Flooding depths and burial effects on seedling emergence of five California weedy rice (Oryza sativa spontanea) accessions

Weedy rice (Oryza sativa f. spontanea Roshev.) has recently become a significant botanical pest in California rice (Oryza sativa L.) production systems. The conspecificity of this pest with cultivated rice, Oryza sativa (L.), negates the use of selective herbicides, rendering the development of non-chemical methods a necessary component of creating management strategies for this weed. Experiments were conducted to determine the emergence and early growth responses of O. sativa spontanea to flooding soil and burial conditions. Treatment combinations of four flooding depths (0, 5, 10, and 15 cm) and four burial depths (1.3, 2.5, 5, and 10 cm) were applied to test the emergence of five O. sativa spontanea accessions as well as ‘M-206’, a commonly used rice cultivar in California, for comparison. Results revealed that burial depth had a significant effect on seedling emergence. There was a 43-91% decrease in emergence between seedlings buried at 1.3 and 2.5 cm depending on the flooding depth and accession, and an absence of emergence from seedlings buried at or below 5 cm. Flooding depth did not affect emergence, but there was a significant interaction between burial and flooding treatments. There was no significant difference between total O. sativa spontanea emergence from the soil and water surfaces regardless of burial or flooding depths, implying that once the various accessions have emerged from the soil they will also emerge from the floodwater. Most accessions had similar total emergence compared to M-206 cultivated rice, but produced more dry weight than M-206 when planted at 1.3 cm in the soil. The results of this experiment can be used to inform stakeholders of the flooding conditions necessary as well as soil burial depths that will promote or inhibit the emergence of California O. sativa spontanea accessions from the weed seedbank.

Mycelium Composites and their Biodegradability: An Exploration on the Disintegration of Mycelium-Based Materials in Soil

In the search for environmentally friendly materials, mycelium composites have been labelled as high potential bio-based alternatives to fossil-based and synthetic materials in various fields. Mycelium-based materials are praised for their biodegradability, however no scientific research nor standard protocols exist to substantiate this claim. This research therefore aims to develop an appropriate experimental methodology as well as to deliver a novel proof of concept of the material’s biodegradability. The applied methodology was adapted from a soil burial test under predefined laboratory conditions and hands-on preliminary experiments. The mycelium composite samples were placed in a nylon netting and then buried in potting soil with a grain size of 2 mm for different time-intervals ranging between one and sixteen weeks. Results showed that mycelium, which acted as the binder, had the tendency to decompose first. A weight loss of 43% was witnessed for inert samples made of the fungal strain Ganoderma resinaceum and hemp fibres after sixteen weeks. The disintegration rate in this method however depended on various parameters which were related to the material’s composition, its production method and the degradation process which involved the used equipment, materials and environmental properties.

Burial-induced deterioration in leather: a FTIR-ATR, DSC, TG/DTG, MHT and SEM study

In this study we used an analytical approach based on complementary techniques that targets all structural levels of collagen in leather to investigate how vegetable-tanned leather deteriorates during soil burial tests. For the first time, a group of deterioration markers specific to molecular, fibrillar and fibrous structure of collagen in leather was associated with the deterioration of buried leather. The application of the second order derivative of FTIR-ATR spectra analysis allowed us to detect loosening of collagen–tannin matrix, de-tanning and gelatin formation based on the behaviour of collagen and tannin spectral components (intensity variation and shifts). Collagen denaturation observed by DSC analysis and its thermo-oxidative behaviour measured by TG/DTG analysis, as well as the altered morphology of collagen (namely melt-like fibres and distorted fibrillar ultrastructure) imaged by SEM confirmed the FTIR-ATR analyis results. These analytical outcomes enabled us to understand the effect of leather hardening/cementing through soil mineral penetration into its fibrous structure and thus correctly interprete the higher-than-expected shrinkage temperatures and intervals determinatd by MHT method. Thus, MHT method proved to be suitable for a quick evaluation method that can direcly support the first conservation decision after excavation. The combination of FTIR-ATR, DSC, TG/DTG and SEM can be particularly useful to provide insights on the deterioration mechanism of archaeological leather and support best decision on its long-term preservation.

