Trickle irrigation of cotton: Effect on soil chemical properties

The management of soil salinity and sodicity in the root zone (0–150 cm) of Panoche clay loam soil was studied during three consecutive growing seasons in a field experiment designed to determine the water requirement of Acala SJ-2 cotton (Gossypium hirsutum L.) under trickle irrigation in the western San Joaquin Valley of California. The trickle irrigation treatments (20, 40, 60, 80 and 100% of the previous day's pan evaporation, PE) were imposed on each of three preplant furrow irrigation depths of 0, 190 and 380 mm. The electrical conductivity, EC, of the irrigation water ranged from 0.4 to 0.5 dS m⁻¹ unless groundwater had to be mixed with the surface supply; this practice raised the EC to 0.6–0.9 dS m⁻¹ for short time periods. The unadjusted sodium adsorption ratio, SAR, of the irrigation water averaged < 4.Soil salinity, as measured by EC_e, was < 5 dS m⁻¹ and sodicity, as measured by SAR_e, was < 15 in the root zone. Changes in these soil chemical properties were more related to the amount of preplant irrigation at the lower (< 40% PE) trickle-irrigation levels than at the higher levels. Results suggest that soil salinity and sodicity can be maintained at acceptably low levels by appropriate preplant irrigation with consideration to amount of winter rainfall; even when during the season only sufficient trickle irrigation is given to meet crop water requirements without regards to leaching needs. The lint cotton yields over the 3-year period ranged from 357 to 1542 kg ha⁻¹; the corresponding applied water ranged from 175 to 744 mm.