By Cory Mosser, formerly of Burge Organic Farm in Mansfield, Ga. and currently Natural Born Tillers
Oh, the humble potato. It’s often considered a beginner’s crop- one that isn’t technically challenging to grow with little need for any additional inputs after planting. While it’s true the potato is a hardy and vivacious plant, it comes with its own difficulties. Truth be told, it’s not hard to grow good potatoes. However, with a little additional effort and planning you can grow (and sell) GREAT potatoes.
The first year I planted potatoes in Savannah; I planted 300# of seed potatoes late in the season in a boggy field and was treated to two solid weeks of rain. EVERY potato seed rotted. Ouch. Subsequent years have afforded experiences with black rot, early sprouting and windfall crops of potato beetles. All of that is to say that the following advice is not from someone who has it figured out, but rather it has been accrued by someone banging his head against the wall. Repeatedly.
For starters, we try to grow the right varieties that match the needs of our farm and our markets. For us, that means having the widest variety over a long period of time. Just like many other vegetables, some potatoes are better suited to long-term storage, and others are more perishable. Storage life of a potatoe can range from 6 weeks to 6 monts depending on variety and storage conditions. A good tool for identifying potato varieties is Washington State University’s Comprehensive List . We try to plant about 10% in early potatoes, 20% fingerlings (They are significantly more expensive and don’t hold well in storage, but they are a great way to start the season), 40% Midseason varieties and 40% Storage types.
We order our potatoes in December to assure availability, and we try to find sources that ship from the southeast since shipping heavy potatoes gets pricy. Last year we planted just under an acre in potatoes and ordered around 800#. We ended up with a harvest of around 5000#. This year we are planting 10 varieties totaling 2500# on three acres and we hope to harvest between 15,000 to 20,000 pounds (it makes me a little nervous just to write that number…)!
Many folks get confused about cutting and pre-sprouting potatoes. On average, you want to have a cut potato piece to weigh roughly 2 oz., and contain at least 3 eyes. Potatoes begin to sprout from the top-down, also known as apical dominance, which basically means the sprouts form on the part of the potato that is furthest from the stem side, or the original connection to the mother plant. Because of this, you can generally cut your pieces quickly by just slicing along the longitudinal axis, although with longer varieties such as russets this will create a greater surface area and predispose you to a greater risk of early rot. We wait until our seed potatoes have just started to sprout before cutting, and then we wait another 3-4 days before planting to allow the wound to heal. If you allow your sprouts to become too large before planting, you risk them breaking of in the planting process and you might have just as well planted unsprouted potatoes.
While it is true that cutting and planting your potatoes in pieces is generally associated with greater yields, there are other factors to consider, including the amount of labor required to hand cut your spuds. Depending on the size of the potatoes and the amount we are going to plant, we may or may not cut our potatoes. This year for example, because we had a large amount of potatoes to plant and a very short window available, we chose to cut only a small portion of our planting stock.
We schedule to plant at the end of February all the way thru March depending on the weather. We dig a furrow and then use a waterwheel transplanter without the wheel to plant the field. It’s only a little faster than three people planting on their hands and knees, but it saves a lot in fatigue. We then cover the potatoes lightly either by raking them in, or by doing a light pass with the tiller to collapse the tops of the furrows. Plants do fine and continue sprouting underground even in cold and snow. Above ground growth will die off, but the plant often continues from the tuber.
Diseases, Pests and Weeds
Potatoes enjoy well-drained, more alkaline soils (basically the opposite of most Georgia soil). Scab disease is much more prolific in acidic soil, so try to lime accordingly the winter before planting your crop. Last year we planted in two different sections- a bottom and a sandy hillside. We had some significant early spring rains last year, and several of the potato cuttings planted in the bottoms rotted in the ground, while those planted on the hill did great. The bottom line is, they don’t like wet feet. Rotate accordingly. Potatoes are also a fairly heavy feeder, so we usually prepare the soil with a light dusting of composted chicken manure, and we side-dress twice more as the plant grows.
One reason I enjoy growing potatoes is that it’s one of the only true row crops that we grow, and instead of weeding, we hill. I can’t tell you how satisfying it is to be able to grow a crop and not ever have to run a wheel hoe through it. Now if only I could find a way to do it with onions… Being able to bury a bunch of weeds is not only deeply satisfying; it also saves valuable time during the spring when you need it most. Hilling the plants also allows them to continue to produce tubers, although it has to be done early enough to make a difference. We usually hill twice during the season once the plants are 8” or so above the ground. We try to bury the plant just so that the top 3-4” are showing on the surface.
