Avaliação do desempenho das máquinas agrícolas na implantação da cultura do girassol

The sunflower oleaginous is the fourth of recognized importance in the oil production and few studies related to agricultural operations adopted for this crop. The objective of the present work was to study the performance of agricultural machines in the conventional tillage and reduced in the plantation of the sunflower crop. The experiment was installed at the Experimental Farm of Lageado, belonging to the Faculty of Agricultural Sciences of UNESP, located in Botucatu-SP. It consisted of two types of tillage (conventional tillage-CC and reduced tillage-CR), with experimental design in randomized blocks and four replications. The treatment CC promoted less coverage of the soil surface protected with waste when compared to CR treatment. The chisel plow was the tillage of equipment that required the tractor higher average traction force, average power traction and slippage, consequently, promoted lower average speed of work. The theoretical field capacity and area of land involved in the treatment CR were superior when compared to treatment CC, thereby lower consumption of fuel per hour worked was lower in CR treatment.

Demanda energética de máquinas agrícolas na implantação da cultura do sorgo forrageiro

Forage sorghum can be grown in areas and environmental conditions dry and warm, where the productivity of other forage plants can often be uneconomical. The soil disturbance can be made only on the lines of planting (direct seeding) or entirely from the area for seeding (conventional tillage), as plowing, harrowing, subsoiling and chiseling (minimum tillage). The displacement speed ideal for planting is one in which the groove is opened and closed without removing the over-ground, allowing the distribution of seed spacing and depth constant. The experiment was conducted in a soil classified as Typic Oxisol at Lageado Experimental Farm, Faculty of Agronomic Sciences, UNESP, Botucatu campus. This study aimed to evaluate the response of sorghum in four forward speeds (3, 5, 6 and 9 km h-1) and four systems of soil management: SD (direct seeding), GP (harrow + sowing), LPG (disc harrow and two light disking + sowing) and CR (scarification and seeding). Data was subjected to analysis of variance in a factorial 4 x 4 and a randomized block design with split plots. The following parameters were determined: average speed, average strength of the drawbar, the average power drawbar, theoretical field capacity of the tractor-equipment, fuel consumption per hour. For the conditions under which the experiment was conducted, it was concluded that the hourly fuel consumption was not influenced by tillage systems and was inversely proportional to the increase of speed work, and that the change of speed in the sowing operation did not provide additional the values of average traction force on the bar of the tractor-planter.

Variáveis morfológicas da cana-de-açúcar em função do regime hídrico durante o desenvolvimento inicial

Water deficit is one of the factors which most limit agriculture yield and growth. Although sugar cane has moderate tolerance to drought, it presents high yield losses under the influence of this abiotic factor. Based on this fact, selection of genotypes tolerant to water stress may represent an alternative for decreasing the amount of water used for irrigation, while keeping or increasing yield. This study was performed in order to evaluate the performance of four sugarcane cultivars during initial development under water stress conditions, by means of morphological variables to select more tolerant genotypes to drought. The experiment was carried out in a greenhouse at the Department of Rural Engineering, College of Agricultural Sciences - UNESP/Botucatu – SP, from November 26th 2010 to April 5th 2011. A total of four sugar cane cultivars were evaluated (RB855453, RB92579, RB965902 and RB965917) under two treatments as follows: control (100% field capacity) and water stress (50% field capacity). Evaluations were performed at 0, 28 and 63 days after treatment application. The following morphological variables were analyzed: plant height, leaf area, leaf length, leaf width, number of green leaves, shoot and root dry matter. The RB855453 and RB92579 cultivars produced more shoot and root dry matter under water stress treatment, while the RB965902 and RB965917 cultivars had lower shoot and root dry matter production under the same conditions. Therefore, the RB855453 and RB 92579 cultivars can be considered tolerant while the RB965902 and RB965917 cultivars can be considered susceptible.

