ABSTRACT
El objetivo de este trabajo fue evaluar métodos para eliminar hongos nativos formadores de micorrizas arbusculares (HMA) o reducir su número en muestras de suelo, sin afectar sus propiedades edáficas y microbiológicas. Se estudió la aplicación de calor húmedo (autoclave), de calor seco (estufa), de hipoclorito de sodio (NaClO) y de formaldehído, en concentraciones entre 100,0 y 3,3 µl/g y 16,7 y 3,3 µl/g, respectivamente. Las semillas de raigrás (Lolium multiflorum Lam.) sembradas en sustratos que recibieron NaClO (100,0-33,3 µl/g) no germinaron y el autoclave incrementó el contenido de fósforo en el sustrato. Estos tratamientos no eliminaron la micorrización por HMA y ambos fueron descartados. En un segundo ensayo se analizaron los tratamientos estufa y formaldehído (10,0 µl/g), asociados o no a la descontaminación de las semillas y a la reinoculación con HMA. Ambos procedimientos redujeron o eliminaron la micorrización por HMA nativos en suelos con 12 a 29 mg/kg de fósforo y permitieron la multiplicación de inóculos de HMA. El tiempo de ventilación de las muestras y los requisitos de seguridad fueron mayores con la aplicación de formaldehído
The objective of this work was to evaluate methods to eliminate or reduce the number of indigenous arbuscular mycorrhizal fungi (AMF) from soil samples without affecting their edaphic or microbiological properties. At an early trial we evaluated moist heat (autoclaving), dry heat (oven), sodium hypochlorite (NaClO) and formaldehyde at a range of 100.0-3.3 µl/g and 16.7-3.3 µl/g respectively. There was no germination in plants of ryegrass (Lolium multiflorum Lam.) sown on substrates receiving NaClO (100.0-33.3 ul/g), whereas autoclaving significantly increased the available soil phosphorous content. Both treatments failed to eradicate AMF colonization at 9 weeks; therefore, they were discarded. In a second trial, oven and formaldehyde (10.0 µl/g) treatments were analyzed to assess the effects of seed decontamination and AMF reinoculation. Both procedures were effective in reducing or eliminating indigenous AMF at a range of soil P availability of 12-29 mg/kg. However, the time between soil treatment and AMF multiplication and safety requirements were greater in the case of formaldehyde application
Subject(s)
Soil Analysis , Laboratory and Fieldwork Analytical Methods/methods , Mycorrhizae/radiation effects , Sodium Hypochlorite/pharmacology , Land Conservation/analysis , Glomeromycota/radiation effects , Formaldehyde/pharmacology , Fungicides, Industrial/analysisABSTRACT
A erodibilidade do solo é representada por fatores de efeito integrado dos processos que regulam a infiltração de água, a resistência do solo à desagregação e o transporte de partículas do solo. Com isso, o presente estudo objetivou estimar a erodibilidade dos solos na microbacia Córrego do Tijuco, SP tendo como finalidade nortear produtores rurais na tomada de decisão para a aplicação de técnicas de conservação do solo. Para tanto foram coletadas amostras de solo com espaçamento regular de 500 m, obtendo no total 310 pontos, na profundidade de 0 0,20 m, numa área de aproximadamente 8000 ha. Para estimar a erodibilidade do solo (K) foi utilizado um modelo matemático no qual leva em consideração o teor de matéria orgânica, as frações areia e silte, a permeabilidade do solo e o diâmetro médio das partículas para cada ponto de amostragem de solo. Valores estimados maiores que 0,040 Mg ha h ha-1 MJ-1 mm-1, foram encontrados para a erodibilidade do solo, sendo estes considerados muito alto para este fator. Nas áreas com valores altos de erodibilidade ocorre o predomínio de Argissolos que apresentam alta susceptibilidade ao desenvolvimento de erosão laminar devido a seu comportamento em relação ao gradiente textural, entretanto a erosão laminar pode ser muito intensa devido à rápida saturação do horizonte superior, incrementando assim a erosão. Já nas áreas onde ocorrem os Latossolos observou também altos valores de erodibilidade, que em condições de ocupação inadequada do solo, conduzem ao escoamento superficial da água de chuva, levando ao favorecimento de voçorocas profundas.
