Directory UMM :Data Elmu:jurnal:S:Soil & Tillage Research:Vol54.Issue1-2.Mar2000:
Soil & Tillage Research 54 (2000) 63±75
Managing legume leys, residues and fertilisers to enhance the
sustainability of wheat cropping systems in Australia
1. The effects on wheat yields and nutrient balances
Anthony M. Whitbreada,*, Graeme J. Blairb, Rod D.B. Lefroyc
a
CSIRO, Tropical Agriculture PO Box 102, Toowoomba, Qld 4350, Australia
Division of Agronomy and Soil Science, University of New England, Armidale, NSW 2351, Australia
c
International Board for Soil Research and Management, PO Box 9-109, Jatujak, Bangkok 10900, Thailand
b
Received 22 April 1998; received in revised form 4 December 1998; accepted 6 December 1999
Abstract
Farming activities practiced on many Australian soils have resulted in substantial losses of soil organic matter (SOM),
nutrient loss, soil structural degradation and declines in cereal yield and quality. Field trials, consisting of a legume or fallow
phase followed by three wheat (Triticum aestivum L.) crops, were established on a degraded Ferric Luvisol (Red Earth) soil in
New South Wales to investigate the effect of crop residue and fertiliser management on wheat yield and nutrient balances.
There were no effects of a chickpea (Cicer arietinum L. cv Amethyst), barrel medic (Medicago truncatula L. cv Sephi), or
fallow phase on the grain yields of three subsequent wheat crops. Grain yield was depressed by 12% following a lucerne
(Medicago sativa L. cv Trifecta) crop from which the plant residues had been removed, relative to when residues were
returned or grazed. Consecutively, higher wheat grain yield losses of 7.4 and 8.6% in 1994 and 1995 were found on treatments
from which wheat stubble was annually removed from the system. Grain yield losses of 6, 7 and 13% in three consecutive
wheat crops were found where no fertiliser was applied at sowing. Nutrient balances, based on inputs of nutrients in fertilisers
and residues, and the export of nutrients in grain and crop residue were found to be useful in describing the ¯ow of nutrients in
a farming system and predicting possible soil nutrient depletion. Fallow systems provide no nutrient inputs and result in N
losses of up to ÿ189 kg haÿ1 over three wheat crops. The balance of nutrients such as potassium (K), which are contained in
larger proportions in stubble, were found to be ÿ102 kg haÿ1 on the wheat stubble removed treatments and 8 kg haÿ1 on the
stubble retained treatments. Better recycling of crop residues and improving ley system to increase nutrient and C inputs have
the potential to improve soil fertility and grain production. # 2000 Elsevier Science B.V. All rights reserved.
Keywords: Wheat yield; Nutrient balance; Legume rotation; Crop residue; Stubble management
*
Corresponding author. Tel.: 61-74688-1200; fax: 61-746881193.
E-mail address: anthony.whitbread@tag.csiro.au
(A.M. Whitbread).
1. Introduction
Many farming practices exploit soil organic matter
(SOM) to provide essential nutrients for plant growth.
0167-1987/00/$ ± see front matter # 2000 Elsevier Science B.V. All rights reserved.
PII: S 0 1 6 7 - 1 9 8 7 ( 9 9 ) 0 0 1 1 2 - 9
64
A.M. Whitbread et al. / Soil & Tillage Research 54 (2000) 63±75
The mineralisation of SOM releases nutrients to the
soil which may become available for plant uptake,
converted to unavailable forms, lost to the atmosphere
or leached and eroded. The rate of this process depends
on climatic conditions and the nature of individual
nutrients. When a farming system is unbalanced, e.g.,
when the export of nutrients is greater than inputs, the
demand for nutrients affects the SOM. As SOM is
depleted, both chemical and physical soil fertility are
lost and the required input costs are increased.
The long term effects of cropping and cultivation in
Australian farming systems have been well documented. The cropping of soil which had previously been
under native vegetation has been shown to cause losses
of SOM, C and nutrients (Dalal and Mayer, 1986;
Blair et al., 1995), soil structural declines (Connolly
and Freebairn, 1996) and soil degradation. Many
Australian wheat growing systems are characterised
by falling grain protein concentrations and land degradation, both of which are related to declines in soil
chemical and physical fertility. It has been estimated
that approximately 10 mha of agricultural land in
Australia have been affected by some form of erosion
and more than 30 mha have suffered fertility decline
(Hamblin and Williams, 1995). Dalal et al. (1991)
showed that in the once fertile soils of the Darling
Downs and brigalow lands of subtropical eastern
Australia, the protein concentration of wheat grain
had dropped from 0.16 kg kgÿ1 to less than
0.11 kg kgÿ1 after 25 years of cropping to less than
0.09 kg kgÿ1 after 50 years of cropping and that yield
declines of up to 50% had occurred. At a time when
high grain protein concentrations and low production
costs equate to better pro®tability, farming systems
that optimise the ef®cient use of fertilisers and crop
residues and ley phases need to be developed.