Desempenho efetivo e influência no sistema de limpeza da colheita mecanizada de cana-de-açúcar utilizando diferentes velocidades de deslocamento e rotações do extrator primário

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Desempenho operacional de transplante manual e mecanizado da cultura da alface

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

TRANSVERSAL DISTRIBUTION COMPARISON OF SOLID FERTILIZERS APPLIED OVER ANNUAL CROPS

Centrifugal spreaders dominate the application of solid materials in agriculture offering expressive operational field capacity and extended range of applied rates. Field tests for characterization of theirperformance are conducted without any physical obstacles (such as the presence of plants) during the parabolic trajectory of the falling particles of fertilizer to the soil. The purpose of this study was to comparatively evaluate the transverse distribution of solid fertilizers applied on cropped corn, soybeans and cotton. Evaluations of the spreaders were designed according to ASAE S341.3/99 Standard. Tests consisted in aligning side by side collectors in-between the cropped rows and weighting the material deposited. The results showed that transverse distribution of solid fertilizers applied over the cotton and corn crops is affected by the crop height, interfering directly on the effective width of the spreader application, which was not observedin the soybean crop, once the fertilizer application is done when the crop was still below the collector's height. The results suggest that evaluation of effective width of the spreaders application need to be done under real crop environment.

Biochar in perennial crops: nutritional, agronomical and environmental implications

Biochar is the solid C-rich matrix obtained by pyrolysis of biomasses, currently promoted as a soil amendment with the aim to offset anthropogenic C emissions, while ameliorating soil properties and growth conditions. Benefits from biochar seem promising, although scientific understandings are beginning to be explored. In this project, I performed a suite of experiments in controlled and in field conditions with the aims to investigate the effect of biochar on: a) the interaction with minerals; b) Fe nutrition in kiwifruit; c) soil leaching, soil fertility, soil CO2 emissions partitioning, soil bacterial profile and key gene expression of soil nitrification-involved bacteria; d) plant growth, nutritional status, yield, fruit quality and e) its physical-chemical changes as affected by long-term environmental exposure. Biochar released K, P and Mg but retained Fe, Mn, Cu and Zn on its surface which in turn hindered Fe nutrition of kiwifruit trees. A redox reaction on the biochar surface exposed to a Fe source was elucidated. Biochar reduced the amount of leached NH4+-N but increased that of Hg, K, P, Mo, Se and Sn. Furthermore, biochar synergistically interacted with compost increasing soil field capacity, fertility, leaching of DOC, TDN and RSOC, suggesting a priming effect. However, in field conditions, biochar did not affect yield, nutritional status and fruit quality. Actinomadura flavalba, Saccharomonospora viridis, Thermosporomyces composti and Enterobacter spp. were peculiar of the soil amended with biochar plus compost which exhibited the highest band richness and promoted gene expression levels of Nitrosomonas spp., Nitrobacter spp. and enzymatic-related activity. Environmental exposure reduced C, K, pH and water infiltration of biochar which instead resulted in a higher O, Si, N, Na, Al, Ca, Mn and Fe at%. Oxidation occurred on the aged biochar surface, it decreased progressively with depth and induced the development of O-containing functional groups, up to 75nm depth.

Respuesta productiva a diferentes programaciones de riego en trigo (Triticum aestivum L.) : región semiárida de Córdoba, Argentina

En la evaluación regional de riego con equipos presurizados, se observa que la mayoría de los establecimientos no hacen uso de programas de riego basados en necesidades hídricas, dando lugar a un uso inadecuado de los recursos hídricos. Por ello, en el presente trabajo se evalúa la producción de trigo (Triticum aestivum L.) bajo riego programado considerando las variables clima-suelo-cultivo. La experiencia se desarrolló en el campo experimental de la Universidad Nacional de Río Cuarto durante los ciclos 1999, 2000 y 2001. Se contó con la información climática de la estación meteorológica instalada en el lugar. En los ensayos se consideró un diseño estadístico en parcelas totalmente al azar con seis repeticiones. Los tratamientos fueron los siguientes: 1. sin riego; 2. reponiendo desde un umbral de marchitez incipiente hasta capacidad de campo; 3. reponiendo desde umbral de marchitez incipiente hasta un nivel que permita el aprovechamiento del agua de lluvia con un 75 % de probabilidad de ocurrencia; 4. riego sólo en el período comprendido entre las etapas fenológicas de macollaje y grano lechoso y 5. considerando el modelo de programación YACU. Los resultados de esta experiencia en los tres años considerados establecen una respuesta significativa al riego complementario, con una producción promedio de los tratamientos bajo riego de 4980 kg.ha-1 en 1999, 5895 kg.ha-1 en el 2000 y 6271 kg.ha-1 en el 2001, contra 3296 kg.ha-1, 4054 kg.ha-1 y 3197 kg.ha-1, respectivamente, para los tratamientos sin riego. Dentro de los tratamientos bajo riego, en los dos primeros años se obtuvieron valores significativamente menores en las parcelas regadas sólo entre macollaje y grano lechoso: 4704 kg.ha-1 en 1999 y 4973 kg.ha-1 en el 2000.

