N2-fixation and weed competition: breaking the connection between crops and weeds

N2-fixation and weed competition: breaking the connection between crops and weeds

Summary

In 2004 we were successful in identifying and hiring technical support and a very capable graduate student (George Place) to assist with this project. Technical support was hired during the summer to assist with the maintenance of the research projects initiated in June (in anticipation of funding) in “double-crop” soybean in two locations, Caswell and Sandhills research stations. Only experiments addressing objective 1 were planted due to the lateness of the season when we received assurance of funding. Also, during late November, George Place committed to attend NC State working on this research and education project. George comes with considerable experience in extension education and interest in sustainable agriculture having served in the Peace Corps in El Salvador working in Sustainable Agro-forestry. We are thankful for his participation and commitment to this project.

The late planting of soybean and weed species at the Kinston and Sandhills locations had some unanticipated consequences. Although we were successful in establishing sicklepod in experiments addressing objective 1, redroot pigweed flowered soon after emerging (most likely due to photoperiod in late June). Although we had hoped to have the first year of data for this objective in 2004, these experiments will need to be repeated in 2005 and 2006 with full-season beans planted at the normal planting time to allow for normal flowering and competitiveness of the pigweed species.

The soils in the Caswell and Sandhills locations (which had not previously been tested) proved to produce plants with low delta values for 15N (i.e. less than 3.0). This resulted in undependably low values that are near the limits of detection. When these experiments are repeated in 2005 and 2006, they will be performed in locations with soils known to have higher delta 15N values (e.g. Clayton and Goldsboro (CEFS)). The experiment was not located at CEFS in 2004 (as originally planned) because of a CEFS quarantine issue involving a federal noxious weed, that should soon be resolved.

Experiments addressing objective 2 will be initiated in 2005 at the Goldsboro (CEFS) and Sandhills locations. This set of experiments does not rely on delta 15N values.

Objectives/Performance Targets

During 2004, we were able to work out each of the techniques that are vital to this research, including germination of weed seed, planting techniques and training for the technical help. Although the soils at the locations of the first year of experimentation proved low in existing delta 15N values, our techniques worked well. In 2005, experiments addressing all objectives will be initiated in areas previously known to have acceptable 15N levels.

Accomplishments/Milestones

• Hired technical support.

  Planted, maintained, harvested, processed, and submitted samples for analysis for experiments addressing objective 1.

  Hired a graduate student.

Impacts and Contributions/Outcomes

• Identified locations that produce plants with low delta 15N status. While these areas will be suitable for simulating a rotation for limited resource farming (objective 2), they are not suitable for experiments relying on the 15N abundance technique.

  Field techniques and plant tissue processing was worked out and personnel were trained in 2004.

Collaborators: