Abstract
Estimating mineralization rates is one of the best ways to predict N availability over time. However, different methods can lead to distinct predictions, especially when different production systems are used. The aim of this study was to compare biological and chemical methods commonly used to estimate the potentially available N in a soil cultivated with maize in succession to cover crops and N fertilization. The experimental area has been cultivated with cover crops (jack bean, velvet bean, millet and spontaneous vegetation) and N fertilization (0, 60, 120 and 180 kg N ha−1) since the year 2000 in a split-plot design with cover crops as the main treatments and N rates as secondary treatments. The biological evaluation of N mineralization was performed by means of an aerobic incubation of soil samples, while the chemical methods were either by the use of saline ((Ca(H2PO4)2, CaCl2, KCl) and Illinois soil test and direct steam distillation (DSD). Soil C and N contents were not affected by the cover crops, even after sixteen years of cultivation. The utilization of N by maize plants was affected by cover crops, especially for jack bean, while N fertilization led to a maximum absorption point, estimated in 158 kg N ha−1. The methods for evaluating the potentially available N behaved differently among treatments. The DSD method has significantly correlated with maize N uptake and yield, which demonstrates that it was the most promising method to estimate the potentially available N, although it is not yet calibrated for all agricultural systems.
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Claims 5
Claim · model-written summary
Soil C and N contents were not affected by cover crops even after sixteen years of cultivation.
Zea maysNot reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“soil cultivated with maize in succession to cover crops”
e1“Soil C and N contents were not affected by the cover crops, even after sixteen years of cultivation”
Claim · model-written summary
Cover crops affected N utilization by maize plants, especially jack bean.
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“soil cultivated with maize in succession to cover crops”
e1“The utilization of N by maize plants was affected by cover crops, especially for jack bean”
Claim · model-written summary
N fertilization led to a maximum N absorption point, estimated at 158 kg N ha-1.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“soil cultivated with maize in succession to cover crops”
e1“N fertilization led to a maximum absorption point, estimated in 158 kg N ha−1”
Claim · model-written summary
The direct steam distillation (DSD) method was significantly correlated with maize N uptake and yield.
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“soil cultivated with maize in succession to cover crops”
e1“The DSD method has significantly correlated with maize N uptake and yield”
Claim · model-written summary
DSD was the most promising method to estimate potentially available N, although it is not yet calibrated for all agricultural systems.
- Outcome
- most promising method to estimate the potentially available Ne1
- Qualifier
- not yet calibrated for all agricultural systemse1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“soil cultivated with maize in succession to cover crops”
e1“it was the most promising method to estimate the potentially available N, although it is not yet calibrated for all agricultural systems”
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