The flat pampas in the state of Santa Fe in Argentina have soils with high silt content, variable carbon content, and diverse degrees of structural degradation. Aggregate stability has been used as an indicator of the structural condition of the soil. This study aimed to quantify the effect of the addition of crop residues and root activity on the agents of aggregation and mechanisms of aggregate breakdown in soils with different carbon contents and textures cultivated under no-till. An experimental trial was conducted on a loamy soil (Typic Hapludoll, SantaIsabel series) and a silty soil (Typic Argiudoll, Esperanza series) under controlled conditions for 112 days with the following treatments: (i) with and without wheat plant growth and (ii) with and without addition of wheat residues. Soil structural stability by a method allowing for differentiation of aggregate breakdown by slaking, mechanical effect and microcracking, total organic carbon content, particulate organic carbon, glomalin and carbohydrate fractions was assessed. In general, the addition of residues and the presence of plant with active roots increased the presence of all aggregation agents and decreased aggregate breakdown processes in both soils. Soluble carbohydrates and proteins related to glomalin were the most important aggregating agents and their function was to reduce the magnitude of breakdown mechanisms, slaking and microcracking, evidencing a greater impact on the silty soil.

On‐farm experimentation using Precision Agriculture technology enables farmers to make decisions based on data from their fields. Results from on‐farm experiments depend on the experimental design and statistical analyses performed. Detailed information about the accuracy of the treatment effect estimates, and Type I error rates of hypothesis testing under different spatial structure scenarios attained by alternative experimental designs and analysis is required to improve on‐farm research experiments. Three thousand yield data sets were drawn from 15 random fields simulated by unconditional Gaussian geostatistical simulation technique and were modeled by applying 10 experimental designs and three estimation methods with experimental units ranging from 138 to 9969 m2. No effect of spatial structure, experimental design, and estimation methods was observed on overall mean yield and treatment bias. Unaddressed changes of nugget/sill ratio and range of variogram had a significant effect on estimator efficiency and accuracy with Type I error rates above the nominal rate, which increased with higher spatial autocorrelation. Spatial methods were robust to changes in spatial structure regardless of the design. Randomization of treatment increased the uncertainty of model estimators. In general, the accuracy of treatment effect estimates increased with the number of replications of smaller size. The opposite trend was observed between those estimates and the size of the plots. Analyses showed that the best designs for testing the overall treatment effect in two‐treatment experiments would be split‐planter, strip‐plots, and chessboard because of their size and number of experimental units. Core Ideas Spatial autocorrelation increases grand mean estimator variance in any design or method. Spatial autocorrelation reduces treatment effect estimator efficiency if not modeled. Spatial autocorrelation increases Type I error if not modeled. Designs with small experimental units (strip plots or chessboard) performed better.

-Eustachys retusa has low sensitivity to glyphosate at the reproductive stage. The purpose of this study was to analyze the effect of glyphosate on adult E. retusa plants in order to identify the traits that make possible their regeneration in no-tillage systems. For this purpose, reproductive-stage specimens from wild populations were treated with glyphosate at two different rates (480 and 1,200 g a.i. ha dose. However, a certain proportion of plants can survive despite having full chlorosis as a consequence of basal bud activation (bud bank) and the presence of reserves in the rhizome. These combinations of morphological traits facilitate the recovery of foliar mass in some plants after the application of the herbicide. This behavior represents a serious problem because E. retusa plants retain the ability to regrow. This shows that, E. retusa management at reproductive stage must be complemented with other cultural and/or chemical tactics.Keywords: argentine fingergrass, herbicide, weed, tolerance, morphological changes. RESUMO -Eustachys

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Drivers for and potential barriers against adoption of controlled traffic farming (CTF) systems in Argentina are reviewed. Traffic compaction is one of the main factors affecting crop productivity within Argentinean agriculture, and has significant although less quantified impacts on the whole-of-farm system. This suggests that the benefits of no-tillage (NT), which represents the dominant form of cropping in Argentina, are not fully realised. Conservative estimates indicate that crop yields could be improved by at least 15% if NT is used in conjunction with CTF. Cost-benefit analyses of available options for compaction management are required. Despite this, and based on reported evidence internationally, a shift toward increased uptake of CTF within Argentinean agriculture is likely to: (1) improve productivity and farm profitability, (2) enhance environmental performance, and (3) maintain competitiveness of the agricultural sector. Appropriate technical advice and support is a key requirement to drive adoption of CTF. Therefore, the adoption process will benefit from collaboration developed with well-established research and extension organisations in Australia and the United Kingdom, and active engagement of machinery manufacturers.

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