Enhancing Oil Palm FFB Yields by Water Management: Sumber Tani Agung Resources’ Experiences

Oil palms (Elaeis guineensis) are generally able to grow economically on various soil types, especially across the regions of Malaysia and Indonesia. However, Fresh Fruit Bunche (FFB) production was lesser in flood-prone areas. In Sumber Tani Agung Resources (STAR), two estates namely (i) Seret Ayon (4289 ha) and (ii) Lembah Bawang (2511 ha) were facing problems of frequent flooding. Annual rainfall of these two estates would fall within 3500 mm - 4000 mm. Out of this, almost 30-40% of the total annual rainfall was recorded in the period of October-December. Furthermore, during the same period, high rainwater from the Forest Reserve of Bengkayang resulted from high water volume in the streams/rivers running across these estates. This caused high incidences of flooding. Therefore, a yield improvement program was embarked on to arise the existing height of riverbanks, literally speaking an ‘embankment or bund management’ on both banks of the river. A survey should be conducted first to demarcate areas that are prone to flooding incidences. Based on the survey results, areas that need improvement by ‘embankment’ would be identified and actions such as construction of flap-gates, building of embankments, and construction of drainage/reservoirs can be made. Outlet drains were desilted and thus, improved the water flow for smooth removal of excess water during the high pour and flooding seasons. FFB yields were satisfactorily increased from 11-14 mt/ha/yr during 2017-2018 to 25-33 mt/ha/yr in 2022. Besides improving FFB yields, palm growth also satisfactorily improved in frequently flooding areas, especially after three years of water management by embankment. In this paper, the commercial FFB yield of Seret Ayon Estate and Lembah Bawang Estate was collected and compared to those from before and after the implementation of efficient water management by embankment.


Introduction
Oil palms (Elaeis guineensis) are generally able to grow economically on various soil types, especially across the regions of Malaysia and Indonesia.Water availability and its management are the key factors that influence the productivity of Fresh Fruit Bunches (FFB) in oil palms.The water footprint (WFp) as an efficiency indicator for water consumption in oil palm also revealed that WFp values for FFB production are in the range of 700 to 1,700 m 3 tons -1 with an average of 1,034 m 3 tons -1 [1].This WFp value (1,034 liters per kg of FFB) is low compared to other vegetable oil crops, almost equivalent to 50-60 % of corn, soybean, peanut, coconut, olive rapeseed, and sunflower [1].Therefore, oil palm is more efficient in consuming water in a more environmentally friendly manner.
Sources and availability of water besides good water control systems are very important for the development of oil palm growth.One of the factors for the successful cultivation of plantations lies in the compatibility of water management between the natural resources and the network of drainage systems.A good water management system maintains the effective water level at 50-70 cm (below the soil surface) [2].However, in flood-prone areas, oil palms were producing lesser FFB.Due to frequent flooding incidences palm growth was generally stunted, and in extreme cases, there were huge losses of palms.
Flooding condition/environment for a longer time (>3 weeks) and continuous waterlogging can produce a strong anaerobic condition due to the accumulation of considerable organic matter from decaying root systems.Under such conditions, oil palm performance is affected adversely.These flood-prone areas are resulting from the overflow of river water as the accumulation of running river water from various locations, inclusive of Lembah Bawang Rain Forest Reserve.
Locations of two estates that are prone to frequent flooding are illustrated in Figure 1.According to the Central Bureau of Statistics [3], annual rainfall in Sambas Region normally ranged from 2,737 to 3,050 mm/year or an annual average of 2,893 mm/year with a monthly average of 241 mm/month.[4] highlighted that if this rainfall falls on the Sambas Groundwater Basin (GWB) area with an area of around 3,229 km 2 or 3,229 million m 2 , a rainfall discharge of around 778,189 million m 3 /year will be obtained.Furthermore, the amount of rain intensity (rainfall divided by rainy days) in the Sambas area ranges from 8.2 to 24.6 mm/day or an average of around 15.9 mm/day.The monthly air temperature in Sambas region generally ranges from 26.12 0 to 27.20 0 C [3].
The irrigation project for oil palm was initiated when rainfall below 200 mm/month was recorded in the northern region of Columbia [5].However, the distribution of rainfall above 200 mm per month is generally considered wet months for oil palms in the South-East Asia region.As such, a monthly average of 241 mm/month rainfall in the Sambas region reflects that both estates generally have a relatively wet climate [3].Apart from rainfall, a large amount of water is also from the Lembah Bawang/Bengkayang National Reserve Forest which is a type of limestone and granite-limestone mixture.The presence of such limestone mixture could allow a considerable amount of rainwater to pass through the hilly areas of Lembah Bawang/Bengkayang National Reserve Forest, reaching the foothills of the study area, even after a couple of days.Some important factors cause flooding incidences such as (i) high intensity of rain in the surrounding areas, (ii) lack of watershed retention /water catchment areas, (iii) faster silt-up in the river channels, and (iv) poor planning in making drainage channels/ditches.Proper maintenance of field drains in the estates also plays an important role as these drains are meant to remove the excess water from the fields.Although a network of drainage systems exists with proper drain depth and sizable dimensions, palms are still exposed to problems of frequent flooding, high water table, and flashflooding as well as wet-foot.Any planters on the ground must be able to identify the status of flooding conditions that are a potential threat to the normal growth of oil palms.
Oil palm is generally tolerant of relatively high water tables [6] and is thus most suited to water management techniques such as maintaining water levels in the drains.For example with proper water management by maintaining water level at 45-60 cm on acid sulfate soils oil palm yields are greatly improved.[7] [8] also stated that FFB yields exceeding 35 tons per ha per year are achievable on acid sulfate areas with controlled drainage by maintaining the water table at 45 to 60 cm as long as possible and not exceeding 75 cm depth.Otherwise, there is a risk of accelerated oxidation of the pyrite layer during dry weather conditions [9].However, oil palm is intolerant to flooding, especially for flooding cases of more than > 3 weeks.Palm growth in flooding areas is stunted as nutrient uptake is affected adversely.Besides poor growth of oil palm, normal/routine operations of plantations also hindered such as; (i) Uncollected bunches after the harvesting of oil palms at each harvesting interval.In a condition of high water table and poor drainage where crop losses of 3-20% were recorded [10].(ii) Extended harvesting intervals as the harvesters are unable to work during floodings/rainy days.(iii) Harvester movement and activity are limited as fields are subjected to (i) wet foot conditions or (ii) wet areas as water still subsides from the aftermaths of heavy rain.As such, there is more hardship for harvesters as well as bunch collectors in the frequent flooding areas.(iv) Missing of bunches harvested palms are equally contributing to lower oil palm production in these flooding-affected areas.
(v) Additional expenditure occurs as the estate need to plan to remove the excess water from the fields/drains as soon as possible.Generally, in frequently flooding areas, flood pumps were employed to pump out excess water.In one such estate, 8 flood pumps with capacities ranging from 50,000 to 80,000 liters/minute were used to remove flood water.In addition, the construction of a continuous peripheral bund (1-2 m high) is vital to minimize the influx of water from the outside into the estate [10].
As such constructing a bund or embankment would be a panacea for controlling the influx of water, especially during wet seasons [6] [10] [11].STAR had embarked on a program of improving fields suffering from frequent flooding.Approximately 600 ha was identified as areas under frequentflooding problems.However, by the end of 2022, the problems of frequent floodings were minimized with the implementation of the embankment project as well as maintenance of the drainage system in the affected areas for Seret Ayon and Lembah Bawang Estates, Sambas, West Kalimantan.In this study, observation of commercial FFB yield was carried out after the implementation of efficient water management and compared with yields before.

