CHARACTERIZATION OF SOIL CARBON STABILIZATION IN LONG-TERM ROW-CROPPED AGRO-ECOSYSTEMS

Soil organic matter (SOM) is a dynamic soil property, sensitive and responsive to many factors. The possibility of increasing soil carbon (C) sequestration by changing land use and management practices has been of great interest recently due to concerns with global changes in the atmospheric carbon dioxide (CO2) balance. Nonetheless, as a result of the complex dynamics of SOM, there is still the need for SOM characterization procedures capable of monitoring SOM stabilization, taking into account all the factors involved. This study characterized SOM stabilization as affected by management practices in three long-term field experiments, considering physical, chemical and biological components. The field experiments are located near Lexington, Kentucky, on a Maury silt loam (fine, mixed, mesic Typic Paleudalfs). The first experiment evaluates tillage and nitrogen (N) rate effects. The second experiment studies manure and N rate effects. The third experiment evaluates the five corn components of three crop rotations [continuous (monoculture) corn, corn-wheat/double crop soybean, and hay-hay-corn-corn-corn]. Soil organic matter content, stability, and composition, for physically separated fractions, were assessed using δ13C natural abundance and diffuse reflectance Fourier transformed infrared (DRIFT) spectroscopy. In addition, management effects on microbial biomass and microbial function as indicated by phenol oxidase enzyme activity were evaluated. The results indicate that management practices affect SOM content, stability, and composition, and these effects differ by the soil aggregate fraction. No-tillage (NT), N fertilization, manure application and increased corn in crop rotations enhanced SOM levels. However, the effect of NT was observed mainly at the soil surface. Soil organic matter storage was determined by the aggregate size distribution. The proportion of recently deposited C was generally positively related to aggregate size, especially for the first and third experiments. Most of the recently deposited C was stabilized in microaggregates within macroaggregates, across the management treatments and field experiments. In addition, this fraction consistently exhibited low to medium SOM reactivity. These results suggest that SOM stabilization, as influenced by management practices, required achieving a specific composition and location within the soil matrix. This implies that soil C forms and aggregate size and stability are closely interrelated

Evaluación de deficiencias nutricionales en el cultivo de quinua (Chenopodium quinoa Willd.) bajo invernadero

This research evaluated the nutritional deficiencies of the quinoa crop (Chenopodium quinoa Willd.). Two greenhouse experiments were implemented. Seedlings were transplanted in pomina and maintained for 60 days. The nutritional deficiencies were induced by using the missing element technique with nutrient solutions under a completely randomized design with fourteen treatments and three replicates for the first experiment and four replicates for the second experiment. The evaluated variables in the first experiment included plant height, stem diameter, color, and chlorophyll. The crop biomass production was evaluated in the second experiment. The results indicated that omission treatments for nitrogen (N), boron (B), and potassium (K) significantly affected all of the evaluated variables and presented visual symptoms of deficiency in the quinoa crop. Nevertheless, suphur (S) and phosphorus (P) deficiencies were also observed at the latest plant growth stages.La presente investigación evaluó las deficiencias nutricionales del cultivo quinua (Chenopodium quinoa Willd.); para el efecto se implementaron dos experimentos en invernadero, donde se trasplantaron plántulas en pomina y se mantuvieron durante 60 días. Las deficiencias nutricionales se indujeron mediante el uso de la técnica del elemento faltante con soluciones nutritivas bajo un diseño completamente al azar con catorce tratamientos y tres repeticiones para el primer experimento; y cuatro repeticiones para el segundo experimento. Las variables evaluadas en el primer experimento fueron altura de planta, diámetro del tallo, color y clorofila. En tanto que la producción de biomasa del cultivo fue evaluada en el segundo experimento. Los resultados indicaron que los tratamientos con omisión de nitrógeno (N), boro (B), y potasio (K) afectaron significativamente a todas las variables evaluadas y mostraron síntomas visuales de deficiencia en el cultivo de quinua. Sin embargo, las deficiencias de azufre (S) y fósforo (P) también fueron evidentes en las etapas de crecimiento más avanzadas

Efecto de la labranza y fertilización nitrogenada en los cultivos de fréjol y maíz sobre indicadores biológicos de la calidad de un suelo andino del Ecuador

