EFFECT OF NITROGEN FERTILIZER AND SUPPLEMENTARY IRRIGATION ON YIELD AND QUALITY OF SOME LOCAL BREAD

Wheat production under climate of northern Iraq depends mainly on annual rain quantity and its distribution. Generally the annual rate is low and poorly distributed ,as a result the yield is low and unstable. Accordingly it has been suggested that small amounts of supplementary irrigation (SI) can alleviate the adverse effects of such unfavorable rain pattern, moreover the optimum dose of nitrogen fertilization is an important factor boosting wheat production and improving quality. The purpose of this study was to investigate the effect of nitrogen fertilizer and abridged (SI) on yield and grain quality. Field experiments were performed during the growing season 2003-2004 at two locations laying out as split-split plot design in RCBD, involving four promising bread cultivars as sub-sub plot, two levels of N fertilizer (zero and 80 kg N/ha) as sub-plot under rainfall alone and with (SI) as a main plot added at booting and heading stages at a rate of 25 mm for each stage. The results showed that N fertilizer had a significant effect on grain yield, grain protein content at both locations. The (SI) affected significantly number of grain/spike, grain yield, the interactions between factors were significant for most characters. INRODUCTION Wheat (Triticum aestivum L.) is the major cereal crop grown in Iraq, especially at northern regions mostly under rain fed condition therefore wheat production depends greatly on annual rainfall amount and distribution . At Ninevah governorate where the study was conducted the annual rainfall is about 350-500 mm and were usually poorly distributed, so the yield are rather low and unstable , the average of wheat yield under rainfall conditions for 1993-2003 was 179 kg/donum with great scattering range comprise from 51.3 to 415.3 kg/don. in 1999 and 2001, respectively (Statistic Issue, 2003), information of previous studies showed that small amount of supplemental irrigation may alleviate the adverse effects of unfavorable rain pattern and leads to improve and stabilize wheat yield (Garabet et al., 1998b; Oweis et al., 1998; Oweis et al.,2000; Adary et al., 2002) . The aim of adding (SI) was to raise the productivity of wheat which suffering from shortage of moisture, for example the rain water use efficiency was raised from 9.1 to 15 kg/ha/mm by adding 68 mm of (SI) in Iraq (Adary et al., 2002) other results showed that addition of 73 mm of (SI) raised the productivity of wheat to about 67% in Jordan, adding 36 mm of (SI) raised the productivity to about 46% in Syria (Nosaif, 2002), (SI) as a practice is still unusual by local farmers, and they are unfamiliar with such system, therefore researches needs to optimize such practices. In addition to (SI), nitrogen fertilization was extensively used to improve yield and grain quality of wheat, but the response for nitrogen depends on rainfall amount or on irrigation, usually Mesopotamia J. of Agric. (ISSN 1815-316X) Vol. (34) No. (4) 2006 sufficient amount of rain or irrigation raise the nitrogen use efficiency (Engel et al.,1993; Engel et al., 2001; Garabet et al. 1998a). Part of Ph. D thesis of the first author Received 29/5/2006 , accepted 16 / 8 / 2006 Furthermore, the response of wheat to nitrogen and irrigation depends on cultivars (Ottman et al., 2000). The agriculture extension should play a role in transferring such results to farmers for adoption. According to literatures reported studies of the relationships between (SI) and nitrogen fertilization on wheat grain quality are rare, therefore the objective of this investigation was to study the effect of nitrogen fertilization and accompanying irrigation and their interaction on some grain quality properties and growth in addition to yield of four local promising bread wheat varieties (three of them are recently released). MATERIALS AND METHODS Field trails were carried out in 2003-2004 growing season at two locations (Mosul and Telkaef 30 km north Mosul), The experiments were designed as a split-split plot in RCBD with three replications, each replicate comprised of 16 plots (1×3) meters; 50cm apart and 150cm between irrigated and un-irrigated plots. Four promising bread wheat cultivars i.e. Abu-Ghraib/3, Tamouz/2, IPA/99 and Iraq were assigned to sub-sub plot, two nitrogen rates namely zero and 80kg N/ha as urea 45% N) were partitioned in two equal doses, the