Soil‐organic‐matter stability in sandy cropland soils is related to land‐use history

Sandy cropland soils in NW Europe were found to contain unusually high organic‐carbon (OC) levels, and a link with their land‐use history has been suggested. This study's aim was to assess the discriminating power of physical and chemical fractionation procedures to yield information on soil‐organic‐matter (OM) stability for these soils. In relict‐ and cultivated‐heathland soils, much higher proportions of 6% NaOCl treatment–resistant but 10% HF–soluble OC (MOC) and N (32.2% and 29.9%) were measured compared to a set of “permanent"‐cropland soils without a history of heathland land use (11.9% and 8.5%). Also, the proportions of 6% NaOCl– and 10% HF treatment–resistant OC and N in the relict and cultivated heathlands (19.2% and 12.0%) were higher than in the permanent‐cropland soils (17.7% and 5.7%). Stepwise multiple linear‐regression yielded a significant relationship between the annual mineralization (g C [100 g OC]^–1), soil OC (g C kg^–1) content, and %MOC: Annual mineralization = 4.347 – 0.087 soil OC – 0.032 %MOC (R² = 0.65). Combinations of incubation experiments for quantification of the labile soil OM pool with chemical fractionation may thus yield meaningful data for development of soil‐organic‐matter models with measurable pools, but their applicability will be limited to specific combinations of former land use with soil, climate, and current management.     

Efficacy,phytotoxicity and economics of different herbicides in aerobic rice

Abstract

Aerobic rice is a potential water-wise rice production system, but high weed infestation has threatened its sustainability, which demands an efficient and cost-effective weed management technique. Eight commercial herbicide products were applied singly or as tank-mix or in sequence to evaluate their efficacy, rice selectivity and cost-effectiveness in aerobic rice. The study was conducted under field conditions in Malaysia during 2010/2011 following a randomized complete block design. Most of the herbicide treatments provided excellent weed control, and produced much higher net benefit than weedy or weed-free check. None of the herbicides caused significant phytotoxicity to rice plants. Among the herbicide treatments, sequential application of Cyhalofop-butyl+Bensulfuron at early growth stage followed by Bentazon/MCPA at mid growth stage provided the highest weed control efficiency, productivity and net benefit. Application of Bispyribac-sodium at early growth stage followed by Bentazon/MCPA at mid growth stage performed very close to the above-mentioned treatments. Sequential application of Pretilachlor/safener just after seeding followed by Propanil/Thiobencarb at early growth stage also provided satisfactory results in terms of efficacy and economic return. Since manual weeding was not economic, herbicide rotation using the above chemicals may be recommended for effective weed management in aerobic rice.     

Weed management in canola (Brassica napus L): a review of current constraints and future strategies for Australia

ABSTRACT

Weeds are a major constraint to canola (Brassica napus L.) production, reducing grain yield and quality. The repeated use of pre- and post- emergent herbicides to control several grasses and broadleaf weeds has escalated the problem of herbicide resistance in weeds. The development of herbicide-tolerant canola cultivars has increased the flexibility of weed management but has also increased the risks of outcrossing with wild relatives and weed shifts to resistance. Herbicide-resistant weed species, and the related biological repercussions, pose a major threat to sustainable weed management. These developing risks have led researchers to examine integrated weed management (IWM) techniques for sustainable weed control. Weed control strategies using non-chemical tactics have valid roles for managing weeds. However, in broad-acre commercial fields, the effectiveness of several non-chemical selections are less proven than commercial chemical herbicides. Canola competition and allelopathy for weed suppression are potential components for integrated weed management in canola. This review examines current chemical and non-chemical options available for developing IWM strategies for profitable canola production, as well as future research directions.     

Arsenic immobilization in soil using starch-stabilized Fe/Cu nanoparticles: a case study in treatment of a chromated copper arsenate (CCA)-contaminated soil at lab scale

Journal of Soils and Sediments - The present study investigates the possible use and effectiveness of starch-stabilized Fe/Cu nanoparticles for in situ immobilization of arsenic in contaminated...     

