Ammonia volatilization from nitrogen fertilizers applied to sugarcane straw

Resumo

Maintenance of crop residues over soil surface under conservational systems limits incorporation of nitrogen
fertilizers into the soil. Application of urea over crop residues enhance N-NH3
volatilization losses, justifying the usage of
urease inhibitors or N sources less susceptible to volatilization under such conditions. This study aimed to evaluate volatilization
losses from N sources applied over sugarcane straw. A field trial was carried out in a sugarcane field in Iracemapolis, Sao
Paulo on a Typic Kandiudox in June 2014. We used a complete block experimental design, with seven treatments and four
replications. Treatments included Control [CO], ammonium nitrate [AN], NS30TM (ammonium nitrate-75% and ammonium
sulfate-25% fused mixture) [NS30TM], ammonium nitrate plus ammonium sulfate (ammonium nitrate-75% and ammonium
sulfate-25% physical mixture) [AN-AS], urea [UR], urea treated with 0.4% Cu and 0.15% B [UR-CuB], urea treated with
530 mg kg-1 of NBPT [UR-NBPT]. Treatments were applied at rate of 100 kg ha-1 N (except CO). Volatilization losses were
quantified up to 30 days after fertilization (DAF). Maximum N-NH3
occurred 16 DAF for UR and UR-CuB and 20 DAF for
UR-NBPT. Accumulated N-NH3
losses ranged from 20% (UR), 17% (UR-CuB), and 14% (UR-NBPT) of applied N; nonamidic sources showed losses lower than 1%. Adding urease inhibitor to urea shows potential in reducing volatilization losses
even under application over large amounts of straw.