ABSTRACT Castor bean (Ricinus communis L.) is an oleaginous plant of economic importance due to its different industrial applications. Edaphic characteristics are used to determine the viability of places considered as suitable to obtain castor oil. The objectives of this study were to determine the edaphic characteristics and oil content of R. communis, and to evaluate elicitation with salicylic acid (SA) in El Marqués, Querétaro, Mexico. Sampling was carried out in a direct way, selecting sites where castor bean plants were found. Samples of 1.5 kg of soil were taken and 3 clusters of castor bean in a mature state were collected from 21 accessions. The physicochemical characteristics of the soil and oil content of seeds were determined. Finally, 300 plants of the Guanajuatoil variety were planted and elicitated with different SA concentrations under greenhouse conditions in order to determine oil content. The physical analysis of the soil samples indicated dark-colored soils, Mollisol and Vertisol types, with different textures: clay, clay loam, sandy clay loam and sandy loam. Soil chemical analyses showed the following soil characteristics: pH 7.22; electrical conductivity 0.52 dS m-1; organic matter 7.17%; cation exchange capacity 26.77; calcium 38.62, magnesium 6.81, sodium 13.41and potassium 6.97 cmol kg-1; and nitrogen and phosphorus contents of 16.32 and 54 mg kg-1, respectively. Castor oil content was higher in clay soils (41.46%). The plants elicited with SA presented oil contents ranging from 28.99% to 52.9%, obtained with 100 and 900 ^M. In conclusion, elicitation with SA is an adequate method to increase oil content in castor bean seeds. The locality of El Marqués has good potential for the production of castor oil.

ABSTRACT An important aspect in the study and understanding of the physical phenomena involved in water movement in the soil-plant system is the need to carry out the hydrodynamic characterization (HC) of non-saturated field soils. Studies of this type have been widely developed in soils of temperate climates, but they are infrequent in the tropics, hence there is a need for further research in tropical Vertisols under field conditions. Hydrodynamic characterization consists of finding the functional relationship between soil hydraulic conductivity (K), matric head (h) and soil moisture content (θ), widely known as K(θ) and h(θ) relationships, being the main objective of this study. The instantaneous profile method (IPM) was applied, in which splines were used for the HC of a bare, tropical agricultural field soil classified as a Vertisol. Field measurements of h and θ were made at five different soil depths (0.15, 0.30, 0.45, 0.60 and 0.90 m) and values of K at the same depths were estimated with the IPM, which allowed for the estimation of pairs of values of the K(θ) relationships in the soil profile. Unlike in other studies with the same objective, the use of splines was proposed to represent the spatial variation of the H(z) and θ(z) functions in the IPM. Subsequently, the van Genuchten equation was adjusted to the specific values determined for the h(θ) relations (r2 value ranged from 0.65 to 0.87), and the Ks values and the point data of K and θ were used to estimate the accuracy of the equation proposed by Mualem–van Genuchten (M-vG): in this case negative values for the exponent l of the M-vG function were determined for the five soil depths under study, ranging from –7.04 (0.45 m deep), to -13.26 (0.90 m deep). In addition, pedotransfer functions for tropical soils proposed in the literature, based on different soil physical properties, were used to estimate the h(θ) and K(θ) relationships and the saturated hydraulic conductivity (Ks). Best square root of the mean squared error (SRMSEθ) observed was 0.02853 cm3 cm-3 at 0.15 m depth and 0.02262 cm3 cm-3 at 0.9 m depth for h(θ) relations, and in all cases, the SRMSEk values are less than 0.0018 m day-1 for K(θ) relationships. The results reveal the utility of splines in the IPM for characterizing the soil profile K(θ) relationships in field studies, as well as the need for more research to the generation of pedotransfer functions in tropical Vertisols.

ABSTRACT The salinity of the soil constitutes today one of the main degradation processes that affects the lands under irrigation; and especially the production of rice. The objective of the research was to estimate the electrical conductivity of the soil by means of spectral information in the cultivation of rice in the Mayarí municipality, Holguín. The research was developed on a Chromic Vertisol, which are the most prone in the territory to trigger degradation processes such as salinity, given by management practices in rice cultivation. Two semi-empirical models proposed from different spectral indices were used, the NDSI and the IS, which were calculated in the QGis 3.10 software with multispectral images from the Landsat 8 OLI / TIRS sensor. The NDSI and the SI-ASTER showed the lowest determination and negative correlation in both models. The SI and the SI-ASTER produce an overestimation of the electrical conductivity values of the soil (EC ≥ 100%), the NDSI, SSSI.1 and SSSI.2 indicate a moderate content of salts in the soil (EC 20% ˂ EC ≤ 40%). Although the use of spectral salinity indices yielded a high determination, the SI and the SI-ASTER indicated an overestimation of the electrical conductivity existing in the soil, which could be due to the presence of a saturation of the signal captured by the sensor and reflected in the indices obtained, which exceeded the values in which the saline index oscillates.

