- Email: [email protected]
Development of a rainfed lucerne-based farming system in the Mediterranean climatic region of southwestern Australia
Agricultural Water Management 53 (2002) 111–116
Development of a rainfed lucerne-based farming system in the Mediterranean climatic region of southwestern Australia Geoffrey A. Beea,*, Graham Laslettb a
Lucerne Consultancy Service, P.O. Box 121, Jerramungup, WA 6337, Australia b Laslett Agronomic Services, Jerramungup, WA 6337, Australia
Abstract In the southern coastal region of southwestern Australia with a Mediterranean-type climate, rising water tables prompted the owner of the farm, ‘Laurinya’, near Jacup, Western Australia (348S, 1198E), to extend small plantings of lucerne near saline streams to large areas of the farm. In recent years, the area under lucerne has increased from 20 to 800 ha. The aim is to ultimately have all pasture on the property as lucerne-based perennial pastures. The lucerne is sown with a no-till seeder in rows 250 mm apart. In two contiguous rows in every five rows, barley is sown with the lucerne to provide protection to the young lucerne plants from sand particles carried by high winds in the sandy-surfaced soils of the region. The barley also provides an income stream in the year of establishment of the lucerne. The lucerne-based pastures are the foundation of a phase-farming system. A period of lucerne varying in length from 2 to 10 years is followed by a cropping phase of 3–10 years. The lucerne pastures are rotationally grazed for 1–2 weeks with 5–6 weeks between grazing. The lucerne provides nitrogen to subsequent crops and assists with the control of volunteer grasses and summer weeds. It also uses water that otherwise would leak past the root zone and lead to rising water tables and secondary salinity. # 2002 Elsevier Science B.V. All rights reserved. Keywords: Sustainability; Secondary salinity; Establishment; Grazing management
1. Introduction Recent developments in crop production technology in southern Australia, such as improved plant nutrition, new cultivars, timely sowing and reduced tillage, have increased crop yields to higher levels than previously thought possible. The potential gross margins * Corresponding author. Tel.: þ61-8-9835-5030; fax: þ61-8-9835-5016. E-mail address: [email protected] (G.A. Bee).
0378-3774/02/$ – see front matter # 2002 Elsevier Science B.V. All rights reserved. PII: S 0 3 7 8 - 3 7 7 4 ( 0 1 ) 0 0 1 5 9 - 7
112
G.A. Bee, G. Laslett / Agricultural Water Management 53 (2002) 111–116
from crop production have been used as evidence that cropping is more profitable than livestock production, particularly sheep and wool. Thus, continuous cropping began to develop as the principal means of generating farm income. However, the gross margins did not account for the investment required in additional machinery or account for the environmental risks associated with continuous cropping. Therefore, many producers chose to stay with their livestock enterprises and used the improved annual pastures to increase crop production, while minimizing risks and limiting the commitment to machinery and labor. The problem with both continuous cropping and annual pastures is that they both have flaws and fallacies that must be taken into consideration. One flaw is that without a robust legume in the system the legume content of the regenerating annual pasture decreases leading to a decline in soil fertility. One fallacy is that higher levels of crop production result in greater levels of water use. It was assumed that if it required 1 mm of rainfall to produce 20 kg of grain (French and Schultz, 1984), then by increasing grain production water use must also increase. Research subsequently showed that in many situations the level of water that was transpired by the crop did increase. The problem however, was that the heavier crop canopies reduced evaporative losses from the soil surface (Gregory and Eastham, 1996; Eastham et al., 1999), so that overall water use did not increase. With our current knowledge of salinity in the southern coastal environment of Western Australia (McFarlane and Williamson, 2002), the use of continuous cropping and livestock enterprises based on annual pastures have been shown to be unsustainable (Hatton and Nulsen, 1999) and leave the producer open to the risk of low profitability in both the short and long term. The practice of pasture manipulation and spraytopping to increase the legume density of annual pasture and to reduce the level of root diseases in the subsequent cereal crop resulted in higher levels of nitrogen production (Bolger et al., 1995) and improved cereal yields. However, again the system relied upon a shallow-rooted annual that did not use water from deep in the profile and was unable to utilize summer rainfall (Bolger and Turner, 1999; Latta et al., 2002; Ward et al., 2002). In order to use higher levels of incident rainfall and thus, lower the rising water tables, agriculture has begun to reestablish trees in the environment (Lefroy and Stirzaker, 1999). However, although trees do have a positive impact (Lefroy and Stirzaker, 1999; White et al., 2002), they are not the only solution available to preserve the farming system.
