Management strategies for drip irrigation systems in sugarcane : SRDC final report BS64S
Two drip irrigation trials were conducted on clay (krasnozem) and sandy loam (gley podzolic) soils to investigate the optimum positioning of drip irrigation tape for effective irrigation on contrasting soil types. Further trials were established on the gley podzolic soil to compare fertiliser application through tape with conventional application; to compare drip and furrow irrigation and to compare drip irrigation performance at different row spacings. The trials comparing deep and shallow placement of drip tubing showed that both are satisfactory for the soil types tested. More frequent watering is necessary if deep tape placement is used on sandy soils and water use efficiency is likely to be less on both soil types if extra water is needed at crop establishment to wet up the soil profile. It is recommended that tape be placed at 100-150 mm below planting depth to minimise these problems. Fertigation through the drip tape showed no difference in crop response compared to conventional solid fertiliser application at recommended nitrogen rates, and the 75% nitrogen rate applied through drip performed similarly to the 100% conventional rate. It was found that application through the drip system in splits throughout the season reduced ccs at the 100% nitrogen rate but there was no effect on ccs at the 75% rate. The comparison between drip and furrow irrigation showed a small but non-significant advantage in water use efficiency with drip but no yield difference between methods. This suggests that under trial or commercial conditions which give abnormally high water use efficiency with furrow irrigation there is no significant benefit from drip irrigation. In the row spacing trial planting at 1.65 m compared to 1.5 m spacing gave similar yields for six varieties showing that some reduction in tape costs could be achieved by moving to wider row spacing. The dual row planting on 1.8 m centres with one tape per two rows gave poor yields due to crop establishment problems but other trial work suggests that this is also a viable alternative for reducing tape costs. Management techniques such as regular chlorination of drip tape and application of trifluralin through the tape to prevent root intrusion into emitters adopted for the trial are recommended as standard practice for drip users to ensure longevity of the drip tape.