Available zinc levels in soils of Argentina

Adequate grain zinc (Zn) concentration is important because of its influence on human health. The Argentina Pampas region (APR) provides between 86% and 90% of total grain exports by the country. Soils of the Argentina Pampas region had high fertility under pristine condition but intensification of agriculture, increasing grain yields, and poor or no Zn fertilization could reduce soil available Zn. The objectives of this work were to determine the distribution of available Zn in agricultural and pristine soils of the Argentina Pampas region and its relationship with some chemical characteristics. Soil samples (0-20 cm depth) were collected and georeferenced (approximately 550 for each condition), and soil organic matter, pH, extractable phosphorus, cation exchange capacity, and available Zn by extraction with diethylenetriaminepentaacetic acid (DTPA-Zn) were measured. For geostatistical analysis, indicator kriging (non-parametric method) was utilized as interpolation method. Agriculture decreased soil organic matter, pH, extractable phosphorus and DTPA-Zn (26.9, 4.6, 57.8 and 69.5%, respectively). Relative decrease of DTPA-Zn was only significantly associated with the relative decrease of soil organic matter, although this association was low (r=0.41). Regionally, the DTPA-Zn distribution was very heterogeneous and soil organic matter, pH, extractable phosphorus and cation exchange capacity did not adequately predicted soil DTPA-Zn concentrations (r2=0.16 to 0.26). Agricultural soils of northern, northwestern and southwestern APR (approximately 12,150,000 ha) showed DTPA-Zn values below 1 mg kg-1 , and therefore would present some degree of Zn deficiency for sensitive crops.Fil: Sainz Rozas, Hernan Rene. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Buenos Aires Sur. Estación Experimental Agropecuaria Balcarce. Área de Investigación en Agronomía; Argentina. Universidad Nacional de Mar del Plata. Facultad de Ciencias Agrarias; ArgentinaFil: Puricelli, Marino Marcelo. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Buenos Aires Sur. Estación Experimental Agropecuaria Balcarce. Área de Investigación en Agronomía; Argentina. Universidad Nacional de Mar del Plata. Facultad de Ciencias Agrarias; ArgentinaFil: Eyherabide, Mercedes. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Buenos Aires Sur. Estación Experimental Agropecuaria Balcarce. Área de Investigación en Agronomía; Argentina. Universidad Nacional de Mar del Plata. Facultad de Ciencias Agrarias; ArgentinaFil: Barbieri, Pablo Andres. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Buenos Aires Sur. Estación Experimental Agropecuaria Balcarce. Área de Investigación en Agronomía; Argentina. Universidad Nacional de Mar del Plata. Facultad de Ciencias Agrarias; ArgentinaFil: Echeverria, Hernan Eduardo. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Buenos Aires Sur. Estación Experimental Agropecuaria Balcarce. Área de Investigación en Agronomía; Argentina. Universidad Nacional de Mar del Plata. Facultad de Ciencias Agrarias; ArgentinaFil: Reussi Calvo, Nahuel Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata; Argentina. Laboratorio Ferilab; ArgentinaFil: Martinez, Juan Pablo. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Buenos Aires Sur. Estación Experimental Agropecuaria Balcarce. Área de Investigación en Agronomía; Argentina. Universidad Nacional de Mar del Plata. Facultad de Ciencias Agrarias; Argentin

Comparison between two plant nitrogen and sulphur determination methods: impact on wheat sulphur diagnostics Comparación de métodos de determinación de nitrógeno y azufre en planta: implicancia en el diagnóstico de azufre en trigo

