JWSS - Journal of Water and Soil Science

---

This research was conducted in Kooshkak Farm Research Station of Shiraz University in 1997 and 1998 in order to determine crop coefficient and water requirements of rice, using lysimeter. The variety used was Champa-Kamfiroozi which is an early mature variety and is grown by most farmers in the area. Results showed that potential evapotranspiration varied from 3.76 to 9.34 mm/day. Penman FAO method was used in calculating reference evapotranspiration. Crop coefficient was 0.97 in the initial growth stage, 1.25 in the mid-season growth stage, and 1.09 at the time of harvest. Total crop evapotranspiration rates in 1996 and 1997 were 560 and 757 mm, respectively. Average deep percolation rates in the growing season was 3.4 and 3.5 mm/day in 1996 and 1997, respectively. Finally the total water requirements of rice in 1996 and 1997 were 1983 and 2361 mm, respectively.

---

Since performing field experiments for determining the optimum amount of water for soil desalinization is costly and time consuming, use of computer models in leaching studies has received more attention. However, the accuracy of the results of these models should be evaluated by comparison with the results of the field experiments. In this study SWAP and LEACHC models were used for the simulation of soil moisture profile and salinity, and the results were compared with those of a field leaching experiment. The SWAP model gave better results in simulating soil moisture movement and profile, compared to LEACHC model, but statistical indexes showed that both models produced satisfactory results in predicting soil moisture profile. LEACHC model gave better results in comparison to SWAP model for the prediction of soil salinity profile at different time, possibly because it takes into account different solute transport mechanisms such as advection, diffusion, dispersion and also chemical interactions such as adsorption, precipitation and dissolution. In spite of the differences between predicted and measured values of salinity in the initial stages of leaching process, both models were able to predict the trend of leaching process with an acceptable accuracy.

---

In order to investigate the effects of moisture stress, nitrogen fertilizer, manure and integrated nitrogen and manure fertilizer on yield, yield components and water use efficiency of SC 704 corn (late maturing, non-prolific and dent). In 2005, a field study was conducted in agricultural experiment station of the college of agriculture, Tarbiat Modares University. The type of design was randomized complete block with factorial arrangement and three replications. For the study, four levels of nitrogen fertilizer (0, 92, 184 and 276 kg N ha-1), integrated fertilizer (46 kg N ha-1 + 2/5 ton ha-1 FYM, 92 kg N ha-1 + 5 ton ha-1 FYM and 138 kg N ha-1 +7/5 ton ha-1 FYM ) and organic Farm Yard Manure (5, 10 and 15 ton ha-1 FYM ) along with three levels of irrigation (optimum irrigation (control), water stress 75% optimum irrigation and water stress 50% optimum irrigation) were used as treatments. The results showed maximum seed yield was produced with 92 kg N ha-1 + 5 ton ha-1 FYM and average of seed yield was 7976 kg ha-1. Maximum corn seed yield resulted when optimum irrigation water was applied and average seed yield was 7041 kg ha-1. When water stress was imposed in 50% and 75% of optimum irrigation, seed yield was decreased by 33 and 12%, respectively. The best seed yield was obtained with interaction of 5 ton ha-1 FYM and optimum irrigation. Also, maximum water use efficiency was obtained in using 50% of optimum irrigation. Maximum water use efficiency was obtained with interaction of 92 kg N ha-1 + 5 ton ha-1 FYM and imposition of water stress in 50% optimum irrigation. Results showed that adequate nitrogen fertilizer slightly increased corn seed yield under stress, and integrated (nitrogen and manure) fertilizer increased corn seed yield under stress. But seed yield greatly increased with optimum irrigation. Integrated fertilizer application increased seed yield even with severe moisture stress. Application of integrated chemical fertilizers and manure produced better seed yield and also decreased the amount of chemical fertilizers and improved soil physical and chemical characteristics.

