Improving green manure quality with phosphate rocks in Ontario Canada

Phosphate rock (PR) was applied to one conventional and two organic dairy fields and planted with buckwheat (Fagopyrum esculentum) as a green manure crop. In total, five types of PR were applied at three application rates in order to determine the yield, concentration of P in the aboveground tissue and the P uptake of buckwheat. It was found that PR of relatively high carbonate substitution and small particle diameter could increase buckwheat tissue concentrations to a quality such that mineralization of the buckwheat mulch could occur. Buckwheat mulch and residual PR increased soil P flux as determined by anion exchange membranes in situ in the following spring. This provides evidence that buckwheat of high P quality has the potential to supply P to a subsequent crop

Decomposition of wheat straw and stabilization of microbial products

Includes bibliographical references (pages 74-77).This research examined the effects of soil environment on the decomposition of cereal crop residues and stabilization of microbial products in the field. Microplots at semi-arid and subhumid field sites were amended with 14C-, 15N-labelled wheat straw and with 14C-labelled glucose plus 15N-labelled NH4NO3 and the fate of the residual C and N was monitored over 10 yr. Mineralization of C and N derived from wheat straw was greater at the site in the more moist environment in the short term (2 yr). In the long term (up to 10 yr), however, the residual C and N at this site decayed at a slightly slower rate, providing evidence of stabilization of organic material in chemically resistant forms, as compared to possible physical protection in the semi-arid clay-textured soil. The total recovery of labelled N was 22.5–24% in the harvested crops with 13.4–16% remaining in the surface soil by the end of the study. Mineralized labelled organic N was used with an efficiency ranging from 32 to 51%. However, after summer fallow the crop apparently used mineralized labelled N with an efficiency of only 7%. This study showed that moistness of the soil environment has a considerable effect on residue decomposition. Stabilization of humic material derived from residues relates more to the recalcitrance of microbial products and their interactions with soil mineral colloids than to the nature of the original residue

Frações húmicas e caracterização termogravimétrica da humina de latossolos húmicos.

Estudos sobre a composição química da matéria orgânica em profundidade de Latossolos com horizonte A húmico (Lh) da região Nordeste do Brasil são escassos. Além disso, a humina, embora represente a fração mais significativa como reserva de carbono orgânico nestes solos, é a fração orgânica menos estudada devido, em parte, à dificuldade de extração e purificação da mesma. O acúmulo de matéria orgânica do solo (MOS) em Lh ainda é pouco compreendido, sobretudo em Lh do nordeste brasileiro. Assim, testou-se as hipóteses: i) o acúmulo da MOS em Lh está relacionado à natureza recalcitrante da MOS; e ii) solos situados em altitudes elevadas apresentam MOS com composição química diferente daqueles situados em menor altitude. Objetivou-se identificar a natureza química da MOS para obter subsídios para explicar a preservação do carbono nestes solos. Foram selecionados três perfis de Lh em diferentes condições de clima e altitude. As amostras de solo foram coletadas das camadas de 0-5, 5-10, 30-40 e 80-90 cm. Foi feito o fracionamento das substâncias húmicas do solo, e medições termogravimétricas na humina purificada com HF 10% por meio de Calorimetria de Varredura Diferencial e termogravimetria. A humina representou a maior reserva de carbono orgânico, seguido dos ácidos húmicos e ácidos fúlvicos. A análise termogravimétrica revelou que cerca de 50 % da humina do horizonte A húmico é constituída por compostos alifáticos em todos os solos estudados, independente da altitude, isso indica que a recalcitrância química não é o principal mecanismo de estabilização do carbono nestes solos

Relações entre o carbono e atributos químicos de latossolos húmicos, Nordeste-Brasil.

