Abstract
A method of evaluating net nitrogen (N) mineralization in shallow petrocalcic soils, based on N balances in non-fertilized plots, is proposed. During 1999, 2000 and 2001, estimated N mineralized in an irrigated maize crop (6.5 months) in Central Spain was: 73.3, 56.2 and 60.5 kg ha-1, respectively. The relationship between EUF-Norg (organic nitrogen extracted from soil by electroultrafiltration) and mean mineralized N, in this experiment during the three seasons, was 1 mg EUF-Norg 100 g-1 soil equivalent to 30 kg N ha-1. The calibration was applied to EUF-Norg values from soil samples analysed before sowing. These values, together with the mineral N, were used to estimate available N and consequently the optimal N rate. To evaluate the effect of N fertilizer rate on NO3 leaching and in N fertilizer-use efficiency (NFUE) three different rates of N were tested in 2000 and 2001: optimal N rate (NO), conventional N rate (NC) and a control no N (C). The NO rates for the maize crop were 150 and 130 kg N ha-1 in 2000 and 2001, respectively. Nitrogen losses of nitrate due to leaching were lower with NO than with the NC rate of 300 kg N ha-1. The NFUE values were higher for NO at 78.8% and 83.5% in 2000 and 2001, respectively than for NC at 48.7% and 49.3% in 2000 and 2001, respectively). However, in spite of the different levels of applied N, there was no difference in grain yield among treatments.
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Claims 9
Claim · model-written summary
Estimated nitrogen mineralization for irrigated maize in 1999 was 73.3.
Zea maysOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“maize”
e0“estimated N mineralized in an irrigated maize crop (6.5 months) in Central Spain was: 73.3, 56.2 and 60.5 kg ha-1, respectively.”
Claim · model-written summary
Estimated nitrogen mineralization for irrigated maize in 2000 was 56.2.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“maize”
e0“estimated N mineralized in an irrigated maize crop (6.5 months) in Central Spain was: 73.3, 56.2 and 60.5 kg ha-1, respectively.”
Claim · model-written summary
Estimated nitrogen mineralization for irrigated maize in 2001 was 60.5 kg ha-1.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“maize”
e0“estimated N mineralized in an irrigated maize crop (6.5 months) in Central Spain was: 73.3, 56.2 and 60.5 kg ha-1, respectively.”
Claim · model-written summary
One mg EUF-Norg per 100 g soil corresponded to 30 kg N per hectare mineralization.
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“maize”
e1“The relationship between EUF-Norg (organic nitrogen extracted from soil by electroultrafiltration) and mean mineralized N, in this experiment during the three seasons, was 1 mg EUF-Norg 100 g-1 soil equivalent to 30 kg N ha-1.”
Claim · model-written summary
The method estimated optimal maize nitrogen rates of 150 and 130 kg N ha-1 in 2000 and 2001.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“maize”
e2“The NO rates for the maize crop were 150 and 130 kg N ha-1 in 2000 and 2001, respectively.”
Claim · model-written summary
Optimal nitrogen rate reduced nitrate leaching compared with 300 kg N ha-1.
- Treatment
- NOe3
- Outcome
- Nitrogen losses of nitrate due to leachinge3
- Direction
- lowere3
- Comparator
- NC rate of 300 kg N ha-1e3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“maize”
e3“Nitrogen losses of nitrate due to leaching were lower with NO than with the NC rate of 300 kg N ha-1.”
Claim · model-written summary
Optimal-rate nitrogen fertilizer use efficiency in 2000 was 78.8%, above conventional-rate 48.7%.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“maize”
e4“The NFUE values were higher for NO at 78.8% and 83.5% in 2000 and 2001, respectively than for NC at 48.7% and 49.3% in 2000 and 2001, respectively).”
Claim · model-written summary
Optimal-rate nitrogen fertilizer use efficiency in 2001 was 83.5%, above conventional-rate 49.3%.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“maize”
e4“The NFUE values were higher for NO at 78.8% and 83.5% in 2000 and 2001, respectively than for NC at 48.7% and 49.3% in 2000 and 2001, respectively).”
Claim · model-written summary
Maize grain yield did not differ among nitrogen treatments.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“maize”
e5“there was no difference in grain yield among treatments.”
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