Abstract
The effects of urea and sulphate of ammonia applied at 0, 90, 120, 150 and 180 kg N ha-1 (from 1989 to 1992) and the time and rate of N application (1992) on the severity of Striga hermonthica infestation and maize yield were studied in order to compare the two sources of N fertilizer, commonly available to farmers in Ghana, in reducing S. hermonthica infestation, and to determine the rate and time of application that would minimise the deleterious effect of Striga on maize. The experiments were carried out under natural field infestations on farmers' fields (6-10 locations each year) in the Guinea Savanna zone of Ghana and replicated three times at each location on plots 5 m long and 3.6 m wide. In 1989 and 1992, higher S. hermonthica population density was recorded when urea was applied compared to sulphate of ammonia. However, there were no differences in Striga population density between the two sources of nitrogen from 1990 to 1991. Applying N at either 4 or 6 weeks after planting (WAP) maize did not affect the number of emerged Striga shoots. The rate of nitrogen applied did not influence the emergence of Striga from 1989 to 1991 as compared to 1992 when Striga population declined with increased rate of nitrogen fertilizer. Maize grain yield was unaffected by the source of nitrogen applied from 1989 to 1991. Similarly, applying N fertilizer at 4 or 6 WAP did not affect maize grain yield in 1992. However, the application of sulphate of ammonia resulted in higher maize yield compared to urea in 1992. Maize grain yield increased with increased nitrogen rate up to 90 kg ha-1 beyond which no appreciable increase was observed. A minimum of 90 kg N ha-1 is therefore required for any meaningful reduction in the deleterious effects of Striga on maize. In addition, to reduce the population of Striga in maize, it is essential to apply N fertilizers early. Ghana Jnl agric. Sci. Vol.30(2) 1997: 127-133
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Claims 11
Claim · model-written summary
Urea had higher Striga population density than sulphate of ammonia in 1989 and 1992.
- Treatment
- ureae0
- Interactor
- S. hermonthica
Striga hermonthicae0weed - Outcome
- S. hermonthica population densitye0
- Direction
- highere0
- Comparator
- sulphate of ammoniae0
Zea maysOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In 1989 and 1992, higher S. hermonthica population density was recorded when urea was applied compared to sulphate of ammonia.”
t0“field-grown maize”
Claim · model-written summary
Striga population density did not differ between nitrogen sources in 1990–1991.
- Treatment
- two sources of nitrogene0
- Outcome
- Striga population densitye0
- Direction
- no differencese0
- Comparator
- two sources of nitrogene0
StrigaOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“there were no differences in Striga population density between the two sources of nitrogen from 1990 to 1991.”
t0“field-grown maize”
Claim · model-written summary
Nitrogen application at 4 or 6 WAP did not affect emerged Striga shoot number.
- Treatment
- Applying N at either 4 or 6 weeks after planting (WAP)e0
- Outcome
- number of emerged Striga shootse0
- Direction
- did not affecte0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Applying N at either 4 or 6 weeks after planting (WAP) maize did not affect the number of emerged Striga shoots.”
Claim · model-written summary
Nitrogen rate did not influence Striga emergence in 1989–1991.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The rate of nitrogen applied did not influence the emergence of Striga from 1989 to 1991”
t0“field-grown maize”
Claim · model-written summary
Striga population declined as nitrogen rate increased in 1992.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“1992 when Striga population declined with increased rate of nitrogen fertilizer”
t0“field-grown maize”
Claim · model-written summary
Maize grain yield was unaffected by nitrogen source in 1989–1991.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Maize grain yield was unaffected by the source of nitrogen applied from 1989 to 1991.”
Claim · model-written summary
Applying nitrogen at 4 or 6 WAP did not affect maize grain yield in 1992.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“applying N fertilizer at 4 or 6 WAP did not affect maize grain yield in 1992.”
Claim · model-written summary
Sulphate of ammonia produced higher maize yield than urea in 1992.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the application of sulphate of ammonia resulted in higher maize yield compared to urea in 1992.”
Claim · model-written summary
Maize grain yield increased with nitrogen rate up to 90 kg ha-1 and then showed no appreciable increase.
- Treatment
- increased nitrogen rate up to 90 kg ha-1e0
- Outcome
- grain yielde0
- Direction
- increasede0
- Qualifier
- beyond which no appreciable increase was observede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Maize grain yield increased with increased nitrogen rate up to 90 kg ha-1 beyond which no appreciable increase was observed.”
Claim · model-written summary
The authors recommend a minimum of 90 kg N ha-1 to reduce Striga harm to maize.
- Outcome
- minimum of 90 kg N ha-1e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“A minimum of 90 kg N ha-1 is therefore required for any meaningful reduction in the deleterious effects of Striga on maize.”
Claim · model-written summary
The authors recommend early nitrogen application to reduce Striga population in maize.
- Outcome
- apply N fertilizers earlye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“to reduce the population of Striga in maize, it is essential to apply N fertilizers early.”
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