RESUMEN La salinidad del suelo constituye hoy en día uno de los principales procesos de degradación que afecta las tierras bajo riego; y en especial la producción de arroz. La investigación tuvo como objetivo estimar la conductividad eléctrica del suelo mediante información espectral en el cultivo del arroz en el municipio Mayarí, Holguín. La investigación se desarrolló sobre un Vertisol Crómico, los cuales son los más proclives en el territorio a desencadenar procesos de degradación como la salinidad, dado por las prácticas de manejo en el cultivo del arroz. Se utilizaron dos modelos semiempíricos propuestos a partir de índices espectrales diferentes, el NDSI y el IS los cuales se calcularon en el software QGis 3.10 con imágenes multiespectrales del sensor Landsat 8 OLI/TIRS. El NDSI y el SI-ASTER arrojaron la menor determinación y correlación negativa en ambos modelos. El SI y el SI-ASTER producen una sobreestimación de los valores de conductividad eléctrica del suelo (EC ≥ 100%), el NDSI, SSSI.1 y el SSSI.2 indican un contenido moderado de sales en el suelo (EC 20% ˂ EC ≤ 40%). Aunque la utilización de los índices espectrales de salinidad arrojó una alta determinación, el SI y el SI-ASTER indicaron un sobreestimación de la conductividad eléctrica existente en el suelo lo cual podría deberse a la presencia de una saturación de la señal captada por el sensor y reflejada en los índices obtenidos, la cual sobrepasó los valores en los cuales oscila el índice salino.

RESUMO O objetivo deste trabalho foi verificar o efeito de diferentes sistemas de manejo sobre a qualidade físico-hídrica de um Vertissolo localizado no domínio climático do Semiárido brasileiro. Os tratamentos foram compostos pelos seguintes sistemas de manejo: (S1) Pastagem (Cynodon spp.) com 4 anos; (S2) Romã (Punicata granatum L.) com 6 anos;(S3) Sorgo forrageiro (Sorghum bicolor L.) com 4 anos e, (S4) vegetação nativa. Avaliou-se a retenção de água no solo por meio da curva característica de umidade, densidade do solo, porosidade do solo (macro e microporosidade e porosidade total), capacidade de aeração do solo e porosidade livre de ar. Os dados foram analisados através da estatística multivariada. Os resultados demonstram que o Vertissolo apresenta elevada retenção e baixa disponibilidade de água as plantas. Melhor qualidade estrutural foi observada no solo sob mata nativa. Conclui-se que os sistemas de manejo composto por pastagem e sorgo estão promovendo mudanças, até o presente momento de forma negativa à estrutura do solo, com redução da macroporosidade e da capacidade de aeração do solo.

ABSTRACT The objective of this work was to verify the effect of different management systems on the physical-hydric quality of a Vertisol located in the climatic domain of the Brazilian Semiarid. The treatments were composed by the following management systems: (S1) Pasture (Cynodon spp.) With 4 years; (S2) Pomegranate (Punicata granatum L.) aged 6; (S3) Forage sorghum (Sorghum bicolor L.) aged 4 years and (S4) native vegetation. The soil water retention curve, soil density, porosity of soil (macro, microporosity and, total porosity), soil aeration capacity and free air porosity. The data were analyzed using multivariate statistics. The results demonstrate that the Vertisol presents high retention and low availability of water to the plants. Better structural quality was observed in the soil under native forest. It is concluded that the management systems composed of pasture and sorghum are promoting negative changes to the soil structure, with a reduction of macroporosity and of the aeration capacity of the soil.

