the sites and was established by underseeding into the cereal crop in early spring.

Where manure had been applied, each of the cover crop species had about 80 to 95 kg/ha of nitrogen in above ground herbage. The average increase in above-ground N content (due to manure) was about 20 to 25 kg/ha for the legume species and 40 to 50 kg/ha for the non-legume species. Assuming that N yield in cover crop roots was also increased by manure application, it is reasonable to assume that 40 to 60 kg-N/ha of manure N was sequestered by the various cover crop species evaluated. Therefore, the cover crop species evaluated demonstrated an ability to potentially reduce Greenhouse Gases, since they clearly tied up to 40 to 60 kg/ha of soil and (or) manure N, which was potentially subject to some form of environmental loss. The economics, feasibility and systems approach to cover crop management including the impact on subsequent soil nitrogen status and corn crop growth will be studied in further detail in the remaining years of this project.

Figure 1. Cover crops of Oats {left} and Oilseed Radish
in October 2003, Embro site.

Figure 2. Differential N rates in the "row-zone" or at
planting may create a relative
reflective index to improve
N rate predictions.
Centre-left row received zero nitrogen;
right row received approximately 35 kg N/ha.

Nitrogen Timing/Placement Strategies

Recent research and producer experience has shown that spring zone tillage (6-12 hours prior to corn planting) can be a very cost-effective tillage system for corn production. This system works best on reasonably well-drained ground when soybeans are the previous crop. It often provides a seedbed that is more favourable than strict no-till under a range of soil nitrogen in both the pre-plant and sidedress window, provides an opportunity to reduce tillage and improve nitrogen use efficiency. Previous research has indicated that a corn plant's "greenness " at the 6-8 leaf stage could potentially be an indicator of a crops eventual nitrogen needs (W. Been, Univ. of Guelph). This research was conducted by adjusting dry starter fertilizer rates to deliver 0 kg/ha N in one row and 30-40 kg/ha N in the neighbouring row. These neighbouring rows were then compared, in terms of their reflected light, to indicate the N status in the plant and soil. (See Figure 2). Having the nitrogen application tied to a pre-plant strip tillage operation reduces the total fertilizer being applied during planting and allows for easy adjustment of P and K rates on the planter. This project will continue to demonstrate that on medium textured soils, following soybeans or cereal crops where the straw is removed, very little tillage is required to optimize corn yields. A spring pre-plant strip tillage may improve planting timeliness and disturbs significantly less of the field than in a full width tillage system, which may contribute to building organic matter. Further examinations of a strip tillage/N banding system will be carried out with the aim of reducing N losses into the environment.

TABLE 1 . Grain corn yields and most economic fertilizer N rate for the nine on-farm demonstration sites evaluating N use on livestock farms (2003).

Site Code


Yield (at 0 kg-N/ha) kg/ha)


Most Economic N Rate kg-N/ha


Yield (Most Economic) kg/ha










































































Improving Nitrogen Use Efficiency on Livestock Farms

A series of on-farm demonstration sites were established to assess overall N use efficiency on livestock farms, and to evaluate technologies, such as the soil nitrate-N test and lower stalk N-test, as tools to advance this nitrogen use efficiency and to accurately predict corn fertilizer N requirements on fields where manure had been recently applied. Accurate estimation of corn fertilizer N requirements is essential to maintain profitable yields, while at the same time, minimizing the amount of soil N not utilized by the corn crop. Unutilized N is subject to environmental losses. Nine on-farm demonstration sites were established across the corn producing regions of Ontario in 2003. On eight of the sites, manure had been uniformly applied during the previous year (2002), on the other site manure had been applied in the fall of 2001. Corn yields at each of the nine sites were relatively high, with yields at the most economic N rate ranging between 9,000 to 12,000 kg/ha (140 to 190 bu/ac). In fact, yields rarely were less than 8,000 kg/ha (127 bu/ac) even where sidedress fertilizer N was not applied, ranging from a low of 7,900 kg/ha (125 bu/ac) to 12,000 kg/ha (191 bu/ac).The estimated most economic N rate (MERN), did not exceed 105 kg-N/ha (951b-N/ac) on any of the nine demonstration sites (Table 1). Three of the nine sites actually did not require any sidedress fertilizer N to achieve most economic yields. Work with soil nitrate testing reinforced the idea that a properly calibrated soil nitrate-N test will not only improve economic returns of corn grown where manure was recently applied, but also will reduce the quantity of soil mineral N remaining at the end of the growing season. This will minimize the likelihood of soil N loss to the environment, including minimizing the production of Greenhouse Gases.

Back to Top