Issue link: https://read.dmtmag.com/i/473131
www.goodfruit.com GOOD FRUIT GROWER MARCH 15, 2015 45 The growing roots of grasses and weeds add organic matter, leading to soft stable soil, with plenty of air and water for roots. PHOTOS COURTESY JUDITH TISDALL AND BAS VAN DEN ENDE Pulverized soil with little organic matter to hold it together is easily eroded by wind. Nutrients are lost to the trees. down to the groundwater away from the roots. However, the orchardist still needs to add inorganic fertilizer to make up for nutrients removed at harvest. What is soil organic matter? Organic matter in soil ranges from fresh unchanged organic materials to highly decomposed organic materials. So the organic matter consists of soil biota (living organisms and roots), plant fragments, and polysaccharides, proteins, fats, lignin, waxes, resin, humus, and charcoal. Where does organic matter come from? Most organic matter is found in the surface soil, where most of the roots are, and so comes mainly from plants and soil biota. Normal, healthy roots continually release organic exudates into soil. Other plant residues, such as leaves and shoots, plus organic mulch or manures added by the orchardist, also contribute to organic matter in soil. Soil biota and decomposition of organic matter Soil biota in the orchard include roots and beneficial and harmful organisms, ranging from the smallest viruses (0.25 micron) to bacteria (0.3 micron) to actinomycetes (0.5 to 2 microns wide) and fungi (less than 15 microns wide) to the largest animals, e.g., earthworms (more than 10 mm wide). Altogether, the soil biota can weigh up to 21 tonnes per hectare (8.5 tons per acre). Soil biota use the organic residues for food and energy and successively decompose complex organic