ABSTRACT Soil compaction causes negative effects on crop yield and its mechanical response analysis has recently gained relevance for research through numerical methods. In this work, Finite Element Method (FEM) using the Mohr-Coulomb (MC) and Hardening Soil (HS) constitutive models were employed to simulate the mechanical response of a Vertisol agricultural soil. First, an experimental study of the unconsolidated-undrained (UU) triaxial compression test with different moisture contents (w = 10%, 20% and 34%) and confining pressures (σ3 = σc = 0.05 MPa, 0.10 MPa and 0.15 MPa) was carried out, to obtain the shear strength parameters cohesion (c) and friction angle (φ), as well as the Young’s modulus (E) of the soil. The experimental study was conducted through a 32 factorial design with three replicates that it was used to evaluate the influence of the w and σc on E of the studied soil. Also, an analysis of the behavior of the φ and c parameters at each w was performed. Numerical simulations were done with similar conditions as the experimental tests with respect to loading and boundary conditions. A comparison of the mechanical response between numerical results and physical experiments was carried out. As a result, the MC model allowed to estimate satisfactorily the stress-strain relationship of the soil for w of 10% and 20%, while HS model exhibited a better approximation for w of 34% in comparison with the MC model. Finally, the methodology and the adjusted parameters of the agricultural soil obtained in this work, can be used in the study of soil compaction produced by the agricultural machinery.

RESUMEN Los Vertisoles presentan factores edáficos limitantes fundamentalmente de carácter físico. El estudio de su hidropedología, apoyado en técnicas multivariadas, es de vital importancia. El trabajo se desarrolló con el objetivo de determinar, mediante análisis multivariado, el comportamiento hidropedológico de un Vertisol Crómico bajo diferentes usos de la tierra. En áreas bajo pasto natural, caña de azúcar y bosque secundario, pertenecientes a la Estación Provincial de Investigaciones de la Caña de Azúcar de Holguín, se escogieron tres puntos al azar en cada una. Se determinó la resistencia a la penetración, la densidad aparente, la humedad gravimétrica y la humedad volumétrica a las profundidades de 0-10, 10-20 y 20-30 cm. Se realizó un Análisis de Componentes Principales y de Correlaciones Canónicas, con los softwares Statistica 7 y Statgraphics Plus XV.II. Se encontró que las dos primeras componentes realizaron la mayor contribución a la varianza, con un 83.09%. Los mayores aportes (1ra componente) estuvieron dados por la humedad en todas las profundidades y por la compactación del suelo en la profundidad de 20-30 cm. La 2da componente estuvo influenciada por la compactación del suelo en las capas de 0-10 y de 10-20 cm. Existió contraposición entre las variables que caracterizan la fase sólida con las que describen la fase líquida del suelo. Existió correlación entre la humedad del suelo y la compactación. Los dos primeros pares de variables canónicas mostraron una fuerte correlación lineal y dispersada regularmente a lo largo de los valores centrales del modelo, con un notable agrupamiento por profundidades.

ABSTRACT Vertisols present edaphic limiting factors primarily of a physical nature. The study of their hydropedology, supported by multivariate techniques, is of vital importance. The work was developed with the objective of determining, through multivariate analysis, the hydropedological behavior of a Chromic Vertisol under different plant covers. In areas under natural grass, sugarcane, and secondary forest, belonging to the Holguín Sugarcane Provincial Research Station, three random points were chosen in each. Soil penetration resistance, soil bulk density, gravimetric moisture, and volumetric moisture at depths of 0-10, 10-20 and 20-30cm were determined. A Principal Component Analysis and Canonical Correlations were performed using Statistica 7 and Statgraphics Plus XV.II. The first two components made the greatest contribution to the variance, with 83.09%. The greatest contributions (1st component) were given by moisture at all depths and by soil compaction at a depth of 20-30cm. The 2nd component was influenced by soil compaction in the 0-10 and 10-20cm layers. There was a contrast between the variables that characterize the solid phase with which they describe the liquid phase of the soil. There was a correlation between soil moisture and compaction. The first two pairs of canonical variables showed a strong linear correlation and regularly dispersed along the central values of the model, with a remarkable grouping by depths.

