Performance of cotton crop grown under surface irrigation and drip fertigation. II. Field water-use efficiency and dry matter distribution

Abstract

ABSTRACT Drip fertigation is a key factor in modern irrigated agriculture, where water and fertilizers are the most expensive inputs for this irrigation method. Drip fertigation experiments were carried out at Hama, north of Syria (Tezeen's Irrigation Research Station), for four consecutive years 1995–1998. Cotton (Gossypium hirsutim L.) variety Aleppo 33/1 was planted after unfertilized maize in order to deplete as much as possible the available N and reduce the field variability on the corresponding experimental units and irrigated thereafter. Treatments consisted of two irrigation methods (surface irrigation, and drip fertigation) and five N rates within drip fertigated cotton, including the control (N0 = 0, N1 = 60, N2 = 120, N3 = 180, N4 = 240 kg N ha- 1). The N fertilizer treatment for surface irrigated cotton was 180 kg N ha−1 in accordance with the recommended rate of Ministry of Agriculture and Agrarian Reform. The experimental design was randomized block design with six replicates. Fertigation resulted in large water saving, and highly improved field water-use efficiency. Further, increasing N application rates under drip fertigation increased dry matter yield. The principal benefit of drip fertigation was the achievement of higher field water-use efficiencies, which were increased more than three-fold for both dry matter and seed cotton yield, relative to surface irrigation. The highest water-use efficiencies were obtained with the addition of 180 and 240 kg N ha−1 in 1995 and 1996 and 120 kg N ha−1 in 1997 and 1998. Dry matter production and partitioning among different plant parts at physiological maturity stage varied due to N input and irrigation methods. The overall dry matter distribution among different plant structures for drip fertigated-treatments was: stems, 20.3–21.3%; leaves, 26.3–28.7%; and fruiting forms, 50–53.2%. For the surface-irrigated treatment, the partitioning was stems, 23.1%; leaves, 28.3%; and fruiting form, 48.6%. The reproductive–vegetative plant parts ratio decreased with increasing N input under drip fertigation. Water saving under drip fertigation exceeded 35% of irrigation water relative to surface irrigation of the cotton crop grown under the same conditions.