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The aim of this research was to study and compare release characteristics of copper (Cu) in 2 groups of soils from Guilan province in northern (SNI) and Fars province in southern Iran (SSI) with significant differences in Cu availability and other soil properties. The patterns of Cu release from the soils by ammonium bicarbonatediethylenetriaminepentaacetic acid (AB-DTPA) were studied using 5 kinetic models. Results showed that the power function, simple Elovich, and parabolic diffusion in SSI, and the power function and simple Elovich in SNI, were the best fitted models. The greater rates and magnitude of Cu released from SNI compared with SSI could be interpreted as the greater capability of the former in maintaining Cu concentration in the sufficient range. The difference in Cu release rates was considerable during initial times. Mean initial Cu release rate from SNI was ~3 times higher than that of SSI. The results reveal that the cation exchange capacity (CEC) and pH were the most influential soil factors causing differences in Cu release patterns between these 2 groups of soils. Greater CEC and lower pH in SNI compared with SSI, are mainly responsible for greater initial rates of Cu release in the former. Difference in CEC and pH of these 2 groups of soils was mainly attributed to different soil organic matter, carbonate content, and clay mineralogy. Additional keywords: copper release, cation exchange capacity, pH, kinetics., Introduction Copper (Cu) availability is low in uncontaminated soils, and deficiencies of this element have been reported in some soils (Lehman and Hatter 1984). In most agricultural soils, Cu availability [...]

In the present study, the effects of different cadmium (Cd) levels of irrigation water (0, 5, 10 and 20 mg L-1) on corn plants (foliage) under different irrigation intervals (1, 3, and 7 days) were investigated. Clear Cd toxicity symptoms appeared on the plants at the end of the experiment. The results showed that stem dry weight (DW) followed by transpiration (T) and plant height were the measured plant parameters most sensitive to increasing Cd levels of irrigation water. In addition, Cd reduced water uptake by corn and led to more soil moisture. The results also demonstrated that corn might produce more shoot biomass with Cd application, which should be taken into consideration if no visible symptoms of Cd toxicity and considerable amounts of the metal uptake are present. Cadmium application through irrigation did not show a marked impairment in the nutrient status of the plants. Moreover, accumulation of Cd in the leaves was more than the stems by 24, 56, and 27% at 1, 3, and 7-day irrigation frequencies, respectively. Also, corn stem was found to be more sensitive to Cd than leaf. The results showed that corn might be used for phytoremediation of Cd under optimum moisture conditions and light contamination of the soil. Furthermore, shoot Cd concentration followed an asymptote pattern as a function of soil Cd, which was expressed by a plateau-type model under each irrigation interval. [ABSTRACT FROM AUTHOR]

The interaction of salt and water stress to infect the roots by Macrophomina phaseolina, and affect the ion composition and growth of sorghum (Sorghum bicolor) was studied in a greenhouse experiment (19-35°C). Treatments consisted of 4 levels of salinity (0, 1400, 2100 and 2800 mg of NaCl kg-1 soil) and three water stress levels (3, 7 and 10 irrigation intervals). Infested soil containing 100 viable microsclerotia g-1 of a melon isolate of M. phaseolina and non-infested soil were used for all treatments. The experiment was arranged in a completely randomized design with four replications. Six-week-old sorghum seedlings after their transferring to infested and non-infested soil were exposed to salt stress, after which, water stress was started. Shoot dry weights were reduced by increasing salinity levels. This reduction was more pronounced in infested soil than in non-infested. Increasing irrigation intervals reduced salt injuries. Shoot and root colonization by M. phaseolina significantly increased by increasing salinity levels up to 1400 mg of NaCl kg-1 soil. Moreover, salinity and M. phaseolina interaction increased the concentrations of Na+ and Cl- compared to salt stress per se, but negatively correlated with increasing irrigation intervals. Concentration of K+ was in contrast with Na+ and Cl-. Also, disease symptoms appeared only in the highest irrigation intervals (7 and 10 days). Consequently, more infected crown and root were observed by increasing irrigation intervals and NaCl levels up to 1400 mg kg-1 soil. [ABSTRACT FROM AUTHOR]

