Soil quality assessment of rice production systems in South of Brazil

Soil quality, as a measure of the soil capacity to function, can be quantified by indicators based on physical, chemical and biological properties. Maintaining soil quality at a desirable level in the rice cropping system is a very complex issue due to the nature of the production systems used. In the state of Rio Grande do Sul, Brazil, rice production is one of the most important agricultural activities in the region. The study presented here was conducted with the following objectives: (i) to identify soil quality factors present from a set of soil indicators, (ii) to identify which selected indicators within these factors could discriminate between management systems or soil classes, (iii) to establish a minimum data set (MDS). Soil quality assessment was based on multivariate statistical analysis using the SPSS program. For this study, 29 soil biological, chemical and physical indicators were evaluated to characterize aspects of regional soil quality. Data were collected from rice fields located in the Camaquã region of Rio Grande do Sul that were under the three main soil management systems for rice. Different factors were found as the most important to discriminate either management systems or soil classes. The most powerful soil attributes retained into MDS for distinguishing differences in soil quality of rice production under different management systems and soil classes were copper, potassium, earthworm number, microbial quotient, manganese, organic matter, magnesium, iron, water stable aggregates, soil respiration, mineralizable N

Measurement of the open-charm contribution to the diffractive proton structure function

Production of D*+/-(2010) mesons in diffractive deep inelastic scattering has been measured with the ZEUS detector at HERA using an integrated luminosity of 82 pb^{-1}. Diffractive events were identified by the presence of a large rapidity gap in the final state. Differential cross sections have been measured in the kinematic region 1.5 < Q^2 < 200 GeV^2, 0.02 < y < 0.7, x_{IP} < 0.035, beta 1.5 GeV and |\eta(D*+/-)| < 1.5. The measured cross sections are compared to theoretical predictions. The results are presented in terms of the open-charm contribution to the diffractive proton structure function. The data demonstrate a strong sensitivity to the diffractive parton densities.Comment: 35 pages, 11 figures, 6 table