Source: UNIVERSITY OF ARIZONA submitted to
NUTRIENT MANAGEMENT FOR ARIZONA PECANS
 
PROJECT DIRECTOR: Walworth, J. L.
 
PERFORMING ORGANIZATION
Soil, Water & Environmental Science
UNIVERSITY OF ARIZONA
TUCSON,AZ 85721
 
NON TECHNICAL SUMMARY: In 2009, Arizona produced 10,890,000 kg of pecans, and approximately half of the pecans produced in the United States come from the desert Southwest states of Arizona, New Mexico, and Texas. Orchard soils in the desert southwest are generally calcareous and alkaline. Among nutrients that are part of most commercial nutrient management strategies in Arizona, the most critical is zinc. Therefore, our studies are focused around application and management of this nutrient. We are investigating various method and formulations for Zn application, to develop superior methods of Zn management. Hedging and topping trees is becoming a standard practice in western pecan production. We are studying the impacts of these practices.
 
OBJECTIVES: Supplying adequate zinc nutrition for pecans is critical both to produce maximum tree growth, nut yield, and nut quality. We have tested several approaches, and achieved some limited success. To build upon our previous research, we will 1) continue to study methods of soil applying zinc, including broadcast application of ZnSO4 with and without animal manure, ZnEDTA applied at planting, and ZnEDTA fertigation. Secondly, studies will be conducted to evaluate effects of tree hedging and topping on nutrient utilization, reduction of alternate bearing, and nut quality will be investigated.
 
APPROACH: We have been conducting a study of annual applications of combinations of ZnSO4 and animal manure in a randomized complete block with four replications. Leaf Zn, and nut yield are monitored to evaluate long-term efficacy. In a newly-planted pecan orchard, Zn-EDTA were applied at planting in a randomized complete block design with four replications. Zn leaf concentration and tree growth are being measured. Two rates of ZnEDTA are being applied through microsprinkler irrigation in a randomized complete block design with four replications. Tree growth is monitored by measuring trunk diameter and shoot growth. Zinc uptake is monitored by collecting leaf tissue several times and Zn deficiency symptoms will be measured by visually observation. A shade-house study is being conducted on potted pecan trees that receive foliar ZnSO4 or soil-applied ZnEDTA. At the end of one growing season, trees will be separated into leaf, stem, and root tissues, each of which will be analyzed for Zn content. Soil in half the pots will be treated with Glyphosate. Zn mobility and interactions between zinc and glyphosate will be evaluated. To evaluate effects of pruning on nut production, quality, nutrient uptake, and alternate bearing, two varieties, Western Schley and Wichita, will be monitored in a commercial pecan orchard. Trees are being hedged and topped on a four year rotation. Nut yield and quality, and leaf nutrient levels, will be monitored annually on trees hedged and topped in the previous dormant season, two years ago, three years ago, and four years ago. Ability of these varieties to recover from pruning will be determined, as will the effect of pruning on alternate bearing.
 
CRIS NUMBER: 0199861 SUBFILE: CRIS
PROJECT NUMBER: ARZT-1365550-H21-145 SPONSOR AGENCY: NIFA
PROJECT TYPE: HATCH PROJECT STATUS: REVISED MULTI-STATE PROJECT NUMBER: (N/A)
START DATE: Oct 1, 2011 TERMINATION DATE: Sep 30, 2014

GRANT PROGRAM: (N/A)
GRANT PROGRAM AREA: (N/A)

CLASSIFICATION
Knowledge Area (KA)Subject (S)Science (F)Objective (G)Percent
102011010606.210%
102011020006.220%
102121110606.240%
205121110602.230%

CLASSIFICATION HEADINGS
KA102 - Soil, Plant, Water, Nutrient Relationships
KA205 - Plant Management Systems
S0110 - Soil
S1211 - Pecan
F1060 - Biology (whole systems)
F2000 - Chemistry
G6.2 - Enhance Soil Quality for Productive Working Lands
G2.2 - Increase Efficiency of Production and Marketing Systems


RESEARCH EFFORT CATEGORIES
BASIC 10%
APPLIED 80%
DEVELOPMENTAL 10%

KEYWORDS: pecan~carya illinoensis~zinc~fertigation~alternate bearing~hedging~mycorrhizae