COMPARATIVE STUDY ON DEGRADATION OF POLYLACTIC ACID/ SYZYGIUM AROMATICUM COMPOSITES AGEING IN OUTDOOR ENVIRONMENT AND SOIL BURIAL

Major environmental problems resulting from non-degradable components of plastic wastes have awakened great attention to bioplastic as an alternative material. Among various bioplastic materials, polylactic acid (PLA) is recognised as a promising material especially as a food packaging material. The development of PLA composites using various fillers has extensively been in focus in order to preserve the high quality, safety, and extended shelf-life of packed food. Among the interesting fillers is Syzygium aromaticum (SA). SA, also known as clove, has biological activities such as antibacterial, antifungal, insecticidal, and antioxidant properties. This work investigated the effects of SA filler on the degradations of virgin PLA (VPLA) and recycled PLA (RPLA). The VPLA/SA composites and RPLA/SA composites were prepared using the solvent casting method. The content of SA filler varied in the range of 0 to 20 wt%. The composites were aged in outdoor environment and soil burial. The results revealed that the degradation rate was increased with the increase of SA filler in both ageing environments. After 10 weeks of ageing in the outdoor environment, the weight loss of VPLA/SA composites and RPLA/SA composites containing 20 wt% of SA were 7.7% and 12.8% respectively. Whereas in soil burial, the weight loss of VPLA/SA composites and RPLA/SA composites with similar SA content were 25.6% and 38.3% respectively. The degradation rate was observed to be more rapid in the soil burial as compared to the outdoor environment. Comparably, RPLA and RPLA/SA composites experienced higher degradation rates than VPLA and VPLA/SA composites. The degradation rate was consistent with scanning electron microscope (SEM) images which observed the formation of holes, cavities, cleavages, and grooves on the surfaces of the samples. Thermogravimetric analysis (TGA) results on aged samples showed that VPLA/SA composites and RPLA/SA composites that had aged in soil burial decomposed at lower temperatures. The shortening of degradation time of the VPLA/SA composites and RPLA/SA composites could increase their potential to be used as food packaging materials. ABSTRAK: Masalah utama terhadap alam sekitar yang disebabkan oleh sisa plastik yang sukar terurai, telah menarik perhatian terhadap bioplastik sebagai bahan alternatif. Di antara pelbagai jenis bahan bioplastik sedia ada, asid polilaktik(PLA) dilihat sebagai bahan yang paling sesuai terutamanya sebagai bahan pembungkusan makanan. Perkembangan di dalam penghasilan komposit asid polilaktik yang ditambah dengan pelbagai bahan pengisi telah menjadi fokus terutamanya bagi tujuan meningkatkan kualiti, kesegaran dan jangka hayat makanan. Salah satu pengisi yang mendapat perhatian adalah Syzygium aromaticum (SA). SA yang juga dikenali sebagai bunga cengkeh mempunyai aktiviti biologi, seperti sifat antibakteria, antijamur, racun serangga dan antioksidan yang tinggi. Didalam kajian ini, siasatan terhadap kesan penambahan SA terhadap penguraian PLA asal (VPLA) dan PLA kitar semula (VPLA). Komposit VPLA/SA dan komposit RPLA/SA disediakan dengan menggunakan kaedah pelarutan pelarut. Kandungan pengisi SA adalah didalam julat 0 – 20% mengikut berat. Komposit tersebut dibiarkan menua didalam persekitaran luaran dan didalam tanah. Keputusan kajian mendapati bahawa kadar penguraian semakin meningkat dengan penambahan peratus berat bahan pengisi SA setelah melalui penuaan didalam kedua-dua persekitaran. Setelah penuaan selama10 minggu di dalam persekiran luaran, pengurang berat komposit VPLA/SA dan komposit RPLA/SA yang mengandungi 20 wt% SA adalah 7.7% dan 12.8%. Manakala bagi penuaan didalam tanah, pengurangan berat komposit VPLA/SA dan komposit RPLA/SA dengan kandungan SA yang sama masing-masing adalah 25.6% dan 38.3%. Kadar penguraian diperhatikan lebih cepat bagi penuan didalam tanah dibandingkan dengan penuaan didalam persekitaran luaran. Disamping itu, RPLA dan komposit RPLA/SA mengalami kadar penguraian yang lebih tinggi berbanding VPLA dan komposit VPLA/SA. Kadar penguraian adalah konsisten dengan imej yang dihasilkan oleh imbasan mikroskop elektron (SEM) dimana dapat dilihat pembentukan lubang, rongga, pembelahan dan alur di permukaan sampel. Hasil analisis termogravimetri (TGA) terhadap sampel yang telah dituakan menunjukkan bahawa komposit VPLA/SA dan komposit RPLA/SA yang melalui penuaan didalam tanah terurai pada suhu yang lebih rendah. Tempoh penguraian komposit VPLA/SA dan komposit RPLA/SA yang lebih pendek ini meningkatkan potensi penggunaannya komposit ini sebagai bahan pembungkusan makanan.

