Planting and Hilling ginger
Ginger, unlike many crops, has an limited root system comprised of fleshy roots that really benefit from having a steady source of rich nutrition in the immediate vicinity of where it's growing. Most farmers will add at least a pound of chicken manure per foot in a row, plus thoroughly till it in prior to planting. However, actual fertilizer amounts should be determined by a soil test (and personal experience with your soil or media).
Next, there is soilless media, such as coco peat. A media like this will require more fertilizers, as it is essentially an tabula rosa (blank slate).
Ginger is commonly referred to as a root, but this is a misnomer. Rhizomes are modified stems that the plant uses to store starches needed regrowth and periods of stress. If left unattended, ginger will grow until the tops of the rhizome will protrude from the soil surface, which could let them be subject to sunburn. When the rhizome reaches the surface, it will automatically begin growing sideways and downwards, and generally will make for a less attractive and workable hand of ginger. This is why ginger growers usually cultivate the plants by mounding or hilling soil around the base of the stems. This practice has other benefits as well, like smothering weeds and making it easy to apply fertilizer in the soil mix, which will cover the plant for ideal absorption into the root zone.
Hoop House/High Tunnel
Whether you're transplanting the pre-sprouted ginger or planting unsupported seed into the soil, temperatures should be at least 55ºF. You can buy some cheap soil probes which are very handy for determining the soil temps - simply place them in several spots throughout the tunnel. If the temperature needs to be increased, you can use row covers placed on the beds to try and help with that, and check back until the temperature is up to where you need it.
Your rows (ditches, furrows or trenches) need to be a minimum of three feet apart, center to center. The reason for the three foot rows is so you will have enough soil to add to your ginger during growing season. Remember, you will plant in the trench, and throughout the season the soil from between the rows will be used for hilling, and by season's end, what used to be a trench will have become a mound (and hopefully that mound is full of ginger or turmeric!). If you have raised beds, apply this same concept. Also, if you need to plant the ginger rows closer, just bring in more medium to simulate mounding. Same goes for planting in bags.
So, you have made your trench or furrow. Let's say it's six inches deep. However, you have taken that soil that was dug up to create the trench and put it to the side or into the aisle (the path between the trenches), so the trench should appear almost a foot deep. Next, place your amendments in the bottom of the trench; if you have compost, add it now. Mix all this into the soil at the bottom of the trench so you have a well fertilized bed. After that, take your seed or sprouted seed and place it on the bed, raking some soul from the side on top of the seed (a hoe or your feet would work for this job too). You only need a couple inches on top of the seed piece.
When placing your sprouted or unsprouted seed pieces in the trenches, space them about 5 inches apart. At this rate, you will need about 20-25lbs of seed to plant 100 row feet.
Due to the fact that we grow mature ginger rather than baby ginger, the photos we have on our website show a slightly different style of planting that what we have described above.
Here in Hawaii we leave a distance of 4'10" between trenches. We do this because we use tillers with tines that throw the soil out when we till (our tillers are like mini ditch diggers). As you will see in the Funky Times section of this website, we also plant a double row of seed in our trench using 45-50lbs per 100 foot row. In addition, we harvest our mature ginger with a tool bar behind our tractor. The tractor tires are about 5 feet apart, so the farther spacing of the beds allows the tractor to straddle the mound and pull the bar under the ginger, cutting the roots and slightly lifting the rhizomes.
Perhaps you will use a tiller or tractor to prep the soil in your field, high tunnel, or raised bed. However, since most of you are growing baby or young ginger, we'd recommend using hand tools to mound the ginger, and when it comes time to harvest you will need to simply pull it out of the ground by the still growing tops or foliage.
After a few weeks, small weeds will begin to emerge. Around this time you can also add a sprinkle of chicken pellets into the trench. Then, using a Hula hoe or stirrup hoe, you can pull a thin layer of soil from the extra you left on the side (or in the aisle, which is also conveniently starting to show sprouts of weeds). This way, you kill two birds with one stone - weeding next to the trench where the seed is planted, and smothering the weeds sprouting from the trench itself. In addition, the two inches of soil that you sprinkled on top of the seed at planting may have settled down to far less than that, possibly even exposing parts of the seed here and there. By pulling the extra soil into the trench, you will have taken care that problem as well.
Alternatively, you can also use a flame weeder to take care of the weeds until the ginger shoots start to emerge.
In about 4-6 weeks after the ginger throws up a shoot and has established roots (this will most likely happen sooner if you planted a sprouted seed), check the shoot bases for swelling and a vibrant pink color. Once you start to see this, hill the crop with a few inches of soil, fertilize again, and check back in another 3-4 weeks. Hill and fertilize again when you see the rhizomes swelling and turning pink near the soil surface, and repeat for a third tome of needed. I prefer not to leave lots of fertilizer on top of the soil, and usually side-dress, then cover the fertilizer when hilling. Farmers here in Hawaii will mix the fertilizers with the soil right in the aisle, then drag the mix onto the ginger shoots.
Note: Mixing or covering the fertilizer is not a hard "rule". If the seed needs nutrients but does not yet need hilling, then a layer of composted chicken pellets as a literal top dressing is quite effective.
Keep in mind that each grower's fertilization requirements will vary. Without a soil analysis, it is not appropriate for us to give out strong recommendations.
Growing in bags is an excellent way to avoid disease that can be transmitted through foot traffic and repeat crops in the ground, although there is no "silver bullet" to combat disease. Still, it is important to follow proper protocols for sanitation. Remember that with too much water, the medium you're using can become mucky and anaerobic, thus easily conducive to disease. Peat moss-based products have more of a tendency to become waterlogged than coconut coir (cocopeat) based products. Make sure your bag or pot has enough holes to facilitate drainage. Watering and drainage are just as important as if was is in the ground, so make sure to maintain an evenly moist (not wet) medium. Coconut coir has an advantage here, as it very easy to rewet should it become dry.
10-15 gallon size pots seem to be a good choice for ease of handling and room for growth. Wider is better than taller, as ginger needs room to stretch out laterally as it grows. But be sure to have enough room for hilling. Keep in mind that hard pots, if too small, can break if you have a good crop of ginger.
Concerning the media itself, be sure to mix in a mild fertilizer and gypsum for every expanded kg of cocopeat or media. When preparing the bag/pot for planting, first fill the bottom with around 4-6 inches of well moistened media. Then, plant the seed (either presprouted or not) into the media, being sure that the seeds are properly spaced to allow enough room to grow. Then simply cover the seed with several inches of media.