Soil Microbial Response to Seven Different Organic Transition Strategies

2013 Annual Report for GNC12-154

Project Type: Graduate Student
Funds awarded in 2012: $9,920.00
Projected End Date: 12/31/2015
Grant Recipient: GNC12-154
Region: North Central
State: Missouri
Graduate Student:
Faculty Advisor:
Dr. Randall Miles
University of Missouri

Soil Microbial Response to Seven Different Organic Transition Strategies

Summary

The three year transitional period from conventional to organic row cropping can be the most challenging time for an organic farmer. Maintaining or improving weed control and soil health is never more vital than during this time, but it is also the period in which a new organic farmer is likely to have the least experience with organic practices. In this experiment we are examining seven transitional cropping systems to gain information on best management practices for weed control and soil building during the transition into organic row cropping. The overall goal of this research project is to improve the competitiveness of transitional organic grain crop producers by documenting critical information on cropping systems that will help maintain or increase productivity, suppress weeds and build soil health.

Objectives/Performance Targets

In Missouri, many farmers transition into organic production by stopping chemical herbicide and fertilizer use while increasing tillage. Increased tillage has been implicated in soil degradation and erosion and is of major concern in a state with 5.3 tons of topsoil loss per acre per year. In organic row cropping, reduced tillage must be accompanied by increased ground cover to reduce weeds. Organic no-till has been found to be successful in some areas of the U.S. and can improve soil carbon retention, water holding capacity and soil structure. In this experiment we compare organic no-till to conventional tillage and modified tillage/cover crop production systems.

 

 

 

Rotational System

Year

 

Cover crop only (CCO)

Modified Cover Crop (MCC)

No-Till Corn-Soybean (NTCS)

No-Till Sorghum-Soybean (NTSS)

Conventional Corn-Soybean (CONVCS)

Conventional Sorghum-Soybean (CONVSS)

Modified Conventional (MC)

2012

winter crop

mix of hairy vetch, winter rye, austrian pea, oats, tillage radish, crimson clover

 

tillage

minimal till

minimal till

none

none

as needed

as needed

minimal till

 

summer crop

sorghum-sudangrass

sorghum-sudangrass hay

soybean

soybean

soybean

soybean

sorghum-sudangrass

2013

winter crop

mix of hairy vetch, winter rye, austrian pea, oats, tillage radish, crimson clover

wheat

 

tillage

minimal till

minimal till

none

none

as needed

as needed

as needed

 

summer crop

buckwheat

sorghum- sudangrass hay

corn

grain sorghum

corn

grain sorghum

soybean

2014

winter crop

mix of hairy vetch, winter rye, austrian pea, oats, tillage radish, crimson clover

wheat

cover crop mix

 

tillage

minimal till

minimal till

none

none

as needed

as needed

as needed

 

summer crop

sunn hemp

corn

soybean

soybean

soybean

soybean

corn

Accomplishments/Milestones

On January 9, 2013 we held an e-organic webinar on developing organic crop plans for row crops that was attended by 90 people. We also conducted a 4-part organic webinar series in 2013 through the University of Missouri Cooperative Extension that hosted Tim Reinbott on April 25 speaking on organic cover crops, Dr. David Hammer on May 16 speaking on soil health, Dr. Newell Kitchen on June 13 speaking on cover crops and soil erosion, and Tim Reinbott on July 18 speaking on cover crop selection and planting.

 

On February 7-9, 2013 Kerry Clark had a booth at the Missouri Organic Association Conference (attendance 400) and provided free soil testing for active carbon levels to participants. Active carbon was explained in an informational poster and related to tillage and crop productivity issues. Free active carbon testing was also provided at all University of Missouri field days in the summer of 2013 (total attendance 635) to get both organic and conventional farmers thinking about soil health and soil water retention.

 

We held a cover crop field day on May 17, 2013 at the Bradford Research Center that was attended by approximately 30 NRCS, Missouri Department of Conservation, Extension staff and farmers. The roller/crimper was demonstrated and different planting methods were demonstrated. We outfitted a Kinzie planter with a variety of different types of closing wheels and planted into a crimped cover crop to determine which set up provided the best seed-soil contact. We then removed the no-till coulters and experimented with that. We also planted into standing cover crop that was subsequently rolled. It was determined by those present that when planting into a cover crop mat the best seed-soil contact is attained by removing the no-till coulters and using cast iron or spiked closing wheels. Planting into a standing cover crop achieves better seed-soil contact than planting into a rolled cover crop but in an organic system that method may create more unshaded ground than rolling before planting.

