Effect of soil organic matter, electrical conductivity and sodium adsorption ratio on tensile strength of aggregates

The properties of soils affected by salinity and processes involving degradation of soil structure have been partly recognized. However, the effects of saline and sodic conditions on mechanical and physical properties of soils have been studied to a lesser extent. In this research, the effects of electrical conductivity (EC) and sodium adsorption ratio (SAR) on soils possessing various amounts of organic matter were assessed under laboratory conditions. The soils contained a uniform clay type, predominantly Illite. The major difference of the soils was their amount of organic matter content. The treatments consisted of solutions with definite EC and SAR (two levels of EC: 0.5 and 4 dS/m and three levels of SAR: 0, 5 and 15). The amount of tensile strength was dependent on organic matter, EC, and SAR in a way that with the increase of SAR, the tensile strength decreased. In similar SAR, treatments with higher EC exhibited greater tensile strength. Also, the soils with higher organic matter showed greater tensile strength. The analysis of variance showed the significant difference (at 1%) between the mean of parameters analyzed (soil type, sampling depth, EC, and SAR). The order of averages of tensile strength were: permanent pasture (Agropyron elengatum)Festuca arusdinaceae)相似文献   

Effects of foliar selenium application on some physiological and phytochemical parameters of Vitis vinifera L. cv. Sultana under salt stress

Abstract

In this research the effect of foliar application of selenium (Se) at four levels (Na₂OSe₄; 0, 5, 10 and 20?mg L^?1) was evaluated on some phytochemical characteristics of Sultana grapevine under different salinity levels (NaCl; 0 or 75?mM). The vines were fed twice a week with Hoagland nutrient solution and Se was foliar applied twice with 24 intervals. During growing period, plant height, leaf number and leaf area were recorded. Moreover, at the end of experiment, mature leaves from middle nods of canes were used for measurement of some phytochemical indices. According to results, Se application had a positive effect on plant height, leaf numbers, leaf area and photosynthetic pigments content especially at 5?mg L^?1 and to some extent 10?mg L^?1 Se levels. Under salinity stress, foliar application of Se at 5?mg L^?1 considerably decreased vines leaves electrolyte leakage and lipid peroxidation values compared to non se-treated plants under salinity stress condition. Selenium had an additive effect on salinity stress (75?mM NaCl) induced accumulation of total phenol, total flavonoid, soluble sugars and proline content in leave of vines. Moreover, the interaction of salinity and Se at 5 and 10?mg L^?1 improved leaves antioxidant enzymes activities in Sultana grapevine. Likewise, foliar application of Se improved leaf mineral content in 75?mM NaCl -treated vines. Totally, foliar application of selenium (Se at 5 or 10?mg L^?1) increased salt tolerance through improvement in nutritional balance and by enzymatic and non-enzymatic antioxidant capacity in grapevine leaves.     

Carboanhydrase-Aktivität und extrahierbares Zink als Maßstab für die Zink-Versorgung von Pflanzen

Carboanhydrase activity and extractable zinc as indicator of the zinc supply of plants 1. Maize, millet, tobacco, sugar-beet and vine were grown under controlled environmental conditions with different zinc concentrations in the substrate. Plant growth, zinc and phosphorus content of the dry matter, extractable zinc and carbonic anhydrase activity in the leaves were measured. 2. Increasing supply of zinc to strongly zinc deficient plants resulted in a marked increase of growth, whereas total zinc content of the leaf dry matter was only slightly and carbonic anhydrase activity was strongly affected. In extremely zinc deficient plants carbonic anhydrase activity was close to zero even though the zinc content of the dry matter was higher than 10 μg/g. Therefore carbonic anhydrase activity appears to reflect the amount of physiologically active zinc in the leaf tissue. It seems to be useful to decide critical cases even at latent zinc deficiency. 3. The P/Zn ratio is also an indicator of zinc supply when plants are extremely zinc deficient, but not under latent deficiency. Moreover the P/Zn ratio can vary in a wide range when plants are well supplied with zinc. 4. The zinc concentration of aqueous leaf extracts increased with increasing level of zinc. 2-3 μg Zn/ml extract were found to be sufficient for all plant species used and all conditions of growth applied. Apparently, the Zn-concentration of the aqueous leaf extract is a better parameter of zinc supply than total zinc or carbonic anhydrase activity which, in addition, is much more difficult to determine.     

Zinc Uptake by Spinach (Spinacia oleracea L.) as Affected by Zn Application Rate,Zeolite, and Vermicompost

Zinc deficiency in calcareous soils is a serious problem, which may be ameliorated by the application of some soil amendments. A completely randomized factorial experiment was done to investigate the effect of zeolite, vermicompost, zeolite + vermicompost, and Zn application to a calcareous soil on Zn availability, dry weight of spinach (Spinacia oleracea L.), and Zn concen-tration in spinach. Results indicated that zeolite had no effect on soil Zn availability, dry weight, and Zn concentration in spinach. Vermicompost significantly increased dry weight (1.33 g pot^?1) and decreased Zn concentration in spinach (16 mg kg^?1). Application of zeolite + vermicompost significantly increased dry weight (by 2.8 times) and Zn uptake in spinach and it also decreased Zn concentration in spinach less than vermicompost. Zinc application increased Zn concentration in spinach (up to 496 mg kg^?1), but did not affect dry weight except in soils treated with zeolite + vermicompost. Generally, application of zeolite + vermicompost is recommended instead of separate zeolite or vermicompost application for improvement of soil Zn fertility and Zn uptake by spinach.     

