shahrzad kabirinejad

Preceding crops as a source of organic matter are an important source of micronutrient and can play an important role in the soil fertility and the micronutrients cycle of soil. In addition to the role of the organic matter in increasing the concentration of micronutrients in soil solution, attention also should be paid to the role of the kind and the quantity of the root’s exudates that are released in response to the incorporation of different plant residues in the rhizosphere. Present research was conducted with the objective of studying the effect of the kind of preceding crops: Trifolium (Trifolium pretense L), Sofflower (Carthamus tinectirus L), Sorghum (Sorghum bicolor L), Sunflower (Heliantus annus L) and control (fallow) on the chemical forms of copper in the wheat rhizosphere and the bulk soil and Cu uptake by wheat and also investigating the correlation between the fractions of Cu in soil and Cu uptake in wheat.
The present research was conducted as split plot in a Randomized Complete Block design (RCBD) with 3 replications and 5 treatments, in field conditions. In the beginning, the preceding crops were cultivated in the experimental plots and after ending growth, preceding crops were harvested. Then the wheat was cultivated in the experimental plots. Finally, after harvesting the wheat, soil samples were collected from the two parts of the root zone (the wheat rhizosphere and the bulk soil). The soil samples were air dried ground and passed through a 2-mm sieve and stored for chemical analysis. Soil pH (in the soil saturation extract) and organic matter (Walkley–Black wet digestion) were measured in standard methods (1). The Total Organic Carbon (TOC) was measured by Analyzer (Primacs SLC TOC Analyzer (CS22), Netherlands). The available Cu in soil was extracted by DTPA and determined using atomic absorption spectroscopy (2). The fractionation of soil Cu was carried out using the MSEP method (3).
The results showed that the preceding crops significantly decreased soil pH, also significantly increased the DOC and DTPA-extractable Cu.These changes were higher in the Trifolium preceding treatment in the rhizosphere soil. Also, the preceding crops significantly decreased Carbonate -Cuand Residual-Cu fractions in the wheat rhizosphere compared with the bulk soil. The preceding crops (except Trifolium) significantly increased Oxide-Cu fraction. The soil Oxide- Cu fraction was higher in the rhizosphere in comparison with the bulk soil. The preceding crops increased the Organic-Cu in both the wheat rhizosphere and the bulk soil and it was higher in Trifolium treatment. The preceding crops increased Cu uptake by wheat and Organic-Cu positively correlated with Cu uptake by wheat.
The Organic-Cu fraction increased in the rhizosphere compared with the bulk soil, whereas Oxide- Cu, Carbonate–Cu and Residual-Cu fractions decreased. According to the results, the observed increase in the copper concentration of organic fraction in the rhizosphere was due to the decrease in the copper concentration of carbonate, oxide and residual fractions. In fact, the main process is the transmission of copper from carbonate, oxide and residual fractions to another fraction. Also, the results showed that the root exudates of the preceding crops and wheat affected the different forms of copper in the soil solid phase. Furthermore, the results of copper forms correlation analysis with Cu uptake by wheat showed that the Organic-Cu fraction had more important role in supplying copper was needed for wheat. Therefore, the preceding crops increased the copper concentration of organic fraction in the rhizosphere compared with the bulk soil, and these changes are associated with increasing the amount of copper uptake in wheat.