Caracterización de tres suelos en Hidalgo y Querétaro, México: disponibilidad y daño tóxico por arsénico en garbanzo (Cicer arietinum L.)

La presencia de arsénico (As) en suelos permite su migración hacia cultivos como el garbanzo (Cicer arietinum L.). En este trabajo se comparan contenidos de As en tres suelos de dos estados de la República Mexicana, y su acumulación en C. arietinum L. Los suelos resultaron moderadamente alcalinos, no salinos, reductores intermedios y con potenciales zeta (pZ) que indican suspensiones coloidales moderadamente estables. Con moderados contenidos de humedad y texturas franco- arcillosas, densidad aparente, capacidad de campo, agregados estables y capacidad de intercambio catiónico, significativamente diferentes y semejantes en velocidad de infiltración y espesor del horizonte A. En materia orgánica, carbono y nitrógeno son significativamente diferentes y con bajos contenidos. Existen diferencias importantes entre semillas de C. arietinum L. certificadas o no en su capacidad de germinación y desarrollo de raíces. El efecto genotóxico del As en raíces de C. arietinum L. se apreció por inducción de micronúcleos, reducción de 2,8 veces la división celular de muestras tratadas con agua con As, respecto de muestras control. Se apreció incremento de As de 9,5 veces en plántulas germinadas en suelo de El Salitre, que en suelo de Bella Vista, indicativo de migración del As. La suma de efectos de concentración de As en suelos y agua se incrementa 15,3 veces. Entre suelos de Bella Vista y Querétaro la correlación fue 2,9 veces mayor. En controles positivos los IBAs resultan 3 veces mayores que en las pruebas experimentales.

Abundance and sizes of European oak species (Quercus petraea (Matt.) Liebl., Quercus robur L.) in dependence of neighborhood and environmental factors

Quercus robur L. (pedunculate oak) and Quercus petraea (Matt.) Liebl. (sessile oak) are two European oak species of great economic and ecological importance. Even though both oaks have wide ecological amplitudes of suitable growing conditions, forests dominated by oaks often fail to regenerate naturally. The regeneration performance of both oak species is assumed to be subject to a variety of variables that interact with one another in complex ways. The novel approach of this research was to study the effect of many ecological variables on the regeneration performance of both oak species together and identify key variables and interactions for different development stages of the oak regeneration on a large scale in the field. For this purpose, overstory and regeneration inventories were conducted in oak dominated forests throughout southern Germany and paired with data on browsing, soil, and light availability. The study was able to verify the assumption that the occurrence of oak regeneration depends on a set of variables and their interactions. Specifically, combinations of site and stand specific variables such as light availability, soil pH and iron content on the one hand, and basal area and species composition of the overstory on the other hand. Also browsing pressure was related to oak abundance. The results also show that the importance of variables and their combinations differs among the development stages of the regeneration. Light availability becomes more important during later development stages, whereas the number of oaks in the overstory is important during early development stages. We conclude that successful natural oak regeneration is more likely to be achieved on sites with lower fertility and requires constantly controlling overstory density. Initially sufficient mature oaks in the overstory should be ensured. In later stages, overstory density should be reduced continuously to meet the increasing light demand of oak seedlings and saplings.

Residual effect of organic zinc complexes in acid and calcareous soils on navy bean (phaseolus vulgaris l.) and flax (linum usitatissimum l.) crops under greenhouse conditions. Influence of the moisture conditions = Efecto residual de complejos orgánicos de zinc en suelos ácido y calizo en cultivos de judía (phaseolus vulgaris l.) y lino (linum usitatissimum l.) Realizados en condiciones de invernadero. Influencia de las diferentes condiciones de humedad