A ocorrência de Latossolos com horizonte A húmico (Lh) espesso (> 100 cm) é rara no Nordeste do Brasil. Nessa região, tais solos ocorrem comumente em elevadas altitudes, constituindo ambientes diferenciados da região semiárida circundante, sendo intensamente utilizados para a agropecuária. A estabilidade da matéria orgânica do solo (MOS) em Lh ainda é pouco compreendida, assim, testou-se as hipóteses: i) o acúmulo de carbono (C) é favorecido pela menor taxa de decomposição da MOS decorrente da maior altitude; e ii) a associação do C com as formas de ferro (Fe) e alumínio (Al) é um mecanismo importante para a proteção da MOS. Objetivou-se relacionar os atributos químicos com a variação do C em profundidade, e obter subsídios para explicar a preservação do C nestes solos. Foram selecionados cinco perfis de Lh em diferentes condições de clima, vegetação e altitude, e os seus atributos químicos determinados, como pH, Ca+2, Mg+2, Al+3 e K+ trocáveis, H + Al, P disponível, C total, orgânico e lábil. Fe e Al nas formas cristalinas, de baixa cristalinidade e formas associadas à MOS extraídos com ditionito-citrato-bicarbonato de sódio, oxalato ácido de amônio e pirofosfato de sódio, respectivamente. Os Lh apresentam acúmulo de C relativamente alto, independente da altitude, e relacionado à reação ácida, distrofia e elevada saturação por Al. O Fe de baixa cristalinidade apresentou maior correlação (r = 0,61, P<0,05) com as formas de C do que as formas de Al livre (r = 0,46, P<0,05) e amorfo (r = 0,44, P<0,05)

Predictors of Radiotherapy Induced Bone Injury (RIBI) after stereotactic lung radiotherapy

<p>Abstract</p> <p>Background</p> <p>The purpose of this study was to identify clinical and dosimetric factors associated with radiotherapy induced bone injury (RIBI) following stereotactic lung radiotherapy.</p> <p>Methods</p> <p>Inoperable patients with early stage non-small cell lung cancer, treated with SBRT, who received 54 or 60 Gy in 3 fractions, and had a minimum of 6 months follow up were reviewed. Archived treatment plans were retrieved, ribs delineated individually and treatment plans re-computed using heterogeneity correction. Clinical and dosimetric factors were evaluated for their association with rib fracture using logistic regression analysis; a dose-event curve and nomogram were created.</p> <p>Results</p> <p>46 consecutive patients treated between Oct 2004 and Dec 2008 with median follow-up 25 months (m) (range 6 – 51 m) were eligible. 41 fractured ribs were detected in 17 patients; median time to fracture was 21 m (range 7 – 40 m). The mean maximum point dose in non-fractured ribs (n = 1054) was 10.5 Gy ± 10.2 Gy, this was higher in fractured ribs (n = 41) 48.5 Gy ± 24.3 Gy (p < 0.0001). On univariate analysis, age, dose to 0.5 cc of the ribs (D_0.5), and the volume of the rib receiving at least 25 Gy (V₂₅), were significantly associated with RIBI. As D_0.5 and V₂₅ were cross-correlated (Spearman correlation coefficient: 0.57, p < 0.001), we selected D_0.5 as a representative dose parameter. On multivariate analysis, age (odds ratio: 1.121, 95% CI: 1.04 – 1.21, p = 0.003), female gender (odds ratio: 4.43, 95% CI: 1.68 – 11.68, p = 0.003), and rib D_0.5 (odds ratio: 1.0009, 95% CI: 1.0007 – 1.001, p < 0.0001) were significantly associated with rib fracture.</p> <p>Using D_0.5, a dose-event curve was constructed estimating risk of fracture from dose at the median follow up of 25 months after treatment. In our cohort, a 50% risk of rib fracture was associated with a D_0.5 of 60 Gy.</p> <p>Conclusions</p> <p>Dosimetric and clinical factors contribute to risk of RIBI and both should be included when modeling risk of toxicity. A nomogram is presented using D_0.5, age, and female gender to estimate risk of RIBI following SBRT. This requires validation.</p

In vivo assessment of catheter positioning accuracy and prolonged irradiation time on liver tolerance dose after single-fraction 192Ir high-dose-rate brachytherapy

