Soil–Water–Irrigation Concepts & Scientists

Concept / Term	Scientist(s)	Year	Key Contribution
Soil Water Classification	Briggs	1894	Gravitational, capillary & hygroscopic water
Moisture Holding Capacity	Hilgard	1896	Water retention against gravity
Capillary Potential	Buckingham	1907	Capillary movement in unsaturated soils
Moisture Equivalent	Briggs & McLane	1910	Water retained after centrifugation
Permanent Wilting Point (PWP)	Briggs & Shantz	1912	Plant cannot regain turgidity
Hygroscopic Coefficient	Alway	1913	Water held by oven-dry soil
Soil-Plant-Atmosphere Continuum (SPAC)	Huber	1924	Water movement soil → plant → air
Field Capacity (FC)	Israelsen & West	1922	Water after gravitational drainage
Ultimate Wilting Point	Taylor et al.	1934	Physiological refinement of PWP
pF Scale & Ratio Law	Schofield	1935	Log scale of soil moisture tension
Tensiometer (Irrometer)	Richards & Gardner	1936	In-situ soil water tension
Gypsum Block Method	Bouyoucos & Mick	1940	Electrical resistance moisture estimation
Permanent Membrane Apparatus	Richards	1941	Water retention curve measurement
Parshall Flume	Parshall	1941	Open channel flow measurement
Pressure Plate Apparatus (PPA)	Richards & Fireman	1941	High-tension moisture determination
Total Soil Moisture Stress (TSMS)	Wadleigh & Aiyer	1945	Capillary + osmotic stress
Potential Evapotranspiration (PET)	Thornthwaite	1948	Climatic PET estimation
Residual Sodium Carbonate (RSC)	Eaton	1950	Irrigation water quality index
Leaching Requirement	Richards	1954	Salt control in soils
Drip Irrigation	Simcha Blass	1964	Root-zone controlled irrigation
Water Expense Efficiency	Parihar et al.	1976	Yield per unit water used
Modified Penman Method	Doorenbos & Pruitt	1977	ET estimation standard
Irrigation Scheduling	Doorenbos & Kassam	1979	Climate + soil approach
Surge Irrigation	Stringham & Keller	1979	Intermittent irrigation technique
Effective Rainfall	N. G. Dastane	—	Rainfall contributing to crop use
Available Water Concept	Veihmeyer & Hendrickson	—	FC − PWP
Darcy’s Law	Henry Darcy	—	Water flow through saturated soil
Water Harvesting Term	Myors	—	Arid-zone water conservation
Water Balance Concept	Thornthwaite	—	Surplus & deficit estimation
Book: Irrigation Agronomy	N. G. Dastane	—	Standard irrigation reference
Book: Irrigation Engineering	A. M. Michael	—	Core irrigation engineering text