Rhizoctonia and Soil Compaction Under Direct Seed

Summary

With increased awareness in reducing tillage in crop production systems, there has been a lot of interest in direct seeding or no-till. After as little as 3 years, Rhizoctonia root rot started to show up in alarming amounts. The questions arose, what can we do to alleviate the Rhizoctonia and what other problems can we address at the same time? Is the restrictive compacted layer that has developed over the years of annual direct seeding compounding our problem with Rhizoctonia? Can we control the Rhizoctonia with a year of fallow, either chemical or traditional summer fallow and will the type of seed opener make a difference? We tried several tacks to reduce the Rhizoctonia and address the soil compaction. Unfortunately we were not able to affect the Rhizoctoina (Figures 1 and 2) (figures and photos are inclued with the written report) or increase yield significantly with any of the treatments we used (Figures 3 and 4). We were able to show that we fractured the compacted layer (Figure 5) but measure no significant difference in soil moisture. Without a significant increase in yield, the extra cost involved of doing the ripping was not economical as well as being questionable agronomically. Yield averages from 2005 through 2007 on the chemical fallow were 23.6 bushels of spring wheat per acre using the low disturbance openers and 25.6 using the high disturbance openers. While the higher disturbance opener’s yield is greater, it was not statistically different. Barley and winter wheat repeat the same results.

In this project we also looked at reducing the spring seeding workload with fall dormant seeding of several different crops. We were unsuccessful at gaining any yield advantage but were able to show that some of the fall crops seeded in this manner could compete with the yield of their spring counterparts (Figure 6). The challenge with the dormant seeding is the inconsistency of establishing stands.

Objectives

There were three objectives of this project. First was to see if we could address a soil compaction problem and at the same time reduce Rhizoctonia. Second was to see if chemical fallow and a hoe-type drill would have an effect on the Rhizoctonia as compared to an ultra-low disturbance disk drill. Third, to see if dormant seeding was viable to help spread the workload during spring seeding.

Results

It has been thought that higher soil disturbance in direct seed or no-till systems would help control Rhizoctonia. To see if we could address both the problem of Rhizoctonia and soil compaction at the same time, we ran a five shank Noble with 7-foot-wide sweeps next to a Case IH 2500 Ecolo-till ripper with shanks on 2½ foot spacing. The sweep was run between 6 and 8 inches deep. The ripper was run 13 inches deep. We included a check of undisturbed crop. In year two we repeated the layout and split the previous year's plot in half going 90 degrees to the previous tillage passes with the Ecolo-till again 13 inches deep. Soil permeability due to the fracturing effect of the ripper was significant (Figure 5) but moisture (data not shown) and yield result differences were insignificant over two years (Figure 3) and the Rhizoctonia was unaffected (Figure 1).

Another hypothesis was, if the Rhizoctonia had no food source using fallow for one year between crops, we would not only control the Rhizoctonia; but increase soil moisture and reap the benefits of both, and if we used a high-disturbance hoe opener we would see significant change. The results tell us otherwise. Three-year averages show that with spring wheat, yields were low disturbance Cross-Slot openers at 23.6 bushels per acre and the high disturbance Kile hoe opener at 25.6 bushels per acre. While the Kile opener showed a higher yield, it was not statistically different. Barley showed the same thing with yields of 1325 lbs/acre using the Cross-Slot and 1343 lbs/acre using the Kile opener. Winter wheat repeated the results with yields of 28.4 bushels per acre for the Cross-Slot and 29.2 for the Kile opener. What we do see with the Kile hoe opener is more vigorous early growth of the plants. This may be due to more soil warming and possibly fertilizer placement.

With the dormant seeding, we ran into a number of problems. First was date of seeding, when to say this is the day. Waiting too long meant soils would be frozen and too early meant no moisture. Survivability was a problem with some crops if they germinated too early and then froze out or dried out because of not enough moisture to do more than just germinate. Another problem was spring growth habit. Spring triticale planted in November was typically heading in April and very susceptible to frost. The winter triticale was the best yielding but because of market value it had no economic advantage. Grassy weeds, downy brome in particular, are a problem with all the fall-seeded cereals. With no moisture early in the fall, there is no flush of grass weeds or volunteer crop to control before seeding. Consequently it all germinates and comes up together.

Benefits or Impacts on Agriculture

With no reduction in the Rhizoctonia being shown by this work, researchers at Washington State University are now looking at wheat that would be resistant to the disease through mutanagenesis.

Producer Adoption

Adoption of direct seeding or no-till in the 12-inch and less precipitation area of eastern Washington has stalled and has lost some acre’s back to tilled summer fallow due to the lack of economic viability. Diseases like Rhizoctonia just compound the economic problems.

Reaction from Producers

While there is still interest in reducing tillage and increasing cropping intensity, with input cost being as high and going higher, there is a lot of skepticism among growers that in the drier areas of eastern Washington, under 12 inches annual precipitation, we will ever get beyond having some sort of tilled summer fallow - winter wheat rotation.

Recommendations or New Hypotheses:
As much as some people may not be comfortable with it, I think it will take a gene that is resistant to Rhizoctonia and possibly other root disease’s to get us over the hurdle of soil-borne pathogens. We must keep looking.

Soil compaction, while it is measurable in direct seeded and no-till situations in eastern Washington, is not limiting yield or moisture. It should, however, be monitored to see at what point does it become economical.

Dormant seeding does work but I don’t see it becoming a practice. The intensity of management for the amount of economic return is not something growers are going to go for.

Outreach

In June of 2006 we held a tour of these research plots. We had a school bus with 35 people. We showed them the plots and discussed what we were attempting and some of the early results of the dormant seeding work and drill opener work. In June of 2008, we will schedule a tour to share the full results.