Few if any farmers are faced with a more complex set of crop priorities than those who grow coffee. Crop yield potential is paramount but so is bean quality, including bean size and strength, and not to mention post-harvest, on-farm processing (wet or dry) of coffee berries and beans. Required to achieve the green coffee commodity, they represent some of the most mechanically rigorous crop processing methods, and from which coffee beans must emerge physically intact. Last but not least is the flavour and aroma of the coffee cup infusion, largely governed by chemical profile of the roasted coffee bean but potentially prejudiced by off flavours caused by a wide spectrum of bean defects.
Coffee crop nutrition and the full gambit of essential plant nutrients clearly plays a pivotal part in achieving high yields of top quality coffee cherries and green coffee beans, but one nutrient in particular is credited with an over-arching role in achieving these goals. This nutrient is calcium which minimises coffee berry drop and maximises resilience of the coffee berry to pests and diseases, and the bean to a range of well-known commercial defects.
Calcium is rarely deficient per se as a soil nutrient, but maintaining sufficient levels of soluble calcium in the soil and in plant-available form is an entirely different matter. Laboured movement of calcium, within the soil and into plant roots, and up the plant as divalent calcium ions (Ca2+) for use in the growth of shoots, leaves, fruits and seeds, is well established and appreciated. And the reason why savvy growers use foliar sprays of soluble calcium to boost low levels of plant-available soil calcium, and to maintain the tissue strengthening attributes which calcium can provide. Calcium is essential in the formation of cell membranes and plant cell walls. It has a specific and prominent role in cementing plant cell walls together, to form strong plant tissue, via the inherently gelatinous (adhesive) middle lamella composed of calcium pectate.
Foliar sprays of calcium delivered under strict timing and concentration schedules allow crop nutritionists and plant physiologists to more accurately predict and pin-point the strengthening roles of calcium. And the minutiae of how these are expressed in specific aspects of plant growth and development, such as minimising coffee berry drop, resilience to pests and diseases and as a bulwark against bean damage and resulting bean defects.
Omex CalMax trialled on coffee in Vietnam
This is exactly what Omex Agrifluids set out to achieve with comprehensive research trials using Omex CalMax, a fully water soluble fluid emulsion product containing a range of essential plant nutrients – nitrogen, magnesium and a full profile of chelated micronutrients together with a high concentration of soluble calcium.
Research was carried out in Vietnam the world’s number two producer of coffee with over 1.5 million tonnes per annum. Ten trials were established in five coffee growing areas (Bao Lam, Di Linh, Lam Ha and Duc Trong) to determine the most effective rate of Omex Calmax in terms of extension growth, berry drop, coffee yield and bean quality. Omex CalMax was applied by foliar spraying to 5-year old Robusta coffee trees. Harvested ripe cherry was processed by the dry method using the sequential steps of sorting and cleaning, sun drying and hulling.
Omex CalMax was applied at three different treatment levels (3.75, 2.50 and 1.25 ml/tree) in multiple applications, starting at the end of March/early April which is post-main flowering stage and beginning of the ‘pin-head’ stage. Harvesting began in September and was completed by end of January/early February.
The three Omex treatments were compared with ‘Farm Check’ trees not receiving foliar sprays of Omex Calmax. Trees within the four different treatment categories were thus compared for a range of growth parameters, yield and bean quality. This included extension growth (new branch length), berry drop (per cent), coffee cherry yield, processed green coffee yield, size-grade of coffee beans and per cent bean defects (black bean, broken bean and mouldy bean).
Omex CalMax ticked almost all the boxes for increased yield and superior bean quality with the highest rate of CalMax (3.75 ml/tree) performing best in virtually all respects.
- Trees treated with CalMax suffered only a 1-2% berry drop and measurably less than the 5% of berries ‘dropped’ from untreated ‘Farm Check’ trees. Calmax treated trees accordingly supported a greater number of cherries in each cherry cluster compared with the untreated Farm Check trees. Average figures for cherries/cluster were: 24, 24, 21 and 13 for, respectively, the 3.75 ml, 2.50 ml, 1.25 ml/tree treatments and the untreated Farm Check trees. Five per cent berry drop is considered as an upper threshold level before a serious impact on yield sets in.
- Average yield of coffee cherry in kg/tree was significantly higher for the CalMax treated trees. Average yield performance of treated trees was CalMax 1.25 (19.23 kg/tree), CalMax 2.50 (20.66 kg/tree) and CalMax 3.75 (21.39 kg/tree). Corresponding weight of coffee cherry harvested from the non-treated (Farm Check) plots was 17.28 kg/tree.
