Demonstration of a Sustainable Integrated Production System for Native Pecan and Beef Cattle Producers and its Effect on Ecology in Flood Prone Areas
In a native pecan and beef production system in naturally flooded or un-flooded sites in Oklahoma and Arkansas the highest pecan yield was from non flooding plots regardless of grazing or forage treatment. Legume plots had the highest nut yield whether grazed or flooded. In the OK trial beef gain was highest on non-flood plots with native vegetation. In flood prone plots beef gain was highest on legume forage. In AR beef gain was highest on legume plots. Grazing reduced tree leaf N content whether flooded or not. Un-grazed legumes met the total N requirements of the pecan trees.
- Demonstrate the effects of a legume based grazed native pecan orchard management system on soil N fixation, soil characteristics and beneficial insect attraction.
Demonstrate trapping and weather monitoring to schedule pecan weevil and scab spray programs compatible with livestock.
Demonstrate a fully integrated and sustainable legume based beef and native pecan production system.
Quantify treatment effects on changes to the plant community.
Quantify the economic benefits of legumes, weevil trapping, scab monitoring and grazing in a native pecan system.
1. Demonstrate the effects of a legume based grazed native pecan orchard management system on soil N fixation, soil characteristics and beneficial insect attraction.
Objective 1 is on schedule for completion. Soil samples have been collected from both sites twice each year and analyzed for nutrient content. The beneficial effects of legumes on tree N nutrition are being effectively demonstrated and the effects of grazing on N in the soil and tree are proceeding as expected. Grazing reduced tree leaf N content whether flooded or not. The highest leaf N level (2.81%) was on un-grazed legume plots in flood prone site. Un-grazed legumes met the total N requirements of the pecan trees (Figures 1 and 2). Supplemental N fertilization in amounts ranging up to 150 lbs N per acre, was required on native plots to maintain tree leaf N content above minimum level of 2.4%.
Pecan aphid populations were slightly greater and beneficial organisms were slightly lower in native forage areas than in legume plots. Pecan nut casebearer adult populations were similar in flooded or un-flooded areas of the orchard but greater in grazed than un-grazed plots. Adult casebearer populations were greater in legume plots than native vegetation plots. Pecan nut casebearer damage was similar across all treatments.
Emphasis for the remainder of the project will be placed on more extensive soil sampling to determine N, P, K content of the soil in each plot. Insect scouting will continue as specified by pest management program.
2. Demonstrate trapping and weather monitoring to schedule pecan weevil and scab spray programs compatible with livestock.
Objective 2 is on schedule for completion. Insect management was accomplished by twice weekly scouting the plots for incidence of pecan weevil, pecan nut casebearer and pecan aphid as well as the beneficial lady beetles and lacewings (Figure 3). The scouting form was completed in triplicate and one copy left with the grower at each visit. Pesticide application was accomplished only as dictated by threshold calculation. During 2000 pecan weevil populations tended to be greater in the non-flood areas than in the flood plane. Weevil numbers recovered were also greater in grazed than in un-grazed sites. Pecan aphid populations were greater in flood areas than in un-flooded sites and higher in grazed than un-grazed plots. Pecan aphid populations were slightly greater and beneficial organisms were slightly lower in native forage areas than in legume plots.
Disease management continues to focus on demonstration of best management practices for control of pecan scab. Scab was effectively controlled and maintained at an economic level in OK with minimum fungicide applications made according to the Oklahoma pecan scab model. Arkansas plots used the phenology scab spray model.
Remaining to do
Scouting disease and insects will continue throughout the remainder of the project and pesticide applications will be scheduled accordingly.
3. Demonstrate a fully integrated and sustainable legume based beef and native pecan production system.
Objective 3 is on schedule for full completion in the OK plot. Comparison benefits from the AR demonstration will be reduced due to expression of what appears to be “bunch disease” in trees in the grazed, native vegetation plot and to tree damage in all plots from an ice storm in December 2000. The disease symptom has gotten progressively worse during the last two years of unusually dry weather. These circumstances will affect yield data comparisons only and will have little effect on the total educational value of the demonstration.
