Arbuscular Mycorrhizal Fungi Associated with Maize (Zea mays L.) in the Formation and Stability of Aggregates in Two Types of Soil.

Knowledge of native Arbuscular Mycorrhizal Fungi (AMF) and their relationship with the edaphic characteristics where they live is important to establish the influence of allochthonous AMF, which were inoculated, on the development and stability of soil aggregates. The objectives of this research were to know the composition of native AMF species from two contrasting soils, and to establish the development and stability of aggregates in those soils with corn plants after inoculating them with allochthonous AMF. The experiment had three factors: Soil (two levels [S1 and S2]), HMA (three levels: without application [A0], with the application of Claroideoglomus claroideum [A1] and with the application of a consortium [A2]) and Fertilization (two levels (without fertilization [f0] and with fertilization [f1])). Twelve treatments were generated, with five replicates (60 experimental units [EU]). The EU consisted of a pot with a corn plant and the distribution was completely random. The results demonstrated that the Typic Ustifluvent presented nine species of native AMF, while the Typic Dystrustert had three; the native AMF in each soil influenced the activity of allochthonous AMF, such as their colonization and sporulation. Likewise, differences were found in the stability of macro-sized aggregates (0.5 to 2.0 mm).

Physiological Responses of Agave maximiliana to Inoculation with Autochthonous and Allochthonous Arbuscular Mycorrhizal Fungi.

The benefits of mycorrhizal interactions are only known in 8 of 210 recognized Agave taxa. We evaluated the effects of autochthonous and allochthonous arbuscular mycorrhizal fungi (AMF) on growth and nutrient assimilation in Agave maximiliana. The autochthonous consortium (Cn) of eight species was propagated from the rhizospheric soil of A. maximiliana, while Claroideoglomus claroideum (Cc) and Claroideoglomus etunicatum (Ce) were employed as allochthonous AMF. Six treatments were included in the study: Cn, Ce, Cc, Ce + Cc, Tf (fertilized control), and Tn (non-fertilized control, not inoculated). Mycorrhizal colonization increased over time, and the colonization percentages produced by Cn and the allochthonous AMF, both alone and mixed together, were equal at 6, 12, and 18 months. Height increased steadily and was higher in AMF-treated plants from seven months onward. Growth indicators of AMF-treated and AMF-free plants were equal at 6 months, but the beneficial effects of allochthonous and autochthonous AMF were evident in all growth indicators at 18 months and in sugar and mineral (P, K, Ca, Mg, and Fe) content. Arbuscular mycorrhizal fungi significantly improved all growth parameters of A. maximiliana regardless of the origin of the inoculums. This is the first study to report the positive effects of AMF colonization in A. maximiliana.

Distribución espacial de la probabilidad de ocurrencia de verdolaga silvestre (Portulaca oleracea L) en la Región Lagunera de Coahuila, México / Spatial distribution of the probability of occurrence of wild purslane (Portulaca oleracea L.) in the Lagunera Region of Coahuila, Mexico

El interés por introducir verdolaga (Portulaca oleracea L.) como planta cultivable se ha incrementado paulatinamente debido a sus propiedades medicinales. Sin embargo, estudios acerca de su distribución espacial y relación con el tipo de suelo son escasos. Los objetivos del presente trabajo fueron determinar la probabilidad de ocurrencia de verdolaga, así como la relación entre su distribución espacial y las características edáficas en la Región Lagunera. Se obtuvieron datos de presencia/ausencia de esta planta y muestras de suelo superficial de sitios en distintas clases de tierra, y se determinaron las características físicas y químicas de los suelos. Los datos obtenidos se utilizaron para estimar la probabilidad de ocurrencia de verdolaga con una regresión logística y se cartografiaron. Los resultados muestran que la arena, la conductividad eléctrica y el pH influyen en la presencia de la verdolaga y su distribución espacial es diferente, donde los suelos de tierras blancas arenosas tuvieron la mayor probabilidad de ocurrencia.

Adición de material pomáceo a sustratos de arena para incrementar la capacidad de retención de humedad / Addition of pumice residues to sand substrates in order to increase water retention capacity / Adição de resíduos de púmice para lixar substrato para aumentar capacidade de retenção de água

Material pomáceo fue mezclado en distintas proporciones a sustratos de arena, con el objetivo de medir la capacidad de retención de humedad de las mezclas y evaluar el uso de piedra pómez de desechos industriales en la elaboración de sustratos con arena. Cuatro diferentes porcentajes, en base a volumen, de piedra pómez (10, 20, 30 y 40%) se adicionaron a sustratos de arena. En la primera parte del experimento se evaluó el comportamiento de la humedad a través del tiempo; en la segunda parte se determinó la frecuencia de reposición de agua a los sustratos que tuvieron una mayor capacidad de retención de humedad. Los resultados muestran que el contenido de humedad aumenta debido al incremento de porosidad producida por las partículas de pómez. El mayor contenido de humedad (43,75%), después de agregar agua, se obtuvo en la mezcla con el 30% de pómez. La piedra pómez de desecho industrial puede ser utilizada en la elaboración de sustratos para incrementar la retención de humedad con bajo costo y fácil obtención.

Pumice material was mixed in different proportions to sand substrates with the purpose of measuring the water retention capacity of the mixtures and of evaluating the use of industrial pumice residues in the production of substrates with sand. Four different mixtures of pumice residues and sand (10, 20, 30 and 40%) were prepared in order to measure, in a first stage, moisture content through time; in a second stage, the frequency of moisture replenishing was determined for the substrate mixtures that showed a higher water retention capacity. The results show that moisture content increased with the amount of pumice added to the sand, due to the porosity increase produced by pumice particles. The greater moisture content (43.75%) after irrigation was accomplished with the mixture with 30% of pumice material. Pumice residues from industrial process can be used in substrate production to increase water retention at low cost and with an easy availability.

Material de púmice estava misturado em taxas diferentes lixar substrato com o propósito medir a capacidade de retenção de água dessas misturas e avaliar o uso de resíduos de púmice de indústria na produção de substrato com areia. Quatro porcentagem fundada mistura de resíduos de púmice e areia (10, 20, 30 e 40%) estava preparado para medir em um primeiro conteúdo de umidade de fase por tempo; e em uma segunda fase a freqüência de umidade que enche às misturas de substrato com capacidade de retenção de água mais alta. Os resultados mostrados aquele conteúdo de umidade aumentado com a quantia de púmice acrescentada à areia, devido ao incremento de porosidade produzido por partículas de púmice. O maior conteúdo de umidade (43,75%) depois que irrigação fosse realizada com a mistura com 30% de material de púmice. Podem ser usados resíduos de púmice de processo industrial em produção de substrato para aumentar retenção de água a baixo custo e disponibilidade de facilidade.