Document Type : Research Paper
Irrigation Department, Shiraz University, Shiraz, I.R of Iran.
Soil water, salinity and nitrogen content are three major factors affecting crop
production in arid and semi-arid areas. This study was performed in two years of
2009 and 2010 in a semi-arid area in order to investigate the effects of irrigation
water quantity (as main plot), quality (saline water, as sub-plot), nitrogen fertilizer
(as sub-sub plot) and their interactions on growth and yield of maize hybrid SC-
704. The experimental design was split plot with three replications. Irrigation
treatments consisted of I1 (1.0 crop evapotranspiration (ETc) + 0.25ETc as
leaching), I2 (0.75I1) and I3 (0.5I1) applied at 7-day intervals. The salinity
treatments were 0.6 (fresh water), 2.0 and 4.0 dS m-1. There were also three
nitrogen (N) treatments including 0, 150 and 300 kg N ha-1. The results showed
that maize under water and salinity stress had longer vegetative stage period by 11
and 16% compared to the control, respectively. The most sensitive trait under
water, salinity and nitrogen stress was grain yield (GY) which reduced by 52.3,
25.2 and 28.0%, for treatments of 0.5I1, 4.0 dS m-1 and 0 kg N ha-1, respectively.
Based on water productivity (WP), applied water is more efficient for GY
production under lower irrigation and N fertilizer usage. Grain yield surface
function approached a maximum under I2 and I1 treatments in response to
increasing water and N levels. The contour plots of GY were developed at each
salinity level and showed that it could be a useful management device of irrigation
and N for maize GY. Based on nitrogen use efficiency (NUE) and nitrogen
recovery (NR), the N application rate of 150 kg ha-1 was the optimum rate for the
study region especially under saline water conditions. Further, interaction result of
the experimental factors showed that with adequate or limited fresh water supply,
application of higher N rate (300 kg ha-1) yielded higher GY. While under saline water application, lower N rates (150 kg ha-1) was appropriate management for
optimum maize GY with sufficient/non-sufficient irrigation. Furthermore, the
threshold values of soil saturation extract, 50% GY reduction, and yield reduction
coefficient of maize showed that in general maize did not tolerate salinity better
under higher N application rate (300 kg ha-1), although in some cases its sensitivity
to salinity decreased by increasing N application rate.
Keywords: Agronomic response; Maize; Nitrogen; Saline water; Salinity indices.