HARVESTING UBOMBO’S FIRST CANE UNDER DRIP IRRIGATION
"UBOMBO completed the installation of a subsurface drip (SSD) irrigation system in February 2015 on a total area of 153ha as a pilot project, a first in the Illovo Group."
UBOMBO completed the installation of a subsurface drip (SSD) irrigation system in February 2015 on a total area of 153ha as a pilot project, a first in the Illovo Group. The first 92ha block at Majombe section planted in September 2014 was harvested in October 2015.
The journey from system installation, through cane husbandry and up to the onset of dry-off by the end of August 2015 presented a number of challenges and lessons which the Ubombo team embraced as they grew the current crop under drip at Majombe section. The variety planted under the drip system is N25. Despite carrying out pre-irrigation prior to planting, one of the intial challenges was poor germination in some areas due to extremely dry conditions at the time of planting. With prompt gapping a good crop was established by the third month of planting. The major learning point was the need for good quality final land preparation to improve the contact between the soil and cane setts. Good pre-irrigation using the drip system was found to be equally critical for good germination.
Fertiliser was applied in four splits. DAP was first applied in the planting furrow to supply N and P (Nitrogen and Phosphate). Three monthly applications were then applied through the system as a liquid fertiliser to supply the required Nitrogen and Potassium. Fertiliser application with drip was found to be efficient and hassle free. The estate had a lot of yellow aphid infestation during the season. At the crop age of three months aphids were noticed to build up on the drip fields as well. The insecticide, Bandit, was applied through the drip system and the effectiveness of control was better than had been seen on other irrigation systems. No other pests or diseases were observed in the field.
A healthy crop under drip behind the cluster house.
MAJOMBE section manager Sibusiso Zwane compares a cane stalk from a drip field (left) and another from an adjacent centre pivot field (right).
The prevention of emitter clogging is at the heart of maintaining the life of a drip irrigation system. Daily flushing of dripper lines has been made an important part of a preventative maintenance program. Although the system at Ubombo was designed for group flushing (10 dripper lines per manifold), in practice it was found that interchanging the group flushing with single line flushing at least once every 3-4 months was more effective. Chemical system maintenance has also been adopted to prevent root intrusion and organic growth inside the dripper line. A herbicide called Trifluralin or Treflan and hydrogen peroxide were injected into the system to prevent root intrusion and to clean the tapes of any organic sediments.
Although CANEPRO was the main tool used for irrigation scheduling, this was complemented by the use of soil moisture probes which were installed in the drip blocks at strategic representative positions. The results from the soil probes were used to correlate and refine the CANEPRO information on a daily basis. Assessments of various growth measurements indicated that the cane under drip irrigation was performing much better than neighbouring plant cane fields. Notwithstanding the fact that the crop would be harvested younger than normal for plant cane, a good crop of at least 120 tons per hectare was anticipated when harvesting was completed in October 2015. The final figure was 122.96 tons per hectare.
The excellent condition of the crop has already generated a lot of interest on the next development amongst the crop production team. Although well focused on yield improvement and longterm water conservation intitiatives, further drip is being cautiously considered along with capacity building to ensure longterm sustainability of this new technology. The Netafim team assigned to the project together with Group Agric has been working very closely with the Ubombo team and there is confidence that all the risks associated with drip irrigation will be well managed.