work will occur over an extended period of time. It is also used on electrical drawings to indicate single- or three-phase power. Their abbreviations are usually as follows: 1PH— abbreviation for a single phase electrical conductor. 3PH—abbreviation for a three-phase electrical conductor.

pH In soil, a measurement of the relative concentration of hydrogen ions; followed by a number. A pH of 7 is neutral. The higher the number is above 7, the higher the alkalinity of the soil. The lower the number below 7, the more acid the soil is. The pH scale is a logarithmic function. Each pH unit represents a 10-fold increase or decrease in relative alkalinity or acidity. A soil with a pH of 6.0 is 10 times more acidic than a soil with a pH of 7.0.

phenology Science dealing with the nexus (connection, link) between climate and periodic biological phenomenon such as flowering, breeding, and migration of plants.

phenotype In botanical terms, being of similar physical makeup as the species, but changed as influenced by environment.

Phillips head The top or driving portion of a screw or bolt that has an indentation shaped like an X to accept a screwdriver with a point that fits into the X indentation (Phillips screwdriver).

other portions of the plant. In woody plants, most bark is formed as this tissue dies and becomes hard.

phillips screws and screwdriver phillips screws and screwdriver phloem The layer (outside of the cambium layer), or the portion of a plant, where tissues conduct organic substances (sugars, amino acids, hormones, vitamins, stored food) from leaves to

(under cambium/ phloem phosphate Any of numerous chemical compounds containing phosphoric acid or a phosphorous compound.

phosphate rock or calcium-magnesium phosphate A fertilizer with about 17% phosphoric acid and about 17% magnesium oxide.

phosphatic Of or relating to phosphate, phosphoric acid, or phosphorus.

phosphoric acid A syrupy tribasic acid used in preparing phosphatic fertilizers.

phosphorus A nonmetallic chemical of the nitrogen family that is a colorless semitransparent, waxy, soft solid; essential to plant and animal life. It is extremely rare in nature as a free form, but is instead found in various compounds, usually phosphates. In fertilizers, this is normally the second percentage listed on a label and has the symbol of P. Plants consistently need this nutrient to sustain growth. It does not leach easily through the soil and should be added to deficient soils. It promotes root establishment and formation as well as flowering. It is commercially available in many forms includ

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