Abstract
Nitrogen is the most required and complex management element in maize crop, promoting the highest responses in crop yield. The objective of this work was to verify the effect of different N sources on topdressing in minimum tillage and conventional tillage systems on the agronomic performance of the Pioneer 32R22YHR single cross and on the severity of common rust disease. Two experiments were carried out in a randomized block design (DBC) in the 2013/14 crop in minimum tillage and conventional tillage systems. The treatments were: control without nitrogen, ammonium sulfate, urea, ammonium nitrate, a physical mixture of nitrate (70%) and ammonium sulfate (30%) and a chemical mixture of these same sources in the same proportion just explained. Nitrogen sources had no significant effect on plant height, ear insertion height, ear prolificacy, grain yield and leaf severity of common rust, regardless of the sowing system. Under conventional tillage, the plants presented higher plant height, ear insertion and grain yield. There was no effect of sowing systems on prolificacy. With the exception of nitrogen free treatment, for all others, the severity of common rust was higher in minimum tillage system.
Highlights
Among the factors that contribute to the low average maize yield in Brazil is the incorrect management of fertilizers, especially nitrogen (MEIRA et al, 2009; OLIVEIRA et al, 2016; VARGAS et al, 2015)
Experimental precision is classified as medium to high considering the values of the coefficient of variation (CV)
The sources of N, at a dose of 120.0 kg ha-1 applied between V4 and V6 stage, evaluated in this work do not influence the agronomic performance and severity caused by common rust in maize
Summary
Among the factors that contribute to the low average maize yield in Brazil is the incorrect management of fertilizers, especially nitrogen (MEIRA et al, 2009; OLIVEIRA et al, 2016; VARGAS et al, 2015). Nitrogen (N) is a strategic element in maize production and the search for more efficient sources of this nutrient has the potential to strongly impact crop production systems. N fertilization in maize is one of the main management tools to obtain high yields (MOTA et al, 2015). N is a constituent of many stable compounds, including some inorganic compounds such as ammonium or nitrate salts and other organic compounds such as amino acids and nucleotides. These compounds differ deeply in their chemical properties (BLOOM, 2015)
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