2. Requirements for a sustainable farming system In order to be sustainable in the long term, a rotational system in the designated region must be developed that
is robust (financially and biologically); utilizes total annual rainfall in at least some years over a rotation of several years; produces a saleable commodity or by-product; provides nitrogen for cereal and oilseed components of the rotation; allows the control of grasses for disease and weed control in cereals and annual crops;
G.A. Bee, G. Laslett / Agricultural Water Management 53 (2002) 111–116
113
provides options for the control of herbicide-resistant weed species and is achievable within physical and economic limits. As perennial cropping systems are not currently available for dryland Mediterraneanclimatic regions, perennial pasture species have been considered the only option available. Early experiments were based primarily on the introduction of perennial grass species, which were ultimately shown to fit few of the requirements of the system. Lucerne (Medicago sativa L.) was however, being grown by a small group of farmers in Western Australia in small landscape-specific strips. Despite the prevailing view in the early 1980s that lucerne could not survive with adequate plant density to be productive in a Mediterranean-type climate with little rain for 6 months per year, it was clear from the limited farmer experience that it could be productive. In addition, the placement of observation tubes to monitor groundwater levels in and around lucerne stands showed that the groundwater was falling under productive and profitable lucerne stands (Roy Latta, personal communication, 2000). A process had to be developed that could utilize the ability of lucerne to ameliorate the rising water tables and could be integrated into a whole-farm system.
3. Development and evolution of a system of utilizing lucerne The growing of lucerne pastures at ‘Laurinya’ farm near Jacup (Jerramungup) in Western Australia (348S, 1198E) progressed from an initial 20 ha planting in 1970 to an area of 800 ha in 2000. There were several stages in this development. The initial lucerne pasture of 20 ha was just an observation plot. The lucerne grew as a result of summer rainfall events and proved useful as supplementary feed for sheep. Additional small areas were planted during the 1970s, but with only moderate success. Reduction of stands by sand blasting of the young plants during periods of high wind velocity and by being over-run by weeds, were major challenges to successful establishment of these early lucerne stands. With the threat of encroaching salinity due to rising water tables, a second phase of planting of lucerne along the borders of the streams was put in place at ‘Laurinya’ in the 1980s. The use of broad-spectrum knock-down herbicides for weed control enabled singlepass seeding, followed by grass-selective herbicides, made these plantings very successful. In the 1980s, a mining company drilling for kaolinite clay found saline water tables at less than 1 m from the surface in higher parts of the landscape, motivating the owners of ‘Laurinya’ to put into place the third and current phase of lucerne planting. This phase involved planting lucerne in the broadacre cropping parts of the farm in order to control deep drainage (leakage) and groundwater recharge. The annual lucerne plantings are now around 200 ha per year and have been successful in lowering soil water levels (Latta et al., 2002). The system involves establishing lucerne, grazing it for a number of years and then going back into crop for a number of years. The length of each phase is determined on a field-by-field basis depending on a number of circumstances. Some locations are not suitable for cropping and are in continuous lucerne. In the remainder, the length of the lucerne phase varies from 2 to 10 years depending on the height of the water table, weed populations, lucerne survival and soil fertility. The length of the cropping phase varies
114
G.A. Bee, G. Laslett / Agricultural Water Management 53 (2002) 111–116
from 3 to 10 years and depends on the profitability of crops, soil type, soil fertility, weed populations and height of the water table. The system continues to evolve as experience and knowledge is gained. 3.1. Establishment The establishment of lucerne is expensive and early experience showed that losses could be high due to death of the young plants from wind-blown sand particles in the sandy-surfaced soils of the region. Undersowing lucerne in a crop was considered, but there were too many instances where the establishment of both the crop and the lucerne suffered. The poor availability of light to the lucerne was considered a significant contributor to poor lucerne establishment under a cover crop. The results were poor lucerne stands and poor cover crops. The lucerne is now sown with a no-till seeder in rows 250 mm apart. Two contiguous rows in every five are sown with barley (Hordeum vulgare L.) to provide shelter from the wind for the young lucerne plants and provide income from the barley in the year of establishment (Fig. 1). 3.2. Grazing management The introduction of lucerne into the broadacre farming system has required changes to pasture management, such as changing from set stocking to rotational grazing. With
Fig. 1. Photograph of three rows of lucerne sown between two rows of barley at ‘Laurinya’ farm. The barley is also undersown with lucerne (photograph by G.A. Bee).