Resumen Se evaluaron tres híbridos de maíz bajo tres niveles de fertilización nitrogenada (50, 100 y 150 kg de N/ha) durante la estación lluviosa 2019 en la Granja Experimental Agrícola de la ESPOL (Escuela Superior Politécnica del Litoral), Guayaquil, Guayas, Ecuador. El suelo donde se implementó el experimento se clasifica como Vertisol y es conocido como de alta fertilidad, teniendo en cuenta su alto contenido de mineral arcilloso tipo 2:1 tales como la montmorillonita y/o ilita. Con una CIC y saturación de bases en la superficie son de 43,9meq/100g y 99,4%, respectivamente. Los híbridos que se experimentaron son: Pioneer 4039 (P4039), Advanta 9313 (AV9313) y Advanta 9139 (AV9139), distribuidos por la compañía FARMAGRO. En el área experimental, se aplicaron tres niveles de fertilización nitrogenada (50, 100 y 150kgN/ha), 50 kg de P2O5 y 50 kg de K2O/ha, respectivamente. Como característica agronómica, se observó diferencia significativa al 1% no sólo para el híbrido sino también para el nitrógeno, así como en la longitud de hoja, obteniendo el más alto valor para el AV 9139. Al igual que el caso anterior, el rendimiento del grano con 14% de humedad, se observó una diferencia significativa al 5% para la interacción. Aunque el más alto rendimiento fue para el AV9139, se observó una tendencia negativa de acuerdo a la mayor dosis de nitrógeno. Recomendándose el híbrido AV 9139 con la aplicación de 50kgN/ha de acuerdo con los resultados obtenidos en el análisis económico.

Resumo Avaliaram-se três híbridos de milho sob três níveis de fertilização com nitrogênio (50, 100 e 150 kg de N/ha) durante a estação chuvosa 2019 na Fazenda Experimental Agrícola da ESPOL (Escola Superior Politécnica do Litoral), Guayaquil, Guayas, Equador. O solo onde implantou-se o experimento é classificado como Vertissolo e é conhecido como de alta fertilidade, levando em conta seu alto teor de mineral argiloso tipo 2: 1 tais como a montmorilonita e/ou ilita. Com uma CTC e saturação por bases na superfície são de 43,9 meq/100g e 99,4%, respectivamente. Os híbridos que foram experimentados são: Pioneer 4039 (P4039), Advanta 9313 (AV9313) e Advanta 9139 (AV9139), distribuídos pela empresa FARMAGRO. Na área experimental, aplicaram-se três níveis de adubação nitrogenada (50, 100 e 150kgN/ha), 50kg de P2O5 e 50kg de K2O/ha, respectivamente. Como característica agronômica, observou-se foi diferença significativa ao 1% não só para o híbrido, mas também para o nitrogênio, assim como na longitude de folha, obtendo-se o maior valor para AV 9139. Ao igual que o caso anterior, o rendimento do grão com 14% de umidade, observou-se diferença significativa ao 5% para a interação. Embora o mais alto rendimento foi para AV9139, observou-se uma tendência negativa de acordo com a maior dose de nitrogênio. Recomendando-se o híbrido AV 9139 com a adubação de 50kgN/ha de acordo com os resultados obtidos na análise econômica.

Abstract It was evaluated three hybrids of corn under the three levels of the nitrogen application (50, 100 and 500kgN/ha) during the rainy season at the Experimental Field in the ESPOL (Escuela Superior Politécnica del Litoral), Guayaquil, Guayas, Ecuador. The soil where the experiment was implemented is classified as Vertisol and it is known as high fertility, taking into account its high content of type 2: 1 clay mineral such as montmorillonite and / or illite. It was 43,9 meq/100g for CEC and 99,4% for the base saturation, respectively. These hybrids which were experimented are: Pioneer 4039 (P4039), Advanta 9313 (AV9313) and Advanta 9139 (AV9139), distributed by the company FARMAGRO. On the experimental area, it was applied 50kgP2O5 and 50kgK2O/ha, respectively. As agronomic character, it was observed the significant difference al 1% not only for the hybrid but also for nitrogen, as well as for length of leave, obtaining the largest for the AV 9139. Like the previous case of the grain yield with 14% moisture, it was observed the significant difference at 5% for the interaction. Although it was the highest performance for the AV9139, it was observed the negative trend in accordance with the higher nitrogen amounts. Recommending the hybrid AV 9139 with the application of 50kgN/ha according to the results obtained with the highest net benefit.

