Enabling small-scale grower sugarcane quality management

Dr Riekert van Heerden
Senior Scientist – Sugarcane Physiology

Published: 14th Nov 2023

In South Africa chemical ripeners are mostly applied by air onto sugarcane fields to improve low cane quality. Through manipulation of plant growth processes these chemicals accelerate stalk ripening. Large-scale growers that implement chemical ripening best practice, unlock RV yields, and associated economic benefits on their farms. An important component of this best practice is informed decision-making about the need for chemical ripening on a field-by-field basis. The PurEst® smartphone application, together with a hand-held refractometer, enable  growers to make these decisions. In contrast to large-scale growers, small-scale growers (SSGs) in South Africa generally have not experienced the benefits of chemical ripening. The small field sizes, and the spatially fragmented distribution of fields, make it difficult and dangerous for conventional aerial crop-spraying methods to accommodate the cane quality management needs of SSGs.

The recent availability of crop-spraying drones in South Africa creates chemical ripening opportunities for SSGs because of the ability of these drones to effectively apply chemical ripeners in fragmented small-field environments. Furthermore, the PurEst® smartphone application can assist these growers with decisions about ripening and harvest scheduling. A technology development project, recently completed by SASRI, introduced cane quality management principles, the PurEst® smartphone application, and crop-spraying drones to the SSG sector. The project was founded on a network of participatory demonstration trials in different SSG communities.

Small-scale growers and other participants at a stakeholder engagement workshop in the Richards Bay region.

Demonstration trial fields were identified in 11 diverse SSG regions in KwaZulu-Natal and Mpumalanga. At each demonstration trial location, a stakeholder engagement workshop was convened with the SSGs, community leaders, contractors, government agricultural advisors, SASRI extension specialists, representatives of the two industry canegrower associations, and cane-procurement personnel from the local sugar mill to create awareness of the project.


These workshops were followed by a field day at each trial site where the concepts of cane maturity assessment and chemical ripening decision-making were introduced. Each demonstration trial field was then sub-divided into an unsprayed (control) and ripener treatment. On the agreed spray date, a field day was convened so that the SSGs and other participants could witness the drone application of the ripener (fluazifop-p-butyl in all trials). Shortly before the planned harvest date another field day was convened at each demonstration site to introduce the concepts of ripener efficacy assessment and harvest scheduling.

Small-scale growers and other participants attending a drone spraying field day in the Pongola region.


In-field estimations of cane yield and RV% with the PurEst® application before drone spraying, and again before harvest, were used to estimate the RV yield response to ripening. Economic analysis involving consideration of RV yield response and input costs related to ripening, harvesting and cane transport to the mill were conducted to estimate the gross margin benefits (R/ha) from ripening.

Aerial photo of a small-scale grower drone ripening demonstration trial in the Mtwalume region. The colour contrast between the control (left) and ripened (right) part of the field can be seen.


A total of 16 drone ripening demonstration trials in association with 48 field days were conducted during the project. This participatory approach led to direct and frequent interaction with SSGs and other industry participants. The ripener treatments led to RV yield increases of between 0.21 – 1.78 t/ha in the various demonstration trials. The magnitude of RV yield response depended on trial location, variety, and climatic conditions during trial execution. Economic analysis revealed gross margin benefits from ripening in the range of R1567 – R8896/ha, which compares well with observations made in large-scale grower demonstration trials. The yield and economic results were shared with the small-scale growers and other stakeholders at post-trial grower days.

Small-scale growers and other participants attending a grower day in the Komatipoort region where demonstration trial findings and potential adoption barriers were discussed.


These demonstration trials elicited considerable interest amongst SSGs in chemical ripening and drone spraying technology. However, during the interactions with the growers it became evident that there are several challenges that will have to be tackled to bridge the gap between demonstration and wider implementation at a mill supply level. Some of these challenges, together with possible solutions, will be addressed in a follow-on knowledge exchange project currently under development by SASRI research and Extension Specialists. The new project will aim to facilitate pilot implementation of drone ripening in SSG regions at mill supply level to improve SSG profitability.


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