Abstract
Urea is the main solid N fertilizer used worldwide. Among its advantages are the high nutrient content, ease of handling and application, and low cost. Urea is subject to high losses through NH3 volatilization if surface-applied on soils. Therefore, ammonium nitrate is the preferred N source, especially in the ratoon cycles. Urea treated with the urease inhibitor NBPT and controlled-release fertilizers are options to replace ammonium nitrate. Controlled-release urea (CRU) is produced by coating the urea granules with resin or synthetic polymers so that the urea in the nucleus is not in contact with soil moisture. This study aimed to test CRU in sugarcane ratoons compared with ammonium nitrate (AN) and urea treated with urease inhibitor (UR-NBPT) at three rates: 60, 120 and 180 kg ha–1. Efficiency was also compared with two control treatments, the N control and the NPK control. Two field experiments were established and conducted in 2020 and 2021 in Sao Paulo state, Brazil. Sugarcane yield was evaluated in both experiments. N losses as NH3 volatilized were measured in the first experiment. All sources were equally efficient in promoting increases in sugarcane ratoon yield in both experiments. The relative yield obtained with N fertilizers and the control without N showed yield increases in the first experiment of 40, 54 and 68% for 60, 120 and 180 kg N ha–1 as AN, respectively; 29, 61 and 61% for 60, 120 and 180 kg N ha–1 as urea-NBPT, respectively; and 32, 62 and 67% for 60, 120 and 180 kg N ha–1 as CRU, respectively. Yields were higher in the second experiment, but increases in yield were lower compared to the first. Increases of 7, 10 and 16% for AN in three doses, 5, 12, 15% for UR-NBPT and 7, 9 and 14% for CRU were observed, respectively. N losses as NH3 volatilized were relatively low; CRU fertilizer showed good protection against NH3 losses by volatilization, protecting urea for about 30 days. This protection, however, did not affect yield. NH3 losses reached 13% of the N applied in the treatment with urea (about 16 kg N ha–1), 11% for Urea-NBPT (about 13 kg N ha–1) and 9% for CRU (about 11 kg N ha–1). Analyzing the results of both experiments CRU did not show an advantage in efficiency compared to AN and Urea-NBPT.
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Claims 14
Claim · model-written summary
All N sources increased sugarcane ratoon yield equally in both experiments.
Not reportedComparator
Verbatim
e0“All sources were equally efficient in promoting increases in sugarcane ratoon yield in both experiments”
t0“sugarcane ratoons”
Claim · model-written summary
AN increased first-experiment yield by 40, 54 and 68% at 60, 120 and 180 kg N ha–1.
Verbatim
e0“yield increases in the first experiment of 40, 54 and 68% for 60, 120 and 180 kg N ha–1 as AN, respectively”
e1“the control without N”
t0“sugarcane ratoons”
Claim · model-written summary
Urea-NBPT increased first-experiment yield by 29, 61 and 61% at 60, 120 and 180 kg N ha–1.
Verbatim
e0“29, 61 and 61% for 60, 120 and 180 kg N ha–1 as urea-NBPT, respectively”
e1“yield increases in the first experiment”
e2“the control without N”
t0“sugarcane ratoons”
Claim · model-written summary
CRU increased first-experiment yield by 32, 62 and 67% at the three N rates.
Verbatim
e0“32, 62 and 67% for 60, 120 and 180 kg N ha–1 as CRU, respectively”
e1“yield increases in the first experiment”
e2“the control without N”
t0“sugarcane ratoons”
Claim · model-written summary
Yield was higher in the second experiment, but its increases were lower.
Verbatim
e0“Yields were higher in the second experiment, but increases in yield were lower compared to the first”
t0“sugarcane ratoons”
Claim · model-written summary
AN increased second-experiment yield by 7, 10 and 16% across three doses.
Verbatim
e0“Increases of 7, 10 and 16% for AN in three doses”
e1“Sugarcane yield was evaluated in both experiments”
e2“the control without N”
t0“sugarcane ratoons”
Claim · model-written summary
UR-NBPT increased second-experiment yield by 5, 12 and 15%.
Verbatim
e0“5, 12, 15% for UR-NBPT”
e1“Increases of 7, 10 and 16% for AN in three doses, 5, 12, 15% for UR-NBPT and 7, 9 and 14% for CRU were observed, respectively”
e2“the control without N”
e3“Yields were higher in the second experiment”
t0“sugarcane ratoons”
Claim · model-written summary
CRU increased second-experiment yield by 7, 9 and 14%.
Verbatim
e0“7, 9 and 14% for CRU”
e1“Increases of 7, 10 and 16% for AN in three doses, 5, 12, 15% for UR-NBPT and 7, 9 and 14% for CRU were observed, respectively”
e2“the control without N”
e3“Yields were higher in the second experiment”
t0“sugarcane ratoons”
Claim · model-written summary
CRU protected urea against NH3 volatilization for about 30 days.
- Taxon
- sugarcanet0
- Treatment
- CRU fertilizere0
- Outcome
- NH3 losses by volatilizatione0
- Direction
- protectione0
- Value
- about 30 dayse0
Not reportedComparator
Verbatim
e0“CRU fertilizer showed good protection against NH3 losses by volatilization, protecting urea for about 30 days”
t0“sugarcane ratoons”
Claim · model-written summary
The CRU protection did not affect yield.
Not reportedComparator
Verbatim
e0“This protection, however, did not affect yield”
e1“CRU fertilizer”
t0“sugarcane ratoons”
Claim · model-written summary
Urea lost 13% of applied N as NH3.
Verbatim
e0“NH3 losses reached 13% of the N applied in the treatment with urea (about 16 kg N ha–1)”
t0“sugarcane ratoons”
Claim · model-written summary
Urea-NBPT lost 11% of applied N as NH3.
Verbatim
e0“11% for Urea-NBPT (about 13 kg N ha–1)”
e1“NH3 losses reached 13% of the N applied”
t0“sugarcane ratoons”
Claim · model-written summary
CRU lost 9% of applied N as NH3.
Verbatim
e0“9% for CRU (about 11 kg N ha–1)”
e1“NH3 losses reached 13% of the N applied”
t0“sugarcane ratoons”
Claim · model-written summary
CRU showed no efficiency advantage over AN and Urea-NBPT across both experiments.
Verbatim
e0“CRU did not show an advantage in efficiency compared to AN and Urea-NBPT”
t0“sugarcane ratoons”
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