Poorly crystalline iron and aluminium oxides contribute to the carbon saturation and sorption of dissolved organic carbon in the soil     

Tania Khandakar  Chris Guppy  Sheikh M. F. Rabbi  Heiko Daniel 《Soil Use and Management》2021,37(1):120-125

Soil carbon (C) saturation implies an upper limit to a soil's capacity to store C depending on the contents of silt + clay and poorly crystalline Fe and Al oxides. We hypothesized that the poorly crystalline Fe and Al oxides in silt + clay fraction increased the C saturation and thus reduced the capacity of the soil to sorb additional C input. To test the hypothesis, we studied the sorption of dissolved organic carbon (DOC) on silt + clay fractions (<53 µm) of highly weathered oxic soils, collected from three different land uses (i.e., improved pasture, cropping and forest). Soils with high carbon saturation desorbed 38% more C than soils with low C saturation upon addition of DOC, whereas adsorption of DOC was only observed at higher concentration (>15 g kg^?1). While high Al oxide concentration significantly increased both the saturation and desorption of DOC, the high Fe oxide concentration significantly increased the desorption of DOC, supporting the proposition that both oxides have influence on the DOC sorption in soil. Our findings provide a new insight into the chemical control of stabilization and destabilization of DOC in soil.  相似文献   

Exogenous application of allelopathic water extracts helps improving tolerance against terminal heat and drought stresses in bread wheat (Triticum aestivum L. Em. Thell.)          下载免费PDF全文

M. Farooq  F. Nadeem  M. Y. Arfat  M. Nabeel  S. Musadaq  S. A. Cheema  A. Nawaz 《Journal of Agronomy and Crop Science》2018,204(3):298-312

The allelopathic water extracts (AWEs) may help improve the tolerance of crop plants against abiotic stresses owing to the presence of the secondary metabolites (i.e., allelochemicals). We conducted four independent experiments to evaluate the influence of exogenous application of AWEs (applied through seed priming or foliage spray) in improving the terminal heat and drought tolerance in bread wheat. In all the experiments, two wheat cultivars, viz. Mairaj‐2008 (drought and heat tolerant) and Faisalabad‐2008 (drought and heat sensitive), were raised in pots. Both wheat cultivars were raised under ambient conditions in the wire house till leaf boot stage (booting) by maintaining the pots at 75% water‐holding capacity (WHC). Then, managed drought and heat stresses were imposed by maintaining the pots at 35% WHC, or shifting the pots inside the glass canopies (at 75% WHC), at booting, anthesis and the grain filling stages. Drought stress reduced the grain yield of wheat by 39%–49%. Foliar application of AWEs improved the grain yield of wheat by 26%–31%, while seed priming with AWEs improved the grain yield by 18%–26%, respectively, than drought stress. Terminal heat stress reduced the grain yield of wheat by 38%. Seed priming with AWEs improved the grain yield by 21%–27%; while foliar application of AWEs improved the grain yield by 25%–29% than the heat stress treatment. In conclusion, the exogenous application of AWEs improved the stay green, accumulation of proline, soluble phenolics and glycine betaine, which helped to stabilize the biological membranes and improved the tolerance against terminal drought and heat stresses.  相似文献   

Impact of grassland contract policy on soil organic carbon losses from alpine grassland on the Qinghai–Tibetan Plateau          下载免费PDF全文

J. Cao  Y. Gong  E. T. Yeh  N. M. Holden  J. F. Adamowski  R. C. Deo  M. Liu  J. Zhou  J. Zhang  W. Zhang  S. Zhang  D. Sheng  S. Yang  X. Xu  M. Li  Q. Feng 《Soil Use and Management》2017,33(4):663-671

