Release and retention of N and P during crop decomposition

Non-Peer ReviewedUnderstanding the release and retention of nutrients from decomposing crop residue is critical to gain insight of nutrient cycling for sustained crop production. Using the mesh bag technique, we compared the mass loss and mineralization of N and P from straw and root residues of pea, canola and wheat in the 10 months following crop harvest. Wheat straw decomposed more slowly than either pea or canola mostly because of low N content, and released no measurable amount of N. By spring, pea straw had lost 25% of its N (7 kg N/ha) and canola straw 18% (2.5 kg N/ha). However, between spring and summer, these straw residues immobilized 1.5 to 2 kg N of soil N per ha. Wheat root lost more mass at the end of the study period than pea or canola root: Net mineralization of root residue N was 1 to 1.5 kg/ha. Residues of all test crops released P into the soil, however, the total amount from root and straw was less than 1 kg P/ha

Influence of pea cultivars on soil N balance and sequent crop production

Non-Peer ReviewedThree field experiments were conducted in northwestern Alberta to determine the influence of pea cultivars on the N economy and the performance of the sequent wheat crop: four pea cultivars were tested with barley as the check. All but one experimental year had below average growing season rainfall. Dinitrogen fixation decreased in the following order among the peacultivars: Grande > Carerra > Eiffel > Swing, the same order as net productivity. Only Grande pea resulted in balanced soil N; soil N deficit, in kg N ha-1, was 7-38 for Carrera, 20-37 for Swing, and 18-37 for Eiffel. Grain N uptake by the sequent wheat was well-correlated with N fixed by pea (r =0.843**). Even where the soil N balance was negative, wheat following pea mostly had higher seed protein content and yield than wheat following barley. The greater N availability after pea is attributed to higher net N mineralization from pea root and rhizodeposits than barley roots and rhizodeposits. It is concluded that selection of a high net productivity pea cultivar should typically result in greater N and yield benefits to the sequent cereal crop than a low net productivity cultivar

The effect of size and composition on structural transitions in monometallic nanoparticles

Predicting the morphological stability of nanoparticles is an essential step towards the accurate modelling of their chemophysical properties. Here we investigate solid–solid transitions in monometallic clusters of 0.5–2.0 nm diameter at finite temperatures and we report the complex dependence of the rearrangement mechanism on the nanoparticle’s composition and size. The concerted Lipscomb’s Diamond-Square-Diamond mechanisms which connects the decahedral or the cuboctahedral to the icosahedral basins, take place only below a material dependent critical size above which surface diffusion prevails and leads to low-symmetry and defected shapes still belonging to the initial basin

Relationship between physical attributes, clay fraction mineralogy and aluminum forms in soil

O alumínio (Al) é um dos elementos mais abundantes em massa nos solos brasileiros, estando presente em diferentes minerais e formas. Considerando a carência de informações sobre a sua participação no comportamento físico do solo, buscou-se, no presente estudo, avaliar a relação entre a mineralogia da fração argila, formas de Al e atributos físicos de diferentes solos. Para tanto, foram coletadas amostras deformadas e indeformadas dos horizontes A e B de solos representativos das Zonas Fisiográficas Sul e Campos das Vertentes do estado de Minas Gerais. As amostras foram submetidas às caracterizações física, química e mineralógica. Estudos de correlação mostraram que os atributos físicos dos solos estudados estavam associados às diferentes formas de Al presentes e à mineralogia da fração argila: as formas de Al amorfas e menos cristalinas associaram-se mais aos atributos físicos relacionados com a agregação das partículas do solo, podendo esta associação ser atribuída à afinidade deste elemento com a matéria orgânica, enquanto os componentes cristalinos associaram-se mais aos atributos físicos relacionados com a organização estrutural dos solos._________________________________________________________________________________ ABSTRACT: Aluminum (Al) is one of the most abundant elements in weight in Brazilian soils, found in different minerals and forms. Considering the lack of information about its participation in the physical behavior of soil, the present study aimed to evaluate the relationship between the mineralogy of the clay fraction, different forms of Al and physical attributes of different soils. Disturbed and undisturbed samples of A and B horizons of representative soils from the South and Campos das Vertentes physiographic regions in the State of Minas Gerais were therefore collected. The samples were subjected to physical, chemical and mineralogical characterizations. Correlation studies performed with the resulting data from the different characterizations showed that the physical attributes of the different studied soils are associated to the different forms of Al and to the mineralogy of the clay fraction: the amorphous and less crystalline forms of Al were more associated to physical attributes related with particle aggregation, such association being ascribed to the affinity of this element with organic matter, while the crystalline components were more associated to physical attributes related with the structural organization of the soils

Replication and Functional Genomic Analyses of the Breast Cancer Susceptibility Locus at 6q25.1 Generalize Its Importance in Women of Chinese, Japanese, and European Ancestry

We evaluated the generalizability of a single nucleotide polymorphism (SNP), rs2046210 (A/G allele), associated with breast cancer risk that was initially identified at 6q25.1 in a genome-wide association study conducted among Chinese women. In a pooled analysis of over 31,000 women of East-Asian, European, and African ancestry, we found a positive association for rs2046210 and breast cancer risk in Chinese women [ORs (95%CI)=1.30(1.22–1.38) and 1.64(1.50–1.80) for the AG and AA genotypes, respectively, P for trend = 1.54 × 10−30], Japanese women [ORs (95%CI)=1.31(1.13–1.52) and 1.37(1.06–1.76), P for trend = 2.51 × 10−4], and European-ancestry American women [ORs (95%CI)=1.07(0.99–1.16) and 1.18(1.04–1.34), P for trend = 0.0069]. No association with this SNP, however, was observed in African American women [ORs (95%CI)=0.81(0.63–1.06) and 0.85(0.65–1.11) for the AG and AA genotypes, respectively, P for trend = 0.4027). In vitro functional genomic studies identified a putative functional variant, rs6913578. This SNP is 1,440 bp downstream of rs2046210 and is in high LD with rs2046210 in Chinese (r2=0.91) and European-ancestry (r2=0.83) populations, but not in Africans (r2=0.57). SNP rs6913578 was found to be associated with breast cancer risk in Chinese and European-ancestry American women. After adjusting for rs2046210, the association of rs6913578 with breast cancer risk in African Americans approached borderline significance. Results from this large consortium study confirmed the association of rs2046210 with breast cancer risk among women of Chinese, Japanese, and European ancestry. This association may be explained in part by a putatively functional variant (rs6913578) identified in the region