PHYSICS OF SOIL

Author: MORET FERNÁNDEZ DAVID.
Year: 2002.
University: LLEIDA [More theses of this university] [www.udl.es].
Place of defense: INGENIEROS AGRONOMOS.
Place of preparation: ESTACIÓN EXPERIMENTAL DE AULA DEL (CSIC) Y ETSEA.

Summary: The main objective of this study was to assess the effect of tillage system on the properties hydro and the balance of water during the fallow rotation ceral-barbecho (crop "year and instead") in a dry arid center Aragon com part of an experiment tillage long term. In the experimental site, soil texture frank (Xerollic Calciothid), has a useful depth of 70 cm and the average annual rainfall is 390 mm. It had three blocks of plots, one with continuous cultivation (CC) of barley and two adjacent to it, in rotation "year and instead" (CF), and compared three tillage systems (conventional tillage, CT; reduced tillage, RT and no-laboreo, NT) for three cycles and fallow crop (1999-2000, 2000-2001 and 2001-2002) in the two farming systems. During the fallow period in CF took place measures bulk density (pb), hydraulic conductivity (K) and curve retencióne water from the soil to 2 and 40 cm deep. To the extent K developed a infiltrómetro disc, which incorporates a system of Reflectometría Domain Temporary (TDR), and enables the automatic reading of the infiltration. Determinations, following a incomplete block design, were made in four of fallow times: before work primaries, immediately after the exercise, after the first rains after work and at the end of fallow. The profile of soil moisture (0-70 cm) was monitored during the trial period by TDR. During cultivation, it was determined biomass and yield. After 8-10 years of testing, Pb NT was higher than in RT and CT to 2 cm. NT presented tambión to that depth to a lower moisture saturation and water available to plants, and lower K due to fewer macroporos and mesoporos. The work carried out in primary CT (vertedera) and RT (chisel) Pb reduced by increasing porosity and aeration to reduce the water available to plants. There was also a reduction of the pore size representative and an increase in pore water transmitters, and thus unaK higher. The rain increased after work primaries PB on the surface in RT and CT, which reduced the porosity and aeration K through fewer transmitters pore water. The primary tasks increased significantly the rate of vaporación during the first 24 hours after work. However, work secondary favored water conservation land in the medium term to reduce the rate of evaporation compared with NT. The efficiency of fallow to accumulate water in the soil (PSE) was low (11%), siendom ayor in fallow periods with high rainfall in the last three months of fallow. On average, the system CF stored at the end of fallow 22 billion more water than the DC system. Furthermore, the tillage system had no significant effect on the efficiency of fallow. The application of the model SiSPAT to simulate the balance of water during the fallow showed that in the absence of work during the fallow, the floor beneath NT tends to evaporate more water than in RT and CT, which favors deep drainage. Comparing the average PSE field with estimated by the model are observed in years with a first phase of the work fallow very rainy favor water losses due to evaporation, reducing the PSE. The yield of barley was higher in years with heavy rains effective in the spring, being in the aggregate, 49% higher than in CF CC. However, CC, paid 34% more than when CF grain production was adjusted to an annual basis considering the rainfall between two consecutive harvests and the duration of the bar 8 becho in 1f0 each system. The tillage system had no significant effect on yield.

Author: OJEDA CASTRO FRANKLIN GERARDO.
Year: 2004.
University: AUTÓNOMA DE BARCELONA [More theses of this university] [www.uab.es].
Place of defense: FACULTAD DE CIENCIAS.
Place of preparation: ESCUELA DE POSTGRADO.

Author: LLOVET LÓPEZ JOAN.
Year: 2004.
University: ALICANTE [More theses of this university] [www.ua.es].
Place of defense: FACULTAD DE CIENCIAS.
Place of preparation: FACULTAD DE CIENCIAS.

Summary: At the time of a wildfire, fire affects the soil by increasing the temperature and deposition of ash. Moreover, vegetation and organic horizons disappear in whole or in part, varying the incidence of rain on the soil surface. The general hypothesis of this study is that, in situations of vulnerability to fire, can cause dynamic degradativas after the fire due to rain, channeled through the unbundling yel crusting of the soil surface, and translated into changes in production runoff and carrying sediment. Also, the risk of degradation post-incendio be controlled, among other factors, on the soil type, orientation, the virulence of the fire and land use. The study areas are located north of the province of Alicante, south of Valencia. It has conducted a follow-up to the temporal dynamics of the runoff and sediment production after the fire, as well as a study of parameters associated. It has worked to scale microparcela (through simulation of rain), wide plot of erosion (in the study hillside formerly aterrazadas) and unaltered samples in the laboratory. The results obtained highlight the following: In arid environment soil infiltration capacity maintained a high right after the fire. Both semi-arid environment and in bushes secos-subhúmedos there was a significant increase in the production of runoff and sediment, comparing the periods before and after the action of the rain on a land burned. The structural stability was not amended, or increased, because of the fire. A high structural stability was not enough to prevent land degradation after the fire, but was associated with increased cases of infiltration in the medium term after the fire. No changes were observed in the water repellency due to fire, lithology or orientation, although an increase over time abandoned hillside formerly cultivated. The water repellency was associated with the size of the aggregates, being the smallest especially hidrofobitos. Both the surface compaction as crusting on the surface during the year following a forest fire, were directly related to the percentage of limes soil. The land use significantly changed the ecosystem response to the fire. The recent crop of neglect, occupied by a dry meadow dominated by Brachypodium retusum, were unaffected and returned quickly to the situation prior to the fire. The pine forest with a heavy presence of shrubs germinadores (Ulex parviflorus and various Cistaceas), developed a dynamic degradativa after the fire. This resulted in a crusting on the surface and an increase of several orders of magnitude in productions of runoff and sediment. At all locations studied, vegetation response was a key factor in controlling the degradation after the fire. Wide microparcela coatings higher than 35% were associated with high infiltration and sediment transport low. At the level of plot erosion, the dynamics degradativa post-incendio sent when vegetation more than 50% of coating.

