A study of water use in leucaena-grass systems

Abstract

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

Land and Water Usage in Beef Production Systems

“…In the calculation, data relating to 16 months were used instead of those for 30 months of production in that system. A typical amount applied at 27 °C is shown in Table 2 [29] together with figures referring to pasture that was not irrigated during development.…”

“…The amount of irrigation varies from year to year. The duration of the period on the pasture was 30 months, and the amount used for irrigation at 27 °C was based on data from [29].…”

Productive behavior of sheep in a silvopastoral system of Leucaena leucocephala associated with Megathyrsus maximus var. Mombasa versus natural field

“…Several authors (Oliva et al, 2018Gallego et al, 2017;Gamarra et al, 2018;Caicedo et al, 2018;Oliva et al, 2018;Vásquez et al, 2020) conclude that silvopastoral systems, with herbaceous and tree plants relevant to the environment, facilitate productive pastoral livestock by providing sufficient forage in quantity and quality. Other authors (Escobar et al, 2017;Pachas, 2017;González-Valdivia et al, 2018;Escobar et al, 2020) add that silvopastoral systems provide greater environmental services and biodiversity than grazing areas dominated by grasses. Chará et al (2020) emphasize, for the Latin American region, that the expansion and livestock and environmental benefits of silvopastoral systems will be derived from local validations of species, densities and topology.…”