Maize yield and nitrate leaching affected by nitrogen source and time of application

• Grant number: 23/01726-7
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: April 01, 2023
• End date: March 31, 2025
• Field of knowledge: Agronomical Sciences - Agronomy - Crop Science
• Principal Investigator: Ciro Antonio Rosolem
• Grantee: Marcelo Jose Miranda Filho
• Host Institution: Faculdade de Ciências Agronômicas (FCA). Universidade Estadual Paulista (UNESP). Campus de Botucatu. Botucatu , SP, Brazil

Abstract

The adjustment of nitrogen fertilization is essential to improve the efficiency of N use and maize yield, but little is known about the impact of the early fertilization with nitrogen on yield and N losses by leaching, and whether this is dependent on the source of nitrogen. The objective of the study is to evaluate the nitrate leaching in the soil profile, as well as the nutrition and yield of maize as a function of sources and timing of application of nitrogen fertilizers. The study will be conducted under field conditions, with an experimental design in randomized blocks with four replications. There will be two experiments side by side, and in one of them single maize will be grown with conventional tillage soil, and in the other, maize will be grown in intercropping with ruzisiensis (Urochloa ruziziensis). The treatments will be: (i) control (without N-topdressing), (ii) urea applied in V6-V7, (iii) urea+NBPT applied in V6-V7, (iv) calcium nitrate applied in V6-V7, ( v) urea+NBPT applied in V3, (vi) calcium nitrate applied in V3) and (vii) 130% of the calcium nitrate dose in V3. The rate of 150 kg ha-1 will be used as standard topdressing N. N loss by NO3- leaching will be calculated based on NO3- concentrations in the soil solution collected at 0.8 m depth and estimated drainage below 0.8 m. Soil solution samples will be collected throughout the maize cycle and stored in plastic tubes under refrigeration, and NO3- will be determined. At the R1 stage, ten leaves will be collected from each experimental unit to evaluate the concentration of macro and micronutrients. Yield will also be evaluated, as well as forage biomass at harvest time. The results will be submitted to analysis of variance and, when the F test is significant, the means will be compared by the LSD test (p<0.05), using Sisvar statistical software. In case of significant response to doses, graphs will be plotted using Sigmaplot software.