Most agricultural soils in Iran are usually low in organic matter (OM). Therefore, increasing OM in these soils is of great concern. Environmental pollution caused by chemical fertilizers has created an interest in the integrated use of organic wastes with inorganic fertilizers. The main purpose of this greenhouse study was to evaluate the impact of two organic wastes and phosphorus (P) on the growth, and elemental composition of spinach (Spinacia oleracea L.) and soil chemical properties. Treatments consisted of four levels of municipal waste compost, MWC (0, 1, 2, and 4%), five rates of poultry manure, PM (0, 1, 2, 3, and 4%), and three P levels (0, 25, and 50 mg kg−1 as KH2PO4). Application of P and MWC alone or in combination significantly increased the top dry weight of spinach. However, spinach growth was markedly increased up to 3% PM and suppressed with the higher rate, probably due to an excess of soluble salts in the soil. Moreover, the enhancing influence of P on spinach seedling growth was more pronounced at lower levels of MWC and PM. Plant P concentration tended to increase with increasing P, MWC, and PM application rates, whereas nitrogen (N) concentration was only affected by the two organic wastes treatment. Manganese (Mn) concentrations decreased, and copper (Cu), lead (Pb), and cadmium (Cd) increased by soil P application. However, P addition significantly decreased zinc (Zn) concentration only in MWC-treated spinach. Spinach plants enriched with either of the two biosolids accumulated more Mn, Zn, Pb, Cd, chloride (Cl), and sodium (Na) than control plants. Furthermore, spinach grown on MWC-amended soil contained higher Mn, Zn, Cu, and Pb and lower N, Cl, and Na than those raised on PM-treated soil. Postharvest soil sampling indicated that application of the two biosolids significantly increased concentration of soluble salts, (ECe), OM, TN, NaHCO3-extractable P, and DTPA-extractable iron (Fe), Mn, Zn, Cu, Pb, and Cd. [ABSTRACT FROM AUTHOR]

Iron (Fe) deficiency is common in calcareous soils. Application of FeEDDHA is effective in correction of Fe deficiency in such soils. However, it may decrease concentration and uptake of some micronutrients including manganese (Mn). The effect of Fe on Mn status of different soybean [Glycin max (L.) Merr.] genotypes was studied in a greenhouse experiment in a completely randomized design with three replicates. The treatments consisted of three Fe levels (0, 2.5, and 5 mg Fe kg−1 as FeEDDHA) and 12 soybean genotypes. Results showed that application of Fe increased top dry weight of Wells, Black hack, Elgin, and A3237, but decreased that of Steel and A3935 and had no effect on other genotypes. Addition of Fe increased concentration and uptake of Fe, but decreased that of Mn in all genotypes. The Fe:Mn ratio greater than 0.4 in plant tops when both Fe and Mn were in the nutrient sufficiency range were considered to be an indication of tolerance to Fe deficiency, as these genotypes did not respond to Fe fertilizer. Regression equations showed that the highest reduction of Mn concentration occurred at 2.5 mg Fe kg−1. Manganese concentration was reduced by 13, 17, and 19% due to the dilution effect only in Black hack, A3237, and Elgin, respectively. Iron application did not cause either Fe toxicity in soybean or suppression in root:shoot ratio. It seems that Fe addition reduced Mn concentration in some soybean genotypes probably either by reduction of Mn concentration and/or translocation of Mn from root to shoot. The fact that soybeans are highly sensitive to Fe and Mn deficiencies and use of expensive FeEDDHA might accentuate Mn deficiency or imbalance in soybeans demonstrates a need to screen out and select soybean genotypes resistant to Fe stress. [ABSTRACT FROM AUTHOR]

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