Search

Nitrogen deficiency can severely limit sunflower (Helianthus annuus L.) grain yield and quality. Our objective was to evaluate N diagnosis methods based on: (a) pre‐plant soil nitrate‐nitrogen (NO3––N) test (PPSNT) and soil N mineralized in short‐term anaerobic incubation (Nan), (b) Greenness index (GI) and the normalized difference vegetation index (NDVI) measured at 6 (V6) and 12 (V12) leaves, and (c) grain nitrogen concentration (Nc). Seventeen experiments were carried out between 2010 and 2019 in Argentina, evaluating nine N rates (0, 30, 40, 60, 80, 90, 120, 150, and 160 kg N ha–1). The GI, NDVI, N sufficiency index and relative normalized difference vegetation index (NDVIr) were determined at V6 and V12 growth stages. On average, yield response to N was 492 kg ha–1 and Nc response was 0.25% in 9 and 11 responsive experiments, respectively. The inclusion of Nan improved the PPSNT diagnosis method. The critical N availability (PPSNT + fertilizer N) threshold was 115 kg N ha–1 for experiments with low Nan (<60 mg kg–1), and 90 kg N ha–1 for experiments with high Nan (>60 mg kg–1). The NDVIr at V12 allowed monitoring the crop N status with a 0.95 critical threshold. The Nc adequately diagnosed N deficiencies and the critical threshold was 2.26%. Also, Nc was predicted from the ratio between N availability and grain yield (R2 =.39). Our results would allow to better estimate N availability to recommend adequate N fertilizer rates for sunflower aiming to optimize grain yield and quality, and minimize the economic and environmental cost of fertilization. Core Ideas: Aim: evaluate N diagnosis methods for grain yield and quality of sunflower.Nitrogen mineralized in anaerobic incubation improved the pre‐plant soil NO3––N test.The relative Green Seeker at V12 growth stage was associated with relative yield.Grain N concentration diagnosed N availability in sunflower.The N availability to grain yield ratio defined the N rate required. [ABSTRACT FROM AUTHOR]

Historical increases in grain yields have been associated with an undermining of soil organic matter (SOM) and a reduction of nutrient cycling capacity. Nutrient limitations for grain crop production are ubiquitous, and while yield and economic response to fertilization has been exhaustively evaluated on several crops across different environments, the focus has been mainly on individual crops rather than on the cropping system. Benefits of increased fertilization beyond a single cropping season need to be assessed to help preventing the current soil nutrient mining process in the Argentine Pampas. i) Evaluate the effect of different fertilization strategies over crop yields across rotation cycles and locations (and their interactions); ii) determine the relationship between crop yield response to fertilization and the physical and chemical soil variables; iii) evaluate the economic profit of each fertilization strategy; and iv) determine the residual effect on a soybean crop after six years following different fertilization strategies. The study was conducted across environments in the Salado "A" Basin of the Inland Pampas of Argentina and included seven experiments with a crop rotation of soybean - wheat/second soybean - maize that was managed with different fertilization strategies (with increasing levels of nitrogen N , phosphorus P , and sulfur S), including a non-fertilized control, along six seasons. Additionally, an extra soybean crop was grown in the seventh year to determine the residual influence of previously imposed fertilization treatments. The yield response to fertilization was highest under the more intensified treatments and larger for wheat (up to 150%) and maize (up to 100%) than for soybean (up to 40%) and second soybean (up to 30%). Overall crop yield response to increasing N and P inputs was negatively correlated with initial soil extractable P while the response to S was higher in sites with high proportion of sand and low SOM. The economic profit increased as fertilization was intensified although differences were not always significant across treatments within sites. On average, intensification resulted in an additional profit of U$S187 ha−1 compared to the typical fertilization strategy followed by farmers in the area without considering a residual positive yield response (10–13%) observed in a successive soybean crop. This study provided elements to improve the understanding of complex interactions determining crop yield response to fertilization strategies to help optimizing long-term management decisions affecting the cropping systems with large impact at regional level. [Display omitted] • Fertilization strategies (NSP) were evaluated in seven sites during two rotation cycles. • Fertilization with high N, S and P doses increased crop yields and profit. • High Sand (%) and low soil organic matter sites responded to S, low P-Bray sites responded to P. • Beneficial effects of fertilization with high N, S and P doses were detected even after the treatments were finished. • Implications of fertilization intensification for cropping systems are highlighted. [ABSTRACT FROM AUTHOR]

The main herbicide used in Argentina and worldwide is glyphosate (N-(phosphonomethyl) glycine), an organophosphate herbicide, non-selective, with a broad spectrum of action. Its main degradation metabolite is AMPA (aminomethylphosphonic acid). Several studies affirm that both molecules have been detected in groundwater, despite presenting great affinity for soil. The objective of this work is to evaluate the vertical transport of glyphosate and AMPA in a field experiment, located at the EEA INTA Balcarce (37° 52' 49.64" S, 58° 17' 41.27" W). The soil under study is a typic Argiudoll, Mar del Plata Series. Horizon A is loam (48, 27 and 24% of sand, silt and clay, respectively), B is sandy clay loam (41, 19 and 40% of sand, silt and clay, respectively), and C is sandy clay loam (56, 20 and 24% of sand, silt and clay, respectively). The design of the experiment is a DBCA with three blocks of plots of 10x40 m and two treatments: intensified management (IS) and control management (MT). The first aims to increase the use of inputs and resources, and minimize the use of pesticides, and the second is similar to the management of producers in the area. The blocks are duplicated to simulate the rotation phases. Each phase has an automatic drainage water extraction system, consisting of a tensiometer, a vacuum pump and two ceramic capsules per treatment, located 1.2 m deep. These are connected to collection bottles, from which the soil solution is extracted for analysis in UPLC MS/MS (Waters®). Leachate samples were taken in the period June-2016 to April-2017, and soil sampling was conducted in July 2017 at 0-2; 2-5; 5-10; 10-15; 15-20 cm depth.Both molecules were detected in the leachate samples, in concentrations ranging from <0.1 µg L-1 to 5.93 µgL-1 of glyphosate and from <0.15 µgL-1 to 1.85 µgL-1 of AMPA, coinciding with the highest concentration in the MT treatment, 10/04/17. In soil samples, the treatments presented statistically significant differences for glyphosate only in the first 2 cm, associated with the time of the last application. After 10 cm, the concentration of the herbicide was less than 20 µgKg-1. On the other hand, AMPA presented higher concentrations than glyphosate and it was only differentiated between treatments in one of the cultivation phases. The results obtained so far indicate that both molecules are present in the first centimeters of the soil, and are transported through the profile, at least up to 1.2 m deep. Such results are preliminary and constitute a first step in the study of the process of vertical transport of these molecules at field scale. [ABSTRACT FROM AUTHOR]