SUMMARYField experiments were conducted for the three consecutive cropping seasons of 2003–05, 2004–06 and 2005–07 at the Indian Institute of Sugarcane Research, Lucknow, India, to explore the feasibility of planting sugarcane in autumn as a relay intercrop in standing rice. The cropping systems evaluated were: i) rice-potato-spring sugarcane; ii) rice + autumn sugarcane (planted as a relay intercrop in every sixth row devoid (skipped) of transplanted rice + potato after rice; iii) rice-autumn sugarcane (planted without preparatory tillage) + potato; and iv) rice-autumn sugarcane (planted with preparatory tillage) + potato. In each case, sugarcane was planted in rows 90 cm apart. Rice was transplanted in rows at 20-cm row spacing when followed by potato or sugarcane, but at 18-cm row spacing when intended for sugarcane planting as a relay intercrop in late September. The germination (60.4%) of cane buds, tillers (323 000 ha−1) and number (149 000 ha−1), length (225 cm), girth (2.44 cm) and weight (747 g) of millable canes were markedly better when autumn sugarcane was planted with rice as a relay intercrop in comparison to other cropping systems. Similarly, this cropping system produced the maximum cane (111.4 t ha−1) and sugar (13.2 t ha−1) along with sugarcane equivalent yield (216.4 t ha−1). In turn, relay intercropping system with maximum cane production efficiency of 420 kg ha−1day−1 fetched the highest economic returns (Rs. 258 ha−1day−1) and benefit:cost ratio (1.5). Compared with the rice-potato-spring sugarcane cropping system, the relay intercrop of autumn sugarcane in standing rice produced 35.4% more cane and 38.3% more sugar with 24.1% higher returns besides 79.1% energy saving. This practice will not only benefit cane growers and sugar mill owners in tropical and sub-tropical India, but also in other parts of the world where rice and sugarcane are extensively cultivated.