G.A. Bee, G. Laslett / Agricultural Water Management 53 (2002) 111–116
115
rotational grazing the lucerne is heavily grazed for 1–2 weeks and then left to recover for 5–6 weeks. In turn, this requires sheep flocks to be bigger so that the fields can be rapidly grazed before moving the sheep to the next area of lucerne pasture. 3.3. Weed control Herbicide resistance, particularly in annual rye grass (Lolium rigidum Gaud.), has become a major concern for farmers. The persistence, herbicide tolerance and grazing tolerance of established lucerne stands offers substantial opportunities to control herbicide-resistant grasses and more recently the emergence of resistant broadleaf weeds. Lucerne pastures provide an opportunity to control grasses to very low levels and minimize the carry-over of root diseases on grass weeds to subsequent cereal crops. Additionally, summer weeds do not or cannot compete with lucerne stands. They die over in summer within the stands of lucerne while thriving only metres away where lucerne is not present. Moreover, sheep preferentially eat the weeds prior to grazing the lucerne at certain times of the year, thereby helping to reduce weed populations. This has resulted in a substantial reduction in the costs of weed control prior to a cropping phase, compared with the costs associated with weed control in a continuous cropping system. 3.4. Nitrogen production More knowledge is becoming available on the nitrogen dynamics and nitrogen production by farming systems involving lucerne and the results are very encouraging (Latta et al., 2002). With the complete implementation of a lucerne phase in the cropping system, the full benefits of lucerne should become apparent to researchers, farmers and advisers. What has already become evident is the capacity of lucerne to continue production through significantly drier-than-average winters. This would provide higher nitrogen availability for following crops than is available under an annual pasture system (Latta et al., 2002). Results from cropping after lucerne pasture are encouraging, with wheat after lucerne being the highest yielding wheat on ‘Laurinya’. 3.5. Removal of lucerne One of the major issues now for growers is the best method of removing lucerne so that crops can be successfully grown after a lucerne phase (Angus et al., 2000). As established lucerne is a very strong competitor with crops, it must be removed to obtain optimum crop yields. By continuously grazing sheep on the lucerne from spring through summer (September–February) and up to crop establishment in autumn (April/May), the lucerne is sufficiently weakened so that it can be readily killed with a knock-down herbicide. While this grazing technique has proved to be successful most of the time, there are still some instances when it has not been successful. The factors controlling lucerne regrowth are not clear. More research needs to be conducted so that lucerne can be reliably removed prior to cropping.
116
G.A. Bee, G. Laslett / Agricultural Water Management 53 (2002) 111–116
4. Lucerne in the summer of 1999–2000 Two hundred millimetres of rain at ‘Laurinya’ in the summer of 1999–2000 resulted in the lucerne pastures not being heavily grazed because the sheep needed to be used to restrict weed growth in the cereal stubbles. This provided an opportunity to harvest the lucerne for seed production. While the sheep were grazing the weeds in the crop stubbles and annual pastures, the lucerne was producing seed, building up soil fertility and helping to control the weeds. 5. Conclusions On the basis of experience to date, the owners of ‘Laurinya’ plan for all the pastures on the farm to be based on lucerne. The lucerne provides a more reliable and productive pasture for the sheep. It also provides a very successful legume pasture phase to revitalize the soils to sustain a successful cropping phase. The control of groundwater recharge will also save some of the valuable soil resources from salinization and degradation. While the full rotation of lucerne and crops has not yet been established over the whole of the farm at ‘Laurinya’, it is already clear that the lucerne can provide the benefits of a perennial in ameliorating water logging and secondary salinity. It further provides summer and autumn feed while giving the best benefits of a robust and sustainable pasture, cropping and