Soil Chemistry & Fertility
Part 2 – 66 | Unit 2.2
t figUre 2 .10 | the NItRoGeN CyCLe (ADAPteD FRom mIChIGAN StAte UNIVeRSIty exteNSIoN BULLetIN e-2646)
- Phosphorus (P)
a) Physiological role in plant development
P is present in all living cells, including as nucleic acids (DNA and RNA), as part of
phospholipid cell membranes, and as molecules for energy storage and transfer (AtP).
P also stimulates early growth and root formation, hastens bloom time, and promotes
seed production and size. It is used in protein synthesis and is found in legume nodules.
b) Soil nutrient imbalances
P must be balanced with N both in the plant and in the soil. In the soil, P and N compete
to be taken up. Because N is highly mobile and P is one of the least mobile nutrients,
excessive N availability can cause a P deficiency, even if there is enough P in the soil for
the crop.
Phosphorus deficiency symptoms in plants include:
i. Slow growth, stunting
ii. Purplish coloration on foliage of some plants
iii. Dark green coloration with tips of leaves dying
iv. Delayed maturity
v. Poor grain, fruit, or seed development
Cathy Genetti ReinhardLecture 2: Plant Nutrient Requirements & Nutrient Cycles