Pecan Orchard Canopy Mapping in Cochise County, Before the Shake

Drive east from Willcox on I-10 towards Bowie and San Simon and the thing you notice is the pecans. Not a grove. Mile after mile of them, in square grids, young blocks next to mature ones, with the Dos Cabezas behind.

Most of our agricultural work is vineyards: small blocks, priced per visit. Pecans are the opposite case on almost every axis, and they are the reason the per-acre tiers exist on our rate card at all. This article is about what an aerial pass over an orchard shows in late September, a few weeks before the shakers start, and what it costs at orchard scale.

How much pecan there is here

The numbers are large and recent. University of Arizona Cooperative Extension's 2023 bulletin on pecan water use puts Arizona at "more than 30,000 acres of pecans," nearly double the 2013 figure, "with nearly all new production located in Cochise County." USDA's National Agricultural Statistics Service counted 26,000 bearing acres in Arizona in 2023, producing 45.5 million pounds in-shell, which made the state third in the country behind New Mexico and Georgia. The difference between those two acreage numbers is young trees not yet in bearing, and most of them are in this county.

In 2017 the Extension's commercial horticulture agent told Western Farm Press that growers had planted about 2,500 acres that year alone, double the year before, with a sizeable share around San Simon, McNeal and Bowie. Those trees are now coming into production. We have not found a Cochise County pecan acreage published by USDA or Extension, so we are not going to quote one.

What an orthomosaic shows of an orchard

An orchard pass is flown as a mapping mission: parallel lines, high overlap, stitched into a single flat, scaled, georeferenced image with a canopy index computed from it. At 300 ft over 25 to 35 ft trees the pixels are a centimetre or two.

Tree count. Every tree is a discrete object on a regular grid, which makes orchards the easiest crop there is to count from the air. The Extension's Bowie study orchard, for reference, is Western Schley planted in 1978 on 40 ft rows at 20 ft in-row. On that geometry a 160-acre block is about 8,700 trees, and the orthomosaic tells you how many are actually there.

Canopy cover. This is the number that matters most, and the one a drone measures better than anything else. Extension's water-use bulletin scales orchard consumptive use by effective canopy cover — the fraction of the orchard floor shaded at solar noon — to turn a reference figure into a water budget for a specific block. Measured cover per block, from an image shot near solar noon, is a direct input to that arithmetic. At Bowie the bulletin measured 51.4 inches of consumptive use per growing season on a mature sprinkler-irrigated orchard; a young block at 40% cover is nowhere near that, and the map tells you how far off.

Gaps, dead and declining trees. A missing tree is a hole in the grid. A dead one is a grey crown. A declining one is the harder and more useful case: a crown noticeably smaller or thinner than its eight neighbours, which on a canopy map is a low value in a sea of high ones. The output is a list — row, position, coordinates — that a crew can drive to.

Irrigation uniformity. Flood and micro-sprinkler blocks fail differently and the map shows both. A flood block shows head-to-tail differences: the tail end that never quite gets wet, the levee leaking into the next border. A sprinkler block shows tree-level variation: a run of smaller crowns along one lateral, one tree bright in a row of dull ones where a head is stuck open. Neither needs a special sensor. It needs the whole block in one image, measured.

Late September, before the shake

The harvest here is later than people from other crops expect. KJZZ, reporting on the Arizona Pecan Growers Association in 2017, put the harvest season at "November through January." A southern Arizona grower told Western Farm Press in 2021 that his early shake went in right after Thanksgiving and the second ran to late January. The mechanics are as Extension describes: once the nuts release from the husk, a shaker clamps the trunk and the crop comes down.

So a late September flight is six to eight weeks ahead of the first shaker, and that is the point of it. Extension gives the Arizona pecan growing season as late March through mid-November, so at the end of September the canopy is still full and the map is the last full-canopy look of the year. Three things come out of that.

• A canopy baseline to set against next spring's leaf-out and against the same week next year. One image is a snapshot. Two a year apart are a trend.
• The floor. Nothing should be on the orchard floor when the nuts hit it. The orthomosaic shows where the weeds, washouts and standing water from the monsoon still are, block by block, before the floor crew starts.
• Access. Where the shakers and harvesters get in, which farm roads the August rains cut, where a trailer can turn. Documented once, with a scale bar, for everyone on the property in December.

Why pecans are where per-acre pricing applies

Vineyard work is a flat $425 a visit for a block up to 50 acres, because at a few dollars an acre a small block does not cover the drive. Pecans are the other end of the curve. Blocks here are 160, 320 and 640 acres; at that scale the drive is a rounding error and the honest price is per acre.

The rate drops because the fixed part of the job — mobilisation, ground control, processing set-up, the report — is the same for 160 acres as for 800, so it amortises. It does not drop to zero because the variable part does not: an 800-acre orchard is three or four launch points under Part 107 line-of-sight rules, and processing time scales with the number of images, which at a centimetre a pixel is a lot of images. A prescription layer, if you want canopy cover written out as a grid for your irrigation controller, is $4 an acre on top.

Travel: Bowie is Zone 2 at $50, waived on any job over $600, which is every orchard in these tiers. San Simon is further out; ask and we will quote the travel plainly. The full rate card is published, and the agriculture service page has the deliverables.

What we do not do

And one more: we cannot count nuts. An aerial pass does not give a yield estimate. It gives you the canopy that produced the yield, which is the only part measurable from the air.

If you run pivots as well as trees, the same flight covers both; what a pivot problem looks like from 300 feet is written up separately. The dated orthomosaics also serve as the irrigated-acreage record the Willcox AMA now makes worth keeping.

If you want a measured canopy map of your blocks before the floor crew goes in, send us the acreage and the location and we will quote it per acre, with travel stated.