- Green coffee bean yield was enhanced by foliar applications of Omex Calmax. Using standard conversion figures for converting fresh cherry into green coffee, the yield of beans/tree in kg averaged out at 7.71 kg, 8.71 kg and 9.06 kg/tree for, respectively, the 1.25 ml, 2.50 ml and 3.75 ml CalMax treatments. Average yield of green coffee beans per untreated (Farm Check) trees was 6.15 kg/tree.
- New extension growth rates were also heightened by treatment with Omex CalMax. New branch length in cm measured 25.67 cm, 30.67 cm and 33.67 cm for, respectively, the 1.25 ml, 2.50 ml and 3.75 ml CalMax treatments. Average new branch length for trees in the untreated (Farm Check) plots was 21.33 cm.
- Bean quality as measured by size also benefitted from foliar sprays of CalMax. Per cent of beans from trees treated with CalMax at 2.50 ml and 3.75 ml and caught by Screen No 13 was 85% and 83%, respectively. Screen No 13 is commonly used for assessments of Farm Average Quality (FAQ). Current on-shore trading benchmark in Vietnam lies between 75 to 80%. Percentages for the CalMax 1.25 and Farm Check (no CalMax) treatments were 79% and 78%, respectively.
- There were measurable and significant reductions in the incidence of some common defects of coffee beans from trees treated trees with CalMax, and with the 3.75 ml CalMax treatment coming out on top in this respect. Per cent incidence of ‘Black Bean’, Broken Bean’ and ‘Mouldy Bean’ for the CalMax 3.75 ml treatment was 5.56%, 1.44% and 1.84%, respectively. Equivalent figures for untreated (Farm Check) trees were 5.99%, 2.08% and 2.04%.
Omex CalMax (3.75 ml/tree) demonstration trial
Following these preliminary results which showed Omex CalMax at 3.75 ml/tree as the best treatment, a ‘Demonstration Trial’ to confirm CalMax at this rate in providing significant commercial benefit for farmers was set up. The trial covered 12 sites spread across Dak Nong, Dak Lak and Gia Lai with age of coffee robusta trees varying from 9 to 23 years depending on the site.
Ten sprays of Omex CalMax (3.75 ml tree) were applied at 30 day intervals, starting on 15th April 2018 and ending after harvest which took place on 10 January 2019. A full comparative assessment of extension growth (average length of new branches), yield (fresh picked cherry and green coffee in kg), coffee bean quality (bean size and incidence of common bean defects) was made and results summarized.
The significant positive effect of Omex Calmax applied at a rate of 3.75 ml/tree on extension growth, yield and bean quality, compared with Farm Check coffee trees, was confirmed. And despite an ‘across the board’ reduction in yield for the 2018/19 season, compared with 2017/2018, due to climate and weather related factors.
Results can be summarized as follows:
- Average yield of coffee cherry picked from Omex CalMax treated trees at 16.16 kg/tree was 30.8% higher than 12.36 kg/tree harvested from Farm Check plots
- Use of standard conversion figures to convert fresh coffee cherries to green coffee beans showed the Omex CalMax treatment gave a 34.4% increase in green coffee yield on a per hectare basis – 4,060 kg green coffee/ha compared to 3,026 kg/ha for Farm Check trees
- Bean quality, expressed as bean size, was similarly superior with 86.8% of beans from CalMax treated trees retained by Screen No 13 compared with 82.2% for beans from Farm Check trees.
- Incidence of black beans (3.1%), mouldy beans (1.9%) and broken beans (1.0%) was less for harvests from Omex CalMax treated trees compared with Farm Check trees. Respective figures for beans harvested from Farm Check trees were 5.0%, 3.2% and 2.9%.
In consultation with Vietnam’s coffee inspectorate the researchers concluded the following: ‘Based coffee bean quality the price value of beans harvested from Omex CalMax treated trees could be reasonably expected to be 10 to 12% higher than beans harvested from the ‘Farm Check’ (untreated trees) and around 13 to 15% higher than the prevailing market price. They concluded by saying: “Using Omex CalMax on coffee brings benefits to the trees, elevates yield, improves coffee bean quality and increases profits for farmers.”
Omex CalMax is widely used by coffee growers throughout the Asia/Pacific region.