 

On June 26, 2013 Kerry Clark gave a talk on soil health and organic vegetable production at the Lincoln University Conservation Ag Symposium. This was attended by 35 LU and MU extension professionals. On June 29, Kerry Clark gave a presentation on biodiversity on an organic farm at a field day at the farm of organic cooperator David Gray (attendance 35) in Montgomery County, MO. On July 23, she spoke to 75 agriculture professionals at the MU Crop Injury and Diagnostic Clinic on water retention and runoff in no-till fields with cover crops versus conventional tilled fields.

 

The University of Missouri Bradford Research Center First Annual Organic Field Day was held August 1, 2013 and was attended by 160. This half day event featured talks and demonstrations on organic vegetables and row crops.

 

On August 9-10 we hosted a statewide soil health expo and Tim Reinbott presented data to approximately 200 on our results with organic no-till. Kerry Clark organized a soil health workshop for 50 LU and MU extension staff on October 8-9 at the Bradford Research Center and presented data on organic management impacts on soil health. On November 2, 2013, she presented these results at the National Small Farm Conference in Columbia, MO, attended by 75. On September 10, she spoke to approximately 200 high school students at the MU FFA field day on what it takes to be an organic farmer.

 

A case-study video of organic no-till on the David Grey organic farm was produced in July, 2013 and posted on the Bradford website at http://aes.missouri.edu/bradford/. In November, a video on cover crops in organic systems in Missouri was also posted at this website and on YouTube.

Impacts and Contributions/Outcomes

Drought in 2012 and 2013 had major effects on the germination and growth of plots in this experiment. The drought was less severe in 2013 due to heavy spring rains that had been lacking in 2012, but extreme dryness this summer still had a large impact on yields. The wheat plots in the modified conventional tillage treatment in study one averaged 27.9 bushels/acre and were fairly heavily infested with curly dock, a perennial weed. Corn was planted at a density of 35,000 seeds/acre. Germination was low in both the conventional and no-till plots and yield was lower in the no-till plots than in the conventional till plots. Corn in the no-till plots was visibly yellower, indicating that the cover crop breakdown could be tying up nitrogen. The no-till plots had about 800 more lbs/acre of weed biomass than the conventional tilled corn plots and yielded 27 bu/acre less. Grain sorghum yields were severely affected in the no-till plots with the rolled cover crop. Germination was reduced and it appeared that the small grain sorghum plants had difficulty emerging through the thick cover crop mat. Because of slow early growth of grain sorghum in the conventional tilled plots, row cultivation was delayed, which allowed early weed growth that adversely impacted grain sorghum yields. The double crop beans were planted after the wheat harvest at 140,000 seeds/acre and had only about 40% germination, probably due to very dry conditions at the time of planting. Growth of the soybean plots was so limited they were not harvested for yield.

 

In study two, soybean germination was only 44-58% of the planted population. Unfortunately, this experiment was not designed with a treatment that does not utilize winter cover crops so it is unknown if the cover crop is affecting soybean germination. We had excellent winter cover crop stands, but apparently still did not attain a high enough biomass for improved weed control by the rolled cover crop mat. The sorghum sudangrass plots produced very large amounts of biomass and had excellent weed control. Soybean yields were very low as a result of drought and heavy weed pressure.
We have analyzed soil samples from 2012 for phospholipid fatty acid markers that identify microorganism groups. So far seasonal differences are evident but treatment differences are not readily identifiable after only one year of data. The 2013 soil samples have not yet been analyzed. The most prevalent weeds were water hemp and foxtail and most weed growth occurred in the crop rows.

 

Active carbon levels were also evaluated from year one but no trends are evident after only one year of treatments.

 

Drought was probably the most significant factor in both years one and two of this research. Dry weather impeded crop growth and reduced yields. Poor germination may be an effect of the cover crop. The rolled cover crop impeded milo germination significantly but corn germination was equal in rolled plots and plots where the cover crop was mowed and disked. Sorghum sudangrass has proven to be an excellent biomass producer this year and a very effective weed control. After very bad crop growth in study one the first year, we were afraid that the entire plot area would need to be abandoned. However, in plots where sorghum sudangrass was grown, weed control improved and after the three year transition may be well suited for improved crop productivity.

 

 Study two was implemented as a repeat of the treatments in a field that had a long history of row crops and chemical use. Although we had excellent cover crop growth, annual weed pressure in this field was very heavy in plots where we planted soybean. After two years of using organic no-till in multiple experiments we have concluded that researchers need to design methods to deal with mid and late season weed emergence through the cover crop mat. In study two we are using between-row mowing in no-till plots. This achieves about the same level of weed control as cultivation in tilled plots.

 

 

Collaborators:

Dr. Randall Miles

milesr@missouri.edu
Associate Professor
University of Missouri Dept of Soil, Environmental and Atmospheric Science
302 ABNR
Columbia, MO 65211
Office Phone: 5738826607