Fertilization

Nutritional program comes in second, but in arid areas, irrigation and weed control are equally important. Young pecan trees have a small root system.  This limits their ability to deeply explore the soil for available nutrients. Therefore, during the first year, a complete fertilizer such as 13-13-13 is the best choice. Fertilization of newly planted trees starts shortly after budbreak at 0.25 to 0.5 lb/tree of 13-13-13. Should the trees be making good growth, the same rate must be applied 2-3 more times at 2-week intervals. Second year trees receive 0.5 to 1.0 lb/tree of 13-13-13 shortly before budbreak and this needs to be applied 3 more times at 2-week intervals using the same rate.  Third year rates are increased to 1 to 2 lb/tree following the same schedule as year two. Fertilizer must be applied 18-24 inches from the trunk, in a band 2-3-feet long.  To avoid salt damage that might kill the tree, don’t clump fertilizer near the trunk.

Mulching

Mulching trees is important as this aids growing conditions by conserving moisture and aiding in weed control.  Weed control combined with mulching will minimize the need for irrigation within the first few years. Wood chips are one of the best materials for mulching pecan trees and, when applied only once at planting, usually deteriorates by the time production begins.  Wood chip mulch must be 4 to 6 feet in diameter and approximately 6 inches deep

Fertilization

Nutritional program comes in second, but in arid areas, irrigation and weed control are equally important. Young pecan trees have a small root system.  This limits their ability to deeply explore the soil for available nutrients. Therefore, during the first year, a complete fertilizer such as 13-13-13 is the best choice. Fertilization of newly planted trees starts shortly after budbreak at 0.25 to 0.5 lb/tree of 13-13-13. Should the trees be making good growth, the same rate must be applied 2-3 more times at 2-week intervals. Second year trees receive 0.5 to 1.0 lb/tree of 13-13-13 shortly before budbreak and this needs to be applied 3 more times at 2-week intervals using the same rate.  Third year rates are increased to 1 to 2 lb/tree following the same schedule as year two. Fertilizer must be applied 18-24 inches from the trunk, in a band 2-3-feet long.  To avoid salt damage that might kill the tree, don’t clump fertilizer near the trunk.

Foliar Zinc Applications

In areas where there is a zinc shortage, young, growing pecan trees must receive foliar zinc applications at approximately 2 week intervals, while the leaves and shoots are still expanding.An effective treatment is Zinc sulfate (36% Zn) at 2 lb/100 gal of water applied to the foliage. Foliar application of Zn is essential any time trees  are actively growing.Zinc is not effectively translocated within the tree, and so must be directly applied to new, expanding foliage.  Irrigation is a priority for all pecan orchards where the goal is consistent production of top-quality pecans.If weeds are controlled well, and trees are mulched, it is possible to delay initial irrigation installation within the orchard.Irrigation is necessary to reduce losses and improve the growth of young trees. During extreme droughts, or in areas that are quite arid, irrigation can make the difference between trees thriving versus death.

Irrigation

There are four main types of irrigation available:

  • Sprinkler, both moveable and solid set
  • Micro-sprinkler
  • Drip, both surface and buried
  • Flood

All of the above have been proven to be effective, but the preferred type will depend on factors such as production region, water availability, water quality and labor supply.

Orchard Design & Planting:

Many considerations that go into designing an orchard will have important short-and long-term consequences for the orchard. Cultivar placement within the orchard is among the most basic of these orchard design elements. For adequate pollination, pecan orchards need a minimum of two permanent cultivars with opposite pollination pattern and good reciprocal overlap of pollen-shed and pistillate-receptivity. Often orchards are planted with a single main cultivar that makes up the majority of trees in the block. But at least 20% of the trees planted should be pollinated cultivar trees and no main cultivar tree should be further than 46 m (150 ft) from a pollinated tree. The greater the pollinizer diversity in the orchard, the lower the risks of low main cultivar yield due to poor pollination-so planting two or three different pollinated cultivars is recommended.