El Zn es un elemento esencial para el crecimiento saludable y reproducción de plantas, animales y humanos. La deficiencia de Zn es una de las carencias de micronutrientes más extendidas en muchos cultivos, afectando a grandes extensiones de suelos en diferentes áreas agrícolas. La biofortificación agronómica de diferentes cultivos, incrementando la concentración de micronutriente Zn en la planta, es un medio para evitar la deficiencia de Zn en animales y humanos. Tradicionalmente se han utilizado fertilizantes de Zn inorgánicos, como el ZnSO4, aunque en los últimos años se están utilizado complejos de Zn como fuentes de este micronutriente, obteniéndose altas concentraciones de Zn soluble y disponible en el suelo. Sin embargo, el envejecimiento de la fuente en el suelo puede causar cambios importantes en su disponibilidad para las plantas. Cuando se añaden al suelo fuentes de Zn inorgánicas, las formas de Zn más solubles pierden actividad y extractabilidad con el paso del tiempo, transformándose a formas más estables y menos biodisponibles. En esta tesis se estudia el efecto residual de diferentes complejos de Zn de origen natural y sintético, aplicados en cultivos previos de judía y lino, bajo dos condiciones de riego distintas (por encima y por debajo de la capacidad de campo, respectivamente) y en dos suelos diferentes (ácido y calizo). Los fertilizantes fueron aplicados al cultivo previo en tres dosis diferentes (0, 5 y 10 mg Zn kg-1 suelo). El Zn fácilmente lixiviable se estimó con la extracción con BaCl2 0,1M. Bajo condiciones de humedad por encima de la capacidad de campo se obtuvieron mayores porcentajes de Zn lixiviado en el suelo calizo que en el suelo ácido. En el caso del cultivo de judía realizado en condiciones de humedad por encima de la capacidad de campo se compararon las cantidades extraídas con el Zn lixiviado real. El análisis de correlación entre el Zn fácilmente lixiviable y el estimado sólo fue válido para complejos con alta movilidad y para cada suelo por separado. Bajo condiciones de humedad por debajo de la capacidad de campo, la concentración de Zn biodisponible fácilmente lixiviable presentó correlaciones positivas y altamente significativas con la concentración de Zn disponible en el suelo. El Zn disponible se estimó con varios métodos de extracción empleados habitualmente: DTPA-TEA, DTPA-AB, Mehlich-3 y LMWOAs. Estas concentraciones fueron mayores en el suelo ácido que en el calizo. Los diferentes métodos utilizados para estimar el Zn disponible presentaron correlaciones positivas y altamente significativas entre sí. La distribución del Zn en las distintas fracciones del suelo fue estimada con diferentes extracciones secuenciales. Las extracciones secuenciales mostraron un descenso entre los dos cultivos (el anterior y el actual) en la fracción de Zn más lábil y un aumento en la concentración de Zn asociado a fracciones menos lábiles, como carbonatos, óxidos y materia orgánica. Se obtuvieron correlaciones positivas y altamente significativas entre las concentraciones de Zn asociado a las fracciones más lábiles (WSEX y WS+EXC, experimento de la judía y lino, respectivamente) y las concentraciones de Zn disponible, estimadas por los diferentes métodos. Con respecto a la planta se determinaron el rendimiento en materia seca y la concentración de Zn en planta. Se observó un aumento del rendimiento y concentraciones con el efecto residual de la dosis mayores (10 mg Zn kg-1) con respecto a la dosis inferior (5 mg Zn 12 kg-1) y de ésta con respecto a la dosis 0 (control). El incremento de la concentración de Zn en todos los tratamientos fertilizantes, respecto al control, fue mayor en el suelo ácido que en el calizo. Las concentraciones de Zn en planta indicaron que, en el suelo calizo, serían convenientes nuevas aplicaciones de Zn en posteriores cultivos para mantener unas adecuadas concentraciones en planta. Las mayores concentraciones de Zn en la planta de judía, cultivada bajo condiciones de humedad por encima de la capacidad de campo, se obtuvieron en el suelo ácido con el efecto residual del Zn-HEDTA a la dosis de 10 mg Zn kg-1 (280,87 mg Zn kg-1) y en el suelo calizo con el efecto residual del Zn-DTPA-HEDTA-EDTA a la dosis de 10 mg Zn kg-1 (49,89 mg Zn kg-1). En el cultivo de lino, cultivado bajo condiciones de humedad por debajo de la capacidad de campo, las mayores concentraciones de Zn en planta ese obtuvieron con el efecto residual del Zn-AML a la dosis de 10 mg Zn kg-1 (224,75 mg Zn kg-1) y en el suelo calizo con el efecto residual del Zn-EDTA a la dosis de 10 mg Zn kg-1 (99,83 mg Zn kg-1). El Zn tomado por la planta fue determinado como combinación del rendimiento y de la concentración en planta. Bajo condiciones de humedad por encima de capacidad de campo, con lixiviación, el Zn tomado por la judía disminuyó en el cultivo actual con respecto al cultivo anterior. Sin embargo, en el cultivo de lino, bajo