As far as insect control goes the only real problem, obviously, is the potato beetle. They can decimate plants in a bad year (last year was pretty bad for us), but more importantly they are vectors for blight, as well as other diseases. We usually make field notes and if we see more than on average 1 bug per plant, we consider it a problem that needs controlling. The key is to get them in the larval stage. Once they have the harder shell of an adult beetle (2-3 weeks from the time they appear), they are harder to control and they will go about their business immediately producing the 2nd generation that can be even more populous than the first. We use Entrust (it’s high-concentrate Spinosad so it doesn’t interfere with beneficial organisms and doesn’t create leaching issues) and it works extremely well in our experience when used correctly. The biggest trouble is that it is ridiculously expensive (1# for over $500!), but a little bit goes a long way, and it does control a whole host of insects. For last year’s crop, we only sprayed twice and each time we used around 1/2 ounce per acre. (Entrust comes in 4- ¼# bags, so I suggest going in with a couple of other farmers- we use way less than 1/4# per year).
Harvest and Storage
Ok, now your plants are big and beautiful and weeded and bug free. Now you get to watch them die… Correctly harvesting and then storing your crop is the most important stage of producing potatoes, second only to proper variety and site selection. It is tempting to pick potatoes as the plants start to wilt, but we restrict ourselves to harvesting no more than 15% of the total crop as “new potatoes”. New potatoes can be harvested from about the time the plant begins to flower. You can plan on losing a between a third to a quarter of your yield by harvesting young potatoes. Average maturity for potatoes ranges from 80 days for fingerlings and new potatoes to 120 days for later maturing and storage varieties. For our main crop, we wait to make sure the plants are completely dead before digging. Most commercial growers mow the tops off of their potatoes to allow the vines to die down more quickly, and we may try it this year. We’ve found that if the tubers are allowed to fully develop underground, the skins seem to not to scrape off as easily during harvest and are able to store longer. The other important factor is to harvest the potatoes when it is as dry as possible. Wet weather not only makes digging the potatoes more of a chore, but it also can contribute to storage rot. In the past, we’ve done a mixture of hand harvesting, combined with an initial run-through with a sub-soiler outfitted with a large furrower. Last year, it took almost 75 labor hours to harvest our crop, which takes place in June, when time is really at a premium. Our interns reported this was one of the most miserable jobs of their stay. It can be a pain, especially when done by hand.
This year we are very excited about our newest piece of farm equipment- a PTO-driven conveyor potato digger. Like our transplanter, we are sharing this piece of equipment with a neighboring farm, which helps out tremendously as far as cost is concerned (as an aside, this is something I think that farmers should really do more often, it has allowed us to grow more efficiently and work cooperatively with our neighbors). Although I have only used it so far to dig some over-wintered beets, I highly recommend it as an addition to a medium-size operation. Also, it is able to harvest sweet potatoes, onions, peanuts and turnips as well. We are estimating that it will pay for itself within one season. In addition, the model we decided on has a stand-alone PTO-driven hydraulic pump and motor, which is a handy power source that can be easily removed and retrofitted for other purposes (we are working on designing a drip tape winder as well as a row-cover remover, which will save additional time).
Once the potatoes are unearthed and sorted, we store them unwashed in ¾ bushel boxes (or ½ bushel for fingerlings and new potatoes). We allow the potatoes to cure in our barn for about a week before we place them in our cool room at 55 degrees. After another week, we reduce the temperature to between 45-42 degrees (I read somewhere that gradually reducing the temperature allows the potatoes to maintain dormancy over a longer period of time). During the hottest summer months, we run a fan on the potatoes to try to mitigate the heat let in by opening the doors repeatedly. We also will go through boxes on a regular basis to determine if the potatoes have begun to sprout. Fingerlings can last about 2 months in the cooler, whereas longer storage varieties like Canela can last up to 6 months. Last year, most of our potatoes started to sprout in September, and we are hoping to be able to hold them until November this year by handling them more delicately during harvest. If your potatoes do sprout, you can try to hold on to them for next year’s planting by reducing the temperature slightly. A fellow farmer suggested that we try to overwinter some sprouted potatoes in one of our hoophouses, and after dying back a couple of times, the plants have sprung back and are almost mature and are now yielding beautiful new potatoes just in time for market!
Well, that’s it; I hope that you find some of this information helpful. Hopefully, you’ve done everything right and now all you have to do is worry about selling your bountiful harvest (which we all know is no problem at all, right?). This year we’ve gone spud crazy are planting more than 3 acres of potatoes, so I’m sure I will have a 30-page addendum to this article next year available entitled “Up To My Eyes In Spuds: Why You Should Never Grow Too Many Potatoes”. I wish all of you a wonderful year of heavy harvests and light weeds!