In older orchards in the western US pollinated trees are sometimes scattered more or less randomly throughout the orchard, perhaps at a slightly higher density on the up-wind side of the block. This approach has the disadvantage of not permitting the grower to manage or harvest the different cultivars separately. A for better approach, which is becoming the norm in new orchards, is to plant all rows to a single cultivar. From an economic point of view, one of the most important short-term considerations is the number of years that it takes for the orchard to reach first harvest and to reach maximum production. To shorten establishment time, the most obvious orchard design tool available to producers is increasing tree density in the orchard. Especially in places where farmland is expensive, high and even very high planting density (120-272 trees per ha or 48-109 trees per acre) can be a good choice in pecan orchards-but only if there is a good plan in place to manage tree crowding and self-shading that will inevitably arise in future years in densely planted orchards. At this time, the only proven effective options for managing crowding and self-shading are tree thinning (i.e., tree removal), mechanical hedge pruning, or a combination of thinning and hedging.

Pecans require adequate moisture. They are not a particularly drought tolerant species {in Arizona and New Mexico pecans use approximately 42 inches of water per season}. Neither do they like prolonged wetness; pecans perform best in well-drained soils. In orchard surveys conducted in Arizona, pecan production was greatest in trees growing in sandy loam soils. Yields generally decreased as clay content increased above approximately 15%, and as sand content decreased below 60%.

If tree thinning is part of the overall future management plan, growers can plant very precocious cultivars (e.g., ‘Cheyenne’ or ‘Shoshoni’) as temporary trees to get the fastest possible payback for those temporary trees. There are two common thinning patterns that have been used successfully in densely planted pecan orchards: 1} temporary trees placed in every other planting position in every other row and 2} temporary trees planted as a solid line in every other row. If a different, more precocious cultivar is used for the temporary trees, the first pattern makes it more difficult to manage and harvest cultivars separately.

If mechanical hedge pruning is part of the long-range plan, it is necessary to consider the process of hedging in the orchard design. Trees must be planted for enough apart to allow the hedging equipment, which are often quite large, to pass in the directions to be pruned-many hedgers in the US require at least 9.1 m (20 fti distance between trees to pass easily. Some planting patterns lend themselves well to making hedging passes ‘in two or more different directions (including diagonal directions). For example, a diamond pattern with 10.7 m (35 ft) between North-South oriented rows and 10.7 m (35 ft) between trees in the row gives 10.7 m of room for the hedger to travel north-south, 8.9 m (29.2 ft) to travel in a straight line in two diagonal directions (NW-SE and NE-SW), but only 5.4 m (17.7 ft) in a straight line in the E-W direction. On the other hand, a rectangle pattern with 12.2 m (40 ft) between N-S oriented rows and 6.1 m (20 ft) between tree rows would probably allow most hedging equipment to pass only in the N-S direction.

The type of irrigation system and location of irrigation emitters (i.e., sprinkler risers and heads) can place restrictions on hedge pruning in the future, as can the location of earthen borders (e.g., separating flood irrigation checks). To maximize efficiency of hedging, long tree rows are generally better than short pruning passes (to minimize the amount of time turning around) and there must be sufficient space between the ends of tree rows and fences or other obstructions for the equipment to turn around easily.

A Double Row System for Establishing Pecans

One of the greatest deterrents to establishing a new pecan orchard is the long period of time it takes from tree planting to first commercial nut harvest. In experience at a Pecan Experiment Field, an orchard must grow ten seasons before it produces enough nuts to warrant mechanical harvest. It seems to take about ten years regardless of the way the orchard was established—direct seeded, transplanted seedlings, or transplanted grafted trees.

A decade is a long time to wait for a crop to return a profit. This delay in cash flow has led several growers to experiment with planting intercrops between trees during the establishment years. Many agronomic crops have been used as intercrops between young pecan trees including soybeans, wheat, corn and milo. Hay crops have also been used including several clover/grass mixes.

One of the first problems growers face in planning a new orchard/intercrop system is deciding on the spacing for the trees. When pecan trees are the only consideration in orchard planning, the recommendation will usually be spacing of 10m by 10m. Adding an intercrop into the mix makes things a little bit more complicated. Growers planning to farm between tree rows start thinking about the width of common farm equipment and if it’s possible to get a combine down between the trees rows. Row crop farmers often end up spacing their trees 15m by 15m. Wide spacing makes intercropping easier but seriously delays the onset for economically viable pecan yields.

Intercropping has one drawback often not considered when designing a planting plan. Planting a crop on both sides of a tree row makes it nearly impossible to access the trees for critical summertime tasks such as; tree training, grafting, weed control, insect control, and watering. Lack of care during the early years of tree growth can significantly stunt the entire tree planting, delaying on onset of commercial nut production.

