Jorge D. Etchevers Barra

Structure and pedofeatures of Guanajuato (Mexico) Vertisol under different cropping systems

Abstract Little is known about the crop influence and the long-term effects of tillage systems on physical and morphological properties of Vertisols in the high plateau of the intertropical zone of Mexico. The purpose of the present study was to evaluate the impact of crop rotation on the development of structure and pedofeatures of Eutric Vertisols of Guanajuato, Mexico. Disturbed and undisturbed samples from the top soil (0–20 cm) of five agroecosystems differing in crop rotation (semipermanent alfalfa, two cereal crops per year, one vegetable and one cereal crop per year, three vegetable crops per year, and dryland maize) were collected. A second no-till soil sample was obtained from a nearby site under secondary vegetation and used as reference soil. Continuous and intensive cultivation lead to a significant reduction in Vertisol organic matter and total nitrogen contents. Tillage and crop rotations affected air-dried aggregate bulk densities, soil microstructure and development of pedofeatures. Calcite crystalline pedofeatures seemed to be more directly affected by the management systems used. Nodules, the most common crystalline pedofeatures in top soil of all cultivated Vertisols, were absent in no-till soils.

Generación de un inoculante acelerador del compostaje

Composting was performed using a mixture of ovine manure and straw. Inoculum was extracted at five different phases of the composting process (18, 23, 28, 33 and 38 days after the start of the composting process) and its effect on reducing biotransformation time was evaluated in the composted ovine manure. The samples were preserved in a deep freezer, then lyophilized to obtain the inoculum, 50g of which was added to each treatment in the second experimental phase. Six treatments were established; C=straw (P)+ovine manure (E), T1=P+ E+inoculum 18 days after the start of the composting process (I18), T2=P+E+I23, T3=P+E+I28, T4=P+E+I33, T5=P+E+I38, with three replications. Treatments were placed in a controlled-environment chamber at 45% relative humidity and 30°C along with flasks containing 50g of material to measure daily production, CO2 accumulation, temperature, pH, electric conductivity (dS/m), organic matter (%), total nitrogen (%), total carbon (%), C: N ratio, particle size (Tp) and bulk density (g/l). CO2 production (mg) showed a significant difference (p ≤.05) of treatments T2 and T5 with respect to the others, which demonstrated that the inoculum of these treatments accelerated the dynamics of microorganisms and the composting process. The quality and maturity of the compost are guaranteed as the amount of CO2 decreases.