Management options for increased wheat yield and profit: A review of high input wheat production research in North Dakota in 2003

Compiled by J.K. Ransom

Several experiments were conducted in North Dakota during the 2003 growing season with the objective of identifying practices that could be used to increase the productivity and profitability of wheat in North Dakota.  Although the objectives of the various research projects reviewed for this report where similar, the treatments in the experiments varied from site to site.  All experiments included two or more of the following factors: seeding rate, N rate, N timing, variety, and fungicide. 

The intent of this report is to synthesize and summarize the salient findings of these somewhat diverse experiments in order to develop recommendations on how to increase the productivity and profitability of wheat.  The more detailed results of the individual experiments that have only been summarized here are available from the Research and Extension Centers where the research was conducted and/or from the principal investigators who conducted the research.  Experiments that were reviewed for this report and contact details of the principal investigators are found in Table 1. 

Table 1. Wheat management experiments conducted in North Dakota in 2003.

For most of the state, the 2003 growing season was very favorable for wheat production, particularly if the crop was planted early.  The cool spring allowed for the development of high yield potential and the lack of disease pressure permitted the crop to develop with minimal losses due to diseases.  In most of the experiments, wheat development was excellent and yields were high.  Nevertheless, due to differences in planting dates and location effects in the state, there was a fairly wide range in the yields obtained from the various experiments, thus allowing for more confidence in extrapolating these findings to a broader range of growing environments. 

All of the experiments were designed in such a way to identify interactions between the various factors.  Positive interactions between management practices are considered desirable as it means that the output of two or more inputs is greater than the output of each input alone.  Unfortunately, there were few significant and consistent interactions between the main factors included in the experiments reviewed here.  For that reason I will focus on the effect of each factor separately in this review. 

Seeding rate

Although there has been a fair amount of research conducted in the past on determining the optimum seeding rate of wheat, much of the research conducted in 2003 included seeding rate in order to determine if it would interact with other factors such as N timing and fungicides (e.g. would a higher seeding rate produce fewer tillers and enable more uniform coverage of the spikes with fungicide?).  The interactions between seeding rate and other factors were generally non-significant or inconsistent across the different trials this year.  When considering the main effect of seeding rate, the results indicate that there was little, if any, yield advantage to increasing seeding rates beyond 1.0 to 1.2 million seeds per acre (Table 2).  In fact, in the highest yielding trial at Carrington, there was a slight but significant decrease in yield with the higher seeding rate.

Table 2.  Effect of seeding rate on wheat yield in North Dakota, 2003.

⁺ N.S. means that there is no statistically significant difference between the values within an experiment, *, ** means there are statistically significance differences at the 5% and 1% level, respectively.

Nitrogen Fertilization Timing

In the two trials (Casselton and Carrington1) conducted by B. Otteson, where both N rate and N timing were included, there was a significant interaction between these two factors. Basically, this interaction resulted from there being less response to split applications when more total N was applied; the higher N rate (200 and 250 Ibs N/acre for Casselton and Carrington, respectively) masked any beneficial effect of the split.  Therefore, in summarizing the effect of N timing from the various experiments, I have included only the results from the lower N rates (Table 3).  In half of the experiments applying all of the N at or before planting resulted in the highest yield.  In the two irrigated trials at Carrington, the yield increase from splitting the application of N was fairly substantial but only if the split was applied early (i.e. 3 to 4 leaf stage).  When all of the nitrogen was applied post emergence, delaying the application to the 6^th leaf stage consistently yielded less than treatments where fertilizer was applied earlier (i.e. 3 lf and PPI).

Table 3. Effect of N timing on wheat yield in various experiments in ND, 2003.

⁺ N.S. means that there is no statistically significant difference between the values within an experiment,

*, ** means there are statistically significance differences at the 5% and 1% level, respectively.

Fungicide

There was limited Fusarium Head Blight (FHB) pressure this year at all of the sites.  Nevertheless, the Folicur treatments that were applied primarily to prevent the spread of FHB consistently resulted in increased grain yield (Table 4), although at two of the three sites the increase in production would not have paid for the cost of the chemical and its application.  At Carrington, the application of Folicur was highly profitable, resulting in a yield increase of over 30%.

Table 3. Effect of applying Folicur at flowering on wheat yield in various experiments in ND, 2003.

⁺ N.S. means that there is no statistical significant difference between the values within an experiment, *, ** means there is statistical significance at the 5% and 1% level, respectively.

Conclusions and Recommendations

            Based on the results of the various experiments conducted in 2003 that were summarized in this report, I would suggest the following (one should always be somewhat cautious with recommendations based on only one year of data):

• In these experiments the data suggests that there is little or no advantage to increasing the seeding rate of wheat beyond 1 to 1.2 million seeds per acre.  The results presented here were based on seeding rates and not on plant stands per se, which is the critical yield component that is managed through seeding rate.  Factors that affect seedling emergence such as year to year and environmental differences and seed quality may justify higher seeding rates than were considered optimum in these studies.  These data suggest, however, that it may be more profitable for you pay for treating your seed or purchasing certified seed if you were planning on using bin-run seed than to go with an excessively high seeding rate. 
• In most environments sampled by these studies reported here, applying all of the nitrogen before planting was less expensive and more effective in terms of wheat yield than applying it in splits.  When applying N post emergence, the earlier the application the better (i.e. it is best to apply all of the nitrogen before the 6 leaf stage).  A reasonable strategy for applying nitrogen might be to apply the entire N requirement based on a modest yield goal at planting.  Then, if early in the season, it appears that your crop has the potential to exceed your goal, apply additional N prior to the 6 leaf stage. 
• Folicur applied at heading has the potential of increasing yields by protecting the flag leaf from foliar disease even in years and regions of the state where FHB pressure is low.  Fungicide trials conducted in previous years have consistently shown a yield advantage of between 15 and 20% if there is any disease pressure.  The 2003 data and previous research suggest that for crops with a reasonable yield potential, applying Folicur will likely be profitable in the wetter regions of the state and in seasons which are conducive to disease development.