Research Projects

Tree-Crop Interaction Studies, Milton, Florida

Project Team

• S. Jose, Principal Investigator, University of Florida, Milton, Florida

• B. Brecke, Associate Center Director, WFREC, University of Florida, Milton, Florida

• Kye-Han Lee, Post-doc, University of Floirida, Milton, Florida

• Craig Ramsey, Post doc, University of Florida, Milton, Florida

• Diomides Zamora, Grad student, University of Florida, Gainesville, Florida

• In addition, OPS student technicians, Ms. Cathy Hardin and Mr. Ryan Campbell, were hired to help in the field and lab activities related to the project.

Description

Alley cropping systems (established in 1999) with loblolly pine, longleaf pine, and pecan planted with cotton in the alleys were used to quantify tree-crop interactions. Pine trees (6ft x 6ft) are planted to create two different alley widths (38 ft and 60 ft.). Pecan is planted in single rows with an intra-row spacing of 35 ft. and inter-row (alley) spacing of 60 ft. 

Rationale/Objectives

A better understanding of the tree-crop interactions in alley cropping systems is crucial to the refinement of the system. The overall objective is to quantify productivity and tree-crop interactions in pecan and pine alley cropping systems. 

Objective 1. Examine system design (tree spacing, and tree-crop system configurations) and its role in system productivity. The specific questions are:

1. How is crop (cotton) yield influenced by different tree row configuration and alley width?
2. How is tree (loblolly pine, longleaf pine, and pecan) growth influenced by crop management practices?

Objective 2. Determine the biophysical interactions between system components and their impact on the system. The specific questions are:

1. How do tree rows modify microenvironmental factors such as light, temperature, humidity, wind speed, soil temperature, and soil moisture within the alleys? How do crop physiology (mainly photosynthesis, transpiration, and stomatal conductance) and growth respond to these microenvironmental changes?
2. How does competition for water between trees and crops influence the overall system productivity?
3. How does competition for nutrients between trees and crops impact tree growth and crop yield?

Objective 3. Evaluate different alley cropping systems for their environmental benefits such as reducing ground water pollution and sustaining soil productivity. The specific questions are:

1. Do trees help to reduce groundwater contamination through better nutrient capture and cycling in alley cropping systems compared to monoculture systems?
2. Does alley cropping increase soil productivity by improving soil physical and chemical properties?

  Accomplishments through 2004

The three major objectives of the project are listed below with a suite of specific questions that will be addressed under each objective.

Pecan/cotton alley cropping system, Jay, Florida

Measurements: Spatial variation in crop yield in relation to tree rows was quantified in all the trials by harvesting plots by row from October 2000 to November 2003. To understand the role of shading on crop productivity, diurnal pattern of photosynthetically active radiation (PAR) was measured using a Decagon AccuPAR Ceptometer along the same spatial scale mentioned earlier. Further, net photosynthesis was also measured on selected plants in each row using a LiCOR-6400 infrared gas analyzer. Spatial variation in soil water (using Water Content Reflectometry) at fixed distances away from the tree rows was quantified to assess the competitive effects of tree roots on soil water availability. Diurnal variation in whole tree and crop water uptake was measured using Dynamax stem flow gauges to quantify competition for water between trees and crops. Nutrient competition was assessed using ¹⁵ N enriched Ammonium Sulfate fertilizer application in selected trials. Percent nitrogen derived from fertilizer, and percent utilization of fertilizer nitrogen were calculated for trees and crops to determine the degree of competition for nitrogen. Nutrient leaching down the soil profile was quantified biweekly by using ceramic cup lysimeters installed at different distances from tree rows and in monocultural systems. Changes in soil organic matter content, soil microbial biomass, and soil respiration were quantified along a chronosequence of alley cropping systems, from 3-year-old to 47-year-old.

Field day: In addition to hosting a small tour (20 participants) as part of the Santa Rosa Leadership Training, we hosted the CSTAF Advisory Council tour following last year’s annual meeting in Milton. We intend to use the trials for the World Agroforestry Congress tour this summer.

Outputs

The project resulted in one M.S. thesis, one Ph.D. dissertation, several conference presentations, seven journal/proceedings articles and one extension publication during the last four years. Details are given below:

Theses/Dissertations:

Allen, S.C. 2003. Nitrogen dynamics in a pecan-cotton alley cropping system in southern U.S.A. Ph.D. Dissertation, University of Florida.

Wanvestraut, R. H. 2002. Competition for water in a pecan (Carya illinoessis) and cotton (Gossypium hirsutum) alley cropping system in the southeastern United States. M.S. Thesis, University of Florida.

