$hake it till you make it

Author: Adam Hanbury-Brown

It’s the busiest time of year in California’s central valley where nut tree growers are working hard to harvest millions of pounds of nuts from their orchards. Given Terviva’s current interest in mechanical harvesting for pongamia, we have been paying close attention to the growers’ activities on our doorstep.

California produces approximately 2 billion pounds of almonds per year, and at $2 per pound that represents 4 billion in revenue. Given how much money is at stake, it is no wonder that growers take their harvest very seriously. Paramount Farms alone is forecasting 550 million pounds of pistachios this year, and when they’re selling at $2.20 per pound even a small percentage of yield left behind could result in millions of lost revenue.

As a nut tree farmer like Paramount Farms, your revenue is not simply contingent upon what your trees produce; rather, you get paid for what makes it out of your orchard in a marketable state. Therefore, one of the most critical elements of a profitable season is a successful harvest. An orchard overflowing with nuts is useless unless there is a cost effective and efficient way to get your nuts off the trees and safely on their way to the processing facility. Each tree crop has its own biological idiosyncrasies that the grower must contend with when developing the optimal harvest strategy. For the most well developed tree crops such as almonds, pistachios, and walnuts, these strategies have become remarkably sophisticated. Left is an example of a tree shaker. green-pistachio

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A successful tree crop harvesting strategy requires the harmonious marriage of machinery and biology. For example, as anyone who has ever eaten a pistachio knows, every pistachio has a slit in its side. The slit slowly starts to open as the nut matures on the tree. Although a properly split pistachio can make things easier for the consumer when trying to take the shell off, it causes a conundrum for the grower. If a pistachio with an open slit hits the orchard floor, it has potentially become irreversibly contaminated. Removing dirt and the chance of harmful bacteria from inside the slit of a pistachio is not an economically viable option so every nut that hits the ground is lost revenue. Therefore, pistachio growers use an ingenious machine that shakes the trees, catches the falling pods, conveys them into crates (or a bulk carrying device), and separates out leaves- all in the same machine! Above (left) is a picture of one such machine in operation.

Similar machines are also used by stone fruit growers. But what about nuts that fell to the floor before your harvester got there? What about nuts that might still be immature and on the tree? In pistachios they can help alleviate those problems by doing an earlier pass and then a later pass a few weeks later in the harvest season.  For other species, there are issues that make shaking onto catchframes totally non viable.9_26_2013 159Coe_Tree_Shaker

For example, walnuts growers can’t use catch frames for two reasons 1) a walnut tree is much bigger and 2) walnuts have the unfortunately phenological attribute of dropping a not insignificant portion of their nuts before the bulk of them are ready. This is what growers refer to as windfall, and you can bet that they want to sell it. Therefore, when it comes time to shake the trees (using machinery such as that shown on the left), they let the nuts remaining in the crown to fall onto the ground to join their early falling counterparts. Due to the fact that the edible parts of a walnut are completely enclosed in shell, it is not a health hazard to let the nuts fall to the ground. Once the nuts are on the ground, they are swept and blown into windrows (shown on the right), and then picked up by a large harvesting machine. Clearly there are more steps, and more pieces of equipment involved in this harvesting strategy, but the idiosyncrasies of the tree’s biology dictates that this is the most economically effective means of getting the product to market.

At Terviva we are paying close attention to the how growers are matching their nut crops to specific harvesting strategies. This will help us find the best possible solution for our own tree- pongamia. Even though it is early days for the large scale commercialization of pongamia, it is clear that we will need an efficient mechanical harvesting process in order to maximize profits to the grower. Preliminary conversations with harvesting experts indicate that equipment that is already available should work well with pongamia. Making fine tune adjustments will come as the pongamia industry grows. For now, we are looking to our doorstep in California’s central valley to learn from some of the most sophisticated nut growers in the world. This invaluable information is shaping the way we think about genetic selections, plantation layout, and orchard management.

Adam Hanbury-Brown is a Research Associate at Terviva

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