Abstract
Previous experiments have shown that, at harvest of winter wheat, recovery of fertilizer N applied in early spring [tillering, Zadok’s growth stage (GS) 25] is lower than that of N applied later in the growth period. This can be explained by losses and immobilization of N, which might be higher between GS 25 and stem elongation (GS 31). It was hypothesized that a higher crop density (i.e. more plants per unit area) results in an increased uptake of fertilizer N applied at GS 25, so that less fertilizer N is subject to losses and immobilization. Different crop densities of winter wheat at GS 25 were established by sowing densities of 100 seeds m –2 (S low ), 375 seeds m –2 (S cfp = common farming practice) and 650 seeds m –2 (S high ) in autumn. The effect of sowing density on crop N uptake and apparent fertilizer N recovery (aFNrec = N in fertilized treatments − N in unfertilized treatments) in crops and soil mineral N (N min ), as well as on lost and immobilized N (i.e. non‐recovered N = N rate − aFNrec), was investigated for two periods after N application at GS 25 [i.e. from GS 25 to 15 days later (GS 25 + 15d), and from GS 25 + 15d to GS 31] and in a third period between GS 31 and harvest (i.e. after second and third N applications). Fertilizer N rates varied at GS 25 (0, 43 and 103 kg N ha –1 ), GS 31 (0 and 30 kg N ha –1 ) and ear emergence (0, 30 and 60 kg ha –1 ). At GS 25 + 15d, non‐recovered N was highest (up to 33 kg N ha –1 and up to 74 kg N ha –1 at N rates of 43 and 103 kg N ha –1 , respectively) due to low crop N uptake after the first N dressing. Non‐recovered N was not affected by sowing density. Re‐mineralization during later growth stages indicated that non‐recovered N had been immobilized. N uptake rates from the second and third N applications were lowest for S low , so non‐recovered N at harvest was highest for S low . Although non‐recovered N was similar for S cfp and S high , the highest grain yields were found at S cfp and N dressings of 43 + 30 + 60 kg N ha –1 . This combination of sowing density and N rates was the closest to common farming practice. Grain yields were lower for S high than for S cfp , presumably due to high competition between plants for nutrients and water. In conclusion, reducing or increasing sowing density compared to S cfp did not reduce immobilization (and losses) of fertilizer N and did not result in increased fertilizer N use efficiency or grain yields.
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Claims 12
Claim · model-written summary
At GS 25 plus 15 days, non-recovered nitrogen reached 33 kg per hectare at the lower nitrogen rate.
- Taxon
- Winter Wheat
Triticum aestivumt0 - Treatment
- 43e0
- Outcome
- non‐recovered Ne0
- Direction
- higheste0
- Value
- 33 kg N ha –1e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“At GS 25 + 15d, non‐recovered N was highest (up to 33 kg N ha –1 and up to 74 kg N ha –1 at N rates of 43 and 103 kg N ha –1 , respectively)”
t0“Winter Wheat”
Claim · model-written summary
At GS 25 plus 15 days, non-recovered nitrogen reached 74 kg per hectare at the higher nitrogen rate.
- Taxon
- Winter WheatTriticum aestivumt0
- Treatment
- 103 kg N ha –1e0
- Outcome
- non‐recovered Ne0
- Direction
- higheste0
- Value
- 74 kg N ha –1e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“At GS 25 + 15d, non‐recovered N was highest (up to 33 kg N ha –1 and up to 74 kg N ha –1 at N rates of 43 and 103 kg N ha –1 , respectively)”
t0“Winter Wheat”
Claim · model-written summary
Sowing density did not affect non-recovered nitrogen.
- Taxon
- Winter WheatTriticum aestivumt0
- Treatment
- sowing densitye0
- Outcome
- Non‐recovered Ne0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Non‐recovered N was not affected by sowing density.”
t0“Winter Wheat”
Claim · model-written summary
Later remineralization indicated earlier non-recovered nitrogen had been immobilized.
- Taxon
- Winter WheatTriticum aestivumt0
- Organ / stage
- later growth stagese0
- Outcome
- non‐recovered N had been immobilizede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Re‐mineralization during later growth stages indicated that non‐recovered N had been immobilized.”
t0“Winter Wheat”
Claim · model-written summary
Nitrogen uptake from later applications was lowest at low sowing density.
- Taxon
- Winter WheatTriticum aestivumt0
- Material
- S lowe0
- Outcome
- N uptake ratese0
- Direction
- loweste0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“N uptake rates from the second and third N applications were lowest for S low”
t0“Winter Wheat”
Claim · model-written summary
Non-recovered nitrogen at harvest was highest at low sowing density.
- Taxon
- Winter WheatTriticum aestivumt0
- Material
- S lowe0
- Outcome
- non‐recovered N at harveste0
- Direction
- higheste0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“so non‐recovered N at harvest was highest for S low”
t0“Winter Wheat”
Claim · model-written summary
Non-recovered nitrogen was similar at common and high sowing densities.
- Taxon
- Winter WheatTriticum aestivumt0
- Material
- S cfp and S highe0
- Outcome
- non‐recovered Ne0
- Direction
- similare0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“non‐recovered N was similar for S cfp and S high”
t0“Winter Wheat”
Claim · model-written summary
Highest grain yields occurred at common sowing density with 43 + 30 + 60 kg N per hectare dressings.
- Taxon
- Winter WheatTriticum aestivumt0
- Material
- S cfpe0
- Treatment
- N dressings of 43 + 30 + 60 kg N ha –1e0
- Outcome
- grain yieldse0
- Direction
- higheste0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the highest grain yields were found at S cfp and N dressings of 43 + 30 + 60 kg N ha –1”
t0“Winter Wheat”
Claim · model-written summary
High sowing density yielded less grain than common sowing density.
- Taxon
- Winter WheatTriticum aestivumt0
- Material
- S highe0
- Outcome
- Grain yieldse0
- Direction
- lowere0
- Comparator
- S cfpe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Grain yields were lower for S high than for S cfp”
t0“Winter Wheat”
Claim · model-written summary
Changing sowing density from common practice did not reduce fertilizer nitrogen immobilization and losses.
- Taxon
- Winter WheatTriticum aestivumt0
- Treatment
- reducing or increasing sowing densitye0
- Outcome
- immobilization (and losses) of fertilizer Ne0
- Comparator
- S cfpe0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“reducing or increasing sowing density compared to S cfp did not reduce immobilization (and losses) of fertilizer N”
t0“Winter Wheat”
Claim · model-written summary
Changing sowing density from common practice did not improve fertilizer nitrogen use efficiency.
- Taxon
- Winter WheatTriticum aestivumt0
- Treatment
- reducing or increasing sowing densitye0
- Outcome
- fertilizer N use efficiencye0
- Comparator
- S cfpe0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“reducing or increasing sowing density compared to S cfp did not reduce immobilization (and losses) of fertilizer N and did not result in increased fertilizer N use efficiency or grain yields.”
t0“Winter Wheat”
Claim · model-written summary
Changing sowing density from common practice did not increase grain yields.
- Taxon
- Winter WheatTriticum aestivumt0
- Treatment
- reducing or increasing sowing densitye0
- Outcome
- grain yieldse0
- Comparator
- S cfpe0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“reducing or increasing sowing density compared to S cfp did not reduce immobilization (and losses) of fertilizer N and did not result in increased fertilizer N use efficiency or grain yields.”
t0“Winter Wheat”