Premium
Exploring the potential contribution of irrigation to global agricultural primary productivity
Author(s) -
Ozdogan Mutlu
Publication year - 2011
Publication title -
global biogeochemical cycles
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.512
H-Index - 187
eISSN - 1944-9224
pISSN - 0886-6236
DOI - 10.1029/2009gb003720
Subject(s) - primary productivity , productivity , agriculture , irrigation , environmental science , agricultural productivity , water resource management , primary (astronomy) , agricultural economics , natural resource economics , geography , agronomy , ecosystem , ecology , economics , biology , archaeology , macroeconomics , physics , astronomy
The potential contribution of irrigation to global agricultural net primary productivity (NPP) was explored using the Carnegie Stanford Ames Approach (CASA) model, modified for irrigation inputs. Excluding the effects from cultivar choice, fertilizer application, and water availability, removing climatic constraints to productivity through irrigation has the potential to increase carbon uptake by global cropland areas (which already have an average carbon uptake rate in excess of 175 gC/m 2 /yr) by an average of 25 gC/m 2 /yr with a maximum of 627 gC/m 2 /yr, especially in heavily irrigated semiarid areas such as northern India, the Indus River Valley, northeast China, the western United States, and the Nile River Valley. When accumulated across all irrigated areas and years, the total contribution of irrigation could exceed 0.40 Pg C per year, a value equivalent to the total NPP of U.S. croplands (0.41 PgC). The results also reveal that the relationship between cropland productivity affected by irrigation and climatic moisture availability is nonlinear: in locations that receive less than 1500 mm/yr rainfall, cropland productivity has a strong response to moisture; as humidity increases, additional moisture has very little impact on the productivity of crop areas. Moreover, the relationship between irrigation amount and productivity increase is also nonlinear: in humid locations, NPP response to irrigation is small but persistent; as aridity increases, irrigation has a substantial impact but its effect quickly saturates for irrigation input above 800 mm/yr, which may point to the efficiency of irrigation for different precipitation regions.