<p>Abstract</p> <p>Background</p> <p>To assess brachytherapy catheter positioning accuracy and to evaluate the effects of prolonged irradiation time on the tolerance dose of normal liver parenchyma following single-fraction irradiation with ¹⁹²Ir.</p> <p>Materials and methods</p> <p>Fifty patients with 76 malignant liver tumors treated by computed tomography (CT)-guided high-dose-rate brachytherapy (HDR-BT) were included in the study. The prescribed radiation dose was delivered by 1 - 11 catheters with exposure times in the range of 844 - 4432 seconds. Magnetic resonance imaging (MRI) datasets for assessing irradiation effects on normal liver tissue, edema, and hepatocyte dysfunction, obtained 6 and 12 weeks after HDR-BT, were merged with 3D dosimetry data. The isodose of the treatment plan covering the same volume as the irradiation effect was taken as a surrogate for the liver tissue tolerance dose. Catheter positioning accuracy was assessed by calculating the shift between the 3D center coordinates of the irradiation effect volume and the tolerance dose volume for 38 irradiation effects in 30 patients induced by catheters implanted in nearly parallel arrangement. Effects of prolonged irradiation were assessed in areas where the irradiation effect volume and tolerance dose volume did not overlap (mismatch areas) by using a catheter contribution index. This index was calculated for 48 irradiation effects induced by at least two catheters in 44 patients.</p> <p>Results</p> <p>Positioning accuracy of the brachytherapy catheters was 5-6 mm. The orthogonal and axial shifts between the center coordinates of the irradiation effect volume and the tolerance dose volume in relation to the direction vector of catheter implantation were highly correlated and in first approximation identically in the T1-w and T2-w MRI sequences (<it>p </it>= 0.003 and <it>p </it>< 0.001, respectively), as were the shifts between 6 and 12 weeks examinations (<it>p </it>= 0.001 and <it>p </it>= 0.004, respectively). There was a significant shift of the irradiation effect towards the catheter entry site compared with the planned dose distribution (<it>p </it>< 0.005). Prolonged treatment time increases the normal tissue tolerance dose. Here, the catheter contribution indices indicated a lower tolerance dose of the liver parenchyma in areas with prolonged irradiation (<it>p </it>< 0.005).</p> <p>Conclusions</p> <p>Positioning accuracy of brachytherapy catheters is sufficient for clinical practice. Reduced tolerance dose in areas exposed to prolonged irradiation is contradictory to results published in the current literature. Effects of prolonged dose administration on the liver tolerance dose for treatment times of up to 60 minutes per HDR-BT session are not pronounced compared to effects of positioning accuracy of the brachytherapy catheters and are therefore of minor importance in treatment planning.</p

Plant Trait Diversity Buffers Variability in Denitrification Potential over Changes in Season and Soil Conditions

BACKGROUND: Denitrification is an important ecosystem service that removes nitrogen (N) from N-polluted watersheds, buffering soil, stream, and river water quality from excess N by returning N to the atmosphere before it reaches lakes or oceans and leads to eutrophication. The denitrification enzyme activity (DEA) assay is widely used for measuring denitrification potential. Because DEA is a function of enzyme levels in soils, most ecologists studying denitrification have assumed that DEA is less sensitive to ambient levels of nitrate (NO(3)(-)) and soil carbon and thus, less variable over time than field measurements. In addition, plant diversity has been shown to have strong effects on microbial communities and belowground processes and could potentially alter the functional capacity of denitrifiers. Here, we examined three questions: (1) Does DEA vary through the growing season? (2) If so, can we predict DEA variability with environmental variables? (3) Does plant functional diversity affect DEA variability? METHODOLOGY/PRINCIPAL FINDINGS: The study site is a restored wetland in North Carolina, US with native wetland herbs planted in monocultures or mixes of four or eight species. We found that denitrification potentials for soils collected in July 2006 were significantly greater than for soils collected in May and late August 2006 (p<0.0001). Similarly, microbial biomass standardized DEA rates were significantly greater in July than May and August (p<0.0001). Of the soil variables measured--soil moisture, organic matter, total inorganic nitrogen, and microbial biomass--none consistently explained the pattern observed in DEA through time. There was no significant relationship between DEA and plant species richness or functional diversity. However, the seasonal variance in microbial biomass standardized DEA rates was significantly inversely related to plant species functional diversity (p<0.01). CONCLUSIONS/SIGNIFICANCE: These findings suggest that higher plant functional diversity may support a more constant level of DEA through time, buffering the ecosystem from changes in season and soil conditions

Normal tissue toxicity after small field hypofractionated stereotactic body radiation

Stereotactic body radiation (SBRT) is an emerging tool in radiation oncology in which the targeting accuracy is improved via the detection and processing of a three-dimensional coordinate system that is aligned to the target. With improved targeting accuracy, SBRT allows for the minimization of normal tissue volume exposed to high radiation dose as well as the escalation of fractional dose delivery. The goal of SBRT is to minimize toxicity while maximizing tumor control. This review will discuss the basic principles of SBRT, the radiobiology of hypofractionated radiation and the outcome from published clinical trials of SBRT, with a focus on late toxicity after SBRT. While clinical data has shown SBRT to be safe in most circumstances, more data is needed to refine the ideal dose-volume metrics