land management system. References Angus, J.F., Gault, R.R., Good, A.J., Hart, A.B., Jones, T.D., Peoples, M.B., 2000. Lucerne removal before a cropping phase. Aust. J. Agric. Res. 51, 877–890. Bolger, T.P., Turner, N.C., 1999. Water use efficiency and water use of Mediterranean annual pastures in southern Australia. Aust. J. Agric. Res. 50, 1035–1046. Bolger, T.P., Pate, J.S., Unkovich, M.J., Turner, N.C., 1995. Estimates of seasonal nitrogen fixation of annual subterranean clover-based pastures using the 15 N natural abundance technique. Plant Soil 175, 57–66. Eastham, J., Gregory, P.J., Williamson, D.R., Watson, G.D., 1999. The influence of early sowing of wheat and lupin crops on evapotranspiration and evaporation from the soil surface in a Mediterranean climate. Agric. Water Manage. 42, 205–218. French, R.J., Schultz, J.E., 1984. Water use efficiency of wheat in a Mediterranean-type environment. Part 1. The relation between yield, water use and climate. Aust. J. Agric. Res. 35, 743–764. Gregory, P.J., Eastham, J., 1996. Growth of shoots and roots and interception of radiation by wheat and lupin crops on a shallow duplex soil in response to time of sowing. Aust. J. Agric. Res. 43, 555–573. Hatton, T.J., Nulsen, R.A., 1999. Towards achieving functional ecosystems mimicry with respect to water cycling in southern Australian agriculture. Agrofor. Syst. 45, 203–214. Latta, R.A., Cocks, P.S., Matthews, C., 2002. Lucerne pastures to sustain agricultural production in southwestern Australia, Agric. Water Manage. 53, 99–109. Lefroy, E.C., Stirzaker, R.J., 1999. Agroforestry for water management in the cropping zone of southern Australia. Agrofor. Syst. 45, 279–302. McFarlane, D.J., Williamson, D.R., 2002. An overview of water logging and salinity in southwestern Australia as related to the ‘Ucarro’ experimental catchment. Agric. Water Manage. 53, 5–29. Ward, P.R., Dunin, F.X., Micin, S.F., 2002. Water use and root growth by annual or perennial pastures and subsequent crops in a phase rotation. Agric. Water Manage. 53, 83–97. White, D.A., Dunin, F.X., Turner, N.C., Ward, B.H., Galbraith, J.G., 2002. Water use by contour planted tree belts comprised of four Eucalyptus species. Agric. Water Manage. 53, 133–152.
Development of a rainfed lucerne-based farming system in the Mediterranean climatic region of southwestern Australia Geoffrey A. Beea,*, Graham Laslettb a
Lucerne Consultancy Service, P.O. Box 121, Jerramungup, WA 6337, Australia b Laslett Agronomic Services, Jerramungup, WA 6337, Australia
Abstract In the southern coastal region of southwestern Australia with a Mediterranean-type climate, rising water tables prompted the owner of the farm, ‘Laurinya’, near Jacup, Western Australia (348S, 1198E), to extend small plantings of lucerne near saline streams to large areas of the farm. In recent years, the area under lucerne has increased from 20 to 800 ha. The aim is to ultimately have all pasture on the property as lucerne-based perennial pastures. The lucerne is sown with a no-till seeder in rows 250 mm apart. In two contiguous rows in every five rows, barley is sown with the lucerne to provide protection to the young lucerne plants from sand particles carried by high winds in the sandy-surfaced soils of the region. The barley also provides an income stream in the year of establishment of the lucerne. The lucerne-based pastures are the foundation of a phase-farming system. A period of lucerne varying in length from 2 to 10 years is followed by a cropping phase of 3–10 years. The lucerne pastures are rotationally grazed for 1–2 weeks with 5–6 weeks between grazing. The lucerne provides nitrogen to subsequent crops and assists with the control of volunteer grasses and summer weeds. It also uses water that otherwise would leak past the root zone and lead to rising water tables and secondary salinity. # 2002 Elsevier Science B.V. All rights reserved. Keywords: Sustainability; Secondary salinity; Establishment; Grazing management
1. Introduction Recent developments in crop production technology in southern Australia, such as improved plant nutrition, new cultivars, timely sowing and reduced tillage, have increased crop yields to higher levels than previously thought possible. The potential gross margins * Corresponding author. Tel.: þ61-8-9835-5030; fax: þ61-8-9835-5016. E-mail address: [email protected] (G.A. Bee).