condiciones de humedad por debajo de la capacidad de campo, se obtuvieron cantidades de Zn tomado superiores en el cultivo actual con respecto al anterior. Esta tendencia también se observó, en ambos casos, con el porcentaje de Zn usado por la planta. Summary Zinc is essential for healthy growth and reproduction of plants, animals and humans. Zinc deficiency is one of the most widespread micronutrient deficiency in different crops, and affect different agricultural areas. Agronomic biofortification of crops produced by an increased of Zn in plant, is one way to avoid Zn deficiency in animals and humans Sources with inorganic Zn, such as ZnSO4, have been used traditionally. Although, in recent years, Zn complexes are used as sources of this micronutrient, the provide high concentrations of soluble and available Zn in soil. However, the aging of the source in the soil could cause significant changes in their availability to plants. When an inorganic source of Zn is added to soil, Zn forms more soluble and extractability lose activity over time, transforming into forms more stable and less bioavailable. This study examines the residual effect of different natural and synthetic Zn complexes on navy bean and flax crops, under two different moisture conditions (above and below field capacity, respectively) and in two different soils (acid and calcareous). Fertilizers were applied to the previous crop in three different doses (0, 5 y 10 mg Zn kg-1 soil). The easily leachable Zn was estimated by extraction with 0.1 M BaCl2. Under conditions of moisture above field capacity, the percentage of leachable Zn in the calcareous soil was higher than in acid soil. In the case of navy bean experiment, performed in moisture conditions of above field capacity, amounts extracted of easily leachable Zn were compared with the real leachable Zn. Correlation analysis between the leachable Zn and the estimate was only valid for complex with high mobility and for each soil separately. Under moisture conditions below field capacity, the concentration of bioavailable easily leachable Zn showed highly significant positive correlations with the concentration of available soil Zn. The available Zn was estimated with several commonly used extraction methods: DTPA-TEA, AB-DTPA, Mehlich-3 and LMWOAs. These concentrations were higher in acidic soil than in the calcareous. The different methods used to estimate the available Zn showed highly significant positive correlations with each other. The distribution of Zn in the different fractions of soil was estimated with different sequential extractions. The sequential extractions showed a decrease between the two crops (the previous and current) at the most labile Zn fraction and an increase in the concentration of Zn associated with the less labile fractions, such as carbonates, oxides and organic matter. A positive and highly significant correlation was obtained between the concentrations of Zn associated with more labile fractions (WSEX and WS + EXC, navy bean and flax experiments, respectively) and available Zn concentrations determined by the different methods. Dry matter yield and Zn concentration in plants were determined in plant. Yield and Zn concentration in plant were higher with the residual concentrations of the higher dose applied (10 mg Zn kg-1) than with the lower dose (5 mg Zn kg-1), also these parameters showed higher values with application of this dose than with not Zn application. The increase of Zn concentration in plant with Zn treatments, respect to the control, was greater in the acid soil than in the calcareous. The Zn concentrations in plant indicated that in the calcareous soil, new applications of Zn are desirable in subsequent crops to maintain suitable concentrations in plant. 15 The highest concentrations of Zn in navy bean plant, performed under moisture conditions above the field capacity, were obtained with the residual effect of Zn-HEDTA at the dose of 10 mg Zn kg-1 (280.87 mg Zn kg-1) in the acid soil, and with the residual effect of Zn- DTPA-HEDTA-EDTA at a dose of 10 mg Zn kg-1 (49.89 mg Zn kg-1) in the calcareous soil. In the flax crop, performed under moisture conditions below field capacity, the highest Zn concentrations in plant were obtained with the residual effect of Zn-AML at the dose of 10 mg Zn kg-1 (224.75 Zn mg kg-1) and with the residual effect of Zn-EDTA at a dose of 10 mg Zn kg-1 (99.83 mg Zn kg-1) in the calcareous soil. The Zn uptake was determined as a combination of yield and Zn concentration in plant. Under moisture conditions above field capacity, with leaching, Zn uptake by navy bean decreased in the current crop, respect to the previous crop. However, in the flax crop, under moisture conditions below field capacity, Zn uptake was higher in the current crop than in the previous. This trend is also observed in both cases, with the percentage of Zn used by the plant

