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Looking for expert help with Mel's Mix

Posted by MindfulHal 8b/9 (My Page) on
Wed, May 29, 13 at 22:11

I have two 4' x 8', 2' deep raised beds, both setup this spring and filled with standard Mel's Mix. One (the farthest away in the attached picture) is producing the best garden I've ever had -- simply amazing results with tomatoes, cucumbers, chard, potatoes, sweet potates, eggplant and bell peppers. The other bed (closest in the picture) is clearly unhappy (low germination rates, signs of nutrient deficiencies, irregular growth patterns and stunting) with corn, green onions, carrots, lettuce, beans, peas and the same species of tomatoes that are flourishing in the successful bed. (I'm getting good results in the unsuccessful bed only with a few square feet of red grano onions.)

I've mixed the approximately 128 cubic feet of planting mix about 18 cubic feet at a time. I'd start with a compressed 3 cu ft peat moss bale (which should technically expand to 6 cu ft), then add 6 cu ft of coarse vermiculite, then 6 cubic ft of mixed compost. The typical batch would include 1.5 cu ft of turkey compost, 1.5 of cheap composted bark, 1 of chicken manure compost, 1 of cow manure compost and 1 of mushroom compost. Once the beds were nearly full, I mixed about 40 lbs of worm castings into the top six inches of each bed. All products were common bagged brands from big box or farm supply stores.

I tested both beds with the local extension service and found the following:

Successful bed: (elemental unit = ppm)
pH 7.35
P 1150
K 1276
Ca 7487
Mg 1856
Na 343
S 46
Cu 4
Zn 65

Unsuccessful bed:
pH 7.20
P 510
K 661
Ca 6672
Mg 1316
Na 220
S 28
Cu 7
Zn 61

Clearly, I need to drop the pH on both beds. I'm assuming that my peat moss wasn't as compressed as I estimated and I ended up with a larger proportion of compost in my mix and not enough peat to drop the pH below 7. I'm also thinking that some of my compost included manure that was treated with lime to reduce smell, because Calcium levels are crazy high and the pH is elevated. Seems like excess calcium carbonate to me. I'm planning to add more peat moss to bring the pH down because I'm reluctant to add Sulfur with the levels already so high in both beds.

If both beds were giving me problems, I'd look no further, but the fact is that the HIGHEST pH bed is performing beautifully at 7.35 while the 7.20 bed is unhappy. Plus, 7.2 isn't THAT bad. So I'm reluctant to decide it's just a pH thing. The nutrient levels are super high in both beds but that's normal for Mel's Mix and if the problem was that the levels were TOO high, why is it that the highest levels are in the successful bed? The beds are side by side with virtually identical sun exposure. They receive the same water at the same time of day for the same length of time.

I'd appreciate some expert opinions on this. What am I missing? What do you think about the plan to add peat versus raising the Sulfur levels even higher? Anyone out there have similar problems and find a solution?

Thanks in advance for your help! :)

Follow-Up Postings:

RE: Looking for expert help with Mel's Mix

My extension report comes with recommendations. The county agent might be helpful. I personally love the basic theory of sfg but I find the MM way too complicated and expensive. I just use equal parts of peat and a quality organic compost mixed into my native soil and then add a 10 10 10 fertilizer on a regular basis. From your photograph it's hard to tell what you mean by "unsuccessful". Your irregular corn growth? The way the middle is tall and the sides short, that could be a shading issue or a water issue or combination and not necessarily soil. "Boxed" raised beds are hard to water evenly. The edges tend to dry out.

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