A question is commonly asked about optimal orchard row width for almond orchards in order to maximize production and returns. With the goal being to maximize production as early as possible, many operations want to plant rows as close as possible, but wide enough to provide access for equipment. Therefore, most operations within California plant between 21-22,’ with some orchards as close as 20′ and wide as 24.’
With row spacing, are maximum production and equipment access the only variables in making this decision? Mostly, but one must balance the possibility of increased production with increased costs of establishing and maintaining more rows at a denser row spacing. When deciding on spacing, there are many other factors to consider, including the cost of increasing row density, the varieties and rootstock selected for planting, expected orchard vigor, anticipated cultural practices, and risk of inclement weather at harvest. Each one of these are outlined in further detail below.
Establishment and operational expense. As the width of the aisle decreases the number of rows per acre increases. With an increasing number of rows, establishment and cultural costs also increase (the more rows the more risers, irrigation line, and passes made per acre). Changing row width by one foot changes the number of rows by one-half row per acre (assuming a square acre planting). This means that in comparison to a 22′ spacing, a 21′ row spacing will cost an additional $750 per acre for the life of the orchard based on pricing from local companies and the UC Cost Studies ($200 establishment through the third year+ $50/year*22 for a 25 year orchard lifespan).
Varieties. The tree architecture and vigor of certain varieties can facilitate closer spacings. Upright varieties such as ‘Independence’, ‘Aldrich’, ‘Fritz’, and ‘Padre’ provide the ability to plant tighter as they provide easier equipment access. Larger or bushier trees such as ‘Monterey’, and ‘Nonpareil’ varieties, however, often have scaffolds that can interfere with orchard practices and should be spaced wide enough to fit equipment.
Rootstock selection and vigor. Highly vigorous trees can be planted further apart with the intent that they will grow together rapidly. Deep, well drained soils may allow trees to fill space rapidly and deliver high production at wider plantings, while lower quality soils may require closer plantings (depending on rootstock and variety selection) to capture the same light and production potential.
Site. Block dimensions or shape my require differing row widths. Row width should be adjusted to make sure there is adequate room for equipment usage to be completed without crossing the property line or agreed upon easement.
Cultural practices. Wider-spaced rows may require fewer cultural practices. Fewer passes per acre are needed when applying pesticides even though they may need more powerful sprayers. Within wider spaced rows, pruning is often minimized as there are fewer limbs to be removed to “open the middles” and crop drying occurs faster due to more sunlight reaching the orchard floor. Furthermore, the expense and impact of hedging is reduced in wider spaced rows as less canopy is cut due to being fewer rows per acre. Finally, spacing too tight may create issues with foodborne pathogens. Research by Bruce Lampinen, UC Specialist, has found that orchards with greater than 80% light interception have an increased risk of food safety issues due to the favorable conditions suitable for pathogen growth (high humidity, increased surface soil moisture).
Climate conditions. Production areas with increased risk of early rain should consider wider-spaced orchards to assist with crop drying in case of a rain event. Wider-spaced rows are generally thought to have less disease risk since there is more air circulation to reduce leaf wetness.
Determining the proper row spacing for an orchard should be based on more than production and equipment access. Consideration should be given to a number of factors that may be unique to the local growing conditions. Although the trade-off for a wider spaced orchard may be reduced yield in the beginning, it may lead to a reduction in orchard costs and higher quality in the long term.