Mar del Plata, Argentina
Mar del Plata, Argentina

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Reussi Calvo N.I.,Laboratorio Of Suelos Fertilab | Diovisalvi N.,Laboratorio Of Suelos Fertilab
Agronomy Journal | Year: 2015

In-season N applications to spring wheat (Triticum aestivum L.) may increase profits and improve N fertilizer accuracy. The objectives were to develop a calibration tool employing normalized difference vegetative index (NDVI) and SPAD 502 chlorophyll meter (SPAD) measurements for calculating the differential from the economic optimum N rate (dEONR) at growth stages Z22, Z24, and Z31 to Z39 and provide N rate algorithms for use in applying N fertilizer at a variable rate. Sensing was conducted trials over 3 yr encompassing 10 site-years across Southeastern Buenos Aires Province, Argentina. The relationship between sensor indices and dEONR was evaluated by fitting quadratic plateau (QP) regression models. Statistically significant QP models were determined at the Z24, Z31, and Z39 growth stages. Relative SPAD (rSPAD) and relative NDVI (rNDVI) reduced variation and improved the calibration of measured N stress with the dEONR. For Z31 and Z39, the rSPAD had the best goodness of fit statistics when compared to rNDVI [adjusted R2 (adjR2)= 0.67 and 0.57 at Z31 and 0.68 and 0.52 at Z39, respectively]. However, adjustment at Z24 was higher for rNDVI (adjR2 = 0.53 and 0.61 for rSPAD and rNDVI, respectively). A single QP model to estimate the dEONR with 58% confidence was adjusted for the Z31 and Z39 growth stages. This indicates that the same calibration for N rate determination based on rSPAD or rNDVI values can be used during stem elongation in spring wheat. This model can be used as an N rate algorithm for applying N fertilizer in-season. © 2015 by the American Society of Agronomy, 5585 Guilford Road, Madison, WI 53711. All rights reserved.

Reussi Calvo N.I.,Laboratorio Of Suelos Fertilab | Echeverria H.,Laboratorio Of Suelos Fertilab | Berardo A.,Laboratorio Of Suelos Fertilab
Agronomy Journal | Year: 2013

Current wheat (Triticum aestivum L.) N fertility diagnosis models do not take into account organic N provided by mineralization. Anaerobically incubated N (Nan) could contribute to assess this N pool for crops. The aim of this research was to assess the Nan contribution to spring wheat yield without added N (GY0N), to grain N export (GNE), and to N fertilization response. A total of 28 N fertilization experiments were conducted in 2006, 2008, 2009, 2010, and 2011 in southeastern Buenos Aires Province (Argentina). At sowing, soil organic matter (SOM) content, Nan, and NO3 --N availability varied between 44 and 68 g SOM kg-1, 34 and 94 mg NH4 +-N kg-1, and 39 and 130 kg NO3 --N ha-1, respectively. Average grain yield and protein content without N added were 3450, 4330, 5020, 5288 and 6262 kg ha-1, and 116, 97, 95, 91, and 90 g kg-1, for 2006, 2008, 2009, 2010, and 2011, respectively. Initial NO3 --N availability explained only 24% of GY0N variation, but R2 increased to 66% when Nan was integrated into the model. Soil NO3 --N content and Nan explained 58% of GNE variation, with a higher partial contribution of Nan to GNE than to GY0N (51 and 41%, respectively). A model was developed to predict the response to N (RN = -625.7 + 7.2Pp - 31.6Nan + 0.28GY0NPp, where Pp is total precipitation from July to December; R2 = 0.58). Soil Nan determination and initial NO3 --N content should be taken into account together when assessing spring wheat N needs. © 2013 by the American Society of Agronomy, 5585 Guilford Road, Madison, WI 53711. All rights reserved.

Orcellet J.M.,Instituto Nacional de Tecnologia Agropecuaria | Reussi Calvo N.I.,Laboratorio Of Suelos Fertilab | Reussi Calvo N.I.,University of the Sea | Echeverria H.E.,University of the Sea | And 3 more authors.
Ciencia del Suelo | Year: 2015

Nitrogen (N) is the main nutrient limiting yield and industrial quality of barley (Hordeum vulgare L). Nitrogen split applications under humid environments should maximize N use efficiency (EUN). In southeastern Buenos Aires (SEB), the effect of split N rates on yield, EUN, protein percentage (PB) and N recovery efficiency in grain (ERNg) was evaluated. Two experiments (Lobería and Miramar) were conducted during 2012. Treatments consisted in four N rates applied at the two-leaves stage (Z12) (0, 40, 80 and 120 kg N ha-1) and four rates split at different moments (80Nf, 120Nf, 180Nf1 and 180Nf2). Nitrogen rates and split applications affected yield and PB significantly. The N split application with the 80N rate increased yield 674 kg ha-1 in average (p <0,05), however the yield increase with 120N was not significant (280 kg ha-1). Split applications (80 kg N ha-1) increased EUN in 5,3 and 10 kg grain kg N-1 with respect to a single application, for Lobería and Miramar, respectively. Furthermore, fractionation did not affect PB content. The ERNg was higher in the treatments with split rates compared to a single application. In Lobería, the ERNg increased 0,15 and 0,08 kg N kg N f-1 for the 80 and 120 kg N ha-1 rates, respectively, while in Miramar the ERNg was 0,11 kg N kg N f-1 higher for both rates. For SEB, split N rates is a recommended management practice towards maximizing grain yield, EUN and for minimizing the N contamination impact on the environment. © 2015, Asociacion Argentina de la Ciencia del Suelo. All rights reserved.

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