A grazier survey of the long-term productivity of leucaena (Leucaena leucocephala)-grass pastures in Queensland

Radrizzani, Alejandro; Dalzell, Scott A.; Kravchuk, Olena; Shelton, H. M.

doi:10.1071/an09040

Cited by 29 publications

(26 citation statements)

References 8 publications

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“…However, the depth of water extraction and by inference active rooting depth of leucaena observed in this study was much shallower than that reported by Poole (2003), who found physical evidence of roots of 5-10-year-old L. leucocephala to 5.9 m depth. Rooting depths similar to ours have been reported at 2.8 m in 28-month-old leucaena (Dhyani et al 1990), at 2.6 m in 38-year-old leucaena in alley cropping with pasture (Radrizzani, 2009) and at 2 m in an alley cropping system with maize (Rao et al 1993). …”

Section: Root Activity and Water Extractionsupporting

confidence: 67%

“…This was a similar rooting depth to that of the native forest species. Other studies have reported presence of roots at 2.8 m in 28 month old leucaena (Dhyani et al 1990), 2.6 m in 38 year-old leucaena in alley cropping with pasture (Radrizzani, 2009) or 2 m in an alley cropping system with maize (Rao et al 1993). Both of these studies had a restrictive rock layer to this depth.…”

Section: Below-ground Interactionsmentioning

confidence: 97%

“…However, the maximum root density distribution is quite variable probably due to variation in soil condition; some authors reported that most roots occur in the top 0.15 m layer (Akinnifesi et al 2004) while Radrizzani (2009) found that the highest abundance of leucaena roots was from the surface horizon to 0.2 m depth. This zone contained an average of 43% of total leucaena roots.…”

Section: Below-ground Interactionsmentioning

confidence: 99%

“…According to Poole (2003) and Radrizzani (2009), approximately 60% of root biomass of a leucaena-grass pasture was concentrated in the top 0.4 m of the soil profile, with root abundance decreasing rapidly at greater depths, although some roots reached a depth of 6 m under 5-10-year-old leucaena. However, other studies have reported maximum root depth at only 2.8 m in 28-month-old leucaena (Dhyani et al 1990) and at 2.6 m in 38-year-old leucaena in alley cropping with pasture (Radrizzani, 2009) in soils with physical restrictions. Both of these studies reported a restrictive rock layer at these depths, which prevented leucaena from exploring deeper into the regolith.…”

Section: Introductionmentioning

confidence: 99%

“…In Queensland, leucaena densities range between 1,000 and 8,000 trees ha -1 depending on planting configuration which varies with hedgerow spacing, density of plants within the hedgerows and whether single or twin hedgerows are planted (twin hedgerows are typically spaced 0.5-1 m apart). Hedgerows can be spaced from 4 to 15 m apart (Radrizzani et al 2010). Elsewhere in the world, planting density is often much higher.…”

Section: Introductionmentioning

confidence: 99%

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A study of water use in leucaena-grass systems

Pachas¹

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Leucaena [Leucaena leucocephala Lam. de Wit ssp. glabrata (Rose) Zarate] mixed with Rhodes grass (Chloris gayana Kunth), is widely grown in tropical northern Australia in a hedgerow silvopastoral system which is productive, profitable and sustainable for beef cattle production. However, there is poor understanding concerning the most appropriate tree densities and planting configurations for leucaena and grass forage systems. Limited studies have focused on above-ground interactions between the species with even fewer on below-ground competition. Therefore, the main objective of this thesis was to investigate above-and below-ground competition, with emphasis on water use of both the leucaena and grass at a range of leucaena densities. Additional objectives were to determine (a) the effect of plant density on above-ground interactions between the species; (b) spatial and temporal water use of both species; (c) rooting patterns and deep drainage in a commercial leucaena-grass pasture; and (d) the effect of defoliation on water use of leucaena.The following experiments were conducted to address these objectives, firstly a field monitoring experiment in a commercial leucaena-grass pasture system at north-east of Injune, Central Queensland; secondly, two experiments in a controlled glasshouse environment at the University of Queensland, St. Lucia Campus Brisbane; and thirdly, three field experiments at the University of Queensland, Gatton Campus, Gatton Australia.The detailed monitoring analysis, using high-technology soil water moisture sensors, provided water use information and highlighted that there was minimal spatial and temporal complementarity of water use between the species. This was contrary to the general agroforestry hypothesis that trees acquired water from different soil strata when grown in association with grass. A high level of competition for water was evident as most of the water extraction occurred in the top 1.5 m of the soil profile. In the second year, root activity and water extraction became shallower probably associated with overgrazing and severe pruning. Another important outcome of this experiment was the low level of deep drainage to 4 m.The effect of leucaena plant density on above and below-ground interactions was then investigated using a Nelder fan design established at Gatton research farm from

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Section: Root Activity and Water Extractionsupporting

confidence: 67%

Section: Below-ground Interactionsmentioning

confidence: 97%

Section: Below-ground Interactionsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A study of water use in leucaena-grass systems

Pachas¹

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Hydrological and productive impacts of recent land‐use and land‐cover changes in the semiarid Chaco: Understanding novel water excess in water scarce farmlands

et al. 2020

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Over the last decades, the rapid replacement of native forests by crops and pastures in the Argentinean semiarid Chaco plains has triggered unprecedented groundwater level raises resulting from deep drainage increases, leading to the first massive waterlogging event on records ($25,000 Ha flooded in 2015 near Bandera, one of the most cultivated clusters of the Chaco). In this paper, we link this episode to the ongoing deforestation and cropping scheme shifts through the combined analysis of remote sensing data, agricultural surveys, local farmer information and hydrologic modelling. From 2000 to 2015, the agricultural area of Bandera increased from 21% to 50%, mostly at the expense of dry forests. In this period, agriculture migrated from more intensive (i.e., double-cropping) to more water-conservative (i.e., late-summer single crops) schemes as a general strategy to reduce drought risks. These changes reduced regional evapotranspiration and increased the intensity of deep drainage in wet years. Contrasting cropping schemes displayed significant evapotranspiration differences, but all of them experienced substantial drainage losses ($100-200 mm) during the wettest year (2014/2015), suggesting that cropping adjustments have a limited capacity to halt the generation of water excesses. Nearly 50% of the cropped area in Bandera could not be sown or harvested following the groundwater recharge event of 2014/2015. In the ongoing context of shallow and rising water tables, the introduction of novel cropping schemes that include deep-rooted perennials, to promote transpirative groundwater discharge, seems crucial to avoid the recurrence of water excesses and their associated dryland salinity risk in the region.

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