Agriculture Reference
In-Depth Information
Temperature
Plants grow in a certain temperature range, which varies depending on where the plant
evolved. When it gets too hot, they manufacture proteins to protect themselves, and start
breathing more quickly, which means they're releasing more water, which in turn cools
them. We simulate this when we spray a little bit of water on the leaves during a very hot
afternoon. We used to think the water drops magnified the sun and burned the plants, but
more recent research shows this isn't the case.
Before it gets too cold in the fall, annual plants have produced seed and died, perennials
and other deciduous plants have stored their nutrients back in their stems and roots before
discarding their leaves, and other chemical changes have occurred.
But what about the soil? In the soil, most microbes don't get to work until it's warm
enough for them. The overall metabolic activity of the soil food web doubles for every 18
degree Fahrenheit (10 degree Celsius) increase in temperature. This means nutrients in the
soil become available to plants in the spring just when they need them, although there may
be a temporary deficiency in certain nutrients until certain microbes get moving. Phosphor-
us is the most important example of this. Mycorrhizal fungi are major suppliers of phos-
phorus to most plants and they need relatively warm temperatures to get to work. Foliar
fertilizers can be useful during these times because they're quickly taken up by plants.
We also want to have enough air in our soil so that it warms up quickly in the spring. A
compacted, wet soil stays cooler much longer. Traditionally, some farmers would throw
rocks or other substances such as charcoal on their fields to melt the snow more quickly. In
our garden, we may temporarily rake the mulch layer aside so the air and sun can more
quickly warm the soil. We also want to promote a dark, organic soil that absorbs more heat,
and we want a mulch layer in the winter to protect the soil from freezing temperatures, and
in the summer to protect the soil from the heat. Organic matter — a crucial component of
soil health — may even disappear too quickly in the summer if the soil becomes too hot.
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