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Ingold M.,University of Kassel | Al-Kindi A.,University of Gottingen | Jordan G.,University of Kassel | Dietz H.,Royal Gardens and Farms | And 2 more authors.
Organic Agriculture | Year: 2015

Animal manure is one of the major nutrient and carbon (C) sources in many low to medium input systems of irrigated agriculture in subtropical drylands, particularly if managed under the constraints of organic regulations. Under year-round hot and irigated conditions, high losses of C, nitrogen (N) and other nutrients may lead to soil quality deterioration and reduced crop yields. In an effort to develop approaches slowing down decomposition of soil applied manure, activated charcoal (AC) and quebracho tannin extract (QT) were either fed to goats or directly mixed with manure prior to application in a 2-year field experiment conducted with sweet corn (Zea mays L.) and radish (Raphanus sativus L.) in the Batinah Plain of Oman. Sun-dried faeces of goats fed AC had a 15 % higher C concentration and a 25 % higher C/N ratio than pure goat manure, whereas QT feeding only increased sodium (Na) concentration. While sweet corn performed best under equivalent mineral fertilization, the addition of AC and QT to goat feed or to goat manure reduced growth and development of sweet corn by 20 and 30 %, respectively, compared to pure goat manure, regardless of the application method. Radish yielded highest when fertilized with either pure goat manure or AC-amended goat manure, whereas mineral fertilizer and QT-amended manure applications inhibited its growth. Activated charcoal may be a promising additive to increase soil organic matter and increase soil fertility, if it does not hamper nutrient supply to crops. Quebracho tannins, however, impaired crop production, and further research is needed to evaluate whether tannins from other sources added to agricultural soils have similar detrimental effects on crops. © 2015, Springer Science+Business Media Dordrecht.


Jordan G.,University of Kassel | Predotova M.,University of Kassel | Ingold M.,University of Kassel | Goenster S.,University of Kassel | And 3 more authors.
Journal of Plant Nutrition and Soil Science | Year: 2015

Given high mineralization rates of soil organic matter addition of organic fertilizers such as compost and manure is a particularly important component of soil fertility management under irrigated subtropical conditions as in Oman. However, such applications are often accompanied by high leaching and volatilization losses of N. Two experiments were therefore conducted to quantify the effects of additions of activated charcoal and tannin either to compost in the field or directly to the soil. In the compost experiment, activated charcoal and tannins were added to compost made from goat manure and plant material at a rate of either 0.5 t activated charcoal ha-1, 0.8 t tannin extract ha-1, or 0.6 t activated charcoal and tannin ha-1 in a mixed application. Subsequently, emissions of CO2, N2O, and NH3 volatilization were determined for 69 d of composting. The results were verified in a 20-d soil incubation experiment in which C and N emissions from a soil amended with goat manure (equivalent to 135 kg N ha-1) and additional amendments of either 3 t activated charcoal ha-1, or 2 t tannin extract ha-1, or the sum of both additives were determined. While activated charcoal failed to affect the measured parameters, both experiments showed that peaks of gaseous CO2 and N emission were reduced and/or occurred at different times when tannin was applied to compost and soil. Application of tannins to compost reduced cumulative gaseous C emissions by 40% and of N by 36% compared with the non-amended compost. Tannins applied directly to the soil reduced emission of N2O by 17% and volatilization of NH3 by 51% compared to the control. However, emissions of all gases increased in compost amended with activated charcoal, and the organic C concentration of the activated charcoal amended soil increased significantly compared to the control. Based on these results, tannins appear to be a promising amendment to reduce gaseous emissions from composts, particularly under subtropical conditions. Copyright © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Ingold M.,University of Kassel | Dietz H.,Royal Gardens and Farms | Sradnick A.,University of Kassel | Joergensen R.G.,University of Kassel | And 2 more authors.
Biology and Fertility of Soils | Year: 2015

In many arid and semi-arid regions, irrigated vegetable production leads to major carbon (C) and nitrogen (N) losses owing to high turnover rates. The goal of this experiment was therefore to test two amendments, activated charcoal and quebracho tannins, in their ability to stabilize soil organic carbon (SOC) from goat manure application in order to enhance nutrient and water retention. To this end, a 2-year field experiment was conducted on a sandy alluvial soil in Northern Oman investigating the effects of the two amendments either by mixing them with goat manure in the soil (MCmix and MTmix) or by applying manure from goats fed 2.5 % charcoal (MCfed) or 3.6 % tannin (MTfed) of their daily diet. Mineral fertilizer (NPK) and pure goat manure (M) served as controls. Application rates amounted to 335 kg N ha−1 year−1 and 6.4–8.2 t C ha−1 year−1 (depending on C and N concentrations) and 2.0 and 1.4 t activated charcoal ha−1 year−1 and 2.8 and 1.7 t quebracho tannin ha−1 year−1 (in 2010 and 2011, respectively). Goat manure applications, in general, increased SOC, total N, and basal respiration compared with mineral fertilizer. Mineral fertilizer reduced SOC by −25.5 % and total N by −20 %, whereas organic treatments increased SOC by up to 21 % and total N by 19 to 48 %. Basal respiration ranged between 4.1 and 8.5 μg CO2-C day−1 g−1 and was only affected by mineral fertilizer with an average reduction of 25 and 40 % in 2010 and 2011, respectively, compared with organic treatments. The metabolic quotient was not significantly altered by any of the treatments. Charcoal amendments increased SOC by 10.6 % when charcoal was fed to goats and by 21.3 % when charcoal was mixed with manure and reduced net C losses, whereas pure goat manure did not change it significantly. Tannins mixed with manure did not affect soil parameters, whereas tannins fed to goats showed opposite effects to the other goat manure treatments on pH and SOC. © 2014, Springer-Verlag Berlin Heidelberg.


Al-Harthi S.A.,Royal Gardens and Farms | Al-Sadi A.M.,Sultan Qaboos University | Al-Saady A.A.,Royal Gardens and Farms
Crop Protection | Year: 2013

A study was conducted to determine the potential of citrus budlings originating in the Middle East as sources of citrus viroids. A total of 101 citrus budlings belonging to 9 citrus cultivars which originated from 5 countries were collected from commercial nurseries in 2010. A multiplex reverse transcription polymerase chain reaction (mRT-PCR) was used for detection of CEVd, CBLVd, HSVd, CDVd and CBCVd viroids from the budlings. Multiplex RT-PCR analysis, followed by sequencing of representative isolates, showed that 29, 28, 54, 68 and 79% of the citrus budlings are positive for CEVd, CBLVd, HSVd, CDVd and CBCVd viroids, respectively. Viroids were detected in citrus budlings originating in Oman, Lebanon, Syria, Egypt and Jordon. Viroids from Oman were found to share 94-100% nucleotide similarity with viroids from other parts of the world. Findings from this study provide evidence for circulation of citrus viroids via budlings originating in the Middle East. Strict quarantine measures and certification programs are required to reduce widespread distribution of citrus viroids via citrus budlings originating in these countries. © 2013 Elsevier Ltd.

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