Summer deficit irrigation strategies in hedgerow olive orchard cv. ‘Arbequina’: Effect on fruit characteristics and yield.

Maximum production in hedgerow olive orchards is likely not achieved with maximum evapotranspiration over the long-term. Thus, regulated deficit irrigation (RDI) should be considered as a management option. Four irrigation treatments were evaluated during the summer when olive is most drought resistant. Control (CON) was irrigated to maintain the rootzone close to field capacity. Severe water deficit was applied by irrigating 30% CON from end of fruit drop to end July (DI-J) and from end July until beginning of oil synthesis (DI-A). Less severe water deficit was applied during July and August (DI-JA) by irrigating 50% CON. Flowering, fruiting, abscission, fruit development, fresh and dry weight of fruits, and oil production were evaluated. There were not significant differences in number of buds initiated, number of fruits per inflorescence and fruit drop. Oil production was significantly different between irrigation treatments in all experimental years. CON produced more oil and fruit with higher oil% than DI-A and DI-JA. Oil production of DI-J was not significantly reduced compared to CON and oil% was greater. DI-J was the most effective RDI strategy; with 16% less applied water relative to CON average loss in oil production of 8% was not significantly different to CON. While DI-JA saved most water (27%), oil production was reduced by 15%. Greatest loss in oil production (21%) was observed in DI-A with water saving of 22%.

Aplicación de distintas metodologías a la monitorización de la humedad del suelo y al cálculo del balance hídrico diario

