Long-Term Direct Seeding Effects: Can we measure them and are they economically important?

By Guy P. Lafond,

Indian Head Research Farm

Making changes in farming practises requires commitment, time and resources. Producers are interested in knowing the long-term benefits of these changes and especially their economic impact. We had the opportunity in 2002 to get some indication of the magnitude of the long-term agronomic and economic benefits of direct seeding.

We measured the response of spring wheat to nitrogen fertilizer on two fields with very different direct seeding histories i.e. 20+ years vs 1 year. The test areas were close enough together to eliminate differences in precipitation as a controlling variable. We used one rate of phosphorus fertilizer (20 lbs P₂O₅/ac). Table 1 provides some general information about the two sites and also some pertinent agronomic information. Both areas were seeded to canola in 2001.

The results from the 2002 study demonstrate clearly that agronomic and economic benefits with direct seeding do accrue over time and have a significant impact on economic performance (Table 2).

The first important observation is the overall yield when no nitrogen fertilizer N is applied. On the long-term zero tillage area (L-T ZT) the yield was 42.6 bus/ac vs 26.2 on the short-term zero tillage area (S-T ZT).

The second important observation is that maximum yield was obtained with 53 lbs N/ac (60 kg N/ha) on the L-T ZT versus 80 lbs N/ac (90 kg N/ha) on the S-T ZT.

The third observation is that the protein content of the 0 N treatment on L-T ZT (13.3%) was higher than the protein content of the S-T ZT with 107 lbs N/ac (120 kg N/ha).

The fourth important observation is that the net returns were higher for the 0 N treatment on the L-T ZT than for any other N treatments on the S-T ZT area.

The fifth observation is the highest return recorded for the L-T ZT area was $83.51/acre versus $42.82/acre for the S-T ZT area.

The results of this study give rise to a number of very important agronomic questions. When the spring nitrate-N levels are compared between the two areas, the differences are small, relatively speaking (Table 1). According to soil test recommendations, the amount of nitrogen required for both areas is similar i.e 39-50 lbs N/acre for the L-T ZT vs 50-60 lbs for the S-T ZT area and yet the outcome was dramatically different both in terms of grain yield and grain protein. This implies that new refinements to our soil test recommendations for nitrogen fertilizer are required. It is also apparent that measuring for residual nitrate-N levels can only provide a partial answer to the N fertilizer recommendation. The other important question is, within the L-T ZT area, can we find areas that differ significantly in productivity and would we expect differences in the response to nitrogen within those different areas? This requires new approaches and methods since the approach using soil testing may not allow proper separation or delineation of these management zones. These results also point to the need to refine our approach to overall land management.

Acknowledgement: This study was made possible with the cooperation of Jim Halford of Vale Farms Ltd, the Indian Head Agricultural Research Foundation, Saskatchewan Agriculture Food and Rural Revitalization, N.M Paterson Co and Agriculture and Agri-Food Canada.

Table 1. Soil and Agronomic Information for 2002.

Table 2. Economic analysis of nitrogen rate response study as a function of long-term and short-term direct seeding conditions.