This study evaluates the potential for adaptability and tolerance of wheat genotypes (G) to an arid environment. We examined the influence of drought stress (DS) (100, 75, and 50% field capacity), planting times (PT) (16-November, 01-December, 16-December and 01-January), and G (Yocoro Rojo, FKAU-10, Faisalabad-08, and Galaxy L-7096) on phenological development, growth indices, grain yield, and water use efficiency of drip-irrigated wheat. Development measured at five phenological growth stages (GS) (tillering, jointing, booting, heading, and maturity) and growth indices 30, 45, 60, and 75 days after sowing (DAS) were also correlated with final grain yield. Tillering occurred earlier in DS plots, to a maximum of 31 days. Days to complete 50% heading and physiological crop maturity were the most susceptible GS that denoted 31–72% reduction in number of days to complete these GS at severe DS. Wheat G grown with severe DS had the shortest grain filling duration. Genotype Fsd-08 presented greater adaptability to studied arid climate and recorded 31, 35, and 38% longer grain filling period as compared with rest of the G at 100–50% field capacity respectively. December sowing mitigated the drought and delayed planting effects by producing superior growth and yield (2162 kg ha−1) at severe DS. Genotypes Fsd-08 and L-7096 attained the minimum plant height (36 cm) and the shortest growth cycle (76 days) for January planting with 50% field capacity. At severe DS leaf area index, dry matter accumulation, crop growth rate and net assimilation rate were decreased by 67, 57, 34, and 38% as compared to non-stressed plots. Genotypes Fsd-08 and F-10 were the superior ones and secured 14–17% higher grain yield than genotype YR for severely stressed plots. The correlation between crop growth indices and grain yield depicted the highest value (0.58–0.71) at 60–75 DAS. So the major contribution of these growth indices toward grain yield was at the start of reproductive phase. It's clear that booting and grain filling are the most sensitive GS that are severely affected by both drought and delay in planting.

Synthetic herbicides are posing problems owing to the development of weed resistance and emerging debate on their associated health hazards and ecological threats. Allelopathic manipulations are evolving as applicable substitutes for weed management in agroecosystems. In order to assess the efficacy of potential allelopathic water extracts from different plant species, field experiments were conducted during 2010 and 2011. Sorghum bicolor L., Helianthus annuus L., Brassica napus L., Oryza sativa L., Zea mays L. and Morus alba L. aqueous extracts in different combinations alone or along with a reduced dose of herbicide were evaluated for weed suppression in a maize crop. A weedy check and two herbicidal treatments, S‐metolachlor + atrazine (pre‐emergence) and atrazine alone (early postemergence), were included for comparison. Sorghum, brassica or sunflower tank‐mixed with 25% of the recommended dose of atrazine significantly suppressed the total weed density and dry biomass, along with a concomitant decrease in the crop resistance indices and treatment efficacy indices over the control. The weed density and dry biomass that were recorded at 60 days after sowing showed a strong negative correlation, while the leaf area index, crop growth rate, dry matter accumulation and net assimilation rate predicted a strong positive correlation, with the stover and grain yield of maize.

Understanding the critical period of weed competition is indispensable in the development of an effective weed management program in field crops. Current experiment was planned to evaluate the critical growth period ofSetaria and level of yield losses associated with delay in weeding in rain-fed drip irrigated wheat production system of Saudi Arabia. Field experiment was conducted to evaluate the effect of weeding interval (07-21, 14-28, 21-35, 28-42 and 35-49 days after sowing) and drought stress (75% and 50% of field capacity) on Setaria growth, wheat yield and water use efficiency. Season long weedy check and wellwatered (100% FC) plots were also maintained for comparison. Weeding interval and drought stress significantly (p ≤ 0.05) affected the growth and yield of Setaria and wheat. Drought stress from 75% to 50% FC resulted in reductions of 29-40% in Setaria height, 14-27% in Setaria density and 11-26% in Setaria dry biomass. All weeding intervals except 35-49 DAS significantly suppressedSetaria growth as compared with control. Delay in weeding increased weed-crop competition interval and reduced wheat yield and yield contributors. Therefore, the lowest yield of 1836 kg ha-1 was attained for weeding interval of 35-49 DAS at 50% FC. Water use efficiency and harvest index increased with decreasing FC levels but reduced with delay in weeding. Correlation analysis predicted negative association ofSetariadensity with wheat yield and yield contributors and the highest negative association was for harvest index (-0.913) and water use efficiency (-0.614). Early management of Setaria is imperative for successful wheat production otherwise yield losses are beyond economical limits.

Abstract. This study was conducted at the Agricultural Research Station, King Abdulaziz University at Hada El-Sham during 2007 and 2008 seasons to improve the seed yield of sesame (Sesamum indicum L.) in the Makkah Region, Saudi Arabia. Split plot design with four replications was used in this study. Main plot treatments were four nitrogen rates (0, 100, 150 and 200 kg N/ha) and the sub plot treatments were three diverse sesame cultivars, Saudi Local cv., Egyptian cv. "Shandaweel" and Sudanese cv. "Sudan-1". The obtained results of the combined analysis of the two seasons showed significant interaction effects on the flowering date, plant height, No. of branches/plant, No. of fruits/plant, seed weight/plant and seed yield/ha, while no significant effects were found for the N fertilizer rate × cultivar interaction, nitrogen fertilizer or sesame cultivars on seed oil content.Saudi Local cv. under the 150 and 200 kg N/ha produced the highest significant seed yield/ha comparing with the other treatments. Seed yields/ha were 862.47 and 869.45 kg/ha for Saudi Local cv. under the 150 and 200 kg N/ha, respectively. Shandaweel cv. occupied the 2 nd rank concerning seed yield/ha with 733.37 and 729.89 kg/ha under 150 kg N/ha and 200 kg N/ha, respectively. Sudan-1 cv. produced the lowest seed yield under the different nitrogen fertilizer rates. Oil contents of the three cultivars were 45.37, 45.96 and 45.80%, for Saudi Local cv., Shandaweel cv. and Sudan-1 cv., respectively.