0378-3774/02/$ – see front matter # 2002 Elsevier Science B.V. All rights reserved. PII: S 0 3 7 8 - 3 7 7 4 ( 0 1 ) 0 0 1 5 9 - 7
112
G.A. Bee, G. Laslett / Agricultural Water Management 53 (2002) 111–116
from crop production have been used as evidence that cropping is more profitable than livestock production, particularly sheep and wool. Thus, continuous cropping began to develop as the principal means of generating farm income. However, the gross margins did not account for the investment required in additional machinery or account for the environmental risks associated with continuous cropping. Therefore, many producers chose to stay with their livestock enterprises and used the improved annual pastures to increase crop production, while minimizing risks and limiting the commitment to machinery and labor. The problem with both continuous cropping and annual pastures is that they both have flaws and fallacies that must be taken into consideration. One flaw is that without a robust legume in the system the legume content of the regenerating annual pasture decreases leading to a decline in soil fertility. One fallacy is that higher levels of crop production result in greater levels of water use. It was assumed that if it required 1 mm of rainfall to produce 20 kg of grain (French and Schultz, 1984), then by increasing grain production water use must also increase. Research subsequently showed that in many situations the level of water that was transpired by the crop did increase. The problem however, was that the heavier crop canopies reduced evaporative losses from the soil surface (Gregory and Eastham, 1996; Eastham et al., 1999), so that overall water use did not increase. With our current knowledge of salinity in the southern coastal environment of Western Australia (McFarlane and Williamson, 2002), the use of continuous cropping and livestock enterprises based on annual pastures have been shown to be unsustainable (Hatton and Nulsen, 1999) and leave the producer open to the risk of low profitability in both the short and long term. The practice of pasture manipulation and spraytopping to increase the legume density of annual pasture and to reduce the level of root diseases in the subsequent cereal crop resulted in higher levels of nitrogen production (Bolger et al., 1995) and improved cereal yields. However, again the system relied upon a shallow-rooted annual that did not use water from deep in the profile and was unable to utilize summer rainfall (Bolger and Turner, 1999; Latta et al., 2002; Ward et al., 2002). In order to use higher levels of incident rainfall and thus, lower the rising water tables, agriculture has begun to reestablish trees in the environment (Lefroy and Stirzaker, 1999). However, although trees do have a positive impact (Lefroy and Stirzaker, 1999; White et al., 2002), they are not the only solution available to preserve the farming system.
2. Requirements for a sustainable farming system In order to be sustainable in the long term, a rotational system in the designated region must be developed that
is robust (financially and biologically); utilizes total annual rainfall in at least some years over a rotation of several years; produces a saleable commodity or by-product; provides nitrogen for cereal and oilseed components of the rotation; allows the control of grasses for disease and weed control in cereals and annual crops;
G.A. Bee, G. Laslett / Agricultural Water Management 53 (2002) 111–116
113
provides options for the control of herbicide-resistant weed species and is achievable within physical and economic limits. As perennial cropping systems are not currently available for dryland Mediterraneanclimatic regions, perennial pasture species have been considered the only option available. Early experiments were based primarily on the introduction of perennial grass species, which were ultimately shown to fit few of the requirements of the system. Lucerne (Medicago sativa L.) was however, being grown by a small group of farmers in Western Australia in small landscape-specific strips. Despite the prevailing view in the early 1980s that lucerne could not survive with adequate plant density to be productive in a Mediterranean-type climate with little rain for 6 months per year, it was clear from the limited farmer experience that it could be productive. In addition, the placement of observation tubes to monitor groundwater levels in and around lucerne stands showed that the groundwater was falling under productive and profitable lucerne stands (Roy Latta, personal communication, 2000). A process had to be developed that could utilize the ability of lucerne to ameliorate the rising water tables and could be integrated into a whole-farm system.
