Se reprodujo en condiciones de laboratorio la práctica desarrollada por campesinos cubanos de la región central del país, en la conservación de las raíces de yuca en agua para su posterior utilización como fuente de alimento para los cerdos. Se probó el efecto de añadir o no 20 mL de yogur de soya al agua que recubría 700 g de raíces peladas y picadas, conservadas en microsilos de dos kg, durante 1, 3, 5 y 7 días, o 9, 16, 21 y 31 días, de acuerdo con un arreglo factorial donde los factores fueron la adición de yogur o una y de dos a cuatro semanas de conservación. No hubo en ningún caso manifestación organoléptica de deterioro en las raíces conservadas. No se encontró efecto significativo (P0.05) en la interacción yogur x semanas de conservación. Tampoco hubo efecto significativo (P0.05) por la adición o no de yogur. Después de siete días de conservación el pH cayó significativamente (P0.001) y la acidez total aumentó también significativamente (P0.001). No hubo cambios de importancia en la concentración de amoníaco y AGCC durante el mes transcurrido con las yucas conservadas en agua. La concentración de ácido láctico se correspondió con la disminución del pH, lo que creó las condiciones óptimas necesarias para inhibir la proliferación de microorganismos no deseados, y así garantizó la conservación de las raíces de yuca. Se comprobó además, que al menos en las condiciones en que se desarrollaron estos estudios, la adición de yogur no representó una ventaja manifiesta en el comportamiento del silo. | The practice developed by Cuban farmers from the central region of the country consisting in conservation of cassava roots under water and thereafter using it for feeding pigs, was reproduced at laboratory scale. The effect of addition of 20 mL soybean yoghurt to the water covering 700 g pf peeled and chopped cassava roots conserved in 2 kg microsilos during 1, 3, 5 and 7 days, and 9,16, 21 and 31 days, according to a factorial arrangement where factors were yoghurt addition and either one or two to four weeks of conservation. In any case there was not organoleptic expression of spoiling in the conserved roots. There were no significant (P0.05) effect of yoghurt x weeks of conservation interaction. No significant (P0.05) effect as originated by yoghourt addition was found either. After seven days of conservation, pH significantly (P0.001) decreased and total acidity significantly (P0.001) increased too. There were no changes of importance in ammonia and SCFA concentration during the month elapsed with cassavas conserved under water. Lactic acid concentration corresponded to a decrease in pH values, then contributing to necessary conditions for inhibition of undesirable microorganism proliferation, therefore warranting cassava root conservation. It was corroborated that at least in those conditions where these studies were conducted, acidification due to yoghurt addition did not represented an evident advantage in silo performance.

Foi conduzido um experimento visando estudar o efeito de diferentes laminas de agua e turnos de rega sobre o rendimento e densidade de raízes do feijão comum (Phaseolus vulgaris L.), linhagem CNF-0010. O estudo foi realizado no Centro Nacional de Pesquisa de Arroz e Feijão CNPAF/EMBRAPA, Goiânia, GO, em Campo, sob um abrigo móvel de proteção contra chuva, na estação de inverno de 1982. Os tratamentos consistiram em irrigações com laminas de 2, 4 e 6 mm/dia e turno de rega de 1,4, 7 e 10 dias. Realizaram-se estudos de regressão múltipla entre a produção de grãos, densidade de raízes no solo e os tratamentos. A produção de grãos foi mais afetada pela lamina de agua (R2=85,33%) do que pelo turno de rega (R2=5,86%); e as maiores produções foram conseguidas com laminas de agua mais altas. A produção de grãos decresceu linearmente com o aumento do turno de rega nas laminas de 4 e 6 mm/dia, e a maior densidade de raízes no solo ocorreu na lamina de 4 mm/dia. Os tratamentos de 2,4 e 6 mm/dia consumiram, em media, 173, 295 e 411 mm de agua, respectivamente. Os diferentes tratamentos provocaram pequena variação no ciclo da cultura.