Carbon storage in the soils on the Qinghai–Tibetan Plateau plays a very important role in the global carbon budget. In the 1990s, a policy of contracting collective grasslands to smaller units was implemented, resulting in a change from the traditional collective grassland management to two new management patterns: a multi‐household management pattern (MMP: grassland shared by several households without enclosures) and a single‐household management pattern (SMP: grassland enclosed and used by only one household). In 2016, 50 MMP and 54 SMP winter pastures on the Qinghai–Tibetan Plateau were sampled to assess the differences in soil organic carbon (SOC) between the two management patterns. Results showed that average SOC was significantly greater under MMP than under SMP, with an estimated 0.41 Mg C/ha/yr lost due to SMP following the new grassland contract. Based on the government's grassland policy, four grassland utilization scenarios were developed for both summer and winter pastures. We found that if the grassland were managed under SMP, likely C losses ranged between 0.31 × 10⁷ and 6.15 × 10⁷ Mg C/yr across the Qinghai–Tibetan Plateau relative to MMP, which more closely resembles pre‐1990s grassland management. Previous estimates of C losses have only considered land use change (with cover change) and ignored the impacts driven by land management pattern changes (without cover change). The new data suggest that C losses from the Qinghai–Tibetan Plateau are greater than previously estimated, and therefore that the grassland contract policy should be reviewed and SMP households should be encouraged to reunite into the MMP. These findings have potential implications for land management strategies not only on the Qinghai–Tibetan Plateau but also other grazing regions globally where such practices may exist.  相似文献   

Utilizing a DUALEM‐421 and inversion modelling to map baseline soil salinity along toposequences in the Hunter Valley Wine district          下载免费PDF全文

U. Stockmann  J. Huang  B. Minasny  J. Triantafilis 《Soil Use and Management》2017,33(3):413-424

In the oldest commercial wine district of Australia, the Hunter Valley, there is the threat of soil salinization because marine sediments underlie the area. To understand the risk requires information about the spatial distribution of soil properties. Electromagnetic (EM) induction instruments have been used to identify and map the spatial variation of average soil salinity to a certain depth. However, soils vary with depth dependent on soil forming factors. We collected data from a single‐frequency and multiple‐coil DUALEM‐421 along a toposequence. We inverted this data using EM4Soil software and evaluated the resultant 2‐dimensional model of true electrical conductivity (σ – mS/m) with depth against electrical conductivity of saturated soil pastes (EC_p – dS/m). Using a fitted linear regression (LR) model calibration approach and by varying the forward model (cumulative function‐CF and full solution‐FS), inversion algorithm (S1 and S2), damping factor (λ) and number of arrays, we determined a suitable electromagnetic conductivity image (EMCI), which was optimal (R² = 0.82) when using the full solution, S2, λ = 3.6 and all six coil arrays. We conducted an uncertainty analysis of the LR model used to estimate the electrical conductivity of the saturated soil‐paste extract (EC_e – dS/m). Our interpretation based on estimates of EC_e suggests the approach can identify differences in salinity, how these vary with parent material and how topography influences salt distribution. The results provide information leading to insights into how soil forming factors and agricultural practices influence salinity down a toposequence and how this can guide soil management practices.  相似文献   

Comparative effect of advanced soy products or corn protein concentrate with porcine meal on growth,body composition,and distal intestine histology of Florida pompano,Trachinotus carolinus     

Romi Novriadi  Elizabeth Spangler  D. Allen Davis 《Journal of the World Aquaculture Society》2019,50(2):433-447

The present study was designed to investigate the effects of diets containing advanced soy products (enzyme‐treated soy and fermented soy) or corn protein concentrate (CPC) in combination with porcine meal (PM) to completely replace poultry byproduct meal (PBM) on growth performance, body composition, and distal intestine histology of Florida pompano, Trachinotus carolinus. Four experimental diets were formulated to be isonitrogenous and isolipidic, to contain 400 g/kg crude protein and 80 g/kg lipid. A reference diet (PBM diet [PBMD]) contained 150 g/kg PBM and 495 g/kg soybean meal (SBM), and three test diets were formulated replacing PBM with 15 g/kg of CPC (CPC diet [CPCD]) or replacing all SBM and PBM with 535 g/kg fermented soy (fermented soybean meal diet [FSBMD]) or 451.3 g/kg enzyme‐treated soy (enzyme‐treated soybean meal diet [ESBMD]). All three test diets were supplemented with 38 g/kg of PM. Diets were fed based on a percentage of bodyweight adjusted after sampling the fish every 2 weeks to triplicate groups of Florida pompano juveniles (mean weight 8.06 ± 0.22 g). After 8 weeks of feeding, fish fed CPCD and ESBMD performed equally well in terms of final body weight, thermal growth coefficient, and percentage weight gain in comparison to fish fed PBMD. In all cases, feeding FSBMD resulted in poor feed conversion and lower feed intake compared to other treatments. Protein retention efficiency, whole‐body proximate composition, phosphorus, sulfur, potassium, magnesium, calcium, sodium, and zinc contents were not significantly influenced by the dietary treatments. The results obtained in the present histological study showed no significant differences in the thickness of serous layer, muscular layer, and submucosal layer of the intestine among treatments. Fish fed CPCD showed a significant widening of the lamina propria with an increase of cellular infiltration and higher presence of goblet cells compared to other dietary treatment. Based on these results, 451 g/kg ESBM or combination of 150 g/kg of CPC and 495 g/kg SBM supplemented with 38 g/kg PM can be utilized to develop a practical diet for juvenile Florida pompano without impacting growth, nutritive parameters, and several distal intestine health parameters.  相似文献   

