Thursday, May 17, 2012

sustainable farm

The barn was part of the original farm that the Valle Crucis Conference Center now leases to the Sustainable Development Program. The barn houses tools, farm implements (including a biodiesel powered tractor), a composting toilet, chickens and our barn cat Belatrix.
Cold frames are a way to extend the season. They can be of various sizes and materials; we have built ours from recycled wood and windows. Unlike the greenhouse, the cold frames have no thermal mass to collect heat during the day and radiate it out at night. The soil does act as a solar collector, though. We have successfully grown lettuces and other greens without frost bite on the leaves. Draping a layer of Remay over the plants inside the cold frame on very cold nights (< 150 F) gives some extra protection and traps some of the soil warmth to keep the plants comfortable.
The modified passive solar greenhouse is a conventional hoop-style greenhouse that we have changed a bit to better capture the winter sunlight for heating the structure. The main (long) axis is East-West, so that more sun can reach into the structure during the winter. The North side is insulated with Tekfoil (bubble-wrap coated with aluminium foil on both sides). There are 20 50-gallon drums filled with water serving as thermal mass; they soak up sunlight as heat during the day, and radiate the stored heat at night to warm the interior. Even on a very cold night, the interior stays 200 F warmer than the ambient outdoor temperature without any backup heat source. It does dip below freezing on very cold nights, but this is not a problem when growing cold-hardy crops such as lettuces, arugula, chard and onion starts. And nothing taste better than an organic locally grown salad during the winter!!
The farm uses a variety of materials and methods to build the soil and feed the creatures living in her. Our main material is the food waste compost prepared at the ASU physical plant (a mix of pre- and post-consumer food wastes composted in a wood chip basis). We also compost our own crop wastes and byproducts on the farm, and include chicken litter and horse turts when available. All beds not having overwintering food crops are planted with cover crops (winter wheat, seed rye, clovers, alfalfa and hairy vetch) during the winter, while about 20% of the beds are planted with buckwheat, Sudan grass, clover, millet, cowpeas or soybeans during the summer months. In addition to protecting the soil and trapping end-of-season leftover nutrients, cover crops add fertility to the soil when they are plowed under. We also use some cover crops as living mulches (white clover) or as 'dead' mulches (rye/vetch or wheat/crimson clover) to provide a ground cover for crops such as tomatoes, peppers and squashes. Mulches keep the soil cool and moist, and diminish 'soil splash' of fungal spores that can cause crop diseases (eg. late and early blights).
The bulk production rows allow crops to be grown on a larger scale for sale at local markets.

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