Returning crop residue to the soil exerts favorable effects on physical and chemical properties of soil. In fact, the plant residues can affect soil conditions such as pH and important role in soil fertility and cycling of elements in the soil may have. In addition to the role of the organic matter from decomposition of crop residue in increasing the concentration of micronutrients in soil solution is very important.  Present research was conducted with the objective of studying the effect of the kind of crop residues: sunflower (Helianthus annnus L. cv. Allstar), sudan grass (Sorghum bicolor L. cv. Speed Feed), trifolium (Trifolium pretense L.) and safflower (Carthamus tinctorius L. cv. Koseh-e-Isfahan), with control on chemical properties of soil and effect on bioavailable of copper. In this study complete randomized block field experiment, consisting of 3 replications and 5 treatments. After 3 weeks, increasing crop residues, soil samples collected and were used to measure some properties of soil and concentration of Cu in soil. Results showed that crop residues significantly decreased soil pH and the largest increase was observed for Trifolium treatment. EC significantly increased by affected crop residues application. The crop residues significant increased the concentration of dissolved organic carbon (DOC). the largest effect was dependent  for Trifolium treatment. The crop residues significant increased the concentration of DTPA-extractable Cu. The highest effect was obtained for Trifolium treatment. Therefore, Trifolium residues application decreased the amount of soil pH and consequent increase of DOC which in turn elevated the concentration of DTPA- extractable Cu. Trifolium was the most effective in increasing the phytoavailability of Cu in soil.

Returning crop residues into the soil as a source of organic matter are an important source of copper and can play an important role in the soil fertility. In addition to the role of the organic matter in increasing the concentration of micronutrients in soil solution, attention should be also paid to the role of the kind and the quantity of the root’s exudates released in response to the incorporation of different crop residues  in soil.  Present  research was conducted with the objective of studying the effect of the kind of crop residues : Trifolium (Trifolium pretense L) and Sorghum (Sorghum bicolor L), with control on chemical forms of copper in soil solid phase and relationship with bioavailable of copperin a complete randomized block field experiment, consisting of  3 replications and 3 treatments. After 30 days, increasing  crop residues, soil samples collected and were used to measure Cu chemical forms in soil solid phase. Results showed that the crop residues  significant increased the concentration of DTPA-extractable Cu. The highest effect was obtained for Trifolium treatment. Crop residues significantly decreased the concentration of soil Cu-Carbonate and the largest increase was observed for Trifolium treatment. Sorghum  treatment significantly increased the concentration of soil Cu-Oxide in comparison with the control. Concentration of Cu-Organic both in Trifolium and Sorghum  treatments increased as compared with the control. But the highest effect was obtained for Trifolium treatment. Cu-Oxide and Cu-Residual forms showed a significant negative correlation and Cu-Organic form  showed a significant positive correlation with the concentration of DTPA-extractable Cu. Therefore, Trifolium  residues application decreased  the amount of soil Cu-Carbonate and soil Cu-Oxide forms (less soluble forms) and consequent  increase of Cu-Organic which in turn elevated the concentration of DTPA- extractable Cu. Trifolium was the most effective in increasing the phytoavailability of Cu in soil.

The application of biosolid as a fertilizer in agricultural cultivation is a common practice in many countries. This study investigates the effects of sewage sludge and compost usage on soil chemical properties and Zea mays nutrition in comparison with those of iron and manganese sulfate solution. The experiment was carried out in a completely randomized block design with the following treatments: sewage sludge and compost with three levels (0, 25 and 50 t ha−1 ) and iron and manganese sulfate solution (1 g l−1 solution) with three replications.

The application of sewage sludge (50 t ha−1 ) had highly significant (P < 0.01) positive effects on cation exchange capacity and organic matter, total nitrogen, phosphorus, iron and manganese diethylenetetramine-pentaaceticacid-extractable in soil, and nitrogen, phosphorus, iron and manganese in plant. Also, compost application (50 t ha−1 ) increased significantly (P < 0.01) the electrical conductivity in soil and potassium in soil and plant. Dry biomass increased significantly (P < 0.01) from 7.7 to 28.7 g per pot with sewage sludge application (50 t ha−1 ).

Application of biosolid as fertilizer sources has become a common practice in Iran, especially in the agricultural lands. The reuse of these nutrients had some beneficial effects on soil fertility, such as increased cation exchange capacity, pH, organic matter, total nitrogen, phosphorous, iron and manganese. However, these benefits were limited by the presence of some potentially toxic trace metals in biosolid.