Abstract
Cereal production in the summer-dominant rainfall region of Australia, especially the north-east, has relied heavily on natural soil fertility. Continued cereal production has so depleted the fertility of some soils that corrective strategies are required to restore the production of high protein wheat needed for domestic and export markets. Application of nitrogen (N) fertilisers, along with other strategies to improve soil N status, was evaluated between 1987 and 1994 on a Vertisol located in an area of unreliable winter rainfall. Responses of wheat grain yield and protein content to applied N (0-150 kg/ha) under zero tillage (ZT) and conventional tillage (CT) were determined each year, except 1991 when severe drought prevented wheat sowing. The ZT practices increased grain yields, particularly in 1988 and 1992-93 when antecedent soil water supplies were moderate (about 1 m wet soil in 1988 and 1992) or low (about 0.6 m wet soil in 1993), apparently due to increased antecedent soil water. Tillage practice had little effect on available nitrate-N (kg/ha) to 1.5 m, but the greater water supply in ZT soil usually benefited the wheat crop when N was applied. Applying N increased returns from 5 of the 7 crops because of grain yield and/or grain protein responses. Grain yield responses were inconsistent in the year of fertiliser application where no N fertiliser had been applied to preceding crops. Nevertheless, grain protein usually increased with increasing N application at sowing, except in 1994, when drought after sowing prevented secondary root development and fertiliser uptake. Where N was applied with each successive crop, the crops receiving small N applications (0, 12.5 or 25 kg/ha.crop) produced grain of a low protein concentration (<10%) and lower yields (<90% maximum yield) than crops which received larger N applications (75 kg/ha.crop). Profits were substantially reduced where the rate of N applied was insufficient to raise grain protein concentration to >11.5%, due to the low market value of low protein wheat, or because of lower grain yields. Routine N application to crops over the period 1987-94, which included the longest drought (1990-94) in the lifetime of most producers, caused similarly inconsistent grain yield increases but increased grain protein concentrations (>11.5%) in all except the first crop (1987). Increased frequency of high protein wheat and a high anticipated market value of the higher protein grain should encourage greater producer confidence with routine application of N throughout this region.
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Claims 11
Claim · model-written summary
Zero tillage increased wheat grain yield, particularly in 1988 and 1992 to 1993.
Not reportedTaxonComparator
Verbatim
e0“The ZT practices increased grain yields, particularly in 1988 and 1992-93 when antecedent soil water supplies were moderate”
Claim · model-written summary
Tillage had little effect on available soil nitrate N.
Not reportedTaxonComparator
Verbatim
e0“Tillage practice had little effect on available nitrate-N (kg/ha) to 1.5 m”
Claim · model-written summary
Greater soil water under zero tillage usually benefited wheat when nitrogen was applied.
- Taxon
- wheat
Triticum aestivume0 - Treatment
- N was appliede0
- Outcome
- wheat crope0
- Direction
- benefitede0
- Setting
- ZT soile0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the greater water supply in ZT soil usually benefited the wheat crop when N was applied.”
Claim · model-written summary
Nitrogen application increased economic returns for five of seven wheat crops through yield or protein responses.
Not reportedComparator
Verbatim
e0“Applying N increased returns from 5 of the 7 crops because of grain yield and/or grain protein responses.”
Claim · model-written summary
Grain yield responses to nitrogen were inconsistent when prior crops had received no nitrogen.
- Outcome
- Grain yield responsese0
- Direction
- inconsistente0
- Qualifier
- no N fertiliser had been applied to preceding cropse0
Not reportedTaxon
Verbatim
e0“Grain yield responses were inconsistent in the year of fertiliser application where no N fertiliser had been applied to preceding crops.”
Claim · model-written summary
Grain protein generally increased with nitrogen applied at sowing, except in the 1994 drought.
- Treatment
- N application at sowinge0
- Outcome
- grain proteine0
- Direction
- increasede0
- Qualifier
- except in 1994e0
Not reportedTaxonComparator
Verbatim
e0“grain protein usually increased with increasing N application at sowing, except in 1994, when drought after sowing prevented secondary root development and fertiliser uptake.”
Claim · model-written summary
Repeated low nitrogen rates produced wheat grain protein below 10%.
Verbatim
e0“crops receiving small N applications (0, 12.5 or 25 kg/ha.crop) produced grain of a low protein concentration (<10%)”
Claim · model-written summary
Repeated low nitrogen rates produced wheat yield below 90% of maximum.
Not reportedTreatment
Verbatim
e0“lower yields (<90% maximum yield) than crops which received larger N applications (75 kg/ha.crop).”
Claim · model-written summary
Insufficient nitrogen rates substantially reduced wheat profits when protein failed to exceed 11.5% or yields were lower.
- Taxon
- wheatTriticum aestivume0
- Treatment
- rate of N appliede0
- Outcome
- Profitse0
- Direction
- reducede0
- Qualifier
- >11.5%e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Profits were substantially reduced where the rate of N applied was insufficient to raise grain protein concentration to >11.5%, due to the low market value of low protein wheat, or because of lower grain yields.”
Claim · model-written summary
Routine nitrogen application raised grain protein above 11.5% in every crop except the first.
- Taxon
- cropse0
- Treatment
- Routine N applicatione0
- Outcome
- grain protein concentrationse0
- Direction
- increasede0
- Value
- >11.5%e0
- Qualifier
- except the first crop (1987)e0
Not reportedComparator
Verbatim
e0“Routine N application to crops over the period 1987-94, which included the longest drought (1990-94) in the lifetime of most producers, caused similarly inconsistent grain yield increases but increased grain protein concentrations (>11.5%) in all except the first crop (1987).”
Claim · model-written summary
Routine nitrogen application gave inconsistent increases in wheat grain yield.
- Taxon
- cropse0
- Treatment
- Routine N applicatione0
- Outcome
- grain yielde0
- Direction
- increasese0
- Qualifier
- inconsistente0
Not reportedComparator
Verbatim
e0“Routine N application to crops over the period 1987-94, which included the longest drought (1990-94) in the lifetime of most producers, caused similarly inconsistent grain yield increases”
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