Summary: This study performed two assays to analyze the effect of inoculating mycorrhizal fungi on wheat production during winter both by rotating crop and increasing fertilizer doses to implement agricultural conservation practices. The following treatments were established for the first assay: (1) wheat inoculation with mycorrhizal fungus Glomus mosseae without fertilizer; (2) application of 200 units of N ha-1 without inoculation; (3) inoculation + 100 units of N ha-1; (4) application of 100 units of N ha-1 without inoculation; (5) inoculation + 150 units of N ha-1; (6) application of 150 units of N without inoculation. The second assay assessed the response of wheat production to the two preceding crop rotations: maize‑wheat (G-G) and bean-wheat (L-G) and four increasing nitrogen fertilization doses: 0, 100, 150, and 200 units ha-1. With the inoculation of G. mosseae + 75% of nitrogen fertilization, wheat production had the greatest grain yield (5.6 Mg ha-1) and was 36% greater than the control group with the application of only 100% fertilizer without inoculant. Wheat inoculation without nitrogen fertilizer had the lowest production (2.6 Mg ha-1). On the other hand, wheat production with L-G rotation had a better response (R2 = 0.72) at increasing N doses where the greatest grain yield was obtained with 4.7 Mg ha-1 and only 150 units of N ha-1, which corresponded to 1 Mg ha-1 more compared with the maximum wheat production obtained in the G-G rotation with 2000 units of N ha-1. The use of inoculated biofertilizers, such as mycorrhizal fungi or by the effect of crop rotation with legumes, such as bean, requires supplementary N dosage to boost wheat production; however, it is feasible to decrease nitrogen fertilizer dosage to 25%.

Resumen: Se realizaron dos ensayos para estudiar el efecto de la inoculación de hongos micorrízicos en la producción de trigo de invierno y la rotación de cultivos y dosis crecientes de fertilización, ambos aunados a la implementación de prácticas de agricultura de conservación. En el primero se establecieron los siguientes tratamientos: (1) Inoculación del trigo con los hongos micorrízicos: Glomus mosseae, sin fertilización; (2) aplicación de 200 unidades de N ha‑1, sin inoculación; (3) inoculación + 100 unidades de N ha-1; (4) aplicación de 100 unidades de N ha-1, sin inoculación; (5) inoculación + 150 unidades de N ha-1; (6) aplicación de 150 unidades de N, sin inoculación. En el segundo se evaluó la respuesta, en la producción de trigo, a dos rotaciones precedentes de cultivo: maíz-trigo (G-G) y frijol-trigo (L-G), y cuatro dosis crecientes de fertilización nitrogenada: 0, 100, 150 y 200 unidades ha-1. La producción de trigo, con la inoculación de G. mosseae + 75% de fertilización nitrogenada recomendada, tuvo el mayor rendimiento de grano (5.6 Mg ha-1), y fue 36 % mayor, respecto al testigo con aplicación de sólo 100% de la fertilización, sin inoculante. La inoculación de trigo, sin aplicación de fertilizante nitrogenado tuvo la producción más baja (2.6 Mg ha-1). Por otra parte, la producción de trigo con la rotación L-G tuvo una menor respuesta (R2 = 0.72) a las dosis crecientes de N, y fue donde se obtuvo el mayor rendimiento de grano, con 4.7 Mg ha-1, con sólo 150 unidades de N ha-1, que correspondió a 1 Mg ha-1 más, comparado con la máxima producción de trigo que se obtuvo en la rotación G-G, con 200 unidades de N ha-1. El uso de biofertilizantes inoculados, como los hongos micorrízicos, o por efecto de la rotación de cultivos con leguminosas, como frijol, requiere de dosis completarías de N para potenciar la producción de trigo; sin embargo, es factible disminuir en 25% la dosis de fertilización nitrogenada.

ABSTRACT The soil microbial communities involved in the biogeochemical cycles of plant nutrients are negatively affected by unfavorable agricultural practices. In three tillage systems (traditional tillage, TT; traditional tillage with residue incorporation, TTI; and conservation tillage, CT) with three crop rotations (cereal-cereal, C-C; legume-cereal, L-C; and cereal-legume, C-L) at three soil depths (0-5, 5-15, and 15-30 cm), the effects on the populations of bacteria, actinomycetes, and fungi over a period of six crop cycles (3 yr) were evaluated. The tillage system, crop rotation, and depth affected the concentration of microbes in the soil. Under TT/C-C (regional control), they decreased by 7.5%; in contrast, under CT/L-C and TTI/L-C, they increased by 144% and 76%, respectively. Regardless of the tillage system, rotation with legumes, especially when the legume was cultivated in the spring-summer cycle (C-L), caused significant increases in microbial populations. At the end of 3 yr, under CT and TTI the populations of actinomycetes increased, while the fungal population remained stable and the bacterial populations fluctuated in the different crop cycles. In all treatments, the concentration of microorganisms decreased with soil depth. Local practices represent a risk to the diversity of soil microbiota, and it is imperative that farmers adopt conservation practices to achieve sustainability.

