Gross nitrification in integrated production systems with forage and nitrogen fertilization

• Grant number: 21/13609-0
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: March 01, 2022
• End date: December 31, 2022
• Field of knowledge: Agronomical Sciences - Agronomy - Soil Science
• Principal Investigator: Ciro Antonio Rosolem
• Grantee: Victor Lousada Rodrigues
• Host Institution: Faculdade de Ciências Agronômicas (FCA). Universidade Estadual Paulista (UNESP). Campus de Botucatu. Botucatu , SP, Brazil

Abstract

Understanding the nitrification process (conversion of NH4+ ammonium to NO3- nitrate) within long-term conservation production systems intercropped with forages in tropical soils and climate is essential for sustainable management and management of N in the environment. Research have shown divergent effects regarding the inhibitory potential of forage species related to nitrification, which is largely attributed to the test conduction time and concentration of inhibitor molecules. The objective will be to determine the gross nitrification rates in soil samples collected from a soybean/corn+forage succession system and intercropping system (maize and forages - Urochloa ruziziensis and Megathyrsus maximus), collected in experimental areas with 4 and 7 years of cultivation, respectively, without and with the addition of nitrogen, through the technique of dilution of the 15N isotope. The first experiment was started in 2018, with the following treatments: two forage grass species - brachiaria ruziziensis (U. ruziziensis), Tanzania grass (M. maximum) and control without grass - with and without nitrogen (180 kg ha-1 ). The second experiment started in 2014, with the following treatments: three grass species - brachiaria ruziziensis cv. Common (Urochloa ruziziensis), brachiaria brizantha cv. Marandú (Urochloa brizantha) and Tanzania grass cv. Tanzania (Megathyrsus maximus (Sin. Panicum maximum)) - with and without nitrogen (N) application (270 kg of N ha-1). Soil samples collected in 2021 - offseason - and samples collected at the beginning of the test (Experiment I, 2018 and Experiment II, 2014) will be enriched with 15N (K15NO3) and incubated. The dilution capacity of the added 15N pool, resulting from the conversion of soil organic-N to inorganic-N, will be reported as gross nitrification. The hypotheses are: (i) the inhibition of nitrification responds to the time of the establishment of intercropped corn-forage systems in tropical soils; (ii) the application of nitrogen in intercropped systems increases the inhibitory potential of nitrification; (iii) forage species alter ammonia and nitric pools in tropical soils. Data will be submitted to the normality test (Shapiro Wilk). Given the normal distribution, analysis of variance will be applied and, once significance is found, the means will be compared by Tukey Test P<0.05. (AU)