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This study was carried out to investigate the effect of treated wastewater on soil chemical and physical properties. Field experiment was conducted in Borkhar region in Isfahan province in central Iran with two water treatments of wastewater and groundwater under sprinkler and surface irrigation systems for three crops of sugar beet, corn and sunflower. Soil samples were collected to 120 cm depth to determine concentration of lead (Pb), manganese (Mn), iron (Fe), cadmium (Cd), nickel (Ni), cobalt (Co), copper (Cu) and zinc (Zn). Irrigation systems had no significant effect on extractable heavy metals in soil. The accumulation of Pb, Mn, Ni and Co in the soil increased significantly in the wastewater treatment as compared to the groundwater treatment. The accumulation of Pb, Mn, Ni, Co, Cu and Zn decreases with the soil depth. Treated wastewater showed no effect on the increase of Fe, Cd, Ni, Cu and Zn during growing season. The irrigation system had a significant effect on infiltration rate, bulk density and total porosity. Under sprinkler irrigation system the infiltration rate increased significantly.

In arid and semi‐arid regions, farmers use low quality groundwater because of limited availability of high quality irrigation water; instead, magnetized water can be used for irrigation given its better quality. Magnetized water is obtained by passing water through permanent magnets or through electro‐magnets installed in or on a feeding pipeline. This study at the Gorgan Agricultural and Natural Resources Research Center, Gorgan province, Iran, investigated soil moisture distribution from trickle irrigation. Treatments were magnetic and non‐magnetic water and sub‐treatments involved the addition of 200 mg/L calcium carbonate and 400 mg/L calcium carbonate with well water providing the control. The experiment was laid out with a complete randomized block design with three replications. Soil moisture around the drippers was measured for 1, 2 and 3 days after irrigation during the 3‐month irrigation period. The results show that the differences in soil moisture for days 1, 2 and 3 after irrigation with magnetized irrigation water were lesser than those for the non‐magnetized irrigation water treatments. Irrigation with magnetized irrigation water caused higher soil moisture compared with the non‐magnetized irrigation water for different irrigation water salinities. The use of magnetized water for irrigation is recommended to improve irrigation efficiency.

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Conventional tillage and planting method for rice (Oryza sativa L.) production in northern Iran is wet tillage (puddling). Effect of different puddling intensities on physical properties of a silty clay soil (Typic Haplodalfs) was investigated under laboratory and field conditions. Changes in soil physical parameters and water requirement for puddling were measured. For laboratory experiments, undisturbed cylindrical soil samples (diameter and height of 50 cm), were used. A laboratory puddling apparatus was designed and constructed. The puddling intensity was measured by duration of puddling. Four levels of puddling intensity were used as: P 0 (no puddling, control), P 1 (low), P 2 (medium) and P 3 (high). For field tests, 12 plots of 8 9 4 m were selected. The first tillage was performed with a moldboard plow and then the plots were puddled with different intensity using a rotary tiller. The results showed that under laboratory conditions, water content of the puddled layers decreased with an increase in settling time. During drying period, P 0 dried faster than P 1 , P 2 and P 3 . Puddling with low intensity in laboratory and field conditions caused bulk density of 0-15 cm soil layer to decrease by 24.07 and 25.45%, respectively. Increasing puddling intensity increased the bulk density. Bulk density increased with time as particles settled after halting the puddling. Bulk density increased with depth as well. Under laboratory conditions, increasing puddling intensity from P 1 to P 2 reduced percolation rate significantly. For all puddling intensities, soil moisture characteristic curves of both field and laboratory samples showed that puddling increased the amount of water retained over the whole range of suctions. More water was needed for P 3 as compared to P 1 and P 2 . Under the laboratory and field conditions, the P 3 required 27.72 and 28.58% more water as compared to P 2 , respectively. Although the mechanisms implemented for puddling were different under laboratory and field experiments, the results were similar. Bulk density, soil moisture content and water percolation rate decreased faster in the puddled soil under field and laboratory conditions. Therefore, to reduce the cost and time, the laboratory method could be used to study the effects of puddling intensity on physical properties of paddy soils. Medium intensity puddling was shown to be the proper tillage practice for paddy fields with silty clay soil.

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