Evolution of river course and morphometric features of the River Ganga: A case study of up and downstream of Farakka Barrage

River channel shifting in the deltaic regime is an unabated occurrence. Channel shifting has become one of the concerns as it influences land use/land cover along the riverbank in various ways. For the management of the river, it is indispensable to study the pattern of river course change both in qualitative and quantitative methods. This study is an attempt to understand the pattern of shifting and to quantify erosion and deposition of the river Ganga at upstream and downstream of Farakka Barrage during 1794–2017. The study has been carried out by using various historical maps, aerial photographs, satellite imagery, and remote sensing and GIS technique to understand the dynamic of the river. Over 223 years period shifting of the river accentuates the remarkable oscillation of the river. Perimeter of the river is determined to understand the area covered by the river course in the study area. To evaluate the meandering of the river sinuosity of the river has been computed in this study. The amount of erosion and deposition was calculated in this study by using ArcGIS 10.6. The study found a higher amount of erosion at the east bank where Manikchak, Kaliachak II and Kaliachak III blocks are situated between 1965 and 2017. At the west bank of the river, especially the Rajmahal block, the occurrence of deposition was remarkable during the same period.     

Cadmium Phytoextraction Efficiency of Arum (Colocasia antiquorum), Radish (Raphanus sativus L.) and Water Spinach (Ipomoea aquatica) Grown in Hydroponics

Selection of a phytoextraction plant with high Cd accumulation potential based on compatibility with mechanized cultivation practice and local environmental conditions may provide more benefits than selection based mainly on high Cd tolerance plants. In this hydroponics study, the potential of Cd accumulation by three plant species; arum (Colocasia antiquorum), radish (Raphanus sativus L.) and water spinach (Ipomoea aquatica) were investigated. Arum (Colocasia antiquorum L.) plants were grown for 60 days in a nutrient solution with 0, 10 or 50 μM Cd, while radish and water spinach plants grew only 12 days in 0, 1.5, 2.5, 5 or 10 μM Cd. Growth of radish and water spinach plants decreased under all Cd treatments (1.5 to 10 μM), while arum growth decreased only at 50 μM Cd. At 10 μM Cd treatment, the growth of arum was similar to the control treatment indicating higher tolerance of arum for Cd than radish and water spinach. Cadmium concentrations in different plant parts of all plant species increased significantly with Cd application in the nutrient solution. Arum and water spinach retained greater proportions of Cd in their roots, while in radish, Cd concentration in leaves was higher than in other plant parts. Cadmium concentrations in arum increased from 158 to 1,060 in the dead leaves, 37 to 280 in the normal leaves, 108 to 715 in the stems, 42 to 290 in the bulbs and 1,195 to 3,840 mg kg^?1 in the roots, when the Cd level in the solution was raised from 10 μM Cd to 50 μM Cd. Arum accumulated (dry weight?×?concentration) 25 mg plant^?1 at 10 μM, while the corresponding values for radish and water spinach were 0.23 and 0.44 mg plant^?1, respectively. With no growth retardation at Cd concentrations as high as 166 mg kg^?1 measured in entire plant (including root) of arum at 10 μM Cd in the nutrient solution, arum could be a potential Cd accumulator plant species and could be used for phytoremediation.     

Genetic Variation of Glutelin Acidic Subunit Polypeptides in Bangladesh Rice Genetic Resources