Inducing the highest quantity of roots in tomato seedlings is fundamental at the post-seedling stage, since the appropriate absorption of water and nutrients for their later development depends upon this. The water stress can generate roots growth because the root should search water. In order to achieve this growth, the tomato seedling was placed under a water deficit. The design was totally randomized with 10 treatments and 5 replicates, the treatments consisted in application of 10 levels of water application (0.2, 0.4, 0.6, 0.8, 1.0, 1.2, 1.4, 1.6, 1.8, and 2.0 of evaporation measured in evaporimeter tank installed inside the greenhouse) during the 5 previous days to the transplant. After 40 days, seedlings were transplanted and during one month they were evaluated. Significant differences were not found among the dry weight of leaves, stems and roots. The different levels of water didn’t affect the fresh weight of leaves and stems, foliar area, distribution of dry biomass, root/shoot relationship and final plant height. Significant differences were obtained in the length and fresh weight of the root, in both cases the best treatment was the coefficient 1.6 of the evaporation. The level of water with smaller response was that of 0.2. The level of water of 1.6 of the evaporation generates seedlings with appropriate root systems. | La inducción de la mayor cantidad de raíces en plántulas de tomate es fundamental en la etapa postrasplante, ya que de éstas depende la adecuada absorción de agua y nutrientes para su posterior desarrollo. El estrés hídrico puede generar un crecimiento radicular, ya que la raíz debe buscar agua. Con el fin de lograr este crecimiento, se sometieron plántulas de tomate a un déficit hídrico. El diseño fue completamente al azar con 10 tratamientos y 5 repeticiones; los tratamientos consistieron en la aplicación de 10 láminas de riego (0,2; 0,4; 0,6; 0,8; 1,0; 1,2; 1,4; 1,6; 1,8 y 2,0 de la evaporación medida en un tanque evaporímetro instalado dentro del invernadero) durante los 5 días previos al trasplante. Se trasplantaron 40 d después de la siembra y se evaluaron un mes después. No se presentaron diferencias significativas en el peso seco de hojas, tallos y raíces. Las diferentes láminas de agua no afectaron el peso fresco de hojas y tallos, el área foliar, la distribución de fitomasa seca, la relación raíz/parte aérea ni la altura final de las plantas. Se obtuvieron diferencias significativas en la longitud y en el peso fresco de la raíz; en ambos casos el mejor tratamiento fue el coeficiente 1,6 de la evaporación. La lámina con menor respuesta fue la de 0,2. Una lámina de riego de 1,6 de la evaporación genera plántulas con sistemas radiculares adecuados.

New explorations in the desert of northeastern Zacatecas, in central-northern Mexico, revealed dozens of archaeological and geoarchaeological sites. One of them, Ojo de Agua, contains the remains of a Pleistocene spring-fed hydrographic system located at the southeastern end of a large elongated endorheic basin. The locality yielded a particularly dark, highly organic stratigraphic layer commonly known in the Americas as Black Mat (BM), exposed on the natural profiles of a creek, but not associated with cultural materials. Several radiocarbon assessments confirmed the formation of the Ojo de Agua Black Mat during the Younger Dryas chronozone, with ten calibrated results clustering between 12,700–12,100 cal BP. This multi-proxy study confirmed the peculiarity of the deposit and found similarities and differences with other contexts of Younger Dryas age. The Ojo de Agua Black Mat (stratum C2) is far richer in charcoal specks than the related strata, but lacks phytoliths, diatoms or ostracods. No further biological remains were found in it, except for intrusive capillary roots. Clearly water-lain in a shallow pond, the stratum qualifies as a clayey silt with an acidic-to-neutral pH. Rich in heavy metals and with high contents of titanium, the Ojo de Agua Black Mat yielded significant indicators of intense wildfires during the Younger Dryas, but produced no carbon spherules or nanodiamonds supposedly linked to the impact theory.

The purpose of this study was the statistical quantification of moisture and root systems perpendicularly to the micro-watershed length. It was found that moisture content and root density tended to increase opposite to the runoff area. Also, the root system distribution was quantified in strata of 15 cm down to 60 cm depths in the experimental plots under the treatments micro-watershed (MS), barley straw mulching (C) and volume of water expected to be used per plant (V). The results showed a larger root density in (MS) through all strata but particularly in the first 15 cm, as compared to the normal rows. The larger volume of water per plant (200 L) also induced a greater root density in the first stratum and a light increase in the other strata. With respect to C it was observed that the higher level (0.5 kg/m2) increased root weights in the first stratum, but decreased with depth in comparison with the bare soil. | En este estudio se cuantifico estadisticamente la distribucion de la humedad y de las raices en sentido perpendicular a la longitud de la microcuenca; se encontro que el contenido de humedad y la densidad de raices tienen un mayor pronunciamiento en contra-posicion del area de escurrimiento. Tambien se cuantifico la distribucion radical en estratos de 15 cm hasta una profundidad de 60 cm en unidades experimentales con tratamientos de tamano de microcuenca, cobertura de paja de cebada y volumen de agua a captar por planta. En este muestreo se obtuvo que existe una mayor densidad de raices en la microcuenca de captacion, en cualquier estrato, pero principalmente en los primeros 15 cm, en comparacion con los surcos normales. El mayor volumen de agua por planta (200 L) tambien propicio una mayor densidad de raices en el primer estrato y un incremento ligero en los otros. En cuanto a la cobertura organica, se observo que con el nivel superior (0.5 kg/m2) aumento el peso de raices en la primer capa pero fue disminuyendo con el suelo desnudo.