The envitonraental fate of glyphosate [Ai-(phosphonomethyl)glycinc] was studied in six crop residue (CR) types, three from maize [Zea mays L) (Ml, M2, and M3) and thtee from soybean [Glycine max (L.) Mem] (SI, S2, and S3). Glyphosate adsorption was characterized through isotherms. The glyphosate distribution in CRs was characterized through the balance of '''C-glyphosate radioactivity among the mineralized fraction, the e.xcractabk fractions (water and NH^OH), and the nonextractable fraction. Crop residues wete characterized by elemental composition, organic C, total N, and biochemical parameters (soluble fraction, cellulose, hemicellulose, and lignin). Total microbial activity (TMA) was also assessed. Limited and reversible glyphosate adsorption on soybean and maize CRs was determined. The sorption coefficient A^f index range for maize CR was 1.5 to 8.3 L kg"' and 2.6 to 7.4 L kg"' for soybean CR. Organic C and hemicellulose partially explained adsorption variability. The addition of mineralized and nonextractable fractions of the initial '''C-glyphosate applied on the CRs averaged 56%; however, differences were detected between soybean and maize CRs. Mineralization and nonextractable residues were 30.7 + 11 and 32.5 + 6% (soybean CR) and 44.3 ± 12 and 17 + 7% (maize CR), respectively.We hypothesized that glyphosate molecules could be used initially by microorganisms as a labile C source. High variability in ' ''C-glyphosate mineralization was observed in all crop residues, suggesting that the magnitude of the glyphosate mineralization process would be regulated by accessibility and the lability of^other carbonate sources.

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The recognition of glyphosate [(-phosphonomethyl) glycine] behavioral patterns can be readily examined using a pedoclimatic gradient. In the present study, glyphosate adsorption-desorption and degradation were examined under different scenarios in relationship to soil properties and soil use applications. Three sites with varied pedoclimatic conditions and two crop sequences were selected. Adsorption-desorption and glyphosate distribution in mineralized, extractable, and nonextractable fractions were assessed under laboratory conditions. Glyphosate sorption was characterized by isotherms and glyphosate degradation using the distribution of C-glyphosate radioactivity among mineralized fractions, two extractable fractions (in water, ER1; in NHOH, ER2), and nonextractable fractions. Results showed sorption indices (distribution coefficient and Freundlich sorption coefficient : 13.4 ± 0.3-64.1 ± 0.9 L kg and 16.2-60.6, respectively), and hysteresis increased among soil sites associated with decreasing soil particle size <2 μm, soil organic matter, and other soil properties associated with soil granulometry. A multiple stepwise regression analysis was applied to estimate the relationship between values and soil properties. Cation exchange capacity, water field capacity, and Bray-1 P were the soil properties retained in the equation. Soils under continuous soybean [ (L.) Merr.] (monoculture) treatment exhibited reduced glyphosate adsorption and decreased hysteresis desorption relative to soils under rotation. To our knowledge, these results are the first to demonstrate that soils with identical properties exhibited different glyphosate retention capacities based on crop sequence. We propose possible explanations for this observation. Our results suggested that characterization of the variability in soil property gradients can serve to determine glyphosate behavioral patterns, which can establish a criterion for use in reducing potential environmental risks.

No abstract

This article presents original geospatial data on soil adsorption coefficient (Kd) for two widely used herbicides in agriculture, glyphosate and atrazine. Besides Kds, the dataset includes site-specific soil data: pH, total nitrogen, total organic carbon, Na, K, Ca, Mg, Zn, Mn, Cu, cation exchange capacity, percentage of sand, silt and clay, water holding capacity, aluminum and iron oxides, as well as climatic and topographic variables. The quantification of herbicides soil retention was made on a sample of soils selected by Conditionated Latin Hypercube method to capture the underlying edaphoclimatic variability in Cordoba, Argentina. The glyphosate data presented here has been used to evaluate statistical methods for model-based digital mapping (F. Giannini Kurina, S. Hang, R. Macchiavelli, M. Balzarini, 2019) [1]. The dataset is made publicly available to enable future analyzes on processes that leads the dynamics of both herbicides in soil.