The soil erodibility factor is represented by the integrated effect of processes that regulate the water infiltration, soil resistance and the transport of soil particles. Therefore, this study had as objective to estimate the soil erodibility in the Córrego do Tijuco watershed, São Paulo State, Brazil, for guiding farmers in decision making for application of techniques for soil conservation. The soil samples were collected in a regular spacing of 500 m, resulting in a total of 310 points in a 0-20.0 m depth in an area of approximately 8,000 ha. For the estimation of soil erodibility (K) was applied a mathematical model which takes into account the soil organic matter content, the sand and silt size fractions, the soil permeability, and the particle mean diameter for each point of soil sampling. Estimated values greater than 0.040 Mg ha h ha-1 MJ-1 mm-1 were considered very high for this factor. In areas with greater degree of erodibility occurs the Argisols order predominance, that shows high susceptibility to the development of interrill erosion due to its remarkable performance in relation to textural gradient, thereby, the interrill erosion rates can be very intensive due to rapid saturation of upper horizon, increasing the erosion process. At the Latosols (Oxisols) areas were also observed high soil erodibility values that under inappropriate conditions of soil occupation, concentrating runoff of rain water, leading to appear deep gullies.
Subject(s)
Hydrographic Basins , Land Conservation/analysis , Soil Conditions , Soil ErosionABSTRACT
El sistema integral de diagnóstico y recomendación (DRIS), es un método alternativo para evaluar el estado nutricional de diversos cultivos. Para evaluar nutricionalmente al cafeto en Venezuela mediante el DRIS, se obtuvo información sobre su producción y sobre los niveles foliares de N, P, K, Ca, Mg, Zn, Fe, Cu, Mn y B, procedentes de fincas productoras de Lara, Portuguesa, Trujillo y Yaracuy, a través de un muestreo aleatorio estratificado. Con las medias de los niveles foliares obtenidos, se generaron las normas DRIS para el B (55,05 mg kg-1) y sus interrelaciones con los nutrientes N, P, K, Ca, Mg, Fe, Cu, Mn y Zn. Utilizando cuatro diferentes métodos de cálculo reportados en la literatura, se desarrollaron índices DRIS (IN-DRIS) e índices de balance de nutrientes DRIS (IBN-DRIS) y ambos fueron evaluados contra el rendimiento. Pudo determinarse la existencia de una relación positiva y significativa entre el contenido foliar de los nutrientes del cafeto y los IN-DRIS, independientemente del método de cálculo utilizado para el mismo. Los diferentes métodos de obtener los IN-DRIS, alteraron muy poco los resultados y coincidieron en determinar al K como el nutriente más deficiente y más limitante de la producción.
The diagnosis and recommendation integrated system (DRIS), is an alternative method to evaluate the nutritional status of diverse crops. To nutritionally evaluate the coffee plantations in Venezuela using DRIS, information regarding yields and foliar levels of N, P, K, Ca, Mg, Zn, Fe, Cu, Mn and B, of farms from Lara, Portuguesa, Trujillo and Yaracuy states was obtained through a randomized stratified sampling process. With the obtained means foliar levels, B DRIS norms (55,05 mg kg-1) as well as those among B and its relationship with N, P, K, Ca, Mg, Fe, Cu, Mn and Zn were developed. DRIS indexes (IN-DRIS) and nutrient balance indexes (NBI-DRIS) were developed through four different reported estimation methods and then evaluated against yield. A positive and significant relationship between foliar nutrient content and the IN-DRIS was found, independently of the procedure of calculation used for to obtain them. The different methods of IN-DRIS development altered very little the results and coincided in determining K as the most deficient and most yield limiting nutrient.