Soil degradation due to global warming, water scarcity and diminishing natural resources negatively impacts food security. Soil fertility deterioration, particularly phosphorus (P) deficiency, remains a challenge in the arid and semi-arid regions. In this study, field experiments were conducted in different geographical locations to investigate the effects of organic amendments coupled with P fertilization and irrigation on soil physical-chemical properties, and the growth, yield and quality of wheat. Application of P fertilizers combined with organic amendments mitigated soil salinity, increased organic matter content, available water, hydraulic conductivity and available macronutrients, but decreased soil bulk density. Application of organic amendments slightly increased total Cd, Ni and Pb in soil, but Cd and Ni concentration was below allowable limits whilst Pb reached a hazardous level. Soil P fractions were significantly increased with the combined application of mineral P and organic amendments irrespective of salinity and irrigation. Crop growth yield and quality of wheat improved significantly in response to the integrated application of mineral P and organic amendments. In conclusion, the combination of mineral P sources with organic amendments could be successfully used as a costeffective management practice to enhance soil fertility and crop production in the arid and semi-arid regions stressed with water scarcity and natural resource constraints. Saline soils are an important natural resource but the area of degraded saline soils worldwide has rapidly increased due to climate change and limited rainfall, which poses a great challenge to global food security 1,2. This problem may be solved through a targeted remediation program of such soils. Deficit irrigation (DI) is also projected to increase soil salinity and sodicity, particularly in the arid and semi-arid climatic regions 3 , requiring proper management strategies to alleviate soil degradation. Contamination of soils with heavy metals has become a global concern, due to potential hazardous impacts of these elements on soil quality, crop yield and quality 4 , and food safety and human health 5. Application of organic amendments was reported to remediate saline soils, alleviate salinity and sodicity stress on crops 6 , and reduce toxicity of heavy metals 4. Some organic amendments contain heavy metals, and their application benefits require further studies 7. Organic amendments could improve soil properties by accelerating leaching of sodium and other salts and reducing exchangeable sodium percentage (ESP) 8. Moreover, organic amendments enhance soil biological and enzyme activities and increase organism

Climate change poses a serious threat to arid and low-elevation coastal zones. Kafrelsheikh Governorate, as a large agricultural and coastal region on the Egyptian North Nile Delta, is one of the most vulnerable areas to higher temperature and global sea-level rise. Two DSSAT wheat models (CERES and N-Wheat) were calibrated using a local cultivar (Misr3) grown under irrigated conditions in Egypt. Experimental data of two successive growing seasons during 2014/2015 and 2015/2016 were used for calibration using different treatments of irrigation, planting dates and fertilization. Both models simulated the phenology and wheat yield well, with root mean square deviation of <10%, and d-index >0.80. Climate change sensitivity analysis showed that rising temperature by 1 ᵒ C to 4 ᵒ C decreased wheat yield by 17.6%. However, elevated atmospheric CO 2 concentrations increased yield and could compensate for some of the negative temperature responses. Sea-level rise by 2.0 m will reduce the extent of agricultural land on the North Nile Delta of Egypt by ~60% and would create additional challenges to wheat production in this region.

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Investigating the potential impacts of climate change on food security is a major global concern, but there has been insufficient attention to these issues in arid regions. Therefore, two wheat models (DSSAT: CERES and N-Wheat) were calibrated with two local cultivars (Gemiza9 and Misr1) and baseline simulation were compared with different scenarios of simulations using three Global Climate Models (GCMs) for 2030, 2050 and 2080.Probable impacts of climate change were assessed using three GCMs and the two crop models under the high emission Representative Concentration Pathway (RCP8.5). Results predicted decreased wheat grain yields by a mean of 8.7, 11.4 and 13.2% in 2030, 2050 and 2080, respectively, relative to the baseline yield. Negative impacts of climatic change are likely, despite some uncertainties within GCMs (i.e. 2.1, 5 and 8 %) and CMs (i.e. 2.2, 6 and 9.2 %).Changing the planting date with a scenario of plus and minus 5 and 10 days from the common practice was assessed as a potential effective adaptation option and this may partially offset the negative impacts of climate change. Delaying the sowing date by 10 days (from 20 November to 30 November) was the best scenario decreased the further reduction in wheat yields resulting from climate change to 5.2, 6.8 and 8.5% in 2030, 2050 and 2080, respectively, compared with the 20 November scenario.. Early planting date scenario with 5 days had less effect on adapting climate change, meanwhile 10 days early scenario had negative effect, increasing yield reduction under climate change. The cultivar Misr1 showed higher resistance to rising temperature than Gemiza9. Despite the hazard impacts of climate change on wheat production, water use efficiency would slightly increase. The ensemble of multi-model estimated impacts and adaptation uncertainties of climate change can assist decision-makers in planning climate adaptation strategies.

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