Sunny Slope Orchard

Sunny Slope Orchard
In the coast range foothills overlooking the Sacramento Valley

Wednesday, April 6, 2011

Promoting Balance in the Orchard

It is now early April and we're nearing the end of a very wet rainy season. The cover crop on the orchard floor has flourished, growing tall and dense. Starting in early winter the thick growth of bell beans, vetch, field peas and mustard helped to capture rain runoff and prevented erosion.

Once in the bloom phase the cover crop has attracted and nourished many types of beneficial insects which help keep harmful pests in check.

Just about any flowering plant will attract insects and other creatures both good and bad. The key to natural pest control is to promote a diverse biological environment so natural predators can help keep harmful insects and animals in check. In the photo at left a bell bean plant is infested with black aphids. These aphids do not attack fruit trees, but they do attract lots of green lacewings and lady bugs, which are then present to control the green aphid that does infest fruit trees. And sure enough this plant is covered with dozens of lady bugs and their larvae (the larvae are the alligator like creatures).

Another benefit of a good cover crop is natural soil fertility. Besides mining the soil for deep minerals, the legumes in the mix have the wonderful ability to add nitrogen to the soil. So called nitrogen fixing bacteria in the soil colonize the roots, forming the white nodules shown at right. These bacteria live in a symbiotic relationship with the plant, capturing nitrogen from the air. When the plant dies, excess nitrogen is then available for other crops, in this case the fruit trees.

But as the rainy season ends it is time to conserve as much soil moisture as possible to see the trees through the dry months ahead. So I've just mowed down the cover crop to stop it from drinking up any more of winter's rainfall. I use a flail mower which chops the growth into a uniform layer of mulch. This residue will soon dry to a straw color, reflecting sunlight and keeping the tree roots cool while reducing evaporation from the soil surface. The decaying roots and mulch will now be digested back into the soil in nature's continual process of cycling nutrients from plant to soil to plant again.

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