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A. Doug from metro Detroit writes: "In response to a recent comment you made on the show, I definitely do not want you to have to find honest work, and since you said you were a little short on questions, I'm sending mine.
"I love growing sweet corn but in two years of growing sweet corn in the same in-ground bed I believe I have managed to deplete the soil nutrients. In 2017 I had a fantastic harvest; but in 2018 the corn was stunted and only a handful of cobs were successfully produced. At the start of that second season, I did spread compost on top and added a little bit of light organic fertilizer, but I don't think I used enough, or I didn't use the right stuff as the harvest basically sucked.
"I know I'm supposed to rotate crops, but my raised beds are not deep enough for corn, so I grew it in-ground. For 2019 I'm going to move all my corn to a nearby community garden and use my in-ground beds at home to grow carrots and a lot of potatoes. What should I do to restore full nutrition to those in-ground beds after two seasons of back to back corn growing? Love the show; keep it up; glad you're still going strong!
A. Well thank you Doug! Not sure how strong I feel in these months of ice and snow, but I am still going. (Often three or four times a night!)
Ahem. Now--You are half right about me, but you are not even close to half right about your sweet corns' needs. And that's a good thing, as I believe this will help our listeners learn a lot from your...I'm not going to call them 'mistakes'; let's call them your 'presumptions'. Or mistakes; your choice.
Now: Although I champion the cause of raised beds, those elevated growing platforms are not ideal for every situation; and corn--whether sweet, field, dent or pop--is the shining example. The plants are shallow rooted and tend to fall over in the deep, rich soil of raised beds. (I create what are essentially horticultural boxing rings with stakes and rope to keep them upright.)
So: lesson #1: We're sticking with flat earth.
#2: It is not unusual to have a great crop one year and a pissy one the next--especially when 'the next' is/was an historically wet and unsunny season like 2018.
#3: Yes, it's always a good idea to 'rotate your crops'. A truly good person would, for instance, grow sweet corn one year, then a nitrogen fixing crop or ground cover to replenish the soil in year two, a totally unrelated crop like potatoes in year four, something like tomatoes in year five and then back to corn. Luckily, I am not a good person, am not hamstrung by such horticultural anxieties and would have no fear of growing corn back-to-back for many seasons if the corn and soil are cared for correctly.
#4: Corn is a simple plant that wants just three things--lots of sun, lots of water and lots of Nitrogen fertilizer. It's essentially the same as a lawn, which makes sense, as corn is also a grass. Once the young plants have been up and growing for a few weeks, feed them a good amount of corn gluten meal, well-composted horse manure, composted poultry manure, or an organic fertilizer labeled specifically for use on corn (or lawns). Don't worry about phosphorus and potassium; corn just wants Nitrogen and lots of it.
#5: Corn also wants a lot of friends and relatives close by. The minimum recommendation to get good full ears is a block of 36 plants; that's nine tight rows of nine tight rows--but the more the merrier. Think about what happens at "flowering time"--the stalks that appear at the top of the plants drop pollen down into the developing silks. Every pollen grain that lodges in a silk becomes a kernel of corn, so you want as many plants together as tight as possible. (No growing in 'rows' here; you want 'blocks'.)
#6: Feed a couple of times during the season. The more plants you have crowded together, the more Nitrogen-rich food they'll need--but stick with organic and natural sources. The chemical fertilizers used to grow corn conventionally ruin the soil and kill soil life.
#7: Corn is not necessarily welcome in a community garden, as one gardener's type of corn can cancel out the sweetness of all the others. There are several types of sweet corn:
• "su" or 'standard' sweet corn, which was bred long ago to be sweeter than the field corn fed to animals and used to make corn meal, chips and such.
• "se" which stands for 'sugary enhanced' or 'sugary extended'; its much sweeter than the "su" types; and
• "sh2", which stands for 'supersweet' or 'shrunken', as the kernels contain so much sugar that they take on a shriveled appearance when dried. They can be up to four to ten times sweeter than basic sweet corn but are a bit more finicky in the field.
• And, of course, there's also the old-original field corn (some varieties of which are nice and sweet if picked at the right time, which is called 'the milk stage').
So never mix and match. If different types of corn are grown in close proximity and their pollens mix, all the corn can become bitter and starchy. Pick one variety a season and grow a lot of it.
Oh--and ixnay on the potatoes and carrots in flat earth; these root crops produce best in a light loose soil and are the poster children for growing in raised beds.