3. Development and evolution of a system of utilizing lucerne The growing of lucerne pastures at ‘Laurinya’ farm near Jacup (Jerramungup) in Western Australia (348S, 1198E) progressed from an initial 20 ha planting in 1970 to an area of 800 ha in 2000. There were several stages in this development. The initial lucerne pasture of 20 ha was just an observation plot. The lucerne grew as a result of summer rainfall events and proved useful as supplementary feed for sheep. Additional small areas were planted during the 1970s, but with only moderate success. Reduction of stands by sand blasting of the young plants during periods of high wind velocity and by being over-run by weeds, were major challenges to successful establishment of these early lucerne stands. With the threat of encroaching salinity due to rising water tables, a second phase of planting of lucerne along the borders of the streams was put in place at ‘Laurinya’ in the 1980s. The use of broad-spectrum knock-down herbicides for weed control enabled singlepass seeding, followed by grass-selective herbicides, made these plantings very successful. In the 1980s, a mining company drilling for kaolinite clay found saline water tables at less than 1 m from the surface in higher parts of the landscape, motivating the owners of ‘Laurinya’ to put into place the third and current phase of lucerne planting. This phase involved planting lucerne in the broadacre cropping parts of the farm in order to control deep drainage (leakage) and groundwater recharge. The annual lucerne plantings are now around 200 ha per year and have been successful in lowering soil water levels (Latta et al., 2002). The system involves establishing lucerne, grazing it for a number of years and then going back into crop for a number of years. The length of each phase is determined on a field-by-field basis depending on a number of circumstances. Some locations are not suitable for cropping and are in continuous lucerne. In the remainder, the length of the lucerne phase varies from 2 to 10 years depending on the height of the water table, weed populations, lucerne survival and soil fertility. The length of the cropping phase varies
114
G.A. Bee, G. Laslett / Agricultural Water Management 53 (2002) 111–116
from 3 to 10 years and depends on the profitability of crops, soil type, soil fertility, weed populations and height of the water table. The system continues to evolve as experience and knowledge is gained. 3.1. Establishment The establishment of lucerne is expensive and early experience showed that losses could be high due to death of the young plants from wind-blown sand particles in the sandy-surfaced soils of the region. Undersowing lucerne in a crop was considered, but there were too many instances where the establishment of both the crop and the lucerne suffered. The poor availability of light to the lucerne was considered a significant contributor to poor lucerne establishment under a cover crop. The results were poor lucerne stands and poor cover crops. The lucerne is now sown with a no-till seeder in rows 250 mm apart. Two contiguous rows in every five are sown with barley (Hordeum vulgare L.) to provide shelter from the wind for the young lucerne plants and provide income from the barley in the year of establishment (Fig. 1). 3.2. Grazing management The introduction of lucerne into the broadacre farming system has required changes to pasture management, such as changing from set stocking to rotational grazing. With
Fig. 1. Photograph of three rows of lucerne sown between two rows of barley at ‘Laurinya’ farm. The barley is also undersown with lucerne (photograph by G.A. Bee).
G.A. Bee, G. Laslett / Agricultural Water Management 53 (2002) 111–116
115
rotational grazing the lucerne is heavily grazed for 1–2 weeks and then left to recover for 5–6 weeks. In turn, this requires sheep flocks to be bigger so that the fields can be rapidly grazed before moving the sheep to the next area of lucerne pasture. 3.3. Weed control Herbicide resistance, particularly in annual rye grass (Lolium rigidum Gaud.), has become a major concern for farmers. The persistence, herbicide tolerance and grazing tolerance of established lucerne stands offers substantial opportunities to control herbicide-resistant grasses and more recently the emergence of resistant broadleaf weeds. Lucerne pastures provide an opportunity to control grasses to very low levels and minimize the carry-over of root diseases on grass weeds to subsequent cereal crops. Additionally, summer weeds do not or cannot compete with lucerne stands. They die over in summer within the stands of lucerne while thriving only metres away where lucerne is not present. Moreover, sheep preferentially eat the weeds prior to grazing the lucerne at certain times of the year, thereby helping to reduce weed populations. This has resulted in a substantial reduction in the costs of weed control prior to a cropping phase, compared with the costs associated with weed control in a continuous cropping system. 3.4. Nitrogen production More knowledge is becoming available on the nitrogen dynamics and nitrogen production by farming systems involving lucerne and the results are very encouraging (Latta et al., 2002). With the complete implementation of a lucerne phase in the cropping system, the full benefits of lucerne should become apparent to researchers, farmers and advisers. What has already become evident is the capacity of lucerne to continue production through significantly drier-than-average winters. This would provide higher nitrogen availability for following crops than is available under an annual pasture system (Latta et al., 2002). Results from cropping after lucerne pasture are encouraging, with wheat after lucerne being the highest yielding wheat on ‘Laurinya’. 3.5. Removal of lucerne One of the major issues now for growers is the best method of removing lucerne so that crops can be successfully grown after a lucerne phase (Angus et al., 2000). As established lucerne is a very strong competitor with crops, it must be removed to obtain optimum crop yields. By continuously grazing sheep on the lucerne from spring through summer (September–February) and up to crop establishment in autumn (April/May), the lucerne is sufficiently weakened so that it can be readily killed with a knock-down herbicide. While this grazing technique has proved to be successful most of the time, there are still some instances when it has not been successful. The factors controlling lucerne regrowth are not clear. More research needs to be conducted so that lucerne can be reliably removed prior to cropping.
