A consortium of banana producers started operations in Ghana with a pilot area to evaluate the development of plantations in that region. After the second harvest, the drip systems’ productivity and quality started to decline to marginal levels.
In 2018, it had been roughly four years of spending thousands of dollars per year on expensive imported liquid fertilizers and desalinization chemicals. Under these circumstances, investors realized that it was time to hire Leonel Castillo, a banana expert with many years of experience in Central America and worldwide, to evaluate the project and determine the causes of poor productivity.
Results of the Evaluation
The precipitation delivery design of the drip irrigation system was ineffective for a banana plantation under the local climatic conditions. They had designed the drip irrigation system to deliver 3.2 mm/h for a maximum of 2 hours per day every 3 to 4 days. Also, it was not suitable for the predominantly sandy soils on Farm. The lateral water movement on sandy soils is almost nonexistent. This design resulted in poor and economically unacceptable production levels.
Rainfall and evaporation records on the farm show a prolonged dry season of 8 to 9 months where total or supplementary irrigation is necessary. During the dry season, the daily evaporation rate is typically from 4 to 7 mm, with four to five peaks of up to 9 mm in April and May. These historical conditions correlate to very low relative humidity (RH).
Additionally, they found that the soil wetting pattern along the drip lines did not cover more than 30 cm wide until the moisture reached a silty clay layer located in the subsoil at variable depths between 50 and 100 cm.
Because they irrigated in intervals of 3 to 4 days – in addition to the downtime due to repairs and power outages at the pump stations – the wetting pattern rarely reached the clayey subsoil. This left a very broad, dry band between the drip laterals spaced at 2.5 m. The water applied was not reaching the root system in this area nor the 10 to 15 cm of topsoil between emitters, except during the rainy season (3 to 4 months).
The plantation began to suffer water stress because the soil humidity level was not enough to cover all the plant roots, especially adventitious roots. Also, the water stress led to the deformation of the new offspring in its early growth stages and underdeveloped bunches with few banana hands. In general, the low humidity level could not generate an adequate microclimate for the correct crop development.
Finally, they noticed some salinity along the drip lines where the moisture evaporated before the next wetting cycle.
Trial with Low-pressure Sprinklers
They initiated the trial to test low-pressure sprinklers during the dry season that began in November 2019.
The original installation had two lines of drip hose for each line of banana plants, operating at a valve pressure of 20 PSI. They replaced the drip hoses with Senninger Xcel-Wobbler sprinklers that deliver the same flow rates and work at the same operating pressure as the drip system.
Sprinklers provided a precipitation rate of 3.2 mm/h. Also, they covered the entire irrigated area with a distribution uniformity above 85%. They were installed with a sprinkler density of 70-90 units per hectare.
The Senninger team also supported the producers with a program, which calculates the best precipitation rate and uniformity of various sprinkler models. This allowed them to determine the best options based on the installation parameters and crop needs.
The trial irrigation scheduling was set at 2 hours per day every day versus 2 hours per day every 3-4 days for the rest of the farm under the drip system. Each respectively delivers around 48 mm and 12.8 mm per week.
Results Six Months into the Dry Season
The three basic measurable parameters were the number of leaves of the mother plant at shooting, primary follower height at shooting, and hand class of the bunch.
The comparative results of the sprinkler irrigation using the low-pressure sprinklers versus the drip system were:
• +3 leaves of mother plant at shooting.
• +1.2 m of follower height at shooting.
• +2 hands per bunch.
The micro sprinkler irrigation achieved a 35 percent increase in banana production. It ensured that the return (the plants that grow together with the plants that contain clusters) had a shorter time to produce the next cluster.
Additionally, it helped produce more vigorous bunches, with a higher number of hands and fingers and greater weights. This production is the most stable of all times, with more boxes per cluster, something unusual at the time of the year.
Special thanks for the collaboration of Ingeniero Leonel Castillo Flores, Banana Specialist, recognized worldwide.