Previous research results of Blue Panic (Panicum antidotale Retz) in arid conditions under different irrigation methods proved an increase in forage yield and water productivity (WP) under full and water stress conditions. However, a thorough search in the literature revealed that its water requirement has not yet been determined. Therefore the objective of this research was to measure evapotranspiration (ET c ) and crop coefficient (K c ) for a Blue Panic crop under arid conditions. Four draining lysimeters constructed in Jeddah (21°48 0 3 00 N, 39°43 0 25 00 E) were used to measure its ET c and K c under a plentiful water supply. Results revealed that ET c varied from 141 mm in the first harvest to 292 mm in the sixth, with an average of 225 mm per harvest. The K c value was different from one harvest to another. The average K c over all harvests was 0.7, 1.2, 1.3 and 1.0 for the initial, development, midseason and late stages, respectively. Average fresh and dry forage yields per harvest were 30.5 and 12.6 t ha À1 , respectively. Average WP was 55 kg ha À1 mm À1 . The predicted ET c based on the measured crop coefficient value and ET 0 show a good fit between measured and calculated ET c . RÉSUMÉDes résultats de recherches antérieures sur le panic bleu (Panicum antidotale Retz) en conditions arides sous différentes méthodes d'irrigation ont prouvé une augmentation du rendement fourrager et de la productivité de l'eau (WP) dans des conditions de stress hydrique et des conditions de fourniture complète. Cependant, une recherche approfondie dans la littérature a révélé que son besoin en eau n'est pas encore déterminé. Par conséquent, l'objectif de cette recherche était de mesurer l'évapotranspiration (ET c ) et le coefficient de culture (K c ) pour la culture de panic bleu dans des conditions arides. Quatre lysimètres drainés construits à la station expérimentale agricole de l'Université du Roi Abdulaziz située à 110 km au nord-est de Djeddah (21°48' 3" N, 39°43' 25" E) ont été utilisés pour mesurer ET c et K c sous fourniture complète. Les résultats ont révélé que ET c variait de 141 mm dans la première récolte à 292 mm dans la 6ème récolte avec une moyenne de 225 mm per récolte. La valeur de K c était différente d'une récolte à l'autre. Le K c moyen sur toutes les récoltes était respectivement de 0.7, 1.2, 1.3 et 1.0 pour les stades initial, de développement, mi-saison et tardif. Les rendements par récoltes fourragères moyennes fraîches et sèches étaient respectivement de 30.5 et 12.6 t ha À1 . Le poids moyen était de 55 kg ha À1 mm À1 . Il y a un on ajustement entre l'ET c prédite sur la valeur de coefficient cultural et l'ET c mesurée. † Mesure des besoins en eau des cultures et du coefficient culturales du panic bleu en des conditions arides, avec des lysimètres drainés.

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Effects of 3 industrial activities on the concentrations of toxic metals (Cd, Cr, Ni and Pb) and micro-nutrients elements (Fe, Cu, Zn and Mn) in the leaves of 2 and 4 years old Ziziphus trees grown closed to these industrial areas were studied during March 2013. The highest Cd, Cr, Ni and Pb concentrations in the Ziziphus leaves were found in the trees closed the paints, chemical and paper industrial sectors with values of 4.56, 8.69, 6.15 and 48.47 mg/kg, respectively, while the trees in the control area had 1.09, 1.16, 1.34 and 6.27 mg/kg, respectively. The sector of mineralization, plastic and building materials was the highest in Fe, Cu, Zn and Mn emission pollutants accumulated and absorped by the tree leaves. The 4-years old tree leaves were significantly higher than the 2-years old tree in all studied toxic and micro-nutrients elements.

-Growing concerns about toxicity and development of resistance against synthetic herbicides have demanded looking for alternative weed management approaches. Allelopathy has gained sufficient support and potential for sustainable weed management. Aqueous extracts of six plant species (sunflower, rice, mulberry, maize, brassica and sorghum) in different combinations alone or in mixture with 75% reduced dose of herbicides were evaluated for two consecutive years under field conditions. A weedy check and S-metolachlor with atrazine (pre emergence) and atrazine alone (post emergence) at recommended rates was included for comparison. Weed dynamics, maize growth indices and yield estimation were done by following standard procedures. All aqueous plant extract combinations suppressed weed growth and biomass. Moreover, the suppressive effect was more pronounced when aqueous plant extracts were supplemented with reduced doses of herbicides. Brassicasunflower-sorghum combination suppressed weeds by 74-80, 78-70, 65-68% during both years of study that was similar with S-metolachlor along half dose of atrazine and full dose of atrazine alone. Crop growth rate and dry matter accumulation attained peak values of 32.68 and 1,502 g m for brassica-sunflower-sorghum combination at 60 and 75 days after sowing. Curve fitting regression for growth and yield traits predicted strong positive correlation to grain yield and negative correlation to weed dry biomass under allelopathic weed management in maize crop.