ABSTRACT The rice (Oryza sativa L.) crop is very important worldwide for its contribution to human nutrition. Rice grain yield depends on several agronomic management factors that must also be adjusted to the cropping system such as permanent inundation (anaerobic conditions) or direct seeding (aerobic and anaerobic conditions) mainly in response to the application of nutrients such as N. In Chile, the cropping system with direct seeding has limited agronomic and scientific development. The objective was to determine the effect of increasing N (0, 40, 80, 120, and 160 kg ha-1), P (0, 30, 60, and 120 kg P2O5 ha-1), and K (0, 30, 60, and 120 kg K2O ha-1) rates on grain yield and N agronomic efficiency (NAE) (kg grain produced per kg N applied) in two paddy rice soils for two consecutive seasons. Grain yield had a positive response to increasing N rates in the two evaluated soils (grain yield increased from 6.7 to 8.9 Mg ha-1 in the Vertisol and from 7.4 to 11.0 Mg ha-1 in the Alfisol) and a low response to P rates in the Vertisol. The Alfisol showed no response to increasing P rates, and both soils had no response to K application. The N rates that obtained the highest rice grain yield were 120 and 160 kg ha-1 for Alfisol and Vertisol, respectively. The P rate that obtained the highest rice yield in the Vertisol was 30 kg ha-1 P2O5. In addition, NAE values associated to those N rates were 74 and 61, respectively. In conclusion, direct seeding in rice cropping had a response to high rates of applied N, low response to P, and no response to K.

ABSTRACT Tillage systems can affect soil compaction, water content, soil temperature, and yields of cultivated plants. This work examined a Vertisol and the influence of the tillage system on soil compaction and yield of winter wheat (Triticum aestivum L.) grains. The trial was conducted in the vicinity of Požega, Western Serbia, from 2014 to 2017. Four tillage systems (conventional tillage, reduced tillage, disc harrowing, and no-tillage) were applied in the experiment. Tillage systems have significantly influenced soil compaction, measurement time, and soil depth. Mean soil compaction in 2016- 2017 was 1.96 MPa, which was 0.17 MPa lower than in 2014-2015 and 0.30 MPa higher than in 2015-2016. The highest mean wheat yield occurred in the conventional tillage system (4033 kg ha-1), and it was significantly higher than the yield obtained in other soil tillage systems. There was a strong negative correlation between mean wheat yield and soil compaction. It was necessary to apply complete soil tillage to achieve satisfactory wheat grain yields on the Vertisol, which implies plowing and adequate pre-sowing soil preparation.

RESUMO Vertissolos Háplicos e Neossolos Quartizarênicos estão entre as principais classes de solos utilizadas para a produção de melão, na região semiárida do Brasil. O potássio (K) é o nutriente mais extraído pelos frutos de melão amarelo; por isso, nesses solos, são frequentemente aplicadas altas doses de fertilizantes potássicos. Objetivou-se avaliar as frações de K em solos da região semiárida do Brasil, durante o ciclo de cultivo do melão amarelo fertirrigado. Dois experimentos foram conduzidos em duas classes de solo (Vertissolo Háplico e Neossolo Quartzarênico). Para o Vertissolo, os tratamentos compreenderam arranjo fatorial 7 x 2 [sete períodos de avaliação e duas camadas de solo (0-20 cm e 20-40 cm)], com quatro repetições, totalizando 56 unidades experimentais. Para o Neossolo, os tratamentos compreenderam arranjo fatorial 9 x 2 [nove épocas de coleta e duas camadas de solo (0-20 cm e 20-40 cm)], com quatro repetições, totalizando 72 unidades experimentais. A fração K não trocável foi dominante em ambos os solos, principalmente na camada de 0-20 cm, e representa importante reserva desse nutriente para o cultivo de melão, principalmente no Vertissolo. A diminuição nas concentrações das formas solúvel e trocável e o aumento da forma não trocável indicaram aumento na fixação desse nutriente, por fixação no Vertissolo e lixiviação no Neossolo, ao final do ciclo do melão, quando a quantidade de K acumulada pela planta foi menor.