Author: HENRIQUEZ RODRIGUEZ MANUEL.
Year: 2005.
University: POLITÉCNICA DE MADRID [More theses of this university] [www.upm.es].
Place of defense: E.T.S.I.AGRONOMOS.
Place of preparation: E.T.S.I.AGRONOMOS DE MADRID.

Summary: Land degradation reduces food production and deteriorating environment ambiente.Para provide solutions to this problem, it was proposed as a general objective of this thesis to assess the effect of different organic and inorganic conditioners on the aggregation of particles and specifically on the behavior of physicochemical properties of a kaolin and sand. For this purpose were designed various laboratory tests. The experiments began with the extraction and characterization of mucilage parenchymal extracted from aqueous Cardón Dato (Stenocereus griseus (Haw.) F. Buxb) and the characterization of kaolin and sandy substrate. From Cardón Dato (CD) was assessed soluble and insoluble fraction, it was determined the presence of neutral sugars, acids urónicos rate, the types of links and conducted an analysis of infrared spectrum. From kaolin was determined pH, EC, the cations and anions soluble extract saturation, the cation exchange capacity and cations interchangeable mediente different methods, the real and apparent density, particle size dispersed and not dispersed, the curve feature humidity to 10, 33, 100, 500, 1000 and 1500 kPa and saturated hydraulic conductivity (Ks). The effect of CDs, Fe +3 and Al +3 and in combination was determined, which used two experimental designs: a factorial 23 to evaluate the effect in the absence or presence of CD and the other with completely randomized design to compare dosage and get the best, as a result of factorial, with less concentrated doses CD alone or in combination with conditioners minerals. For other experiments, we used a completely randomized design. The treatments were applied to selected kaolin and sand with four cycles humedecimiento and drying in oven at 60-70 oC, was the first cycle (T1). It humedeció and drained twice more (T2 and T3). The T4 were applied treatments again and again drying. In the samples dried and without disturbing was determined infiltration snapshot (Ii) and the infiltration basic or stabilized (Ib), then the samples were desmenuzaron to <2 mm and were characterized in terms of physical and chemical. The results reveal that the mucilage CD has high percentage of galactopiranosa with links glucosidic 1.4 and 1-4,6 that are unique and branched polysaccharide neutral in the carbon 6, and these are formed by polysaccharide chains rhamnose, galactose, arabinose and acid urónico typical of pectins. The kaolin is a material with 54% clay and 46% of fine silt with a basic pH, EC 0.65 dS / m, CIC, 13 cmol + kg-1 and Ks of 0.07 cm h-1. The sand was a material with 96.6% sand, basic pH, EC 0.36 dS / m, CIC, 0.31 cmol + kg-1 and Ks> 1500 cm h-1. The kaolin is composed of: caolinita (82-85%), montmorillonite (3-6%), mica (7-10%) and quartz (3-4%). The sand is composed mainly of quartz. The mucilage of cardon data on concentration of 50 mg L-1 is as effective as anionic polyacrylamide in concentration of 10 mg L-1 for clarification of the suspension, but the volume of floculado with cardon figure is higher because of the swelling wet mucilage. The increase in esponjosidad of floculado favors permeability and aeration of the substrate treaty. Small doses CD (5 mg L-1) reinforcing the effect of clarifying the Fe +3 and Al +3 without greatly increase the volume occupied by the floculado, which is useful in treating turbid waters. The mucilage of cardon data on concentration of 50 mg L-1 and anionic polyacrylamide in concentration of 10 mg L-1 increase the stability of the aggregates and Ks but not controlling the outbreak caused by the rapid rise in air pressure in pore over the humedecimiento. The treatments with mineral conditioners based Fe3 + and Al3 + are more effective in terms of stability and persistence of ag 8 watered 3b6 because the links are stronger. Cardon The data can be used as a source of mucilage, which used to clarify murky waters and condition soil structure is unstable economically viable without involve environmental risks of xenobiotic substances persistent.