During 2002, a new block of pecan trees were established as a Pecan Experiment Field using an intercropping system that may offer a better compromise between trees and crops.

A double tree row planting plan was developed (Fig. 1). The objectives for this design were to:

  • plant enough trees/acre to ensure a commercial harvest by year ten,
  • provide adequate room for intercropping,
  • provide access to the trees at all times.

Figure 1: A double row planting plan for pecan orchards. Distances are in feet.
Trees locations marked by circles.

Layout of the planting

  • Start by marking tree rows 24m apart.
  • Within each of these primary rows, spaces the trees 12m apart.
  • To make the double rows, plant the second row of trees only 7m to the east of each primary row.
  • The trees in the companion row were also spaced 12m apart but arranged in such a way that no tree within a double row is closer than 9m apart.

(Fig. 1) For maximum sunlight exposure for the trees, the trees were laid out in double rows in a north-south direction

(Fig. 2) Seedlings were used to establish this planting.

After all the trees were planted, a bluegrass/ perennial rye alley were established within the double row to allow access to the trees. Along each tree row, herbicides
were used to keep a weed free strip about 1m wide. Between each set of double rows, a 15m of intercrop (wheat, oats and soybeans) were established.

The double row system that was developed met all of our objectives but sacrifices more land to trees than most traditional intercropping schemes. In this specific
experiment, about 2/5 of the land area is devoted to trees and the grass alleyway, while 3/5 of the land area can be intercropped.

Figure 2: The double row pecan planting systems 2 years after tree establishment. Soybean intercrop.

Figure 3 A&B: Trees grafted in the field of the double row systems.

Figure 3A: Pecan tree 3 years after establishment and the 1st summer after grafting

Figure 3B: Grafted tree, 2nd summer after grafting

Intercropping in pecan nut orchards

Due to the relative long period between establishing a pecan nut orchard and the first economic crop, intercropping is considered. This could help to offset some of the initial costs. However, intercropping should NEVER compromise the pecan trees. The pecan orchard will render an economic crop for more than 35 to 50 years and cannot be compromised during the initial stages. Any adverse condition during the establishing of an orchard will delay the first economic crop and shorten the productive live of an orchard.

When intercropping is considered, growing conditions for the intercrop is of secondary importance to that of the pecan tree. Do not deviate from the orchard layout or requirements to establish an economic pecan orchard. Therefore practises like spacing, irrigation, fertilisation, weed and pest control for the intercrop should not jeopardise the pecan tree. Rather sacrifice the return of the intercrop before sacrificing the pecan tree.

In pecan nut production tree spacing of 10x10m is considered optimal. When intercropping is then considered, lanes of 8m during year one, 7m during year 2, 6m during year 3 and 4 and 5m during years 5 and 6 after planting can be considered available for intercropping. Select the interplant crop with the pecan nut tree in mind.

Fertilise, irrigate etc the pecan tree optimally and if required separately from the intercrop. Grass crops without legumes are considered not suitable if the fertilisation is according to the requirements of the grass crop. Inter-cropping may therefore be an alternative, but remember most crops will compete with trees for water and nutrients. Furthermore, most crops will need water at different times than pecan trees. Then the yield of the intercrop should be sacrifice and not the growth and development of the pecan tree.

When considering intercropping or not, ensure that the soil is prepared properly before planting. This include proper loosening of the top 500mm (at least) layer of soil and addition of fertilisers to optimise the nutrient status of the soil for pecan trees. After planting keep a two meter strip (1m on both sides) free of weeds or the intercrop. Irrigate and do pest control according to the requirements of the pecan tree.

During the second season after planting, remove the intercrop from a strip of 50cm on both sides of the tree in order to leave a 3m clean strip. Use a herbicide if necessary. If heavy and/or continuous traffic were operated in this 50cm strips, loosen the soil using a ripper plough fitted with a small wing at the tip.

During the third season after planting, remove the intercrop from another strip of 50cm on both sides of the tree in order to leave a 4m clean strip. If heavy and/or continuous traffic were operated loosen the soil as described above.

Repeat the reduction of the width of the intercrop strips and loosening of the vacant soil until the intercrop is considered redundant.

Figure 4 A&B. The double row system in the fourth year after establishment with a spring oats inter crop

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