Salty, with reference to sodium chloride. Soils can become saline from inappropriate irrigation which allows excessive surface evaporation and salt accumulation. The ancient civilisations of the Tigris-Euphrates Valley declined, in part, from soil salination, but also from soil erosion. Sanitation

Plant sanitation is generally taken to mean the use of clean seed, equipment, and soil, all with a view to reducing plant disease. Sapodilla

See: Manilkara zapota. Saprophyte

Loosely, a saprophyte is an organism that derives its nutrients from dead material, as opposed to a parasite that derives its nutrients from living material. Strictly, a saprophyte is a plant, and any other organism living in this way is a saprotroph. Saturation technique

This is a technique for ensuring that no vertical resistance are functioning during screening for horizontal resistance. For example, it is no longer necessary to use the one-pathotype technique when breeding for resistance to potato blight in the Northern Hemisphere, because the presence of the second mating type (A2) ensures that all vertical resistances will be matched very quickly. Equally, when screening for horizontal resistance to wheat stem rust, the presence of the alternate host, which is barberry, will produce a similar saturation of vertical pathotype. However, it is illegal in some countries to cultivate barberry in this way. Scab

A plant disease that produces scab-like symptoms. For example, potato common scab is caused by the bacterium Streptomyces scabies, and potato powdery scab is cause by the fungus Spongospora subterranea. Scale insects

Members of the Homoptera (aphids, whiteflies, etc.), scale insects are often pests of crops. The first instar is an active insect with legs and antennae, but the subsequent instars are immobile and protected with a scale-like covering. Some species are valuable and are cultivated to produce shellac or cochineal. Scarlet runner

See: Phaseolus coccineus. Schistocerca gregaria

The desert locust. A species of grasshopper that has huge population explosions and very destructive migrations in Africa and the Middle East. A large swarm may conrain a million tons of locusts, and each insect eats its own weight in green matter every day. This is the most destructive of many species of grasshopper with similar habits in various parts of the world. Schlanstedt rye

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