The performance of permanent bed RW systems in the north-western IGP has generally been disappointing to date, mainly due to poor yields of both transplanted and direct-seeded rice on beds, with problems of weed control and nematodes, and iron deficiency in the case of direct-seeded rice. Nor has the performance of wheat on PRB in the north-west reached the expectations of generally higher yields. In contrast, PRB RW systems in the eastern IGP consistently produced significantly higher yields of both rice and wheat. The main differences between the west and east are the much higher rainfall prior to and during the rice season in the east, and a greater level of machinery traffic using 35-50 hp tractors in the north-west. Further work is needed to properly determine the causes of the poorer performance of PRB in the north-western IGP and the means to overcome this. While PRB may reduce irrigation amounts in many situations, this is not always the case, as it is influenced by factors such as age of the beds, depth of water in the furrows and irrigation scheduling. It is still unclear how much, if any, real water saving is achieved through adoption of PRB in comparison with conventional tillage. Clear guidelines are needed on irrigation management for PRB to optimise yield and water use.
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