---

In order to evaluate the interaction effects of nitrogen and organic matter on growth and yield of dryland wheat, an experiment was conducted at the research station of the College of Agriculture, Shiraz University at Bajgah in 2005 and 2006. The experimental design was split plot in which three levels of nitrogen (0, 40, and 80 kg N ha ^-1) were main factors and additive organic matters including liquorice root residue at 15 and 30 Mg ha ^-1, municipal waste compost at 10 and 20 Mg ha ^-1, and wheat residues at 750 and 1500 kg ha ^-1 (all rates equivalent to 50 and 100%) were sub factors. A check treatment (no additive materials) was also included in the experiment. Results indicated that with increasing nitrogen level from zero to 40 and 40 to 80 kg ha^-1, wheat yield increased significantly. Among yield components, number of seeds per spike increased significantly with zero to 40 and 40 to 80 kg nitrogen ha^-1, but number of spikes m^-2 increased significantly only when nitrogen level was increased from zero to 80 kg ha^-1. Compared to check (no additive materials), maximum wheat grain yield (32%) was obtained from 100% compost application. Results of nitrogen and organic matters interaction effects indicated that 100% compost application and increasing nitrogen level from 40 to 80 kg ha ^-1 had no significant effect on dryland wheat yield. This showed the positive impact of compost application on the reduction of nitrogen fertilizer. Thus, it appears that 50% of the required nitrogen fertilizer could be replaced by compost. Applying organic matter increased soil water in both years, however, among organic matters, compost had a more pronounced effect on increasing soil water.

---

Iran, with an average annual precipitation of about 252 mm (413 BCM) and renewable freshwater resources of 130 BCM, has irregular distribution of water resources. With a high population growth rate, agriculture remains the greatest water user in Iran but its production still does not meet the total food demand of the country. Due to unreliable water availability, the competition for water from other sectors and the increasing demand for food and better diets, Iran will experience water stress. In this study, virtual water trade in relation to water resources availability has been assessed as a way of relaxing water stress in Iran. The results showed that from the 21 food products, cereals, pulses, nuts and oilseeds are water-intensive crops according to their estimated virtual water content, while fruits, vegetables and industrial crops are not water-intensive. Considering the volume of virtual water entering the country through food imports, more water will be available for other essential uses. However, the virtual water trade has been developed rather unconsciously regarding water use and crop water productivity during the past two decades. For instance, wheat with a share of 58.5% in the virtual water import to Iran, was the dominant imported crop during 1983-2003. By importing 10.4 Mt of wheat, 11.6 BCM of water has been saved within the country during 1999-2003. However, Iran became self-sufficient in wheat production in early 2005. Consequently, this latest drive for self-sufficiency in the production of wheat, as a water-intensive crop, put tremendous pressure on domestic water resources. The trend in crop trade in terms of quantity and virtual water for other groups of crops has also been shown in the study. Seemingly, crop production and import have been greatly influenced by the weather conditions. With the increasing water scarcity, the role of virtual water in food security is expected to rise continuously in Iran. Thus, conscious virtual water trade as a policy measure in water management and judicious adjustment in agricultural structure will ensure sustainable food security and water availability in Iran.

---

Oil seed rape (Brasica napus) is an important crop, which is cultivated in Iran for oil production. As a management practice deficit irrigation strategy is applied to cope with water shortages, especially during drought periods. This research was conducted to study the effect of water stress on physiological parameter of oil seed rape in the experimental research field of Collage of Agriculture (of shiraz university) during 2004- 2005 and 2005- 2006. Licord cultivar of oil seed rape was planted and experimental design was random block with five treatments and four replications. Treatments were full irrigation in all growth stages, water stress in vegetative stage in early spring, water stress in flowering and podding stages, water stress in grain filling stage and dry land treatment with supplemental irrigation in time of planting. Water stress caused decrease in water potential of plant, an increase in canopy temperature, and decrease in plant height especially in dry land treatment. Leaf area index decreased as water stress increased. The decrease in leaf area index was more severe in vegetative stage water stress treatment. At the end of water stress period leaf area index increased again. Rate of decrease in leaf area index at the end of the growing season was higher in grain filling stage of water stress treatment.

---