Dada la importancia de conocer la humedad del suelo de forma precisa y en tiempo real, se ha realizado este trabajo de investigación cuyo objetivo principal ha sido seleccionar un Balance Hídrico del Suelo (BHS) diario y validar sus estimaciones de humedad del suelo frente a medidas obtenidas “in situ”, aplicándolo a tres emplazamientos seleccionados en la zona centro con características edáficas y climáticas diferentes, y de este modo estimar con cierta precisión la humedad del suelo como Agua Disponible (AD) para las plantas y a su vez permitir la realización de estudios climáticos. Los observatorios meteorológicos seleccionados fueron: Guadalajara/El Serranillo en la zona aluvial del río Henares; Colmenar Viejo/Base Famet en la rampa sur del Guadarrama sobre rocas metamórficas; y Radiosondeo/Madrid(Barajas) en arenas arcósicas de grano grueso. Se realizó una caracterización morfológica y un estudio de las propiedades físicas, químicas e hidrofísicas de los suelos en cada emplazamiento. El suelo de Guadalajara, Xerorthent Típico presenta una secuencia genética de horizontes (Ap-AC-C1-C2) siendo su clase textural entre franco-arenosa a franca, con menos del 2% de elementos gruesos, presencia de caliza a lo largo de todo el perfil, destacando la homogeneidad en vertical y horizontal de sus propiedades. El suelo de Colmenar, Xerorthent Dystrico, presenta una secuencia genética de horizontes (A-C-C/R) apareciendo el horizonte C/R entre 20-30 cm; y la roca aproximadamente a unos 30 cm; destacando en este perfil su acidez y el alto contenido de elementos gruesos. El suelo de Radiosondeo, Haploxeralf Típico, presenta la secuencia normal de horizontes de los alfisoles (A-Bt1-Bt2-C/Bt); destacando su heterogeneidad principalmente en el plano horizontal, con presencia del Bt a diferentes profundidades en un corto espacio longitudinal. En una primera fase de experimentación (2007-2008) se seleccionaron BHS diarios que sólo utilizaban como datos de entrada la información de variables meteorológicas y el valor del Agua Disponible Total (ADT) para cada tipo de suelo y profundidad. Se probaron BHS diarios con agotamiento exponencial y directo de la reserva, utilizando la evapotranspiración de referencia de Penman-Monteith recomendada por FAO. Al mismo tiempo que se disponía de los datos estimados de humedad de suelo mediante diferentes BHS diarios en los tres emplazamientos, también se realizó una monitorización de la humedad del suelo “in situ” mediante el método gravimétrico, con adaptación de dicha metodología a la problemática de cada suelo, para determinar en cada fecha tanto la humedad del suelo como su contenido de AD para una profundidad de 0 a 30 cm. Se tomaron en cada fecha de muestreo 5 muestras para la profundidad 0- 10 cm, otras cinco para 10-20 cm y otras cinco para 20-30 cm, realizándose el correspondiente tratamiento estadístico de los datos. El ADT se calculó a partir de los datos de capacidad de campo y punto de marchitez obtenidos en laboratorio con membrana de Richards. Los resultados de esta primera fase permitieron conocer que el BHS exponencial diario era el que mejor estimaba el AD en Guadalajara considerando la capacidad de campo a una presión de 33 kPa, mientras que en Colmenar se debían considerar para un mejor ajuste, 10 kPa en lugar de 33 kPa. En el observatorio de Radiosondeo debido a que en cada fecha de muestreo la profundidad en la que aparecía el horizonte Bt era diferente, no se pudo demostrar si el BHS exponencial diario tenía un buen comportamiento. En una segunda fase de experimentación (2009-2012) y con el objeto de aminorar los problemas encontrados en Radiosondeo para la medida de humedad del suelo por el método gravimétrico, se procedió a la instalación y utilización de diferentes sensores de medida de humedad de suelo en el mismo observatorio: TDR (time domain reflectometry - TRIME T3 de IMKO); FDR capacitivo (frecuency domain reflectometry - ECH2O EC-20 de DECAGON) y otros. Esta segunda fase de experimentación tuvo una duración de 4 años y se compararon las medidas de humedad de suelo obtenidas a partir de los sensores con las estimadas del BHS exponencial hasta una profundidad de 0 a 85 cm. En laboratorio se realizaron calibraciones específicas de los sensores TDR y FDR para cada uno de los horizontes más diferenciados del Haploxeralf Típico, utilizando diferentes tipos de regresión. Los valores de humedad de suelo con el equipo TDR, corregidos mediante la calibración específica de laboratorio, fueron los que más se ajustaron a las medidas realizadas por método gravimétrico “in situ”, por lo que se utilizó el TDR para las comparaciones con los valores obtenidos del BHS exponencial diario durante los cuatro años de esta segunda fase experimental. Se realizaron diferentes estimaciones del ADT, partiendo de datos de laboratorio y/o de datos procedentes de humedad de los sensores en campo. Los resultados mostraron de nuevo la conveniencia de utilizar el BHS exponencial diario, pero en este caso, con la estimación del ADT realizada a partir de las gráficas de los sensores. Mediante la utilización de los datos de humedad del BHS exponencial diario se han realizado comparaciones con el mismo tipo de balance pero utilizando un periodo semanal o mensual en lugar de diario, para conocer las diferencias. Los valores obtenidos con periodicidad mensual han dado valores de AD inferiores a los balances calculados semanalmente o diariamente. Por último se ha comprobado que los resultados de un BHS exponencial diario pueden complementar la información que se obtiene del Índice de Precipitación Estandarizado (SPI) y pueden mejorar el estudio de la sequía agrícola. ABSTRACT Due to the importance of a better knowledge of soil water at real time and in a more precisely way, this research work has being carried out with the main objective of selecting a daily Soil Water Balance (SWB) to estimate soil water content, and validate it in comparison to “in situ” measurements. Three locations, differing in soil and climate characteristics, were selected in central Spain in order to estimate with certain acuity soil