PROGRESS: Jan 1, 2009 TO Dec 31, 2009
OUTPUTS: 1. A soil-applied Zn study was started in 2005. Zn sulfate (74 kg Zn/ha) and Zn EDTA (19 kg Zn/ha) were soil banded on established Wichita pecans growing in a calcareous soil. Following this one-time treatment, foliar Zn levels in the Zn-EDTA treatments have been higher than those in untreated trees in approximately 25% of the monthly leaf samples. In 2009, leaf Zn concentrations were not significantly different in the various treatments. Foliar Zn levels increased annually during the first three years of the study in all trees, perhaps due to a shift to organic production methods. Yields have not been affected by treatments. Monitoring of these plots will be discontinued. 2. A study was initiated in 2006 to investigate the effect of combinations of Zn sulfate and animal manure on Wichita pecans. Initial treatments were: manure (12 ton/ha), manure plus Zn (12 ton/ha plus 129 kg of Zn/ha as ZnSO4), and an untreated control. In 2007, two more treatments were added with doubled manure and Zn rates. Treatments were re-applied in March 2009. As in 2008, the manure 2x plus Zn 2x treatment had significantly higher leaf Zn concentrations than the control treatment or the treatments receiving only manure. 3. A corollary study was started in February 2008 on potted one-year old Wichita pecan trees planted in 40 L containers filled with calcareous soil. Treatments included an untreated control, soil-applied Zn sulfate, Zn EDTA, Zn Avail, manure, manure plus Zn sulfate, and foliar applied Zn sulfate. The manure application rate was 11.4 ton/ha, and the Zn application rate was 74 kg Zn/ha for each material. The foliar sprayed solution was ZnSO4 (0.24% w/v) plus urea ammonium nitrate (0.25% v/v). Soil treatments were applied once on April 4. Foliar sprays were applied every three weeks from. In the first year, plant growth (height and stem diameter) was not affected significantly by treatments. but foliar Zn concentrations were greatly elevated by application of ZnEDTA to the soil or ZnSO4 to the foliage. In the second year following soil treatments, however, foliar Zn levels in trees treated with ZnEDTA were not significantly greater than those of untreated trees. Soil sorption studies conducted to determine the effect of Zn source indicated that soil adsorption of Zn from Zn EDTA solutions was insignificant. It is believed that the leaching that occurred during irrigation of the pots resulted in leaching of ZnEDTA from the soil. However, leachate samples were not collected during the study. 4. In 2009 a field Zn uptake study was initiated in a newly planted orchard. Young Wichita trees were treated during transplanting with: Zn-EDTA (two rates), pisolithus, scleroderma, or a combination of pitholithus and scleroderma. Leaf samples were collected from the trees on September 24, 2009. Although the mycorrhizal treatments did not affect foliar Zn concentrations, application of the higher rate (70 ml/tree) of ZnEDTA increased foliar Zn to 56 ppm compared to 27 in the untreated trees. Trees treated with 35 ml/tree of ZnEDTA had a foliar Zn of 33 ppm, which was not significantly different than the untreated controls. PARTICIPANTS: This research is conducted in collaboration with Dr. Bruce Wood Southeastern Fruit and Tree Nut Research Laboratory, USDA-ARS and in coordination with Dr. Richard Heerema, Extension Specialist, New Mexico State University. TARGET AUDIENCES: The target audiences of this program include soil and plant researchers, particularly those working with tree crops in the Southwestern United States, as well as growers in this region. PROJECT MODIFICATIONS: A study is being set up in a new orchard that will allow us to apply ZnEDTA through micro-sprinklers in a newly planted orchard of Wichita trees. The infrastructure of this study is being installed at the present time. Trees will be planted in the winter of 2010-2011, and treatments will be initiated in the 2011 growing season.

IMPACT: 2009-01-01 TO 2009-12-31 Our research has shown that, with proper management strategies, soil-applied zinc can be successful on Southwestern pecans. However, we have not yet been able to prove the efficacy of specific practices to the point that grower practices will change significantly. Some growers are starting to apply zinc directly to soil, and we are recommending soil-applied zinc at the time of planting in newly-established orchards.

PUBLICATION INFORMATION: 2009-01-01 TO 2009-12-31
Nunez-Moreno, H., J.L. Walworth, A.P. Pond, and M.W. Kilby. 2009. Soil Zinc Fertilization of Wichita Pecan Trees Growing under Alkaline Soils Conditions. HortScience 44(6):1736-1740.

PROJECT CONTACT INFORMATION
NAME: Walworth, J. L.
PHONE: 520-626-3364
FAX: 520-621-1647