first dose was added during seed sowing and the second was added at tillers stage, as sub-plot , under rain alone and with (SI) as a main plot ; (SI) was applied at booting and heading stages at a rate of 25 mm for each stage using perforated bucket to resemble sprinkler irrigation. Telkaef field was sown before fall first rain at 2011-2003, while Mosul field was sown at 11-12-2003 after fall of approximately 75 mm rain. The seeds were sown in plots as 5 rows, 20 cm between rows at a depth of 3-4 cm and at a rate of 100 kg/ha. The recorded characters were plant height, number of effective tillers/m and grain yield kg/ha. The obtained grains from each treatment were sieved and cleaned manually. Grain nitrogen content was determined by using Micro Kjeldahl method according to (AACC 46-11, 1976) the crude protein percentage was calculated by multiplying the nitrogen percentage by nitrogen factor(5.7). Grain sample for each treatment was prepared and tempered to 15.5% moisture, thereafter, 100g of tempered wheat was ground using (Quadrumat Junior Mill, Germany), and finally sodium dodecyle sulphate sedimentation was calculated according to Axford et al.(1979). RESULT AND DISCUSSION Yield components: Application of nitrogen resulted in insignificant enhancement in number of spikes/m, number of grain/spike at both locations (Tables, 1and 2), similar results have been reported by Alkaff and Ba-Momin (1998) and Singh et al.(2003). Supplemental irrigation led to a significant increment in number of grain/spike and insignificant increment in number of spike/m at Telkaef which was planted 22 days before Mosul site. Such results were argued by Al-Ma-mury (1986) Al-Rawi and Al-Hadethi (1988) and Alam et al.( 2003 ). Cultivars showed significant differences in these characters at both Mesopotamia J. of Agric. (ISSN 1815-316X) Vol. (34) No. (4) 2006 locations, IPA-99 variety recorded highest number of spike/m at Telkaef site, while Iraq cultivar gave highest value for number of grain/spike at both locations which was significantly different from other cultivars this was related with reduction in number of spike/m which led to minimize the competition on nutrient absorption from soil and those synthesized in plant as well. These results are in general agreement to those of Klar and Hossokawa (1996) and Saleem et al. (2003) . The effect of interaction between irrigation and fertilizer was insignificant for number of spikes/m at Telkaef location, although it caused a remarkable increment with (SI) or N fertilizer or both which was significant at Mosul location, maximum number of spike/m was recorded for the combination of (SI) with N fertilizer which was (341.8-380) spikes/m at Telkaef and Mosul respectively, number of grain/spike was increased at both locations with (SI) alone or (SI) with N fertilizer which reached 51.28 and 42.51 at Telkaef and Mosul, while least number of grain/spike was recorded with no irrigation and fertilizer which was 42.72 and 39.07 for both locations, respectively. The interaction between irrigation with cultivars was significant for most characters at both locations. IPA-99 gave highest number of spike/m with (SI) at Telkaef, while Abu-Ghraib-3 was superior to other cultivars at Mosul site. The Least values were recorded for Iraq cultivar at both locations. This was inversely reflected on number of grain/spike, therefore, Iraq cultivar gave the highest number of grain/spike at both locations, as a result of decrease in number of spike/m and weak competition on nutrient, the reverse was true. The interaction of fertilizer with cultivars behaved similar trend of the interaction of (SI) with cultivars. The second order interaction (cultivars × nitrogen × irrigation) showed that number of spikes/m, number of grain/spike increased gradually by adding N fertilizer, supplemental irrigation or both for all cultivars. Grain yield: Grain yield increased significantly due to nitrogen application at both locations (Table 3), the percentage of such enhancement was 13.02% and 8.6% at Telkaef and Mosul site respectively . These results were confirmed by Ottman et al. (2000); Al-Haidary (2003); Boehm et al.(2004); and Hossain et al.(2004). Table (1) : Effect of Nitrogen level, supplementary irrigation, cultivars and their interaction on number of spike/m. Water level Nitrogen level Wheat cultivar Water level x nitrogen level Water level means Nitrogen means AbuGhraib3 IPA-99 Tamouz-2 Iraq