Soil nitrogen contribution to grasslands and its implication for nitrogen use efficiency

Abstract

In pasture systems of southern Chile, nitrogen (N) fertilization is mostly carried out without considering soil N supply, while seasonal N plant uptake is partially accounted for. These aspects are fundamental to correctly decide N fertilization. The aim of this work was to determine soil N contribution to grasslands yield in southern Chile and its implication for N use efficiency. Three treatments were distributed in a completely randomized block design with four replicates. A negative control treatment without N application and a positive control without N deficiency (450 kg N ha -1 ) were considered. An optimized treatment was also used, so that the total amount of mineral N applied as fertilizer was only that necessary to account for the arithmetic difference among plant uptake and N soil supply, resulting in the application of 171 kg N ha -1 only. Soil mineralization was high (241-934 kg N ha -1 ) and strongly affected by soil available N (VIP > 0.8). The 450 kg N ha -1 treatment produced 1,726 kg DM more than the 171 kg N ha -1 treatment. Nevertheless, this increase was associated to the application of an extra 279 kg N ha -1 , so that the extra yield was produced at a 6 kg DM kg -1 N efficiency. This value was one third of that showed by the optimized treatment, which was 1.8 times more efficient in the use of N than the 450 kg N ha -1 treatment, on average. Results suggest that it is possible to adjust pasture's N fertilization considering soil N contribution via mineralization, and that this improves resources efficiency while maintaining pasture productivity.

Chemical Characterization of Volcanic Soils Using Near Infrared Spectroscopy (Nirs)

“…Phosphorus concentration in Andisols was lower than that registered in Ultisols, in agreement with Cardenas et al (2013), who found Olsen P concentrations five and ten-times lower in Andisols than in Ultisols, respectively, in southern Chile. The concentrations of OM found for each soil type in this study coincide with the values reported by other authors (Vistoso et al, 2012;Lobos et al, 2016). Volcanic soils have a high OM concentration, and it is common to find 14% to 20% of OM within the first 15 cm of soil in Andisols (Carvajal et al, 2016), whereas it is slightly smaller in Ultisols (Clunes et al, 2014).…”

“…This difference is probably explained by the fact that the data of the present study correspond to fertilized and non-fertilized soils, while the studies mentioned before included Mg fertilizer application. Potassium concentration found in Ultisols was 1.9 times greater than that of Andisols and coincide with the levels reported by other authors (Vistoso et al, 2012;Lobos et al, 2016). The average values of pH (water), Sodium concentration and exchangeable Al were similar to those reported by Cardenas et al (2013), Carbajal et al, (2016 and Lobos et al (2016) for similar soil types.…”

“…Potassium concentration found in Ultisols was 1.9 times greater than that of Andisols and coincide with the levels reported by other authors (Vistoso et al, 2012;Lobos et al, 2016). The average values of pH (water), Sodium concentration and exchangeable Al were similar to those reported by Cardenas et al (2013), Carbajal et al, (2016 and Lobos et al (2016) for similar soil types. Finally, the concentration of ammonium and nitrate was similar to that found by Dixon et al (2011) in volcanic ash soils in southern Chile.…”

Validation of a critical nitrogen dilution curve for hybrid ryegrasses

“…The use of increasing amounts of N fertilizer to improve grass yield is well documented and past work summarized by Hopkins () indicates a linear phase of response followed by a plateau. In ryegrasses (Loaiza, Balocchi, & López, ; Marino et al., ; Martin et al., ; Pembleton, Rawnsley, & Burkitt, ), tall fescue (Errecart, Agnusdei, Lattanzi, Marino, & Berone, ; Greenwood et al., ) or naturalized pastures (Lobos‐Ortega, Alfaro, & Martinez‐Lagos, ), a positive yield response occurs when increasing the N‐fertilizer rates.…”

Permeabilidad y difusión de aire en el subsuelo de un Andisol sujeto a distintas estrategias de mejoramiento de praderas

“…Grazing systems constitute an important part of the landscape and play a relevant role for dairy and meat production in southern Chile (1,340,400 ha). Over 44% of these pastures are degraded and relatively low in productivity (4,000 kg dry matter ha -1 year -1 ) if compared to pastures with e.g., moderate nitrogen fertilization (Lobos et al, 2016). Various strategies have been implemented to improve these grasslands (Zúñiga et al, 2015) which result in alterations within the plantsoil-atmosphere-continuum (Ordóñez et al, 2018).…”