Squash growing experience

I mainly added two secondary macronutrients: calcium and sulfur, and two micronutrients: boron and molybdenum to my one acre. A total of 500 lbs ag lime, 280 lbs gypsum, 25 lbs borax and 1 lb sodium molybdate. I plan on ordering one more ton of lime this fall. It was based on my soil and weather conditions and history of harvests/mineral removal so it may not apply to others.

I started the garden in a grassy area presumably cleared from the upland oak/black walnut forest. Soil is acidic and low in most things. So after adding lots of organic matter, things were thriving in the first few years, growing food seemed easy. I mistakenly assumed fertility would stay high that way with regular addition and recycling of organic matter but the system started to get less and less effective.

I did some modeling and it fits if one or more trace elements are depleting faster than others. First I suspected boron, because most OM I got was grass based and monocots have low boron content (<10ppm in dry weight). Vegetables I grow are largely dicots that need 10x more boron (10-100ppm). Squash in particular, has a really high toxicity threshold (1000 ppm). So when I grew lots of squashes, they had been accumulating boron in the leaves. Those leaves decompose quickly at the end of the season, but my weather is too cold to grow dicot covercrops to recycle the boron but not cold enough to retain it in ground. Over time the ratio drops to a point it is limiting plant growth and can't be corrected from organic input alone.

Similarly, my soil has low molybdenum in the first place, being highly leached and acidic. Local trees all have very high tannin to help them retain and recycle Mo. BTW, Mo is the least abundant essential element (1 to a million to nitrogen), and the only micronutrient that availability is reduced when pH drops and the only one that can be mobilized to the seeds. So after lots of harvests and removing clippings, Mo became so low at one point clovers were gone and beans and brassicas looked sickly with poor quality seeds. Perennials including fruit trees started a slow death as well. The more nitrogen added, organic or not, just made things worse. I did a small quantitative rescue test and the Mo needed was equivalent to a 50# bag of alfalfa pellet (3ppm Mo DW) per 10 sq ft. Again, not feasible in large scale.

I guess for most people with decent soil, adding mature derived from legumes leaves or seeds would be sufficient. I am just having a too low base line to start with. I wish I had those minerals added to the soil before gardening but luckily it's never too late. After I amended the soil, legume, cool season broadleaf and deep-rooted weeds reappeared in my yard, earth worms returned and moles areated the ground. I then just followed the usual organic practices of chop and drop, composting, inoculating biochar with weed tea etc and things are back to normal.