Allen, S., Jose, S., Nair, P.K.R., and Brecke, B.J. 2004. Competition for nitrogen in a pecan-cotton alley cropping system in the southern United States. Plant and Soil (in press)

Allen, S., Jose, S., Nair, P.K.R., Nair, V.D., Graetz, D. and Brecke, B.J. 2004. Nitrogen mineralization in response to soil water and source of nitrogen in a pecan-cotton temperate alley cropping system. Biology and Fertility of Soil (in review)

Allen, S., Jose, S., Nair, P.K.R., Brecke, B.J., Nkedi-Kizza, P. 2004. Safety net role of tree roots: Experimental evidence from an alley cropping system. Forest Ecology and Management 192:395-407.

Jose, S., Gillespie, A.R., and Pallardy S.G. 2004. Interspecific interactions in temperate agroforestry. Agroforestry Systems (in press)

Lee, K.H. and Jose, S. 2003. Soil respiration and microbial biomass in a pecan-cotton alley cropping system in southern USA. Agroforestry Systems 58:45-54.

Ramsey C. L., and Jose, S. 2002. Management challenges of pecan and pine based alley cropping systems of the Southern United States. Pp. 158-163. Temperate Agroforestry: Adaptive and Mitigative Roles. Schroder W. and Kort, J. (eds). Plains and Prarie Forestry Association, Regina, Canada.

Wanvestraut, R., Jose, S., Nair, P.K.R., and Brecke, B.J. 2004. Competition for water in a pecan-cotton alley cropping system in the southern United States. Agroforestry Systems 60: 167-179.

Workman S., Allen, S.C., Jose, S. 2003. Alley cropping combinations for the southeastern U.S. Florida Cooperative Extension Service Fact Sheet, FOR 106. 6p. UF/IFAS EDIS Database, http://edis.ifas.ufl.edu/BODY_FR142

Allen, S.C., Jose, S., Nair, P.K.R., Nair, V.D., Graetz, D. 2003. Competition for nitrogen in a temperate alley cropping system with pecan and cotton. Eight North American Agroforestry Conference, June 22-25, Corvallis, Oregon.

Allen, S., Jose, S., Nair, P.K.R., Nair, V.D., Graetz, D., and Ramsey, C.L. 2003. Nitrogen mineralization in a temperate alley cropping system in the southern United States. ASA-CSSA-SSSA Annual Meeting, November 2-6, Denver, CO.

Allen, S., Jose, S., Nair, P.K.R., Brecke, B.J, and Ramsey, C.L. 2003. Experimental evidence for the safety-net hypothesis from a temperate alley cropping system. ASA-CSSA-SSSA Annual Meeting, November 2-6, Denver, CO.

Allen, S.C., Jose, S., and Nair P.K.R. 2002. Groundwater nitrogen dynamics in a temperate alley cropping system with pecan and cotton. ASA-CSSA-SSSA Annual Meeting, November 10-14, Indianapolis, IN

Allen, S.C., Jose, S., and Nair P.K.R. 2001. Groundwater nitrogen dynamics in a temperate alley cropping system with pecan and cotton. Seventh North American Agroforestry Conference, August 12-15, Regina, Canada.

Jose, S. 2003. Tree-crop interactions in temperate alley cropping: Ecological principles and evaluation techniques. Ecology Seminar Series, School of Environmental Science and Management, Southern Cross University, October 3, Lismore, NSW, Australia (invited).

Lee, K.H. and Jose, S. 2003. Soil respiration and microbial biomass responses to soil water and nitrogen source in a pecan-cotton temperate alley cropping system. Eight North American Agroforestry Conference, June 22-25, Corvallis, Oregon.

Lee, K.H.* and Jose, S. 2002. Soil respiration and microbial biomass in a pecan-cotton temperate alley cropping system. ASA-CSSA-SSSA Annual Meeting, November 10-14, Indianapolis, IN

Lee, K.H. and Jose, S. 2001. Soil respiration under different land management practices in Northwest Florida. Seventh North American Agroforestry Conference, August 12-15, Regina, Canada.

Ramsey C. and Jose, S. 2001. Management challenges of pecan and pine based alley cropping systems of the Southern United States. Seventh North American Agroforestry Conference, August 12-15, Regina, Canada.

Wanvestrout, R. Jose, S. and Nair, P.K.R. 2002. Competition for water in a pecan-cotton alley cropping system in southern U.S.A. ASA-CSSA-SSSA Annual Meeting, November 10-14, Indianapolis, IN

Zamora, D. and Jose, S. 2003. Competition for light between pecan and cotton in a pecan-cotton temperate alley cropping system. Eight North American Agroforestry Conference, June 22-25, Corvallis, Oregon.