Biological parameters are used as early indicators of the quality of an agricultural soil (ICS), due to their quick response to the anthropic soil management. The main objective of this research was to determine the effect of the tillage system: no-till (SD) and conventional tillage (LC), and to the nitrogen fertilization in bean and corn crop on certain biological indicators of soil quality. The study was carried out on a mollisol from the Andean region of Ecuador. Microbial biomass (MB), microbial respiration (RM), and enzyme activity (acid phosphatase, hydrolysis of fluorescein diacetate [FDA], and β-glucosidase [β-G]) were determined. The results showed that the phosphatase presented the highest activity under LC, the FDA responded to the effect of high nitrogen levels application (N), the activity of the β-G enzyme was higher under LC. Additionally, the principal component analysis selected these biological indicators studied as ICS. It is concluded that the biological indicators of the soil were affected by the management practices studied.Los parámetros biológicos son usados como indicadores tempranos en la calidad de un suelo (ICS) agrícola, ya que responden rápidamente al manejo antrópico. El objetivo de esta investigación fue determinar el efecto del sistema de labranza: siembra directa (SD) y labranza convencional (LC), y de la fertilización nitrogenada después de los cultivos de fréjol y maíz, sobre ciertos indicadores biológicos de la calidad del suelo. El estudio se realizó sobre un molisol de la región andina del Ecuador. Se determinó la biomasa microbiana (BM), respiración microbiana (RM), y actividad enzimática (fosfatasa ácida, hidrólisis de la fluoresceína-diacetato [FDA], y β-glucosidasa [β-G]). Los resultados mostraron que la fosfatasa presentó la mayor actividad bajo LC, la FDA respondió al efecto de los niveles altos de nitrógeno (N), la actividad de la enzima β-G fue mayor en LC. Adicionalmente, el análisis de componentes principales seleccionó a los indicadores biológicos estudiados, como ICS. Se concluye que los indicadores biológicos del suelo fueron afectados por las prácticas de manejo estudiadas

Evaluación de defciencias nutricionales en el cultivo de quinua (Chenopodium quinoa Willd.) bajo invernadero

This research evaluated the nutritional deficiencies of the quinoa crop (Chenopodium quinoa Willd.). Two greenhouse experiments were implemented. Seedlings were transplanted in pomina and maintained for 60 days. The nutritional deficiencies were induced by using the missing element technique with nutrient solutions under a completely randomized design with fourteen treatments and three replicates for the first experiment and four replicates for the second experiment. The evaluated variables in the first experiment included plant height, stem diameter, color, and chlorophyll. The crop biomass production was evaluated in the second experiment. The results indicated that omission treatments for nitrogen (N), boron (B), and potassium (K) significantly affected all of the evaluated variables and presented visual symptoms of deficiency in the quinoa crop. Nevertheless, suphur (S) and phosphorus (P) deficiencies were also observed at the latest plant growth stages.La presente investigación evaluó las defciencias nutricionales del cultivo quinua (Chenopodium quinoa Willd.); para el efecto se implementaron dos experimentos en invernadero, donde se trasplantaron plántulas en pomina y se mantuvieron durante 60 días. Las defciencias nutricionales se indujeron mediante el uso de la técnica del elemento faltante con soluciones nutritivas bajo un diseño completamente al azar con catorce tratamientos y tres repeticiones para el primer experimento; y cuatro repeticiones para el segundo experimento. Las variables evaluadas en el primer experimento fueron altura de planta, diámetro del tallo, color y clorofla. En tanto que la producción de biomasa del cultivo fue evaluada en el segundo experimento. Los resultados indicaron que los tratamientos con omisión de nitrógeno (N), boro (B), y potasio (K) afectaron signifcativamente a todas las variables evaluadas y mostraron síntomas visuales de defciencia en el cultivo de quinua. Sin embargo, las defciencias de azufre (S) y fósforo (P) también fueron evidentes en las etapas de crecimiento más avanzadas

Noticeable Shifts in Soil Physicochemical and Biological Properties after Contrasting Tillage Management in Crop Rotations of Bean, Maize, and Amaranth in Ecuadorian Highland Soils

Soil biological properties are sensitive indicators of soil quality changes due to perturbations occurred under agricultural management. The effects of contrasting tillage, increasing nitrogen fertilization doses, and crop rotations [e.g., bean, maize, bean (BMB) and bean, amaranth, bean (BAB)] on soil physicochemical and biological properties in an Andean soil from Ecuadorian highlands were evaluated in this study. Acid phosphatase, β-Glucosidase, fluorescein diacetate hydrolysis, microbial biomass carbon (Cmic), soil basal respiration (BR), arbuscular mycorrhizal fungi (AMF) spore density, total glomalin content (TGRSP), and soil physicochemical properties were analyzed. Conventional tillage (CT) and crop rotation showed significant effects on soil physicochemical and biological properties. Towards the final crop rotations, no-tillage (NT) promoted BR, TGRSP, and higher AMF spore density in both crop rotations; the Cmic kept stable along time in BMB and BAB, while BR doubled its value when compared to CT. Results indicated that the AMF spore density increased by 308% at the end of the BMB, and 461% at the end of the BAB, while TGRSP increased by 18% and 32% at the end of BMB and BAB, respectively. Biological traits demonstrated to be strongly associated to the organic matter accumulation originated from crop residues under the NT post-harvest which improved soil moisture, biological activity, and AMF interaction. The conservative soil management system has definitively improved general soil properties when compared to soil conditions under the intensive soil management system in this research