Grass and legume leys incorporated into a farming
system can potentially improve soil fertility, crop
yields and pro®tability (Holford, 1992; Armstrong
et al., 1997). However, the effect of the commonly
used short term (
Managing legume leys, residues and fertilisers to enhance the
sustainability of wheat cropping systems in Australia
1. The effects on wheat yields and nutrient balances
Anthony M. Whitbreada,*, Graeme J. Blairb, Rod D.B. Lefroyc
a
CSIRO, Tropical Agriculture PO Box 102, Toowoomba, Qld 4350, Australia
Division of Agronomy and Soil Science, University of New England, Armidale, NSW 2351, Australia
c
International Board for Soil Research and Management, PO Box 9-109, Jatujak, Bangkok 10900, Thailand
b
Received 22 April 1998; received in revised form 4 December 1998; accepted 6 December 1999
Abstract
Farming activities practiced on many Australian soils have resulted in substantial losses of soil organic matter (SOM),
nutrient loss, soil structural degradation and declines in cereal yield and quality. Field trials, consisting of a legume or fallow
phase followed by three wheat (Triticum aestivum L.) crops, were established on a degraded Ferric Luvisol (Red Earth) soil in
New South Wales to investigate the effect of crop residue and fertiliser management on wheat yield and nutrient balances.
There were no effects of a chickpea (Cicer arietinum L. cv Amethyst), barrel medic (Medicago truncatula L. cv Sephi), or
fallow phase on the grain yields of three subsequent wheat crops. Grain yield was depressed by 12% following a lucerne
(Medicago sativa L. cv Trifecta) crop from which the plant residues had been removed, relative to when residues were
returned or grazed. Consecutively, higher wheat grain yield losses of 7.4 and 8.6% in 1994 and 1995 were found on treatments
from which wheat stubble was annually removed from the system. Grain yield losses of 6, 7 and 13% in three consecutive
wheat crops were found where no fertiliser was applied at sowing. Nutrient balances, based on inputs of nutrients in fertilisers
and residues, and the export of nutrients in grain and crop residue were found to be useful in describing the ¯ow of nutrients in
a farming system and predicting possible soil nutrient depletion. Fallow systems provide no nutrient inputs and result in N
losses of up to ÿ189 kg haÿ1 over three wheat crops. The balance of nutrients such as potassium (K), which are contained in
larger proportions in stubble, were found to be ÿ102 kg haÿ1 on the wheat stubble removed treatments and 8 kg haÿ1 on the
stubble retained treatments. Better recycling of crop residues and improving ley system to increase nutrient and C inputs have
the potential to improve soil fertility and grain production. # 2000 Elsevier Science B.V. All rights reserved.
Keywords: Wheat yield; Nutrient balance; Legume rotation; Crop residue; Stubble management
*
Corresponding author. Tel.: 61-74688-1200; fax: 61-746881193.
E-mail address: anthony.whitbread@tag.csiro.au
(A.M. Whitbread).
1. Introduction
Many farming practices exploit soil organic matter
(SOM) to provide essential nutrients for plant growth.
0167-1987/00/$ ± see front matter # 2000 Elsevier Science B.V. All rights reserved.
PII: S 0 1 6 7 - 1 9 8 7 ( 9 9 ) 0 0 1 1 2 - 9
64
A.M. Whitbread et al. / Soil & Tillage Research 54 (2000) 63±75
The mineralisation of SOM releases nutrients to the
soil which may become available for plant uptake,
converted to unavailable forms, lost to the atmosphere
or leached and eroded. The rate of this process depends
on climatic conditions and the nature of individual
nutrients. When a farming system is unbalanced, e.g.,
when the export of nutrients is greater than inputs, the
demand for nutrients affects the SOM. As SOM is
depleted, both chemical and physical soil fertility are
lost and the required input costs are increased.
The long term effects of cropping and cultivation in
Australian farming systems have been well documented. The cropping of soil which had previously been
under native vegetation has been shown to cause losses
of SOM, C and nutrients (Dalal and Mayer, 1986;
Blair et al., 1995), soil structural declines (Connolly
and Freebairn, 1996) and soil degradation. Many
Australian wheat growing systems are characterised
by falling grain protein concentrations and land degradation, both of which are related to declines in soil
chemical and physical fertility. It has been estimated
that approximately 10 mha of agricultural land in
Australia have been affected by some form of erosion
and more than 30 mha have suffered fertility decline
(Hamblin and Williams, 1995). Dalal et al. (1991)
showed that in the once fertile soils of the Darling
Downs and brigalow lands of subtropical eastern
Australia, the protein concentration of wheat grain
had dropped from 0.16 kg kgÿ1 to less than
0.11 kg kgÿ1 after 25 years of cropping to less than
0.09 kg kgÿ1 after 50 years of cropping and that yield
declines of up to 50% had occurred. At a time when
high grain protein concentrations and low production
costs equate to better pro®tability, farming systems
that optimise the ef®cient use of fertilisers and crop
residues and ley phases need to be developed.
Grass and legume leys incorporated into a farming
system can potentially improve soil fertility, crop
yields and pro®tability (Holford, 1992; Armstrong
et al., 1997). However, the effect of the commonly
used short term (