Assessing Nitrogen and Carbon Pools in a Perennial Biomass Alley Cropping System in Minnesota U.S.A.

View the project final report

• 2014 annual report

Commodities

• Agronomic: grass (misc. perennial), hay
• Additional Plants: native plants, trees

Practices

• Animal Production: feed/forage
• Crop Production: windbreaks
• Education and Training: on-farm/ranch research
• Energy: bioenergy and biofuels
• Natural Resources/Environment: carbon sequestration, hedgerows, hedges - woody, riparian buffers
• Production Systems: permaculture
• Soil Management: organic matter

Agroforestry, the intentional integration of woody perennials with crop or livestock production, is a polyculture cropping strategy that has been proposed as a sustainable means of feedstock production for the bioenergy, biofuels, and bioproducts sectors. In addition to producing feedstocks that can potentially displace carbon intensive fossil fuels, agroforestry systems may be an effective means to sequester atmospheric C in soil and perennial roots while maintaining or even improving agricultural productivity. Furthermore, these systems may present a unique opportunity to improve economic returns for landowners, reduce risk through a more diversified approach to crop production, and provide critical ecosystem services such as water quality improvement and wildlife habitat. However, little is known about appropriate species combinations, planting arrangements, rotation lengths, and long-term production potential for biomass crops in agroforestry systems in the North Central Region of the United States. Understanding these factors is critical because improper species selection and crop spatial arrangement can result in poor crop establishment, reduced overall productivity, and ultimately crop failure due to competition for resources between trees and crops. The overall objective of this research is understand the long-term production potential and ecosystem benefits of alley cropping with short-rotation woody crops and perennial herbaceous biomass crops. To this end, multiple experiments are being conducted to understand what factors affect long term crop persistence and productivity in these structurally and functionally diverse systems. Of particular interest is how trees impact the availability of light, water and minerals to herbaceous crops. For this proposal, the specific research objective is to understand the magnitude and partitioning of carbon and nitrogen pools in a biomass crop based alley cropping agroforestry system.

While part of a larger research project that will attempt to understand spatiotemporal dynamics of light, N, and soil water in the alley cropping system, this project will specifically focus on the accumulation and partitioning of N and C. The goals of this project are to:

1. Quantify the magnitude and partitioning of biomass and C and N pools

2. Determine whether trees and crops are competing for N

To accomplish these goals, the project will be divided into the following activities:

1. Quantify the amount, C and N content, and spatial distribution of tree and crop roots, aboveground biomass, and annual tree leaf litter inputs into the soil.

2. Quantify soil organic N and C and fall residual soil nitrate-N within the alley.

3. Utilize the data collected in Tasks 1- 2, along with productivity data, to define potential spatial or temporal niches in N use for each crop and determine the net impact of trees on herbaceous crops (competitive, neutral, facilitative)