The nitrogen and sulphur ratio (N:S) in plants is often used as a sulphur diagnostics tool in wheat. This ratio requires two different analyses results for its calculation, and thus involves two sources of analytical error. The objective of this work was to compare the accuracy and reliability of the Dumas dry combustion method for N and S determination in plant, compared to traditional methods of wet digestion, and its use as a sulphur diagnostics tool in wheat. The N and S determination was carried out in wheat plant samples from four experiments carried out in the 2006 growing season in the southwestern Buenos Aires province. A highly significant correlation was obtained between both methods (r = 0.99 and r = 0.74 for N and S, respectively). The quantity of N recuperated by the Dumas method was not significantly different to the Kjeldahl method, however, the reliability of the former was higher (low variability coefficient). The method of turbidimetry with wet digestion underestimated (20%) the sulphur concentration compared to the Dumas method. Moreover, the sulphur percent recovered from standard samples was 83 % and 96 % for the turbidimetry and Dumas methods, respectively. The underestimation of plant sulphur concentration by the turbidimetry method resulted in a low percentage of samples correctly diagnosed (25, 18.7 and 50% for Z22, Z24 and Z31, respectively). However, the percent of samples correctly diagnosed was high by the Dumas method (94, 94 and 100% for Z22, Z24 and Z31, respectively). The results of this work indicate that the reliability of the N:S ratio is limited by the S analysis accuracy. On the other hand, the N recovery for both methods was similar.<br>La relación nitrógeno (N): azufre (S) total es utilizada frecuentemente para el diagnóstico de deficiencias de S en trigo. Para determinar este índice es necesario la realización de dos análisis diferentes, y por lo tanto, es afectada por dos errores analíticos. El objetivo fue comparar la precisión del método de combustión seca de Dumas para la determinación de N y S total en planta, respecto a los métodos tradicionales de digestión húmeda y su utilización en el diagnóstico de S en trigo. La determinación de N y S se realizó en muestras de planta provenientes de cuatro experimentos de trigo conducidos durante la campaña 2006 en el sudeste bonaerense. Se obtuvo una correlación significativa entre los métodos utilizados (r = 0,99 y r = 0,74 para N y S, respectivamente). La cantidad de N recuperada por el método de Dumas no difirió respecto del método de Kjeldahl, sin embargo, la precisión del primero fue superior (menores CV). Para S, se determinó una subestimación del 20% en la concentración de S por el método turbidimétrico, respecto al método de Dumas. Además, el porcentaje de S recuperado de una muestra estándar por el método turbidimétrico fue sólo del 83%, mientras que por el método de Dumas la recuperación fue del 96%. La subestimación de la concentración de S en planta se vió reflejada en un bajo porcentaje de muestras correctamente diagnosticadas (25, 18,7 y 50% para los estadios Z22, Z24 y Z31, respectivamente). Sin embargo, cuando se empleó el método de Dumas, dicho porcentaje se incrementó en forma considerable (94, 94 y 100% para los estadios Z22, Z24 y Z31, respectivamente). En síntesis, la baja recuperación del S determinado por el método turbidimétrico afectó la estimación de la relación N:S para el diagnóstico de S; por el contrario, el porcentaje de N recuperado por ambos métodos fue similar

Anaerobically mineralized nitrogen within macroaggregates as a soil health indicator

Anaerobically mineralized nitrogen (AN) in bulk soil (ANBS) has been described as a soil health indicator. Considering that large macroaggregates (2000–8000 μm, MA) are more sensitive to management practices than the bulk soil (i.e. whole soil), AN within MA (ANMA) would be a better soil health indicator than ANBS. The aim of this study was to evaluate if ANMA is a better indicator of: i) soil organic carbon (SOC) and particulate organic carbon (POC) in bulk soil (SOCBS and POCBS, respectively) and ii) aggregate stability (AS) than ANBS. Soil samples were taken at 0–5 and 5–20 cm from 46 continuously cultivated plots (CC) and a reference plot for each CC (pseudo-pristine, PRIS). These soils, located in the Argentinean Pampas, were classified as Mollisols with contrasting surface textural classes. The AS, SOCBS, POCBS, ANBS, SOC (SOCMA), and POC (POCMA) within MA and ANMA were determined separately at 0–5 and 5–20 cm soil depths and estimated at the 0–20 cm layer. The ANMA was a good indicator of SOCBS (R2 0.75, 0.48, and 0.61 at 0–5, 5–20 and 0–20 cm depths, respectively), POCBS (R2 0.66, 0.31, and 0.49, respectively), and AS (R2 0.80, 0.68, and 0.76, respectively). The ANMA performed similarly to predict SOCBS, POCBS, and AS as compared to ANBS, because ANMA was closely correlated to ANBS (r 0.90 at 0–20 cm). Since ANMA determination is more time-consuming than ANBS determination, its use as a soil health indicator would not be convenient. Therefore, the use of ANBS would be recommended over ANMA as a variable to monitor soil health