Options for increasing water use efficiency on sub tropical dairy farms

Mark Callow (2011). Options for increasing water use efficiency on sub tropical dairy farms PhD Thesis, School of Agriculture and Food Sciences, The University of Queensland.

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Author Mark Callow
Thesis Title Options for increasing water use efficiency on sub tropical dairy farms
School, Centre or Institute School of Agriculture and Food Sciences
Institution The University of Queensland
Publication date 2011-10
Thesis type PhD Thesis
Supervisor Max Shelton & Shu Fukai
Total pages 230
Total colour pages 24
Total black and white pages 206
Subjects 07 Agricultural and Veterinary Sciences
Abstract/Summary In the subtropical environment of northern Australia there is potential to intensify dairy production through improving the efficiency of use of water and land. The aim of this thesis was to explore the sources of variation in water use efficiency of milk production (WUEmilk) for a broad range of dairy production systems and to identify the factors contributing to water use efficiency. A combination of (a) on-farm monitoring to investigate differences in WUEmilk between different production systems; (b) a farmlet study conducted over three years to identify the key predictors of WUEmilk; and (c) a component field experiment to determine the water use efficiency of forage utilisation (WUEyield) for winter- and summer-forage based systems was used. From these data, the combination of species and management factors that optimise water use, WUEyield, dry matter (DM) production and forage quality in a subtropical environment were identified. The on-farm monitoring evaluated dairy farms across a wide range of rainfall zones within the subtropical environment. Production systems were categorised into five diverse feed base types depending on the forage species grown and whether the forages were irrigated. The diversity of systems was reflected in the wide range of WUEmilk, with efficiencies recorded between 145 to 1337 L milk ML-1. There was also considerable diversity in management of the farming systems. Higher WUEmilk was associated with comparatively lower total water applied cow-1 with the volume of water applied ranging from 4.4 to 42.0 ML cow-1 (adjusted). Higher stocking rates in the order of 2.3 to 2.4 cows ha-1 (adjusted), higher nitrogen (N) fertiliser use equivalent to 250 kg N ha-1 annum-1 and higher utilisation, were also key agronomic predictors of an increase in WUEmilk irrespective of the farming system. The farmlet study was conducted at Mutdapilly Research Station in southeast Queensland and comprised 5 x 20 cow herds established to evaluate five contrasting production systems. Four of the systems were predominantly grazed, based on nil, limited (<1 ML ha-1) or high irrigation (>6 ML ha-1) with varying combinations of pastures and crops plus high levels of concentrate (10 kg cow-1 day-1). The fifth system was a feedlot that allocated the same amount of concentrate but with home-grown silage and hay fed as a total mixed ration. The results demonstrated that production systems with a high proportion of summer forage crops (C4 species accounting for more than 50% of the total area) and limited irrigation recorded the highest mean WUEyield in excess of 20 kg DM mm-1. This was a reflection of the forage base with C4 species generally producing twice the DM per unit of water with approximately 20 to 30 kg DM mm-1 compared to forage bases with predominantly C3 species with efficiencies ranging from 10 to 15 kg DM mm-1. The annual WUEmilk averaged over three years ranged from 784 to 1316 L milk ML-1. Farmlets with the highest WUEmilk optimised both utilisation and forage quality and this translated into feed conversion efficiency (FCE) of milk output greater than 0.80 L milk kg-1 DM. The lowest FCE of 0.53 L milk kg-1 DM was recorded by the low irrigation cropping base production system. This system produced the highest DM yield but the forage quality was comparatively lower than for the remaining systems. It was concluded that it is necessary to consider the negative interaction between utilisation and forage quality when selecting the most suitable forages species to achieve high levels of WUEmilk. A replicated field plot experiment, also conducted at Mutdapilly Research Station, evaluated 10 improved pasture and crop species commonly grown for milk production in the subtropical dairy regions of northern Australia. There were significant differences in the WUEyield among forage species with values ranging from 7.3 kg DM mm-1 for the cool-season white clover to 47.0 kg DM mm-1 for the warm-season maize crop. The mean WUEyield of the C4 species was greater than 20 kg DM mm-1 which was more than double that of the C3 species, although the fibre content was generally higher for the C4 species. Maximum utilisation of 30 623 kg ha-1 and WUEyield of 21.3 kg DM mm-1 were achieved from a double-cropped combination of C3 and C4 species grown in sequence to fully utilise the cool- and warm-growing seasons e.g. a combination of annual ryegrass plus maize. In a simulated grazed system, annual ryegrass plus forage sorghum yielded 21 465 kg DM-1 with a combined efficiency of 13.7 kg DM mm-1. An analysis of factors affecting WUEmilk showed that a high proportion of the variation (90%) was associated with the variation in WUEyield. Effective management of the feed base was crucial to achieving high WUEmilk accounting for 50% of the variation of WUEmilk. Systems that applied lower total water cow-1, used higher stocking rate, and produced more DM yield high in quality generally had higher WUEmilk. Measurement of soil water content continuously within and below the rooting zone using capacitance sensors and irrigating to maintain soil water within a lower and upper limit was an effective means to schedule irrigation to optimise forage utilisation and maximise DM growth per mm of water. The next highest source of variation was forage species accounting for 25% of the variation in WUEmilk. Selecting C4 species for inclusion in the production system increased the WUEyield because of their comparative growth advantage compared to C3 species. To achieve further gains in WUEmilk, it is necessary to consider the interaction between utilisation and forage quality. The highest efficiencies occurred when forage quality and FCE of milk were greatest. The type of production system and environment were estimated to account for 15% and 10% of the variation in WUEmilk respectively. Thus effective managers of their feed base can achieve a high WUEmilk irrespective of the environment. The large range in WUEmilk demonstrated considerable scope to intensify production systems by improving the efficiency with which water is used to produce milk. The results demonstrated viable options for changes to farming strategy and operational management to manage the feed base to ensure forage utilisation, forage quality and water use are optimised.
Keyword Water use efficiency, dairy production, subtropical environment
Additional Notes 1, 73, 98-101, 112-114, 116-124, 127, 137, 142, 191-192

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Created: Tue, 04 Oct 2011, 07:53:28 EST by Mr Mark Callow on behalf of Library - Information Access Service