Response of New Cotton Variety (Rassafa) to Nitrogen Fertilizer and Partial Rootzone Drying Drip Irrigation

Due to the water shortage and dry Mediterranean condition, determination of water and nitrogen (N) fertilizer requirements is a major challenge for crop production and environment protection. A field experiment was carried out for two consecutive years (2014 and 2015) to evaluate the response of a new cotton variety (cv. Rassafa) to N-fertilizer and drip irrigation.

Treatments consisted of five different N-rates (0, 50, 100, 150, and 200 kg N ha^-1), and three irrigation modes: full irrigation (FI), fixed partial rootzone drying irrigation (FPRD80), and alternate partial rootzone drying irrigation (APRD80). They received 100, 80, and 80% of the seasonal water use, respectively. Cotton was irrigated when soil moisture in the specified active root depth was 80% of the field capacity as designated by the neutron probe.

Results indicated that seed cotton yield (SCY), dry matter (DM), and water productivity (WP) could be optimized at an average N-rate of 140 kg N ha^-1, for the tested cotton cultivar, whatever the irrigation mode used. In contrast to APRD80 mode, the findings showed that both FI and FPRD80 modes exhibited a consistence over years, but with an obvious preference of FI in SCY, DM, and WP.