The Oklahoma flood prone plot area held standing water for about 10 days in the spring and fall of 2000 and again in the spring of 2001. This is consistent with the objectives of the project and adds to the value of the demonstration. Harvest data have been collected for three years at both sites. Grazing data have been collected for two years (2000 and 2001) at both sites with a spring and summer grazing iteration at the OK site.
To date pecan harvest data have been collected for 1999 and 2001 at the OK site. Yield data for 2000 at the OK site were estimated as fall rains extended into the harvest season resulting in standing water on all the flood plots and excessively wet, though not flooded, conditions on the remainder of the plot. Pecan yield in 2001 ranged from 123 to 505 lbs per acre. Non flooding plots produced the highest three year yield average (668 lbs/A) regardless of grazing or forage treatment. Legume plots had produced higher nut yield than native vegetation plots whether grazed or flooded (Figure 4). Nut yield from non-grazed plots in the AR test varied. In grazed plots, trees with legumes out yielded those with native vegetation. During 2000 the AR plots produced 505 lbs of pecans per acre from non grazed plots while the grazed legume plots produced 179 lbs/acre. Trees in the grazed native vegetation plot have produced no nuts during 2000 due to effects of bunch disease (Figure 5).
In the OK trial beef (steer) gain was highest (386 lbs/A) on non-flood plots with native vegetation. In flood prone plots beef gain was highest (245 lbs/A) on legume forage (Figure 6). Data from the July thru August grazing period revealed little or no gain probably due to excessive heat and associated effects on the cattle. The summer grazing period can serve essentially as a holding area for the cattle to take advantage of the microclimate among trees as it likely does no harm to the trees. Cattle must be removed by Sept 1 in preparation for pecan harvest. In AR beef (heifer) gain was highest (143 lbs/A) on legume plots (Figure 6)
Forage crude protein content in Oklahoma during March, 2000, averaged 20.9% in flood prone legume plots and 16.9% in flood prone non-legume plots. Protein content in the non-flood plots averaged 19.5% in legume plots and 20.5% in native plots. Forage in native vegetation plots in the non-flood area was much more lush than in flood prone areas reflecting the greater productivity of that site. Forage crude protein at the Arkansas location averaged 19.8% in legume plots and 17.0% in native plots (Table 1).
Remaining to do
One more grazing iteration remains at each site for 2003 followed by harvest in fall of 2003.
4. Quantify treatment effects on changes to the plant community.
Accomplishment of this objective may be restricted. The ecologist assigned to the project collected initial assessment data on the plots during the summer of 1999. He has since relocated to a job in Canada and has been unavailable to the project. Present plans are to contract with that individual to return to these plots on a consultancy basis if possible. If that is not possible only general assessments provided by forage specialists will be possible.
5. Quantify the economic benefits of legumes, weevil trapping, scab monitoring and grazing in a native pecan system.
This objective is on schedule for completion. A PhD student, Mr. Jason Lopez, under the direction of Dr. Joe Schatzer in the Department of Agricultural Economics has assumed this project as his dissertation project. Mr. Clark Williams, Langston University will assist. All input and production data will be provided to Dr. Schatzer for incorporation into the analysis.
Impacts and Contributions/Outcomes
Over all I would rate this project as highly successful. The Oklahoma demonstration served as an excellent field day site with over 300 persons in attendance in June 2000. A field day scheduled at the Arkansas site for April 2001 was cancelled due to effects of a December 2000 ice storm on the trees. That field day is rescheduled for April 25, 2002. Results of the project were presented at the Langston University Small Farm and Alternative Agriculture Symposium on the Langston University campus during August 2001. Over 150 growers of various crops were in attendance. The economic analysis product of this project will provide the best and most definitive data available relative to this important production system.
A direct spin off of this project is organic pecan production. A full proposal entitled “Validation and Demonstration of an Organic Production and Marketing System for Native Pecan Producers” is in submission to SSARE for possible funding in 2002. If that project is funded it will result in a total production package allowing producers the opportunity to take full advantage of this valuable natural resource.
Extension Plant Pathologist
Department of Entomology and Plant Pathology
112F Noble Research Center
Oklahoma State University
Stillwater, OK 74078
Office Phone: 4057449960
Department of Entomology and Plant Pathology
127K Noble Research Center
Oklahoma State University
Stilwater, OK 74078
Office Phone: 4057449413