Everything is chemical
When I studied chemistry in college I had to learn about Avogadro’s number. Back then, information was harder to come by, so I never found out about Avogadro’s garden until recently.
Amedeo Avogadro was born in Turin near the western edge of Italy. He became a respected family-man, renowned scientist and professor – a chemically-balanced individual – so we can envision what he grew in his home garden.
Like everyone else in his neighborhood, Avogadro (let’s call him Av) would have grown cardoon, different chicories, tomatoes, thin sweet peppers, long red onions and strawberries. He probably had a hazelnut tree. Being the smartest scientist on his block, he knew his favorite vegetables appreciate particular chemical balances in the soil, and he would have adjusted his mulches and soil amendments accordingly.
When I am in my laboratory studying properties of various gases, I, of course, use Av’s number (6.02214076×10²³ per mole) all the time. You have to. However, not so much in the garden. That’s where the arithmetic is about pine straw, wood ashes, hickory leaves and mulch but in a chemical way.
Strawberries, sweet potatoes and blueberries benefit from a pine straw mulch because they prefer slightly acidic soil. Pine straw also adds healthy texture to soil as it breaks down. Oak leaves are also acidic but break down slowly.
When Av mulched his cardoon with hazelnut leaves, he was adding moderate alkalinity to the soil. Beets, carrots, onions and lettuce also appreciate hazelnut leaves or wood ashes or greensand for a slightly alkaline balance. Asparagus, too. Vegetables varieties might prefer acidic or alkaline soil, but all of them appreciate a healthy dose of neutral amendments that contribute to friability.
Acidity versus alkalinity is measured by pH values. There are dozens of devices you can buy to test your pH, or you can notice what grows nearby. Huckleberries flourish in acidic soil, and they grow all over the hillside around my garden. I mulch blueberries and strawberries with extra pine straw anyway, but the beet bed gets prepped with wood ashes. Raspberry canes get a dose of both just because.
Warning! We are about to go full periodic. The difference in pH is determined by chemicals. Soil amendments you purchase usually have N-P-K numbers (not the same as Av’s number) on the packaging which indicates relative amounts of nitrogen, phosphorus and potassium. If you give tomatoes too much nitrogen, the energy goes toward lush leaves but fewer fruit, so it’s a lesson in balancing your garden and life.
To simplify: Nitrogen generates life in the plant by its chemical reactions with other elements in the soil, but phosphorus stimulates growth and fruit, flower and seed production. Potassium is important for root development and strong stems through which the nitrogen, phosphorus and everything else will flow. It takes a periodic table to raise a pumpkin.
Good sources of nitrogen include manure from your favorite horse, cow, chicken or rabbit. Fish emulsion is good, too. For small gardens, grass clippings are excellent for nitrogen and improving the soil.
A gardener gets phosphorus from rock phosphate or bone meal, but neither of these will be necessary if organic matter has been added to the soil consistently. As mulches decompose, the phosphorus already in the soil becomes more available.
Organic alfalfa hay is a good source of potassium, but I use wood ashes and mulches of all kinds. I apply a mixture of leaves and organic materials in each bed because everything’s different, and the goal is a rich supply of everything the periodic table has to offer. “All together now,” sang the Beatles.
NPK is only the beginning. I haven’t mentioned zinc, calcium, magnesium, iron or boron, but, as Av would have known, the oak leaves that fall onto my garden mean I’ll never have a manganese shortage.