International Research Journal of Natural Sciences (IRJNS)

EA Journals

Crop coefficient


A field study was conducted on clay loam soil at the research farm of The University of Agriculture Peshawar during Kharif 2012 to determine the crop co-efficient of maize using two traditional (V1=Azam and V2=Jalal) and two hybrid (V3=3025W and V4=30K08) varieties having four replicates. Soil moisture was determined by gravimetric method, actual evapotranspiration (ETa) was worked out by field water balance taking into account soil moisture, rainfall, and irrigation water applied. The Potential evapotranspiration (ETo) was estimated by Pan Evaporation method. Crop coefficient (Kc) was determined by dividing ETa over ETo for all growth stages. ETa of traditional maize variety V1 was found lowest and highest for hybrid maize variety V4. Comparison of seasonal ETa of selected maize varieties showed that V2, V3 and V4 had 3, 24 and 34 % higher values compared to V1. ETa of V1 varied between 2.7 to 4.8 mm d-1, for V2 between 2.6 to 5.2 mm d-1, for V3 between 3.3 to 6.2 mm d-1 and for V4 between 3.4 to 6.5 mm d-1. The seasonal ETa of selected varieties V1, V2, V3 and V4 was found 411, 422, 512 and 550 mm, respectively. Results showed that ETa of hybrid varieties was higher as compared to traditional varieties. Kc values of variety V1 ranged from 0.38 to 0.87, for V2 it ranged from 0.38 to 0.91, for V3 ranged from 0.43 to 1.13 and for V4 ranged from 0.47 to 1.19. It was concluded that FAO reported Kc values of a crop are generalized one for a wide range of climate therefore, Kc value of each crop variety should be investigated and used

Keywords: Actual crop co-efficient, Crop coefficient, Reference crop co-efficient and Crop water requirement.

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