ABSTRACT Haplic Vertisols and Typic Quartzipsamments are among the main classes of soils used for melon production in the Brazilian semiarid region. Potassium (K) is the nutrient most extracted by yellow melon fruits and, for this reason, high doses of potassium fertilizers are often applied to these soils. This study aimed to evaluate potassium fractions in soils of the Brazilian semiarid region, during the cultivation cycle of fertigated yellow melon. Two experiments were carried out with two types of soil (Haplic Vertisol and Typic Quartzipsamment). For the Vertisol, a 7 x 2 [seven evaluation periods and two soil layers (0-20 cm and 20-40 cm)] factorial arrangement was established, with four replications, totaling 56 experimental units. For the Quartzipsamment, a 9 x 2 [nine collection times and two soil layers (0-20 cm and 20-40 cm)] factorial arrangement was used, with four replications, totaling 72 experimental units. The non-exchangeable K fraction was dominant in both soils, mainly in the 0-20 cm layer, and represents an important reserve of this nutrient for melon cultivation, especially in Haplic Vertisols. The decrease in the concentrations of the soluble and exchangeable forms and the increase in the non-exchangeable form indicated an increase in the fixation of this nutrient, by fixation in the Vertisol and leaching in the Quartzipsamment, at the end of the melon cycle, when the amount of K accumulated by the plant was lower.

ABSTRACT Soils in alluvial plains of the lower course of the Acaraú River, Ceará State, Brazil, are weakly developed and have a complex distribution in the landscape. This study reports the pedogenic characterization of such soils in an effort to understand their formation. Soil pits were opened in four representative sites, profile morphology was described, and soil samples were collected for chemical, physical, mineralogical, and micromorphological analyses. All profiles had weak pedogenic development, as inferred from their morphological characteristics, lack of B horizon, and high silt/clay ratio. Organic carbon and particle size distributions were heterogeneous in Fluvisol, Planosol, and Solonchak, in agreement with their sedimentary nature. Intrinsic characteristics of each profile indicated variations in pedogenic processes related to depositional conditions, which, in turn, were determined by the alluvial nature of sediments and water table dynamics. Consequently, Fluvisols at higher elevations showed reduced pedogenic development. In adjacent areas, Planosols showed pores filled with clay minerals and a texture gradient, indicative of past lessivage. Vertisol was identified in small depressions and exhibited intense pedoturbation and high sodium concentration in deep layers. Solonchak had a high degree of hydromorphism, high sodium concentration, and high electrical conductivity. The distinct pedogenesis of alluvial plain soils in Northeastern Brazil is evidenced by their morphological, chemical, and physical properties.

Abstract This research seeks to identify groundwater recharge and discharge areas in the administrative aquifers of the Ayuquila-Armeria river basin in the states of Jalisco and Colima, Mexico. The Ayuquila-Armeria river basin is one of the 15 most important of the 100 rivers running across the Pacific slope, and is among the 43 most important rivers at the country level. The regional climate is warm-humid in lowlands and subhumid temperate in highlands, with a summer rainy season (June to October) and a dry season the rest of the year. The basin shows a striking relief: from sea level to 4260 m a.s.l. at Nevado de Colima. The identification of these areas was based on a multi-criteria analysis of surface indicators of recharge and discharge areas supported by the flow systems theory (FST). This allows a systemic view of the environment, integrating various elements of nature, in addition to acknowledging groundwater and geological agent that causes a wide variety of processes and manifestations on the surface. The integration of Geographic Information Systems (GIS) and the Multi-Criteria Analysis (MCA) made possible to evaluate the potential recharge/ discharge at the regional level by analyzing physical variables such as lithology, soil, relief, slope, vegetation, precipitation, and a topographic humidity index. In the study area, the territory with high recharge potential ranges from 21% to 80%; the area with low and very low recharge potential, from 4% to 30%. The main potential recharge areas are located in the upper portion of mid-elevation and low mountains covered by pine-oak, oak, and tropical deciduous forests, and grasslands, and to a lesser extent, fir and mountain cloud forests. Soil types include mainly Regosol, Leptosol, Cambisol, Luvisol, Andosol, Umbrisol, and Phaeozem in slopes of 15%-30% covering units of rhyolitic tuff, andesite-basalt, andesite, lahar-pyroclastic rock, granite-granite diorite, and limestone. These areas are located mainly in Sierra de Cacoma-Manantl, Sierra Verde, Sierra de Quila, Sierra de Tapalpa, and the Nevado de Colima volcanic complex. For its part, discharge areas are found mainly in the coastal plains of Jalisco and Colima, associated with Calcisol, Arenosol, Fluvisol, Planosol, Gleysol, Solonchak, and Vertisol soils, and with with halophytic-hydrophytic grassland, bulrush, and mangrove vegetation. These are located in inlandlake areas in San Marcos, Sayula, and Zapotlán. Other discharge areas are the plains and intermontane valleys of Union de Tula and Autlán-El Grullo, as well as the bottom of V-valleys in certain areas of the basin. These can act as natural hydraulic boundaries of flow systems, limiting the amount of groundwater in each zone. The lateral alternation of recharge and discharge areas implies that the water recharged in a particular region may flow to a number of discharge areas, i.e., the water discharged in a given region may come from different regions. The above has important implications in the estimation of the availability estimated from the water balance, since groundwater may flow to more than one discharge area within the same “administrative” aquifer. This type of studies are a first approach providing innovative evidence to the systemic study of groundwater, i.e., the recharge-discharge areas. Their application positively supplements the results of the water balance used in the official evaluation of groundwater availability in Mexico.

