Representative photo of the experiment setup (photo courtesy of Ellen Graber)
Rishon LeZion, Israel: Two new studies highlight how nitrogen availability and monitoring tools influence cacao (Theobroma cacao L.) growth, nutrient demand, and water use, offering important insights for sustainable cocoa production.
Among the three major nutrients that plants require in large amounts - nitrogen, phosphorus, and potassium -nitrogen plays the most direct role in plant growth and reproduction. The authors were surprised to find that most cacao worldwide is grown with little or no nitrogen inputs. This raised an important question: how much of cacao's roughly 90% yield gap could be explained by nitrogen deficiency and poor fertilization practices?
To untangle the many factors influencing cacao's response to fertilizer the team designed a long-term experiment under controlled conditions, using well-characterized cacao genetics, growing medium, environment, nutrient treatments, and analytics. This approach allowed them to isolate and measure how different nitrogen levels influence cacao growth, development, and water use.
The first study, "Evaluation of Optical Chlorophyll Meters as Proxy for Nitrogen in Theobroma cacao L.", investigated the accuracy of handheld chlorophyll meters as a practical tool for estimating nitrogen levels in cacao leaves. Results showed that these optical meters can serve as a reliable, rapid, and non-destructive method for assessing plant nitrogen status, potentially reducing the need for costly and time-consuming laboratory analyses.
The companion study, "Nitrogen Affects Cacao (Theobroma cacao L.) Tree Growth, Macronutrient Demand, and Water Use", explored how varying nitrogen availability influences overall tree performance. Researchers found that nitrogen supply significantly affected biomass accumulation, nutrient uptake patterns, and water-use efficiency. These findings underscore nitrogen's central role in cacao physiology and productivity, while also highlighting the importance of balanced fertilization for long-term sustainability.
Together, the two studies provide complementary perspectives on cacao nutrient management-one focusing on the physiological impact of nitrogen and the other on practical monitoring techniques. By linking efficient measurement with a deeper understanding of nitrogen's role, the research offers cacao growers new tools and knowledge to optimize fertilization strategies, improve resource efficiency, and support more sustainable cocoa production systems.
This work was led by PhD. student Maya Weinstein, under the guidance of Dr. Ellen Graber, with contributions from Professor Uri Yermuyahu and Dr. Shahar, all affiliated with the Volcani Institute, Israel.
According to Dr. Graber, "We were motivated by the lack of clear data on nitrogen's role in cacao productivity and the need to develop practical solutions for sustainable cocoa farming worldwide.."
The full article can be read on the Journal of the American Society for Horticultural Science electronic journal website at: https://doi.org/10.21273/JASHS05483-25 and
https://doi.org/10.21273/JASHS05518-25
Established in 1903, the American Society for Horticultural Science is recognized around the world as one of the most respected and influential professional societies for horticultural scientists. ASHS is committed to promoting and encouraging national and international interest in scientific research and education in all branches of horticulture.
Comprised of thousands of members worldwide, ASHS represents a broad cross-section of the horticultural community - scientists, educators, students, landscape and turf managers, government, extension agents and industry professionals. ASHS members focus on practices and problems in horticulture: breeding, propagation, production and management, harvesting, handling and storage, processing, marketing and use of horticultural plants and products. To learn more, visit ashs.org.