BIODEGRADATION OF MANGO SEED STARCH FILMS IN SOIL

The typical petroleum-based plastics have triggered environmental problems. For this purpose, biodegradable polymers such as starch are often used to manufacture biodegradable plastics. At present, the efforts are underway to extract starch as a promising biopolymer from mango seeds and subsequently to produce a biodegradable starch film to be used as plastic packaging. As such, in this work, glycerol-plasticized mango starch films were prepared using a solution casting process, using different amounts of citric acid as a cross-linking agent. The blend ratio of starch to glycerol was set at 3:5 wt. each, while the amount of citric acid ranged from 0 to 10 wt.%. Then, the casted films underwent 21 days of soil burial testing in the natural environment to determine their biodegradability behavior. The soil burial test is one of the common methods chosen to assess the biodegradability of polymers. The idea is that, by burying samples in the soil for a fixed time, samples are exposed to microorganisms (i.e. bacteria and fungi) present in the soil that serve as their food source. This is somehow likely to facilitate the process of deterioration. For this reason, the soil burial test can be regarded as an authentic approach to the process of deterioration in the natural environment. The films' susceptibility to biodegradation reactions was assessed within intervals of seven days through their physical appearance and weight loss. Interestingly, it was found that the cross-linked starch films have been observed to degrade slower than the non-cross-linked starch films as burial time progressed. The declining percentages of weight loss, as well as the presence of microorganisms and eroded surface on the films observed by SEM, explained the degradation behavior of the cross-linked starch films compared to the non-cross-linked starch films. Hence it is believed that cross-linked starch-glycerol films are biodegradable in soil, henceforth, the potential to be commercialized as a biodegradable packaging material soon. At the same time, this plastic packaging is expected to be recognized as a value-added product since the raw materials ergo mango seeds utilized to develop this product are from waste, therefore, environmentally friendly. ABSTRAK: Plastik yang berasaskan petroleum telah mencetuskan masalah persekitaran. Untuk tujuan ini, polimer biodegradasi seperti kanji sering digunakan untuk membuat plastik yang boleh terurai. Pada masa ini, usaha sedang dilakukan untuk mengekstrak pati sebagai biopolimer yang menjanjikan dari biji mangga dan kemudiannya menghasilkan filem pati yang terbiodegradasi untuk digunakan sebagai kemasan plastik. Oleh yang demikian, dalam karya ini, filem pati mangga plastik-gliserol disusun menggunakan proses pemutus larutan, menggunakan jumlah asid sitrik yang berlainan sebagai agen penghubung silang. Nisbah campuran pati dan gliserol ditetapkan pada 3:5 wt.% masing-masing, sementara jumlah asid sitrik berkisar antara 0 hingga 10 wt.% berat. Kemudian, sampel plastik tersebut ditanam di dalam tanah selama 21 hari di persekitaran semula jadi untuk menentukan tingkah laku biodegradasinya. Ujian penguburan tanah adalah salah satu kaedah biasa yang dipilih untuk menilai biodegradasi polimer. Ideanya adalah bahawa, dengan menguburkan sampel di tanah untuk waktu yang tetap, sampel terdedah kepada mikroorganisma (iaitu bakteria dan jamur) yang terdapat di dalam tanah yang berfungsi sebagai sumber makanan mereka. Ini mungkin memudahkan proses kemerosotan. Atas sebab ini, ujian penguburan tanah dapat dianggap sebagai pendekatan yang sahih terhadap proses kemerosotan di persekitaran semula jadi. Kerentanan filem terhadap reaksi biodegradasi dinilai dalam selang waktu tujuh hari melalui penampilan fizikal dan penurunan berat badan. Menariknya, didapati bahawa filem-filem pati berangkai silang telah dilihat menurun lebih perlahan daripada filem-filem pati yang tidak bersilang ketika masa pengebumian berlangsung. Peratusan penurunan berat badan yang menurun, serta kehadiran mikroorganisma dan permukaan yang terhakis pada filem yang diperhatikan oleh SEM, menjelaskan tingkah laku degradasi filem pati berangkai silang berbanding dengan filem pati yang tidak bersilang. Oleh itu, dipercayai bahawa filem kanji-gliserol berangkai silang dapat terbiodegradasi di dalam tanah, dan seterusnya, potensi untuk dikomersialkan sebagai bahan pembungkusan yang boleh terurai tidak lama lagi. Pada masa yang sama, pembungkusan plastik ini diharapkan dapat diakui sebagai produk bernilai tambah kerana bahan mentah ergo mangga yang digunakan untuk mengembangkan produk ini adalah dari sisa, oleh itu, mesra alam.