Effect of feed restriction early in life on humoral and cellular immunity of two commercial broiler strains under heat stress conditions

1. An experiment was carried out to evaluate the effect of early feed restriction (FR) on immunocompetence of Ross and Arian chickens with separated sexes under heat stress (HS) conditions. 2. Chickens consumed feed ad libitum (AL) or were restricted on alternate days from 11 to 20 d of age. From 35 to 41 d of age, the HS groups were exposed to a high ambient temperature of 39 +/- 1 degreesC for 7 h each day, while the thermoneutral groups (TN) were at 33 degrees C. 3. At 21 and 42d of age, the percentage of CD4+ (helper T cells) and CD8+ (cytotoxic T cells) were determined by flow cytometry. Antibody response to sheep red blood cells (SRBC) and heterophil/lymphocyte (H/L) ratio were determined on d 21 and 42. 4. On d 21, FR elevated the CD4+, antibody titre and H/L ratio, but it decreased the CD8+ T cells. On d 42, HS decreased CD4+, CD8+, and antibody titre, but it increased H/L ratio. Under TN conditions, FR chickens had higher CD4+ than AL chickens. On d 42, FR/HS chickens had higher CD4+ and antibody titre, but they had lower CD8+ and H/L ratio than AL/HS chickens. 5. On d 42, the TN-Ross strain had lower CD4+, but they had higher CD8+ and antibody titres than the TN-Arian strain. On d 42, the HS-Arian strain had higher antibody titres and a lower H/L ratio than the HS-Ross strain. 6. Male chickens had higher CD4+, CD8+, antibody titres and H/L ratios 25 in all treatment groups. 7. In conclusion, FR early in life reduced some of the negative effects of the heat stress on the immune system of broiler chickens when exposed to high environmental temperatures later in life.     

Assessing the effect of administering probiotics in water or as a feed supplement on broiler performance and immune response

1.?Two routes of probiotic administration in broiler farms, in water and in feed, were compared using 360 one-day-old male broiler chickens. Controls received no probiotics or antimicrobials. The water group received a probiotic preparation at a rate of 0·5 g/l, and the feed group received it at an inclusion rate of 1 g/kg.

2.?Performance of broilers in terms body weight gain (BWG), feed intake (FI) and feed conversion ratio (FCR) improved when probiotic was provided via drinking water, compared to the control and feed groups. Probiotic administration reduced plasma cholesterol and triglyceride concentrations.

3.?Spleen (28 and 42 d) and bursa (42 d) relative weights were influenced by method of probiotic administration, which also improved T-cell dependent skin thickness response to phytohaemagglutinin (PHA) injection. The effect of challenge by dinitrochlorobenzene (DNCB) depended on the method of probiotic administration.

4.?The method of probiotic administration can influence the performance and immune competence of birds, and administration via drinking water appears to be superior to the more conventional in-feed supplementation method.     

Ultra-structure of intracellular lipid vesicles of porcine GV-oocytes after in vitro fertilization and parthenogenetic activation

The aim of our investigation was to compare the ultrastructure of lipid droplets in porcine pronuclear oocytes obtained after in vitro fertilization (IVF) or parthenogenetic activation (PGA) of Metaphase II (MII) oocytes. The ultrastructure of lipids in the IVF or PGA pronuclear oocytes after vitrification was also studied. There are two kinds of lipid droplets in porcine GV oocytes: 'dark' and homogenous vesicles next to 'grey' vesicles with electron-lucent streaks. After IVF or PGA and following 16-h culture, only the presence of 'grey' vesicles was detected in IVF and PGA oocytes. Ultra-structure of lipid vesicles of PGA and IVF oocytes was similar. The PGA oocytes can be as model of the two pronuclear stage IVF oocytes.     

Responses of cucumber plant to NH4 and NO3 nutrition: The relative addition rate technique vs. cultivation at constant nitrogen concentration

Different N sources (NO₃⁻, NH₄⁺, or NH₄NO₃) at different relative addition rates (RAR) were supplied to cucumber (Cucumis sativus L.), a species sensitive to NH₄⁺ toxicity. For comparison, cucumber plants were also grown at constant concentrations of 1 and 5 mM NH₄⁺ or 5 mM NO₃⁻. The fresh weight of NH₄⁺-fed plants at RAR 0.15 and RAR 0.25 day⁻¹ was similar to that of NO₃⁻-fed plants, while at RAR 0.35 or RAR 0.45 day⁻¹ growth reduction occurred. When available as a constant concentration, NH₄⁺ decreased plant growth at 5 mM. It is concluded that at low rates of N supply the relative addition rate technique can be used for growing cucumber plants with NH₄⁺ as sole N source without deleterious effects.     

A comparison of root distribution of three hardwood species grown on a hillside in the Caspian forest,Iran

Slope is a complex environmental factor that can subject plants to a number of mechanical stresses. The anchorage of roots and improvement of slope stability mainly depend on specific properties of root systems, such as root distribution. In the present study, 24 trees (from three species) growing on gentle slopes (10–20°) were randomly chosen for root distribution analysis. The profile trenching method was used to obtain root characteristics. The findings indicated that root area ratio (RAR) decreased with depth and that maximum RAR values were observed in the upper layers; RAR values were between 0.0004% and 6.6444%. Average RAR values were not statistically different in upslope and downslope layers except in one case. The dot grid method (100 × 150 mm) usually overestimated the RAR values. The amount of roots decreased with depth following a power law. About 50% and 90% of roots were located in the first 30 and 60 cm depths, respectively. Results of analysis of covariance (ANCOVA) showed a significant effect of diameter at breast height (DBH) on total RAR but not on the total number of roots. About 70% of roots had diameter of less than 10 mm. Spearman’s correlation showed significant negative correlation between the total number of roots and the amount of N, P, and K elements, and a positive correlation between DBH and RAR. The results serve to develop understanding of the biotechnical characteristics of root systems of Caspian species.