ABSTRACT In Argentina, cassava (Manihot esculenta) production does not meet the national demand. The aim of this work was to analyze the effects of two planting systems of the stem cuttings (horizontal and vertical), two plant densities (10,000 and 20,000 plant ha-1) and two cassava genotypes (cv. Palomita and Blanca de Santa Catarina) on biometric variables and on root and starch yields by means of a field experiment carried out in Corrientes, Argentina. Eight treatments were distributed following a randomized complete block design. The following variables were evaluated: cutting sprouting percentage, plant height, percentage of intercepted photosynthetically active radiation (PARi); total, shoot and root fresh weight per hectare and/or per plant; starch production per hectare and weed dry biomass. Blanca de Santa Catarina (BSC) demonstrated the best yield potential. Vertical planting determined higher sprouting percentages, plant length and PARi, consequently greater conversion into biomass and starch. Higher plant density was associated with lower weed dry biomass and with lower root yield per plant. In conclusion, in cassava producing areas, such as Corrientes, which has sandy soils, the vertical planting system at a density of 10,000 plant ha-1 with the cv. BSC could be recommended to increase cassava yield without additional costs.

In three departments of the Corrientes province, the performance of 6 seeders was evaluated during corn sowing at three different speeds for each machine. A randomized complete block design was used with nested treatments arrangement. A seeder factor (6 types), a speed factor (3 levels) and three blocks determined a total of 54 experimental units. As for the speed factor, the first level corresponds to speed 2 (Sp 2) which the operator regularly uses. The second level and the third level correspond to a lower speed (Sp 1) and a higher speed (Sp 3) respectively which were used for this study. The equidistance between seeds and sowing depth were analysed as the response variable. Conclusions: 1) Four of the six seeders studied at three chosen speeds showed no differences regarding seed deposition. This was observed considering significant differences between sowing depth and seed spacing in a given line. 2) The two methodologies used to evaluate sowing efficiency, i.e. the coefficient of variation (CV) and the ISO 7256-1 standard, showed differences in evaluation. The second technique was more accurate since no differences between treatments were found with the CV. 3) According to these results, it is possible to conclude that the corn sowing quality in the Corrientes province is acceptable at the sowing speeds used by the contractors.

En tres departamentos de la provincia de Corrientes, se evaluaron el desempeño de 6 sembradoras durante la siembra de maíz a tres distintas velocidades para cada máquina. El diseño experimental fue en bloques completos aleatorizados con arreglo anidados de tratamientos, siendo un factor sembradora (6 tipos) y otro factor velocidad (3 niveles) y tres bloques lo que determinó un total de 54 unidades experimentales. Se analizaron como variable respuesta, la equidistancia entre semillas y la profundidad de siembra. Conclusiones: 1) La mayoría de las sembradoras estudiadas a tres velocidades, no mostraron diferencias en la calidad de deposición de la semilla expresado como diferencias significativas entre la profundidad de siembra y el distanciamiento entre las mismas dentro de la línea. 2) Las dos metodologías utilizadas para evaluar la eficiencia de siembra (coeficiente de variación (CV) y norma ISO 7256-1) mostraron diferencias de evaluación, siendo más exigente esta segunda técnica ya que con el (CV) no se encontraron diferencias entre tratamientos. 3) De acuerdo con los resultados encontrados es posible concluir que la calidad de siembra de maíz en la provincia de Corrientes es aceptable a las velocidades de siembra utilizadas por los contratistas.

The aim of this work was to study soil compaction caused by the traffic of two types of combine harvesters and a tractor plus a grain cart with two loading conditions (fully loaded hoppers-empty hoppers) during corn harvest on vertic argiudoll soil by means of direct seeding system. Soil penetration resistance (PR) and soil bulk density (BD) were measured to a depth of 40 cm in five sampling sites. Response variables determinations were also analyzed. The tractor and the fully loaded grain cart traffic caused greater soil compaction in all the sampling depths, exceeding 60 cm on both sides of the footprint center. What is more, the values obtained from PR and BD measurements were higher than those values considered suitable for normal root growth. This was only evident in the tread width of the tires during the passing of the two fully loaded combine harvesters. The analysis of inflation pressures and tire loads used, indicated in some cases, poor concordance between these variables. The analysis also indicated that the tires were inflated to the limit of resistance.

El objetivo del trabajo fue estudiar la compactación causada por el tráfico de dos tipos de cosechadoras y equipo tractor más carro granelero con dos condiciones de carga (tolvas vacías-tolvas llenas) en la cosecha de maíz sobre un suelo argiudol vértico en sistema de siembra directa. Las determinaciones de las variables respuestas, resistencia a la penetración (RP) y densidad aparente (Da), se hicieron hasta los 40 cm de profundidad y en cinco sitios de muestreo. El tránsito del equipo tractor más carro granelero lleno fue el que mayor compactación causó en todas las profundidades de muestreo superando los 60 cm a ambos lados del centro de huella con datos de RP y Da superiores a los considerados crítico para el normal desarrollo radicular. Esta situación, en el pasaje de las dos cosechadoras en condiciones llenas, solamente se dio en el ancho de pisada de los neumáticos. El análisis de las presiones de inflado y cargas de los neumáticos usados indicaron, en algunos casos, una escasa concordancia entre estas variables y que las ruedas se encontraban en el límite de resistencia a las presiones utilizadas.