The application of nitrogen fertilizers has the purpose to complete soil nitrogen supply to satisfied the crop demands; however, the inappropriate use of these inputs increase the quantity of residual nitrate in soil (Nr) and the risk of its posterior leaching, not being an issue if the fertilizers are synthetic (FS) or organic. The goal is to compare the effect of fertilization over Nr an essay of response to application of nitrogen was made, considering broccoli as crop indicator for its high demand in this nutrient. The elements were FS or green manure, this last applied on transplantation time (AV1) or fifteen days before the same (AV2). The broccoli response was quadratic (300 kg N·ha-1 as optimums physiological rate) with maximum yield of 1.94, 1.55 and 1.31 kg·plant-1 for FS, AV1 and AV2, respectively. The FS release less Nr, followed by AV1 and AV2, so we conclude that if organic fertilizers are not applied on time the Nr will increase, with the subsequent risk of leaching and water table pollution.

A territorial ecological classification of the municipality of San Andres Chiautla was carried out in this research. The methodology employed was the one proposed by INE-SEMARNAP, which applies the variant from the complex systems associated with the SEDUE methodology. The physiographic survey variants were used to characterize the natural and socioeconomic subsystems through the GIS, while the reference terms for the transformations and permanencies of the use of the soil obtained from the State Program of Territorial Classification elaborated by SEDESOL were applied. Eight elements were characterized during the description phase of the natural and socioeconomic subsystems: ecological quality of the natural resources, natural fragility, changes in the use of the soil and vegetation, pressure placed on the natural environment by the local communities, population distribution, levels of well-being in the local communities, space and time dynamics in the local communities, and socioeconomic aspects. After the characterization stage, the integration of the natural subsystem to obtain environmental stability and environmental policies was carried out. As a final result, busage, policy and criteria tables to normalize the use of the territorial space were obtained.

Soil organic matter (MOS) has a significant influence on soil capacity productivity and its conservation is an increasing environmental and economic concern. Dealing with this matter is necessary to understand the process which conducts performance as interaction with soil mineral fraction, where the effect of texture over the accumulation of MOS is a controversial matter, and will be explained throughout this work. On first hand, we establish quantitative relationships between MOS, mineral particles

This work was conducted at the Ajusco volcano, D.F., Mexico, on areas with four prescribed burning treatments (combinations of March and May burns and high and low fire intensity), plus a non burnt control. On these areas were planted Pinus hartwegii seedlings, corresponding to two seedling-qualities: big seedlings and small seedlings. Such seedlings were evaluated after six months, recording survival, diameter, biomass and foliar concentration of nitrogen, phosphorous and potassium. It was found that low intensity March prescribed burns did not affect negatively the tree survival. The trees planted on such treatment had higher biomass. The bigger seedlings had higher potassium foliar concentrations after six months. This last, added to their larger size make them more appropriate for low temperature and moisture limitative environments.

This work was carried out as study of case in the ambient of Viñales, Pinar del Rio, Cuba with the objective of selecting genetic material with special value for the conservation and improvement of the species from nine provenances, finding important differences among origins for the variable height, diameter and branching. The provenances were classified into A,B,C and D quality groups, recommending group A and B for development of the species at this place of extreme poor fertility. The variation coefficient was from 29.5 and 44.8 % should be total height and diameter were the most variable, so selection should be on the base of this characteristics, selecting as superior origin Marbajita, Cajálbana, El Burén, Los Palacios, La Jagua, La Güira and Juan Manuel.

Most perennial plants of cold-temperate zones have a dormancy period during their annual growth cycle. For over fourty years scientists have intended to explain the adaptive value of dormancy through the understanding of the relationships among bud dormancy and specific environmental factors. Current knowledge on this topic is described in this document.

In the year 2006 Yucatan State was settled down approximately 167, 000 hectares with shifting cultivation, in maize associations with beans, pumpkin and vegetables, with different fallow periods afterward three years of use. The objective of this work was to determine the chemical behavior of the soils, by evaluating two leguminous species and two short fallow periods, as well as the phase of maize crop. In three types of vegetal cover; Leucaena leucocephala, Mucuna pruriens and secondary vegetation, with two and four years of fallow, a completely randomized design with four repetitions was established and the nutriment quantities in three intervals were determined: 1998 after two years of established the fallows of four years, 2001 when being complete the fallows of two and four years and starting the maize crop phase and 2004 three years of continuous land use. At the end of the fallow periods, Leucaena improved K, Ca and Mg quantities, while Mucuna the NO3 and the secondary vegetation the organic matter. Fallow of two years registered superior values in organic matter content, NO3 and K, when comparing with 4 years fallow, that better than the two years in Mg.

In this work, the genus Eucalyptus was studied. This genus derives its name from the Greek words eu, that mean well, and kaluptos, that means place setting. These plants play an important role in the closed forests of southern Australia. In these forests, the Eucalyptus genera usually are trees of up to 200 years old, that constitute a stage of transition between the older natural forests damaged by fires and the closed pluvial forests. The eucalyptuses are native of Australia and some countries of Southeastern Asia, where they grow in very diverse conditions of rainfall and temperature. They are known more than 500 species of eucalyptuses. Some of trees have a height of up to 90 m, but in opened zones of short vegetation and little annual rainfall the dwarfed forms of eucalyptus are very current. These dwarfish forms are called “mallees”, and they are characterized for a long underground stem that allow them to survive the periods of drought. When Eucalyptus genus is planted outside his natural habitat, many of their species have shown a high degree of tolerance to extremes latitudes and altitudes. The first great plantations began in Brazil in 1904. At the present time, that country has more of a million hectares of plantations of eucalyptuses. More than 100 countries throughout the world cultivate eucalyptuses in plantations, countries like Mexico, Spain, Portugal, Morocco, Argentina, the United States and many others.

Host plant can be protected against further pathogen attack if they have survived earlier infection by pathogenic viruses, bacteria or fungi. It appears that the first infecting pathogen, or some an injury, “immunizes” the plant against further infections by homologous pathogens. The first infecting pathogen “induced” expression of resistance reactions against subsequently infecting pathogens, regardless of whether they are viruses, bacteria or fungi. This response is called systemic acquired resistance. Systemic acquired resistance refers to distinct signal transduction pathway that plays an important role in the ability of plants to defend them selves against pathogen.

The species Aspidosperma quebracho-blanco Schlecht is the most abundant of the “Parque Chaqueño” region but it is not used for high added value goods production because of its dimensional instability. A way to enhance dimensional stability is the swelling of cell walls with polyethylene glycol (PEG). The aim of this work was to determine the effect of PEG, molecular weight 300 and 600, on the dimensional stability of this wood using the retractability coefficient as control parameter. Samples were impregnated with PEG in a pilot plant through the Bethell process, following the IRAM Nr. 9511 norm. Subsequently the samples were dried until humidity content (HC) of 10 %. The best results were achieved impregnating wood with PEG 600 at a concentration of 50 % in water solution, at a pressure level of 12 kg.cm-2 during 120 minutes. These conditions led to the decrease of 58.2 % of the retractability coefficient of this wood.