Care for Potato Plots — Lab Note 2.02

Recently we helped plant out ten plots for our potato plant study. We are comparing the growth, labor, and yield of five different potato-growing ideas: trench and hill, straw mulch, newspaper-and-straw mulch, containers, and towers. In order to help others reproduce our study or grow potatoes using these techniques, we are providing detailed instructions on our plant-out methods. The last post (Lab Note 2.01) described how to plant the crop. This one will describe how to care for the crop.

General Care: Weeding, Watering, and Pest Management

All plots should be cared for like any other garden plot. Weeds should be pulled occasionally and as needed. With the heavy mulch on each plot, it is unlikely that extra water will be needed unless we are in drought. To check the soil moisture, stick a hand under the mulch and dig fingers into the soil to feel if the soil is moist. If not (and no rain is coming in the next day or two), one heavy watering can be done. In the complete absence of rain, one heavy watering each week is preferable to watering a little each day.

Otherwise, participants are asked to monitor the plants for signs of problems: wilting, spots, pests. Potatoes are susceptible to a variety of fungi, bacteria, and insects and signs of distress should be noted and photographed. If simple steps can be taken to remedy the problem (e.g., removing the Colorado potato beetle, cutting down diseased plants), they should be done. Participants can always write to the organizer if any problems come up. Any of this activity should be recorded (i.e., why, when, and what was done).

Method-Specific Instructions

Trench and Hill

In this “control” method, potatoes will emerge from 6-in-deep trenches between rows of fill. Once they reach 12 in high, any remaining compost can be spread around the base of the plants. Then the rows of fill can be hoed up around the plants, covering up the bottom 6 in of the stems and half of the remaining straw mulch can be spread on the plot. As the plants grow higher (reaching about 18 in above the ground), the rest of the fill can be hilled up around the plant and the rest of the straw mulch can be spread over the plot. We’re using one bale per 24 ft of row for this part of the mulching.

Straw Mulch

Potato plants will grow through the heavy straw mulch in rows. Once they reach 12 in high, the remaining compost can be spread around the base of the plants. Then the the straw mulch between the rows can be raked, hoed, or moved by hand to make a straw hill around the plants, covering at least the bottom 6 in of the plant, if not more, as the straw will subside when water. Half of the remaining straw mulch can be laid in the space between rows. When the plants reach 18 in above the ground, the process can be repeated and the rest of the straw mulch can be spread over the space. We’re using one bale per 24 ft of row for this part of the mulching.

Newspaper-and-Straw Mulch

This is done exactly the same as the “Straw Mulch” method, except care should be taken not to rip up the newspaper layer below the straw mulch.

Containers

Containers are grain bags with rolled-down sides. As the plants reach 12 in high, the sides should be rolled up 6 in. The remaining compost should be distributed evenly among containers and then more straw (from the ground) and a bit of soil can be added to bring the fill up to the edge of the bag. Half of the remaining straw mulch can be spread on the ground to suppress weeds.. When the plants reach 18 in above the ground level, the edges can be rolled up again and more straw and a bit of soil (at least 75 percent straw and no more than 25 percent soil) can be added to the container. This can be done one more time, giving the bags a maximum height of 18 in. The rest of the straw mulch can be spread for weed suppression. Occasionally check the bottom of the containers to make sure they are not pooling water: after a dry period, tip the container and feel beneath for standing water. If any standing water exists, puncture the bottom of the container to avoid drowning the roots.

Potato Towers

The towers are built of wood and require a power drill. They started with one board around the bottom. As the plants reach 12 in above the top of the tower soil, add another board and fill in with the rest of the compost, straw (from the ground), and a bit of soil. Long boards should be secured to the south side of the tower with one screw on each side. The shorter boards should be placed inside the posts on the east and west sides and secured with one screw per end. New straw should be spread on the ground around the towers to suppress weeds. Repeat this process each time the plant gets 12 in above the top of the tower soil (use at least 75 percent straw and no more than 25 percent soil) until all boards are used.

Data Reporting

Each participant is asked to fill out a form to record the plant growth, observations, and hours worked every two weeks. The growers should list their name and identify the begin of the reported two-week period.

Hours worked over that time should be listed and then divided out by growing method. For example, if all methods took the same amount of time and care, all should be listed as 20 percent of the time. If the towers had to be built up and none of the others needed any time, then towers would get 100 percent of the time. This can be approximate and need not be to the second.

Next, participants should record observations about the activities and plants. For each of the methods, growers should note if they watered; weeded; filled, hilled, or built up, controlled pests, carried out other activities, or did nothing. The average height of the plants above the ground surface in each plot should be recorded. Additionally, the condition of the plants in each plot should be recorded: below ground, deep green foliage, flowering, pale green foliage, pests present, disease present, dying plants, and dead plants.

Finally, participants should give a qualitative summary of the weather over these two weeks: “It was exceptionally rainy,” for example. Quantifiable weather data will be drawn from a nearby weather station and participants don’t need to worry about tracking inches of rainfall or amount of sun.

Participants are encouraged to send pictures in to the project organizer.

All of this data can be entered on a form provided to participants or a private google form.

LTI-Research-No-002-PotatoForms
Data form provided to participants.

“Lab Notes” are a series of posts chronicling the progress our research projects. Research Project No. 2 is the testing of potato-growing methods. These notes may be useful for anyone interested in reproducing and testing our results. Others might be interested in just growing potatoes, and videos and other formal publications that will result from this research project will be posted to the website as they are available.


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