Soil organic carbon stabilization mechanisms and temperature sensitivity in old terraced soils

Being the most common human-created landforms, terrace construction has resulted in an extensive perturbation of the land surface. However, our mechanistic understanding of soil organic carbon (SOC) (de-)stabilization mechanisms and the persistence of SOC stored in terraced soils is far from complete. Here we explored the factors controlling SOC stability and the temperature sensitivity (Q10) of abandoned prehistoric agricultural terrace soils in NE England using soil fractionation and temperature-sensitive incubation combined with terrace soil burial-age measurements. Results showed that although buried terrace soils contained 1.7 times more unprotected SOC (i.e., coarse particulate organic carbon) than non-terraced soils at comparable soil depths, a significantly lower potential soil respiration was observed relative to a control (non-terraced) profile. This suggests that the burial of former topsoil due to terracing provided a mechanism for stabilizing SOC. Furthermore, we observed a shift in SOC fraction composition from particulate organic C towards mineral-protected C with increasing burial age. This clear shift to more processed recalcitrant SOC with soil burial age also contributes to SOC stability in terraced soils. Temperature sensitivity incubations revealed that the dominant controls on Q10 depend on the terrace soil burial age. At relatively younger ages of soil burial, the reduction in substrate availability due to SOC mineral protection with aging attenuates the intrinsic Q10 of SOC decomposition. However, as terrace soil becomes older, SOC stocks in deep buried horizons are characterized by a higher temperature sensitivity, potentially resulting from the poor SOC quality (i.e., soil C:N ratio). In conclusion, terracing in our study site has stabilized SOC as a result of soil burial during terrace construction. The depth–age patterns of Q10 and SOC fraction composition of terraced soils observed in our study site differ from those seen in non-terraced soils, and this has implications when assessing the effects of climate warming and terrace abandonment on the terrestrial C cycle.

A Degradable Inverse Vulcanized Copolymer as a Coating Material for Urea Produced under Optimized Conditions

Global enhancement of crop yield is achieved using chemical fertilizers; however, agro-economy is affected due to poor nutrient uptake efficacy (NUE), which also causes environmental pollution. Encapsulating urea granules with hydrophobic material can be one solution. Additionally, the inverse vulcanized copolymer obtained from vegetable oils are a new class of green sulfur-enriched polymer with good biodegradation and better sulfur oxidation potential, but they possess unreacted sulfur, which leads to void generations. In this study, inverse vulcanization reaction conditions to minimize the amount of unreacted sulfur through response surface methodology (RSM) is optimized. The copolymer obtained was then characterized using Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). FTIR confirmed the formation of the copolymer, TGA demonstrated that copolymer is thermally stable up to 200 °C temperature, and DSC revealed the sulfur conversion of 82.2% (predicted conversion of 82.37%), which shows the goodness of the model developed to predict the sulfur conversion. To further maximize the sulfur conversion, 5 wt% diisopropenyl benzene (DIB) as a crosslinker is added during synthesis to produce terpolymer. The urea granule is then coated using terpolymer, and the nutrient release longevity of the coated urea is tested in distilled water, which revealed that only 65% of its total nutrient is released after 40 days of incubation. The soil burial of the terpolymer demonstrated its biodegradability, as 26% weight loss happens in 52 days of incubation. Thus, inverse vulcanized terpolymer as a coating material for urea demonstrated far better nutrient release longevity compared with other biopolymers with improved biodegradation; moreover, these copolymers also have potential to improve sulfur oxidation.