The value of sea urchin,Lytechinus variegatus,egesta consumed by shrimp,Litopenaeus vannamei     

Karen E. Jensen  J. Christopher Taylor  Robert J. Barry  Louis R. D'Abramo  D. Allen Davis  Stephen A. Watts 《Journal of the World Aquaculture Society》2019,50(3):614-621

Sea urchins produce high‐energy, membrane‐bound fecal pellets that contain residual nutrients and large quantities of microbiota. These egesta are readily consumed by the shrimp, Litopenaeus vannamei. Egesta of the sea urchin, Lytechinus variegatus, were evaluated as a feed supplement or total replacement for a commercial shrimp diet. Shrimp were stocked at 0.49 g ± 0.06 g initial body weight and housed individually in 2.8‐L tanks in a commercial recirculating zebrafish system. Shrimp were assigned to one of six diets: commercial shrimp feed, reference sea urchin feed, collected dried sea urchin egesta, collected wet sea urchin egesta, half ration of shrimp feed and half collected wet sea urchin egesta, and egesta naturally produced by two sea urchins in polyculture. Equivalent dry matter amounts of each diet were proffered to shrimp in each treatment twice daily, except for those that had complete access to natural egesta excreted by sea urchins in polyculture. Sea urchins were proffered a reference sea urchin feed at 2% body weight daily. After 27 days, shrimp proffered collected dried or wet egesta did not differ significantly in percent weight gain and showed the lowest weight gain. The percent weight gain of shrimp fed the commercial shrimp diet did not differ significantly from that of the shrimp fed half commercial shrimp diet and half egesta. The highest weight gain was recorded for those shrimp that consumed the untouched egesta produced by sea urchins in polyculture. These data suggest that consumed egesta have noteworthy nutritional value and therefore would be beneficial to the culture of extractive species in an integrated multitrophic aquaculture system.  相似文献   

Replacing Soybean Meal with Alternative Protein Sources in Diets for Pond‐raised Hybrid Catfish, ♀ Ictalurus punctatus × ♂ Ictalurus furcatus          下载免费PDF全文

Menghe H. Li  Brian G. Bosworth  Penelope M. Lucas 《Journal of the World Aquaculture Society》2018,49(4):755-760

The present study investigated the replacement of soybean meal with combinations of two or three alternative protein sources in diets for pond‐raised hybrid catfish, ♀ Ictalurus punctatus × ♂ Ictalurus furcatus. Alternative protein sources evaluated included cottonseed meal, distillers dried grains with solubles (DDGS), peanut meal, and porcine meat and bone meal (PMBM). Hybrid catfish fingerlings with a mean initial weight of 35 g/fish were stocked into 25 earthen ponds (0.04 ha) at a density of 14,826 fish/ha. Fish were fed once daily to apparent satiation for 166 d. No significant differences were observed for total diet fed, net yield, weight gain, survival, carcass yield, fillet yield, or fillet proximate composition among dietary treatments. Results show soybean meal may be completely replaced by combinations of cottonseed meal and one or two other alternative protein sources including DDGS, peanut meal, and PMBM in the diet without markedly affecting production and processing characteristics and fillet proximate composition of pond‐raised hybrid catfish. These alternative diets may be used during foodfish production when prices are favorable.  相似文献   

Replacement of fish oil in plant‐based diets for Pacific white shrimp,Litopenaeus vannamei,by stearine fish oil and palm oil     

Fabio Soller  Luke A. Roy  D. Allen Davis 《Journal of the World Aquaculture Society》2019,50(1):186-203