Bangladesh rice genetic resources collected from six distinct regions of the country were examined to obtain the diversity in glutelin acidic subunit polypeptides. Seed glutelins from 576 Bangladesh rice cultivars representing seven ecotypes were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), isoelectric focusing (IEF) electrophoresis and two-dimensional electrophoresis (2-DE: SDS-PAGE/IEF) analyses. Glutelin acidic subunit was separated into four bands, α-1, α-2, α-3 and α-4, and the variation in each of bands was detected by SDS-PAGE analysis. A higher molecular size component of α-1(α-1′) was identified in the cultivars tested. In case of α-2, α-2H with high molecular mass, α-2L with low molecular mass and α-2H/L were detected. α-3 band variation showed α-3H, α-3L, and α-3H/L, while for α-4, α-4H, α-4L bands were identified. In IEF analysis, a total of 16 bands with independent pI ranging from pI 6.30 to 7.52 were identified for the glutelin acidic subunit among the cultivars. The maximum and minimum numbers of IEF bands found were 13 and 9, respectively. The α-2L less cultivars were also lacking in pI 6.80 polypeptide in IEF. Result of 2-DE showed that pI 6.80 polypeptide was the main component of α-2L band. Transplanted Aman ecotype was the most diverse with respect to glutelin variation. Geographical distribution of glutelin variation in the Transplanted Aman ecotype differed according to the regions. The above results indicate that Bangladesh rice cultivars possess great genetic diversity in glutelin acidic subunit polypeptides. This study of indigenous rice cultivars from Bangladesh provides useful information regarding their breeding potential.     

Surfactants in the Sea Surface Microlayer,Underlying Water and Atmospheric Particles of Tropical Coastal Ecosystems

This study aims to determine the composition of surfactants in the sea surface microlayer (SML), underlying water (ULW) and atmospheric particles (AP). Surfactants were determined colorimetrically as methylene blue active substances (MBAS) and disulphine blue active substances (DBAS) for anionic and cationic surfactants, respectively. The concentration of dissolved inorganic nutrients (DIN) in ULW was determined so as to indicate the influence of ULW to the surfactants in SML. The results showed that the concentration of MBAS and DBAS in SML at both stations ranged between 0.05 and 0.31 μmol L^?1, and between 0.19 and 0.59 μmol L^?1, respectively. Surfactants in ULW influence the concentration of surfactants in SML (r?=?0.65, p?<?0.01, n?=?36). The station influenced by anthropogenic sources showed a higher concentration of surfactants in ULW, SML and AP. This finding suggests fine mode atmospheric particles (FMAP) are the main carrier for anionic surfactants as MBAS in the coastal ecosystem. Anionic surfactants as MBAS were found as better indicator of anthropogenic sources than cationic ones.     

Community level functional diversity and enzyme activities in paddy soils under different long-term fertilizer management practices

Soil microbial community structure and function are commonly used as indicators for soil quality and fertility. The present study deals with the effect of different long-term fertilizer management practices on community-level physiological profiles (CLPP) and soil enzyme activities of paddy soils. Since 1954, chemical fertilizers have been applied in the fields as N–P₂O₅–K₂O, and compost has been added as rice straw at 0, 7.5, 22.5, and 30.0 Mg ha⁻¹ in NPK, NPKC750, NPKC2250, and NPKC3000 treatments, respectively. Community-level functional diversity was significantly enhanced in the plots treated with both chemical fertilizer and compost as compared to only chemical fertilizer and untreated control plots. Average well color development (AWCD) obtained by the Biolog Eco plate indicates that there were few differences among soil samples. Shannon diversity and evenness indices were the highest in NPKC750-treated soil and the lowest in chemically fertilized soil. Dehydrogenase, cellulose, β-glucosidase, and acid and alkaline phosphomonoesterase activities were significantly increased depending on the amount of added compost with inorganic fertilizers; the alkaline phosphomonoesterase activity was the most sensitive to treatments. Our results demonstrated that enzyme activities can be used as sensitive and liable indicators in long-term managed rice-paddy ecosystems.     

Crossability of tetraploid and hexaploid wheats with ryes for primary triticale production

Summary Crossability of wheat and rye was investigated during thirteen crop cycles in two contrasting locations to 1) evaluate tetraploid and hexaploid wheat parents in crosses with rye, 2) identify genotypes with high crossability and 3) assess the impact of environment on seed development. The majority of the tetraploid wheats crossed with rye had seed set around 20%, but very low embryo viability. Several wheat genotypes with seed set above 50% were identified. The hexaploid wheats crossed with rye showed poor seed set, but plant recovery was relatively high. The majority of the hexaploid wheats with highest seed set (20–30%) were from China. The results suggest differences in crossability between the rye populations, and wheat species by rye interactions. The crossability of the tetraploid and hexaploid wheats was affected by climate in the two locations.