Abstract
Polymer coated urea (PCU) have the potential to increase nitrogen (N) use efficiency (NUE) by the release of N following crop demand while reducing losses by volatilization, leaching and denitrification. However, the NUE of PCU is still unclear especially in systems of corn-palisadegrass intercropping. Broadcast application of urea result in ammonia volatilization losses, new technologies must be adopted in order to allow broadcast application of urea. The aim of this research was to evaluate NUE from PCU in the corn-palisadegrass intercropping system and the viability of the broadcast application using PCU. Two field trials were carried out in a 4 × 2 factorial design including fertilization treatments and application forms. Fertilization treatments were: Conventional Urea topdressing (CUT); Conventional Urea at corn planting (CUP); PCU applied at planting to release in 30 days (PCU30); PCU mixture applied at planting to release in 30 and 60 days (PCU30+60); and application forms: broadcast placement and in furrow. 15N-urea was used for the determination of NUE. The corn yield and palisadegrass above-ground biomass were not affected by the fertilization treatments or application forms. PCU did not increase N uptake and the NUE by corn or palisadegrass in relation to urea. The N uptake from fertilizer by palisadegrass intercropped with corn is less than 1% of all N uptake on the intercropping system and at most 2% of the N fertilizer applied. The slow release urea does not enable the broadcast application and its efficiency depended upon the same climatic conditions as those of the conventional urea.
Highlights
The Enhanced Efficiency Fertilizers (EEFs) come with the assertion of increased Nitrogen use efficiency (NUE) by reducing losses from leaching, volatilization and nitrous oxide emissions or by increasing plant uptake through gradual supply.Urea (U) is the most widely N fertilizer used in Brazil, but broadcast application of U result in ammonia (NH3) volatilization losses that average 30% (Silva et al, 2017)
The fertilization treatments were: 1) Conventional urea topdressing (CUT); 2) Conventional urea applied at corn planting (CUP); 3) Polymer coated urea (PCU) applied at planting to release in 30 days (PCU30); 4) A PCU mixture applied at planting to release in 30 and 60 days (PCU30+60); and two application forms: 1) broadcast and 2) in furrow
The dry mass of palisadegrass and corn yield did not change with fertilization treatments or with the application forms in both sites
Summary
Urea (U) is the most widely N fertilizer used in Brazil, but broadcast application of U result in ammonia (NH3) volatilization losses that average 30% (Silva et al, 2017). New technologies must be adopted in order to allow broadcast application of urea without major losses. Several studies reported reduction in denitrification losses following PCU when compared to conventional urea (Hadi et al, 2008; Halvorson et al, 2010; Hyatt et al, 2010; Asgedom et al, 2014). PCU presented lower NH3 volatilization losses when compared to urea (Zhao et al, 2013), but still higher when compared to ammonium nitrate and ammonium sulfate (Nascimento et al, 2013)
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