Soil conditions related to a deficiency of phosphorous:
mineral soils low in organic matter
long history of cropping without adequate levels of P
erosion of phosphorous-rich soils
calcerous soils: alkaline conditions reduce P availability (calcerous soils are mostly/partly composed of calcium carbonate (CaCO3); soil having a water pH of 8.2 or more, due to fee calcium carbonate in soil; also, containing lime or being chalky)
Soils frequently fertilized with phosphorous tend to be deficient in zinc (Zn)
Phosphorous primarily moves through soil by diffusion
Available phosphate is positively correlated to brix (high phosphate = higher brix)
soil factors that affect uptake of phosphorous in the plant:
temperature
the level of decomposition of organic matter
soil test levels
low pH (acidic) soil decreases phosphorous uptake by plants
plant factors that affect phosphorous uptake by plant:
hybrid or variety of plant
stage of growth
interactions with zinc (Zn) or manganese (Mn) and other elements
Roles of phosphorous in the plant:
involved in energy transfer reactions as part of ATP (adenosine triphosphate)
involved in genetic information processes as part of RNA and DNA
is also a component of various enzymes and proteins, and phytin
Sources for Phosphorous:
organic debris, plant residues, and microorganisms are the major sources of phosphorous
Phosphorous Deficiency Symptoms:
purplish color on the lower leaves
overall stunted growth
Phosphorous is very mobile within the plant, so deficiency symptoms will first show in the older leaves, since the plant is moving P from older leaves to newer growth to supply growing points
Phosphorous content in leaves naturally declines with maturity of the plant, so some symptoms of deficiency are normal in those older leaves, as the plant ages
Phosphorous Excess Symptoms:
excess phosphorous can interfere with the metabolism and uptake of zinc