Resumen Esta investigación busca identificar las zonas de recarga y descarga del agua subterránea en la cuenca del río Ayuquila-Armería en los estados de Jalisco y Colima. La identificación de estas zonas se logró mediante un análisis multicriterio con la teoría de los sistemas de flujo (TSF). Esta teoría permite obtener una visión sistémica del ambiente, integrando diversos elementos de la naturaleza, además de reconocer el agua subterránea como agente geológico causante de una gran variedad de procesos y manifestaciones en la superficie a través de condiciones naturales contrastantes entre la zona de recarga y descarga de agua subterránea. La integración de los Sistemas de Información Geográfica (SIG) y el Análisis Multicriterio (AMC) permitió identificar los sitios con mayor potencial de recarga y descarga analizando geología, suelo, topoformas, pendiente, vegetación e índice topográfico de humedad (ITH). La superficie con alto potencial de recarga varía de 21% a 80%, mientras que la superficie de descarga, de 4% a 30%. Las principales zonas potenciales de recarga son la sierra de Cacoma-Manantlán, la sierra Verde, la sierra de Quila, la sierra de Tapalpa y el complejo volcánico del Nevado de Colima. Por su parte, las zonas de descarga se encuentran principalmente en las planicies costeras de Jalisco y Colima, así como en una zona de lagos interiores en San Marcos, Sayula y Zapotlán. Otras zonas de descarga las constituyen las planicies y los valles intermontanos de Unión de Tula y Autlán-El Grullo, así como los fondos de valles en V en determinadas zonas de la cuenca.

ABSTRACT The objective of this research was to compare the spectral signature of two soil types, Cambisol and Vertisol, cultivated with sugarcane in the Villa Clara province, Cuba. The soil samples were collected at two levels: 1) Landscape level of the province (DC), 2) within a field (CE). The vis-NIR spectral signatures were acquired in the laboratory by means of a diode array spectrophotometer covering the wavelength range from 399 to 1697 nm. The results showed that the absorbance spectra of these two soil types can clearly be distinguished, which suggests that the soil type could be derived from the spectra. The light absorbance by the soil varied with wavelength in each soil type in DC and CE. A visual comparison of the spectral shape and the variation between a field and landscape within the same soil group showed some similitude. Around the wavelength of 1400 nm in both soil types the absorbance values increase and consequently decrease again. These characteristics bring a good match of the spectral signatures of DC and CE. In addition, in CE an increasing pattern of soil absorbance was observed as organic matter (OM %) increases. This pattern was observed around 399 nm and 580 nm while for Cambisol and Vertisol respectively.

RESUMEN El objetivo de esta investigación fue comparar las firmas espectrales de dos tipos de suelos agrícolas, Pardo mullido carbonatado y Vertisol, cultivados con caña de azúcar en la provincia de Villa Clara, Cuba. Las muestras de suelo se colectaron en dos niveles: 1) diferentes campos de la provincia (DC), 2) campo específico (CE). Las firmas espectrales vis-NIR se adquirieron a nivel de laboratorio con un espectrofotómetro portátil en el rango de longitud de onda de 399 a 1697 nm. Los resultados mostraron que los espectros de absorbancia de estos tipos de suelos pueden distinguirse, lo que sugiere que el tipo de suelo podría identificarse a partir de los espectros obtenidos. La absorbancia de luz varió con la longitud de onda en cada tipo de suelo en DC y CE. Una comparación visual de la forma de los espectros y la variación entre DC y CE dentro del mismo tipo de suelo mostró alguna similitud. Alrededor de 1400 nm en ambos tipos de suelo, los valores de absorbancia aumentaron y disminuyeron seguidamente. Estas características demuestran una excelente coincidencia entre las firmas espectrales de DC y CE. Además, en CE se observó que el patrón de absorbancia del suelo aumenta en la misma medida en que se incrementa la materia orgánica (MO %). En suelo Pardo mullido carbonatado este patrón se observó a 399 nm, mientras que para Vertisol fue cerca de 580 nm.