<p class="western" style="margin-bottom: 0cm; line-height: 150%;" lang="es-AR" align="justify"><span style="color: #000000;"><span style="font-family: Times New Roman, serif;"><span style="font-size: medium;">Se evaluó sobre el suelo el efecto de diferentes compost, obtenidos mediante igual metodología de compostaje, después de dos años de aplicados. Sobre un suelo Haplustol típico se aplicaron 40 Mg ha</span></span></span><span style="color: #000000;">^{<span style="font-family: Times New Roman, serif;"><span style="font-size: medium;">-1</span></span>}</span><span style="color: #000000;"><span style="font-family: Times New Roman, serif;"><span style="font-size: medium;"> de cada compost, conformando los siguientes tratamientos: CBIO con compost de biosólidos, CF con compost residuos de estiércol bovino, CG con compost de guano de gallina, CROU con compost de residuos sólidos urbanos. También se incluyó un tratamiento con fertilizante inorgánico (FI) y un suelo no tratado o control (C0). El pH del compost afectó ligeramente el pH del suelo, según las características del compost usado. CROU y CBIO incrementaron y disminuyeron el pH, respectivamente (R</span></span></span><span style="color: #000000;">^{<span style="font-family: Times New Roman, serif;"><span style="font-size: medium;">2</span></span>}</span><span style="color: #000000;"><span style="font-family: Times New Roman, serif;"><span style="font-size: medium;">=0,98). Se observó un cambio en la distribución de la materia orgánica del suelo CG, sin incremento en el carbono orgánico total (COT). En CG aumentó un 85 % el </span></span></span><span style="color: #000000;"><span style="font-family: Times New Roman, serif;"><span style="font-size: medium;">C_{fraccion&gt;53um} y creció en 24 % el C extractable en álcali, respecto al control. Finalmente, se observó un enriquecimiento de </span></span></span><span style="color: #000000;">_{<span style="font-family: Times New Roman, serif;"><span style="font-size: medium;"><span lang="es-ES"><span style="background: #ffffff;">Cu_M y Zn_M </span></span></span></span>}</span><span style="color: #000000;"><span style="font-family: Times New Roman, serif;"><span style="font-size: medium;"><span lang="es-ES"><span style="background: #ffffff;">en CROU. Los resultados muestran que una única adición de compost puede modificar las propiedades del suelo dado los múltiples materiales compostados. Se debe monitorear tempranamente las condiciones del suelo para identificar tendencias y evitar efectos ambientales negativos.</span></span></span></span></span></p>

Resilience has become a key concept in agricultural management for sustaining soil quality and preventing soil degradation. Land use is a factor that affects soil organic matter (SOM) concentration, distribution and dynamics. In consequence, several recovery practices have been proposed in order to maintain or enhance SOM contents in agroecosystems, such as zero soil disruption (no-till), farm enclosures and crop rotation. We evaluated the efficiency of recovery practices (after a 5-yr period) in reversing SOM losses in a Typic Haplustoll of the central semiarid region of Argentina. A comparative assessment of the resilience of SOM synthesis (humification process) was performed between the recently adopted restorative management and traditional systems (45 years of plow-tillage) using a native woodland as a baseline. In soil samples (0-20 cm), total SOM, its fractions (non-humic substances, humic substances, humic acids, and fulvic acids), and structure (humification index and polymerization index) were analyzed. Degradation rates, recovery rates and soil resilience classes were calculated. Results showed that in our semiarid environment, plowing has significantly affected the resilience of the humification parameters by high degradation rates, whereas the adoption of recovery practices did not reverse ongoing degradative processes. All the analyzed land uses were included in the same resilience class, suggesting that soils have established a new equilibrium (at low values) with high resistance in front of short-term changes. However, a small tendency of minor degradation rates in the farm enclosure site may indicate the beginning of recovery processes.