A COMPARISON BETWEEN DRIP AND FURROW IRRIGATION IN COTTON AT 2 LEVELS OF WATER-SUPPLY

Optimal soil water status improves cotton yields by increasing flower production and boll retention and by controlling the time to maturity. Drip irrigation presumably improves the soil water regime thus leading to higher crop yields but the extent of its potential in cotton is unclear. A two-year experiment was carried out on a sandy loam soil at Cordoba, Spain, aimed at comparing drip against furrow irrigation in cotton (Gossypium hirsutum L.). The irrigation methods were tested using a split-split-plot design which included two irrigation amounts and two or three cultivars each year. The advantage of one method over the other varied from year to year. The furrow irrigation treatments yielded significantly more than drip irrigation yields in 1985 but less in 1986. The differences in yield were explained by the crop water relations and the seasonal evapotranspiration. The 1986 results pointed to an advantage for drip irrigation under deficit irrigation conditions. Water application efficiency was 30% higher in the drip irrigation treatments indicating a definitive advantage of this method under limited water supply. Midday leaf water potential fluctuated along the season in both drip and furrow irrigation. The fluctuations were related to the irrigation events but not to the soil water deficit.