water as plant-Available Water (AW) and to serve as a tool for the climatic studies. The selected places near meteorology stations were: Guadalajara/El Serranillo an alluvium of the Henares watershed; Colmenar Viejo/Base Famet, in the south raised area of the Guadarrama river basin, over metamorphic rocks; and Radiosondeo/Madrid (Barajas) in coarse arkosic sandstone. Morphology characterization, physical, chemical and hydrologic soil properties were studied in each area. In Guadalajara the soil is a Typic Xerorthent with a (Ap-AC-C1- C2) genetic horizon sequence, loam-sandy to loam textural class, less than 2% of rock fragments, presence of equivalent CaCO3 through the whole profile, outstanding the vertical and horizontal homogeneity of the properties. In Colmenar the soil is represented by a Dystric Xerorthent with a (A-C-C/R) genetic horizon sequence, the C/R is 20-30 cm deep where rock outcrops are approximately at 30 cm; a characteristic feature of this profile is its high acidity and high rock fragments content. In Radiosondeo the soil is represented by a Typic Haploxeralf, with the usual alfisol genetic horizon sequence (A-Bt1-Bt2-C/Bt); outstanding its horizontal heterogeneity, “the variability of the Bt (clay enriched horizon) depth in short distances”. In a first experimental stage (2007-2008), the daily SWB chosen was that which only uses as input data the information from the meteorology variables and plant-Total Available Water (TAW) for each soil type and depth. Different daily SWB (with exponential or direct plant-Available Water depletion) were applied, using the Penman- Monteith reference evapotranspiration (ETo) recommended by FAO. At the same time as soil water content was estimated from the different daily SWB at the three locations, also soil water content was being monitored by “in situ” gravimetric methodology, adapting it to each soil characteristic, to determine every time soil water content and AW to a depth of 0 to 30 cm. In each sampling date, 5 samples for each depth were taken: 0-10 cm; 10-20 cm and 20-30 cm and the data were submitted to the corresponding statistical analysis. The TAW was calculated based on field capacity (FC) and permanent wilting point (PWP) data obtained from laboratory by the Richards pressure plate. Results from this first experimental stage show that the daily exponential SWB was the one which better estimated the AW in Guadalajara considering field capacity at -33 kPa, though in Colmenar, field capacity at -10 kPa must be considered instead of -33 kPa for a better estimation. In Radiosondeo due to the fact that the Bt horizon depth varied in different sampling dates, it could not be established if the daily exponential SWB had a good performance. In a second experimental stage (20019-2012) and with the objective of minimizing the problems encountered in Radiosondeo for measuring “in situ” soil water content by the gravimetric method, the installation of different sensors for measuring soil water content were established and used in the same field location: TDR (time domain reflectometry - TRIME T3 from IMKO), capacitance FDR (frecuency domain reflectometry - ECH2O EC-20 from DECAGON) and others. This second experimental stage lasted 4 years in order to compare the soil water measures from the sensors with the estimations by the exponential SWB form 0 to 85 cm soil depths. At laboratory, specific calibrations for TDR and FDR sensors of the Typic Haploxeralf more differentiated horizons were done using different types of regressions. The results showed that soil water data obtained by the TDR equipment, corrected by the specific laboratory calibration, best fitted to “in situ” gravimetric soil water measures. In this way TDR was used for comparing to the daily exponential SWB during the four years of this second experimentation stage. Various estimations for obtaining TAW were tested; based on laboratory data – and/or on the data obtained of the soil water content field sensors. Results confirmed again, the convenience of using the daily exponential SWB, though in this case, with the TAW obtained from the field sensors graphics. Soil water estimated by exponential SWB on daily basis was compared to weekly and monthly periods, in order to know their reliability. The results obtained for a monthly period gave less AW than the ones obtained in a weekly or daily period. Finally it has been proved that the results obtained from the exponential SWB in a daily bases can be used as a useful tool in order to give complementary information to the SPI (Precipitation Standardized Index) and to help in agricultural drought studies.

Factors driving the carbon mineralization priming effect in a sandy loam soil amended with different types of biochar

The effect of biochar on the soil carbon mineral- ization priming effect depends on the characteristics of the raw materials, production method and pyrolysis conditions. The goal of the present study is to evaluate the impact of three different types of biochar on physicochemical properties and CO2 emissions of a sandy loam soil. For this purpose, soil was amended with three different biochars (BI, BII and BIII) at a rate of 8 wt % and soil CO2 emissions were measured for 45 days. BI is produced from a mixed wood sieving from wood chip production, BII from a mixture of paper sludge and wheat husks and BIII from sewage sludge. Cumulative CO2 emissions of biochars, soil and amended soil were well fit to a simple first-order kinetic model with correlation coef- ficients (r 2 ) greater than 0.97. Results show a negative prim- ing effect in the soil after addition of BI and a positive prim- ing effect in the case of soil amended with BII and BIII. These results can be related to different biochar properties such as carbon content, carbon aromaticity, volatile matter, fixed carbon, easily oxidized organic carbon or metal and phenolic substance content in addition to surface biochar properties. Three biochars increased the values of soil field capacity and wilting point, while effects over pH and cation exchange capacity were not observed.