Stearine fish oil (SFO) and palm oil (PO) have emerged as promising alternatives for the replacement of fish oil (FO) in aquafeeds. This study evaluated the replacement of FO with alternative oils in practical diets for Litopenaeus vannamei. In a clear brackish water study (14.1 g/L) utilizing shrimp (0.29 ± 0.02 g, initial weight), FO was replaced by SFO at inclusion ratios of 100:0, 75:25, 50:50, 25:75, and 0:100 (FO:SFO) and PO as 90% of FO. After 55 days, no significant differences (p < 0.05) in final weight, growth, or survival of shrimp were observed. A second trial (8 weeks) in low‐salinity water (2.1 g/L) with shrimp (0.92 ± 0.02 g, initial weight) evaluated diets with 100% FO, 100% SFO, 90% PO, 90% soybean oil (SO), or 90% flaxseed oil (FXO) as a replacement for FO and four commercially produced diets with 2% of FO, SO, PO, or FXO. One treatment received half rations of the commercial FO diet, and one treatment was based entirely on natural productivity. Results show that the fatty acid profiles of the tail muscle conformed to the lipids of the feed, and highly unsaturated fatty acids (HUFAs) were preserved. Following 8 weeks of culture, there were no significant differences in production performance.  相似文献   

Compatibility of root growth and tuber production of potato cultivars with dynamic and static water‐saving irrigation managements          下载免费PDF全文

S. H. Ahmadi  M. Agharezaee  A. A. Kamgar‐Haghighi  A. R. Sepaskhah 《Soil Use and Management》2017,33(1):106-119

The important root characteristics of root length density (RLD) and root mass density (RMD) generally differ among irrigation managements and potato cultivars. The objective of this study was to investigate the RLD and RMD variations and their functional relationships with gross potato tuber yield for two commercial potato cultivars, Agria and Sante, under different irrigation strategies. Full irrigation and water‐saving irrigation strategies, deficit and partial root drying irrigations, were applied statically (S) and dynamically (D) based on daily crop evapotranspiration. Results showed that SPRD had significantly greater RLD (3.64 cm/cm³) and RMD (132.7 μg/cm³) than other irrigation treatments. Between the potato cultivars, Agria had significantly larger values of RLD (3.50 cm/cm³) and RMD (138.7 μg/cm³) than Sante. The functional relationship between the root growth characteristics and tuber yield showed that under water‐saving irrigations, Agria increased root mass at the expense of gross tuber yield but Sante increased root mass to maintain larger gross tuber yields. However, Agria produced more roots and gross tuber yield than Sante, and it is concluded that Agria is a more drought‐tolerant potato cultivar, which is recommended for tuber production in regions where water might be scarce. It was shown that larger root production in potatoes was associated with improved tolerance to water stress.  相似文献   

Radioisotope and stable isotope ratios (Δ14C, δ15N) suggest larval lamprey growth is dependent on both fresh and aged organic matter in streams     

Thomas M. Evans  Amber R. Bellamy  James E. Bauer 《Ecology of Freshwater Fish》2019,28(3):365-375

Lampreys have a complex life cycle which includes a multi‐year infaunal larval stage (ammocoete). Gut content analysis has generally identified detritus (i.e., unidentifiable organic matter) as the major dietary component to ammocoetes, though algae can also be important. However, gut content preserves only a snapshot of the animal's diet and does not reflect assimilated material. In order to better characterise the nutritional sources supporting ammocoete growth, we analysed ammocoete body tissue and potential dietary sources at two streams using natural Δ¹⁴C and δ¹⁵N to estimate time‐integrated nutritional support. Bayesian isotope mixing models revealed differences in the importance of sources supporting ammocoetes between sites. Ammocoetes from a stream in a mixed land usage area (~50% agriculture, ~40% forest and ~10% developed) were primarily supported (mean: ~50%) by fresh terrestrial organic matter but were also supported by substantial contributions (mean: ~30%) by aged organic matter (AOM) and autochthonous material (algae; mean ~20%). In a predominantly forested (~90%) headwater stream, different modelling scenarios (uninformed or informed priors) suggested that algal support of ammocoete nutrition ranged from 7% to 45%. However, the model relying on informed priors developed from gut content analysis produced the low estimates, suggesting these were more reliable. When algae were a minor component of the nutrition at the forested site, ammocoetes were highly dependent on AOM (83 ± 26%; mean ± SD). Based on these findings, ammocoete growth and development are predicted to be strongly influenced by both land use and the availability of allochthonous and autochthonous materials of varying ages within streams.  相似文献