Biodegradation of cellulose fibers functionalized with CuO/Cu2O nanoparticles in combination with polycarboxylic acids

Sustainable biodegradation of cellulose fibers is critical for composting after the end of a product’s life. In this study, we aimed at investigating the effect of in situ synthesized CuO/Cu2O nanoparticles (NPs) with biocidal concentration on the biodegradation behavior of cotton fibers pretreated with 1,2,3,4-butanetetracarboxylic acid (BTCA) and succinic acid (SUC). Biodegradation of the fibers was evaluated by soil burial tests in garden soil and in model compost after different soil burial times. The results showed that the application of BTCA, SUC, and CuO/Cu2O NPs did not affect the hydrophilicity of the samples and allowed a smooth biodegradation process. The morphological and chemical changes during biodegradation, evaluated by FESEM and FTIR analyses, showed that the presence of CuO/Cu2O NPs slightly hindered biodegradation of the fibers after 18 days in soil. However, biodegradation was much faster in the model compost, where all samples, regardless of their chemical modification, almost completely degraded after only 11 days. Intense microbial growth on the surface of all samples after nine days of burial in garden soil and model compost was confirmed by the presence of proteins produced by the microorganisms. The total number of microorganisms in the garden soil remained almost unchanged and increased in the model compost after the burial test. The only exception was the sample with the highest concentration of CuO/Cu2O NPs, which caused a reduction in microbial growth but not complete growth inhibition. These results clearly showed that during material degradation, the cellulosic material supporting microbial growth prevailed over the suppression of microbial growth by CuO/Cu2O NPs.

Identification and Regionalization of Cold Resistance of Wine Grape Germplasms (V. vinifera)

With the extreme changes of the global climate, winter freezing injury has become an important limiting factor for the development of the global grape industry. Therefore, there is a significant need for the screening of cold-resistant wine grape germplasms and cold regionalization for cold-resistant breeding and the development of grapevine cultivation in cold regions. In this study, the low-temperature half-lethal temperature (LT50) values were determined for the annual dormant branches of 124 wine grape germplasms (V. vinifera) to evaluate their cold resistance. The LT50 values of the 124 tested germplasms ranged from −22.01 °C to −13.18 °C, with six cold-resistant germplasms below −20 °C. Based on the LT50 values, the 124 germplasms were clustered into four types, with cold resistance from strong to weak in the order of type Ⅱ > type Ⅰ > type Ⅳ > type Ⅲ, corresponding to the four cold hardiness zones. Zones 1, 2, 3, and 4 included 6, 22, 68, and 28 germplasms, respectively, with decreasing cold resistance. The number of germplasms in different hardiness zones followed a normal distribution, with the most in zone 3. In Type Ⅱ, the fruit skin color of germplasms was positively correlated with cold hardiness, while the temperature of origin was negatively correlated with cold hardiness. The average LT50 of germplasms in different origin regions ranged from −17.44 °C to −16.26 °C, with differences among some regions. The cold regionalization analysis resulted in the distribution of 124 germplasms in four temperature regions in China with six germplasms in region A (−22 °C ≤ LT50 ≤ −20 °C), 30 germplasms in region B (−20°C ≤ LT50 ≤ −18°C), 71 germplasms in region C (−18 °C ≤ LT50 ≤ −15 °C), and 17 germplasms in region D (−15 °C ≤ LT50 ≤ −13 °C). Strong cold-resistant wine grape germplasms (V. vinifera) were identified, and these could be used as parental material for cold-resistant breeding. In some areas in China, soil-burial over-wintering strategies are used, but our results suggest that some wine grapes could be cultivated without requiring winter burial during overwintering. The results of this study should provide guidance for the selection of promising strains for cold-resistant breeding for expanded cultivation of improved varieties for wine grape production in China.