2004 Annual Report for GNC03-017
Effect of Sustainable Ground Floor Management Systems on Root System Dynamics of Apple and their Contribution to Carbon Sequestration and Nutrient Cycling in the Soil
Summary
The evaluation of three ground-floor management systems for organic apple orchards suggests that the Swiss Sandwich System (SSS) is promising for Michigan and other states that have a similar climate. Mulching (alfalfa hay) increases significantly the amount of available nitrogen and organic matter in the soil compared with the other two systems. Flaming and SSS release similar amounts of nitrogen. Mulching actually releases too much nitrogen – risking leaching problems.
The management systems affect the soil food web. Mulching and SSS create comparable environments, while flaming yields the lowest populations of soil organisms.
Objectives/Performance Targets
Objectives for this project are to:
* Investigate the behavior of apple tree fine roots (timing and rate of growth, and their turnover) subjected to two different ground-floor management systems under the organic protocol.
* Determine the amount of carbon sequestered in the soil by the trees.
* Study the effects of fine root turnover on nutrient cycling, food-web and soil sustainability.
* Introduce the best ground-floor management system for the desired growing conditions.
Accomplishments/Milestones
In 2003 and 2004, 25,000 pictures per year were taken with a mini-rhizotron camera. Due to a delay in the development of software for picture evaluation and measurement, the pictures have been not evaluated yet. The delay is mostly due to the fact that the software is under evaluation from the Property Rights office of both Michigan State University and University of North Carolina. We have to wait until these offices will give us a response on the marketability of the software, then we can start the analysis of the pictures. The analysis will be performed in 2005, since we asked permission to use it for research purposes.
Due to the software delays, we have not been able to determine the amount of carbon released in the soil from the roots. Regarding the above-ground parts of the trees, the amount of pruning wood, trunk calipers, shoot growth, and yield coming from the 2003 season have been measured and analyzed. Same measurements have been taken for the 2004 season except for the pruning wood and the trunk calipers that will be measured after the winter.
Eighty four soil samples have been taken four times a year during 2003 and 2004 (for a total of 336 samples each year) and analyzed for available nitrogen (NO3- and NH4+), total nitrogen, organic matter, and carbon content. 2003 data have been processed and analyzed while 2004 data are still undergoing processing and evaluation.
Forty eight soil samples (collected in April and November in 2003 and 2004) from the treatments have been tested for soil food web composition. 2003 data have been processed and analyzed while 2004 data are still undergoing processing and evaluation.
In 2003, we noticed a difference between the systems related to the amount of carbon and nitrogen returned to the soil from the pruning wood with mulch being the highest and the sandwich system being the lowest. Flaming performed in the middle not differing significantly from the other two systems.
The three systems have an effect on nitrate availability in the soil with mulch (alfalfa hay) showing the highest value. However, the nitrogen content in the soil for SSS and for the flaming system has permitted healthy growth.
The treatments had a significant effect on plant growth as well as the rootstocks, but no interaction between treatments and rootstocks was found. The treatment that produced the highest growth was mulch, followed by flaming and SSS. For the rootstocks, Supporter 4 was the most vigorous followed by M9.NAKB 337 and M9.RN 29.
Regarding the effect of the treatments on soil organic matter content, all three treatments increased organic matter content from 0.5% and 1.0% between 2000 and 2003. No differences between systems were found at the depths of 0-10 cm or 0-30 cm. There was a significant interaction between treatments and rootstocks evident at the time of the first harvest with mulch resulting in the greatest yield. For the 2004 harvest, there was significant interaction between treatment and rootstock with M9.RN 29 producing the highest yields in the sandwich and flaming treatments. The other two rootstocks performed about the same.
All three systems had an impact on soil food web composition with mulch and SSS creating the same environment while flaming produced the lowest numbers of soil organisms.
All of the analyses performed in 2003 and 2004 will be repeated in 2005. However, the mini-rhizotrons will be extracted from the soil because a long presence (more than 2 years) affects root growth. In addition, all data will be analyzed for annual significance and over time to asses the long-term effects.
Impacts and Contributions/Outcomes
In 2003, 60 growers attended a field day. In addition, four presentations about the project were given at local and national conferences.
In 2004, 65 growers attended a field day. In addition, five presentations about the project were given at local, national, and international conferences.
In 2004, a grower volunteered 10 acres to try the Swiss Sandwich System (one of the systems under evaluation in the project) on a commercial scale. We have been contacted by another grower who wants to install the Swiss Sandwich System in his three-acre orchard.