The effect of crop-pasture rotations on the C, N and S contents of soil aggregates and structural stability in a volcanic soil of south-central Chile

Abstract Conservation agriculture using crop rotation benefits the environment, soil fertility, and crop production. A biannual rotation experiment during a period of 2 years was conducted in volcanic soil in south-central Chile in a production system under conservation agriculture. The experiment considered two previous crops, canola (Brassica napus L.) and bean (Phaseolus vulgaris L.), and four levels of residue incorporation (0%, 50%, 100%, and 200% of generated residue). Grain yield (0.41 Mg ha−1), grain sedimentation value (5.5%), grain K (0.031%) and Ca (0.006%) concentrations, and residue K concentration (0.159%) were higher when the previous crop was bean. The Ca concentration (0.037%) in wheat residue increased after the canola crop. The different applied residue levels of the previous crop had no effect on any of the evaluated parameters in wheat. There was a very consistent negative correlation between the grain S concentration and the residue P (− 0.55), K (− 0.55), Mg (− 0.61), and S (− 0.63) concentrations in wheat when it was cultivated after bean. A larger number of study cycles are required to obtain more consistent results about the effect of the different residue levels on these two biannual rotations.

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Intertidal zonation patterns of macroinfauna over a range of exposed sandy beaches in south-central Chile

Marine Ecology Progress Series ◽

10.3354/meps101105 ◽

1993 ◽

Vol 101 ◽

pp. 105-118 ◽

Cited By ~ 57

Author(s):

E Jaramillo ◽

A McLachlan ◽

P Coetzee

Keyword(s):

Sandy Beaches ◽

Central Chile ◽

South Central ◽

Intertidal Zonation ◽

Zonation Patterns

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Cardiorespiratory Fitness: Reference on the Six-Minute Walk Test and Oxygen Consumption in Adolescents from South-Central Chile

International Journal of Environmental Research and Public Health ◽

10.3390/ijerph18052474 ◽

2021 ◽

Vol 18 (5) ◽

pp. 2474

Author(s):

Jaime Vásquez-Gómez ◽

Nelson Gatica Salas ◽

Pedro Jiménez Villarroel ◽

Luis Rojas-Araya ◽

Cesar Faundez-Casanova ◽

...

Keyword(s):

Cardiorespiratory Fitness ◽

Reference Values ◽

Estimation Error ◽

Walk Test ◽

Central Chile ◽

Six Minute Walk Test ◽

Body Adiposity ◽

South Central ◽

Males And Females ◽

Minute Walk

Cardiorespiratory fitness (CRF) provides oxygen to the exercising muscles and is related to body adiposity, with cardiometabolic variables. The aim was to develop reference values and a predictive model of CRF in Chilean adolescents. A total of 741 adolescents of both genders (15.7 years old) participated in a basic anthropometry, performance in the six-minute walk test (SMWT), and in Course Navette was measured. Percentiles were determined for the SMWT, for the V̇O2max, and an equation was developed to estimate it. The validity of the equation was checked using distribution assumptions and the Bland–Altman diagram. The STATA v.14 program was used (p < 0.05). The 50th percentile values for males and females in the SMWT and in the V̇O2max of Course Navette were, respectively, from 607 to 690 and from 630 to 641 m, and from 43.9 to 45 and from 37.5 to 31.5 mlO2·kg·min−1, for the range of 13 to 17 years. For its part, the model to predict V̇O2max incorporated gender, heart rate, height, waist-to-height ratio (WHR), and distance in the SMWT (R2 = 0.62; estimation error = 0.38 LO2·min−1; p <0.001). Reference values can guide physical fitness in Chilean adolescents, and V̇O2max was possible to predict from morphofunctional variables.

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