No abstract

Boron sufficiency supply to plant in calcareous soils of arid regions is severely reduced under arid climatic conditions. Therefore, this study was conducted to determine the effect of Boron (B) fertilization on yield of Wheat grown in calcareous soils of arid regions. Boron was added at two rates namely 0 and 0.5 mg B kg-1 soil to three most common textured class’s soils. Straw and grain yield was determined on oven dried basis. B content of plants was determined as well. Straw and grain yield of wheat was significantly increased by (67.0 and 87.1%), (24.5 and 82%) and (64.5 and 48%) under the addition of 0.5 mg B Kg-1 soil over that of no B addition to clay, loam and sandy loam soil, respectively. Results also showed that wheat grown on the coarse-textured soil had the least B uptake per pot compared to loam and clay textured soils. B content in straw and grain was increased by (77.4 and 121%), (81.2 and 157%) and (184 and 96.9%) under B addition compared to those of zero B addition to clay soil, loam soil and sandy loamy soil, respectively. Response to B addition, significantly, increased in all soils due to increase of available B content in soils which may suggest the importance of adding adequate rate of B application under cropping system of arid regions.

Depleted Uranium (dU) is usually used in the weapon to increase its destruction power inflected to the target. Therefore, this study was conducted to detrmine the effect of of a range of dU concentration in the soil an incident of the desrruction of military tank in southern part of Iraq on radioisotope content in soil and in tomato plant grown in the area. The dU concentration in the incident spots located in Safwan destrict close to Jabel Sanam, north of Rumala oil field was 4000 mg Kg-1 in the soil. The soil also was found to contain a considerable level of 234Th, 226Ra and 40K. Tomato growth was reduced with the increase of dU concentration compared to those grown in same soil of no dU content. It even has failed to grow in the soil with high level of dU. Tomato plant uptake of 238U as determined by radioactivity of its direct daughter 234Th was found to increase with the increase of dU concentration in soil. The dU concentration higher than 500 mg kg-1 soil was lethal to tomato plant.

The current study was conductedas a pot experiment to determine the effect of soil texture on biological nitrogen fixation (BNF) of six most efficient local isolates, specified, of Bradyrhizobium. Cowpea (Vignaunguiculata L.), as a legume host crop, was used as a host crop and 15N dilution analysis was used for accurate determination of the amount of N biologically fixed under experimental parameters specified. Soils used are clay loam, sandy clay loam and sandy loam. Biological Nitrogen Fixation (BNF), in different soil textural classes, was as in the following order: medium texture soil > heavy texture soil > light textured soil. Statistical analysis showed that there is a significant variation in BNF % among six Iraqi isolates in the three soil textural classes. There is a significant variation in the number of the nodules of the six Isolates in one soil texture. However, nodules number does not agree with the BNF% in the same soil for any isolates. Statistical analysis of the data showed that there were significant differences in plant dry weight among the soil textural classes all over local isolates used in this study. Data also showed that there were significant differences in dry weight under different isolates.

The objective of this study was to determine the efficiency of biological nitrogen fixation (BNF) of local Bradyrhizobium isolates in soil of various fertility levels using 15 N dilution technique. Local isolates were obtained from cowpea rhizosphere in fields of different Iraqi provinces. Six isolates were selected in this study, which was conducted as a pot experiment under greenhouse conditions. Effects of the following fertility levels were evaluated: at F1, 0 mg N, P and K was added; at F2, 25 mg N/kg soil, 10 mg P/kg soil and 25 mg K/kg soil were added, respectively; the other two levels were F3 at which 50, 20 and 50 mg/kg soil and at F4 75, 30 and 75 mg/kg soil for N, P and K, respectively, were added. Urea, labeled with 15 N 10% access atom (aa), was used as a source of N. The highest BNF was observed under the lowest fertility level, i.e., F1. BNF across all isolates was markedly decreased with the increase of nutrient application to soil, being totally eliminated at the highest fertility level F4. Numbers of nodules per plant root of all isolates were the least under the zero nutrients application and the highest nodules number were found under the highest levels of N, P and K application. Number of nodules does not necessarily reflect the best BNF efficiency of all isolates. However, fertility levels were of significant effect on average nodule number of all isolates. The lowest plant dry weight was under the first fertility level F1 irrelevant of Rhizobium isolates. In general, the highest plant dry weight was under the second soil fertility level F2.