such as "Introduction", "Conclusion"..etc
Donald (1965) reviewed decadal wheat yields in Australia from 1860 to 1960 and showed that until the turn of the twentieth century yields decreased as nutrients were exhausted. The introduction of the practice of leaving land fallow to conserve soil moisture, the use of shorter-season, better-adapted cultivars, and the use of superphosphate fertilizer and rotations, including legumes, for the supply of nitrogen produced a steady increase in wheat yields between 1900 and 1950. Angus (2001) and Angus et al. (2001) have extended Donald's (1965) findings to the year 2000 and suggest that from 1950 to 1980 wheat yields increased as a result of better rotations and more timely sowing because of mechanization, and increased again in the 1980s and 1990s as a result of the introduction of herbicides and break crops such as lupins, other pulses, and canola into the rotation (Fig. 8). The introduction of semi-dwarf varieties in the 1970s also had a role in increasing yields and enabled agronomic management, such as increased fertilizer use, to benefit yields too. Similar conclusions on the role of agronomic changes have been drawn from studies of the Broadbalk experiment at the Rothamsted Experiment Station (Rasmussen et al., 1998; Miflin, 2000). These increases in yield have occurred as rainfall has remained unchanged, resulting in significant improvements in rainfall-use efficiency. While the early analysis suggested that until 1980 the increase in rainfall-use efficiency could be attributed half to new cultivars and half to increased agronomic practices (Turner, 1997), the surge in yields and rainfall-use-efficiency in the past two decades is considered to be one-third attributable to new cultivars and two-thirds attributable to agronomic management (Angus et al., 2001; Stephens, 2002). Indeed, the combination of agronomists working with breeders to develop appropriate agronomic packages for new cultivars and the ability of modern cultivars to respond to increased agronomic inputs is probably the reason for the recent surge in rainfall-use efficiency in wheat crops in Australia. It is clear that it is not just one factor that has led to the higher rainfall-use efficiency, but rather the combination of appropriate fertilizer use, improved weed/disease/pest control, timely planting, and the increased adoption of a range of rotations. This is the basis of the ‘Green Revolution in Rainfed Environments’.
Financial support by CSIRO, the Australian Centre for International Agricultural Research, the Grains Research and Development Corporation, AgraCorp Pty Ltd, and the Centre for Legumes in Mediterranean Agriculture is gratefully acknowledged. Drs Senthold Asseng and Heping Zhang are thanked for their comments on this paper.
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