Abstract
New urease and nitrification inhibitors and polymer coatings were introduced in recent years, but their effects on N loss and plant N nutrition were scarcely examined in agronomic no-tillage production systems. A field experiment of urea treated with efficiency enhancers was conducted on no-tillage corn (Zea mays L.) in Tennessee, the USA during 2013–2015. A field experiment on urea and ammonium nitrate (UAN) treated with efficiency enhancers was carried out on no-tillage corn in Tennessee in 2014 and 2015. Urea treated with N-(n-butyl) thiophosphoric triamide (NBPT) at concentrations of 20% (NBPT1), 26.7% (NBPT2), or 30% (NBPT3) and polymer coated urea (PCU) were effective but maleic-itaconic copolymer treated urea was ineffective in reducing ammonia volatilization loss and improving N nutrition, grain yield, and N agronomic use efficiency of corn compared with untreated urea. Specifically, NBPT1, NBPT2, or NBPT3 treated urea and PCU reduced the total ammonia volatilization loss by 29.1–78.8%, 35.4–81.9%, 77.3–87.4%, and 59.1–83.3% during the 20 days after N applications, but increased grain yield by 15.6–31.4%, 12.9–34.8%, 18.7–19.9%, and 14.6–41.1%, respectively. The inhibitory effect of NBPT on ammonia volatilization did not improve with NBPT concentration increased from 20% to 30%. UAN treated with NBPT3 or a combination of urease and nitrification inhibitors resulted in 16.5–16.6% higher corn yield than untreated UAN only when they were surface applied. In conclusion, when urea-containing fertilizers are surface applied without any incorporation into the soil under no-tillage, their use efficiencies and performances on corn can be enhanced with an effective urease inhibitor in areas and years with noticeable urea N losses.
Highlights
Nitrogen fertilizer is often applied on the soil surface in no-tillage production systems without any mechanical incorporation into the soil in many areas around the world such as the State of Tennessee[1]
The objectives of this research were to (1) examine ammonia volatilization losses, plant growth and N nutrition, grain yield, and soil N of urea treated with efficiency enhanced products relative to urea and the traditional N fertilizer Ammonium nitrate (AN) via surface application without incorporation for no-till corn; and (2) evaluate the effects of surface applied or knifed-in urea and ammonium nitrate (UAN) treated with NBPT3 or NBPTNI on corn productivity under no-tillage
NBPT1, NBPT2, or NBPT3 treated urea and polymer coated urea (PCU) resulted in lower total ammonia volatilization loss than urea + maleic and itaconic acids (MIC) and untreated urea, but had similar total volatilization loss as AN during the 20 days after N applications
Summary
Nitrogen fertilizer is often applied on the soil surface in no-tillage production systems without any mechanical incorporation into the soil in many areas around the world such as the State of Tennessee[1]. Another inhibitor type is a co-polymer of maleic and itaconic acids (MIC) for treating urea, UAN, and manure originally marketed as Nutrisphere by Specialty Fertilizer Products, LLC (Leawood, KS). It slows down the breakdown of urea-containing fertilizers so that urea N is captured in the soil for a longer time via reducing volatilization and nitrification losses. Results showed that urea + NBPT1 most strongly reduced ammonia volatilization loss when urea is surface applied and not incorporated into the soil quickly by tillage, rainfall, or irrigation[9,10]. Franzen et al.[19] observed that MIC treated N produced similar yield as untreated N in flooded rice (Oryza sativa L.) in Arkansas and Mississippi and spring (Triticum aestivum L.) and durum (Triticum durum Desf.) wheat in North Dakota
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