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Majed Abu-Zreig 《Journal of Soils and Sediments》2006,6(3):137-144
Background Several types of organic polymers with various molecular weights and surface charges are produced for various industrial
and agricultural purposes, and recent studies have shown that high molecular weight anionic polymers are the most effective
in reducing runoff and soil loss. However, anionic polyacrylamide (PAM) is marketed under various commercial names with variable
molecular weight and length according to its chemistry (Barvenik 1994). Consequently, its interactions with soil and efficiency
in reducing soil erosion are expected to vary. Moreover, types of PAM other than those recommended for erosion control may
also be effective in reducing soil erosion.
Objectives The objective of this research is to test the influence of 9 types of polyacrylamide (PAM) on water infiltration and soil
loss of an arid silt loam soil under simulated rainfall conditions.
Method logy. Nine types of organic polymers varied in surface charge, ranging from +20 to –75, and molecular weight ranging from
very low to very high were used in this study. Soil plots with dimensions of 60 cm by 120 cm having moderate slope of3 to
5% were constructed in the field and equipped with runoff collection installations. A specific type of PAM was spread on soil
plots at a rate of 10 kg/ha. Rainfall was supplied from a drip type rainfall simulator at constant intensity and duration
of 80 mm/h and 50 min, respectively. Runoff, infiltration and soil loss were measured for each plot subjected to a specific
type of PAM and compared to control plots.
Results and Conclusions Land application of PAMs significantly increased infiltration prior to runoff but had insignificant effect on total infiltration
volume and final infiltration rate under the present experimental conditions. Experimental results confirmed that anionic
polymers were more effective in reducing soil loss than that of non-ionic or cationic polymers. In fact the cationic, low
molecular weight and low surface charge non-ionic PAMs had insignificant effect on soil loss. High molecular weight anionic
PAM with 30% surface charge (A-130) was more effective(46% reduction) than those having a high molecular weight and a lower
surface charge of 20% (A-110 and A-120) with an aver-age soil loss reduction of 24%. The PAM A-836, described assoil erosion
polymer with 20% surface charge and high molecular weight, reduced soil erosion by 41%. Unexpectedly, the anionic PAM with
low molecular weight but very high surface charge was also effective in reducing soil loss (47% reduction).
Recommendations and Outlook Land application of PAM improves water infiltration and highly reduces soil erosion thus improving agricultural production.
Application of PAM could be the only viable way to improve arid land farming. It seemed that various types of PAMs, other
than those specifically produced for erosion protection can be used to combat soil erosion. This means that farmers in poor
countries can use any type of PAM that is available to them to improve agricultural production. 相似文献
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Chergui M 《Science (New York, N.Y.)》2006,313(5791):1246-1247
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Water harvesting is viable alternatives for rainfed agricultural production in semiarid lands. A field experiment was conducted to evaluate the efficiency of a relatively new water harvesting technique, called sand ditch, for moisture and soil conservation. Twelve field plots of 10 m × 2 m were constructed in two adjacent fields having silt loam soils but varied in soil depth, 0.75 m and 2 m, and slope of 10% and 12%. A 130 L barrel was installed at the downslope end of the plots to collect water and sediments at the end of each rainstorm along the rainy season. Three types of treatments were used in duplicates (12 plots in total); sand-ditch plots in which a ditch of 2-m long, 1 m wide and 0.8 m deep was constructed in the middle of plots across the slope (2 in each field), two compacted plots and two plots covered with plastic mulch in addition to four control plots, 2 in each field. The total amount of runoff, sediment concentration, total infiltration and sediment loss for the experimental plots were measured or calculated after each storm during the winter season 2004/2005. Experimental results showed that sand-ditch technique significantly reduced runoff and sediment loss and increased infiltration and soil moisture compared to control or compacted plots. The overall average runoff and sediment reductions in the sand-ditch plots were 46% and 61% compared to control plots. Sediment losses from compacted plots were about 2.2 and 6 folds higher than control and sand-ditch plots, respectively making soil compaction unsuitable technique for rainfall harvesting under the current experimental and climatic conditions. Construction of sand ditch also increased the dry matter yield of native grass by an average of 62% and 40% in the two experimental fields compared to control. 相似文献
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A total of 100 poultry farms in northern and middle areas of Jordan were sampled to investigate the bacteria associated with airsacculitis in broiler chickens. Of 170 bacterial isolates, 88.2% were identified as Escherichia coli, 8.8% as Ornithobacterium rhinotracheale, and 3% as Bordetella avium. Fourteen serotypes of E. coli were identified among 66 typeable isolates and the remainder were untypeable. The most prevalent serotypes were O1, O8, and O78. The main serotype of O. rhinotracheale was serotype A. Experimental inoculation of O. rhinotracheale via intravenous, intratracheal, and intra-air sac routes resulted in growth retardation, thickening in the air sacs, arthritis, and liver necrosis. Reisolation of O. rhinotracheale from the air sacs, liver, trachea, heart, and spleen at day 7 postinoculation confirmed its role. In vitro susceptibility testing revealed that E. coli isolates were sensitive to gentamicin and colistin, O. rhinotracheale to tetracyline, and B. avium to most of the nine antibiotics examined. 相似文献
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