116
G.A. Bee, G. Laslett / Agricultural Water Management 53 (2002) 111–116
4. Lucerne in the summer of 1999–2000 Two hundred millimetres of rain at ‘Laurinya’ in the summer of 1999–2000 resulted in the lucerne pastures not being heavily grazed because the sheep needed to be used to restrict weed growth in the cereal stubbles. This provided an opportunity to harvest the lucerne for seed production. While the sheep were grazing the weeds in the crop stubbles and annual pastures, the lucerne was producing seed, building up soil fertility and helping to control the weeds. 5. Conclusions On the basis of experience to date, the owners of ‘Laurinya’ plan for all the pastures on the farm to be based on lucerne. The lucerne provides a more reliable and productive pasture for the sheep. It also provides a very successful legume pasture phase to revitalize the soils to sustain a successful cropping phase. The control of groundwater recharge will also save some of the valuable soil resources from salinization and degradation. While the full rotation of lucerne and crops has not yet been established over the whole of the farm at ‘Laurinya’, it is already clear that the lucerne can provide the benefits of a perennial in ameliorating water logging and secondary salinity. It further provides summer and autumn feed while giving the best benefits of a robust and sustainable pasture, cropping and land management system. References Angus, J.F., Gault, R.R., Good, A.J., Hart, A.B., Jones, T.D., Peoples, M.B., 2000. Lucerne removal before a cropping phase. Aust. J. Agric. Res. 51, 877–890. Bolger, T.P., Turner, N.C., 1999. Water use efficiency and water use of Mediterranean annual pastures in southern Australia. Aust. J. Agric. Res. 50, 1035–1046. Bolger, T.P., Pate, J.S., Unkovich, M.J., Turner, N.C., 1995. Estimates of seasonal nitrogen fixation of annual subterranean clover-based pastures using the 15 N natural abundance technique. Plant Soil 175, 57–66. Eastham, J., Gregory, P.J., Williamson, D.R., Watson, G.D., 1999. The influence of early sowing of wheat and lupin crops on evapotranspiration and evaporation from the soil surface in a Mediterranean climate. Agric. Water Manage. 42, 205–218. French, R.J., Schultz, J.E., 1984. Water use efficiency of wheat in a Mediterranean-type environment. Part 1. The relation between yield, water use and climate. Aust. J. Agric. Res. 35, 743–764. Gregory, P.J., Eastham, J., 1996. Growth of shoots and roots and interception of radiation by wheat and lupin crops on a shallow duplex soil in response to time of sowing. Aust. J. Agric. Res. 43, 555–573. Hatton, T.J., Nulsen, R.A., 1999. Towards achieving functional ecosystems mimicry with respect to water cycling in southern Australian agriculture. Agrofor. Syst. 45, 203–214. Latta, R.A., Cocks, P.S., Matthews, C., 2002. Lucerne pastures to sustain agricultural production in southwestern Australia, Agric. Water Manage. 53, 99–109. Lefroy, E.C., Stirzaker, R.J., 1999. Agroforestry for water management in the cropping zone of southern Australia. Agrofor. Syst. 45, 279–302. McFarlane, D.J., Williamson, D.R., 2002. An overview of water logging and salinity in southwestern Australia as related to the ‘Ucarro’ experimental catchment. Agric. Water Manage. 53, 5–29. Ward, P.R., Dunin, F.X., Micin, S.F., 2002. Water use and root growth by annual or perennial pastures and subsequent crops in a phase rotation. Agric. Water Manage. 53, 83–97. White, D.A., Dunin, F.X., Turner, N.C., Ward, B.H., Galbraith, J.G., 2002. Water use by contour planted tree belts comprised of four Eucalyptus species. Agric. Water Manage. 53, 133–152.