Study Area
Locations of the study area (Seret Ayon and Lembah Bawang Estates) are given in Figure 1.An average of 332 mm/month of rainfall was registered in both estates from 2020 to 2022 (Tabel 1).The total rainfall in this region is about 3500 mm to 4000 mm per year.There are four main rivers within these two estates, namely Sebangkau, Setankau, Karangan, and Sepang Rivers.

Details on Rainfall
Generally, the amount of rain in 2020-2022 (at an average of > 3985 mm/year) is very high (Table 1) for both estates.At the end of the year, there is usually quite high rainfall occurs.For example, in Seret Ayon Estate, the total rainfall in 2022 for the months of October, November, and December are 1.124 mm or 28% of the total rainfall in 2022.For the Lembah Bawang Estate, about 32% (1,446 mm) of rainfall occurs in the last 3 months of 2022.As a result, there is a major barrier to harvest, fertilizer, and weed spray programs due to heavy rainfall during these last 3 months annually.Access to the main and minor roads is also poor due to heavy rainfall and this results in difficulty in FFB evacuation and thus, transportation of FFB to mills [10].

Initiation of Embankment Project
There is a huge tendency for areas in both estates for flooding incidences as (i) Annual rainfall of this region is 3500 mm-4000 mm, (ii) Out of this, almost 30-40% of the total annual rainfall is recorded in the period of October-December (iii) Furthermore, during the same period, high rainwater from nearby Forest Reserve of Bengkayang had resulted in high water volume in the streams/rivers running across both estates.Factors from (i) to (iii) generally would cause an overflow of water from both banks which usually became stagnant in the nearby fields (Figure 2).A yield improvement program was embarked on in 2017 and 2019 for Seret Ayon Estate and Lembah Bawang Estates respectively to arise the existing height of riverbanks, literally speaking a 'bund management' on both banks of the river.Basically, by embankment program, overflow of water from both or any side of riverbanks is manageable.

Pre-preparations for Embankment
The steps that need to be taken to identify flooding problems or inundated areas/blocks are as follows: 1.A survey should be conducted first to demarcate areas that are prone to flooding incidences.The survey will also reveal the severity of the impact of floodings on oil palm growth as poor palm growth is evident.Survey results should be analyzed further for any improvement actions required.To analyze this problem, we need to check the water channels in the surrounding area.2. Based on the survey results, areas that need mere improvement such as the desilting of drains should be identified and eliminated from the embankment program.Water flow in such areas could be improved if the desilting of drains is programmed and carried out periodically.3. Decisions for further actions such as the construction of flap-gates, the building of embankments, and the construction of drainage/reservoirs can be made after analyzing the main problem.An action plan should be prepared to rectify the main problem.4. Budgets should be prepared based on action plans.Appropriate maps, time frames, and cash flow should be calculated before the implementation of the embankment program. 5. Once the budget is approved, the estate management should be able to find a suitable supplier to provide the required item on time, such as the machinery items involved in this embankment project.

Basic Designs for Drains in Embankment Areas
The function of the outlet drain is to hold water from all existing drains as well as overflow from plantation areas, then drains it into rivers or other water disposal sites.The outlet drain is made with a size of 5 x 2 with a depth of 1.75 m.This size generally depends on the existing field conditions.
The main drain would collect water from secondary drains, foothills, and smaller drains then channels it to outlets or canal ditches and/or to a larger river.Dimension of the main drain is 3 m x 2 m with a depth of 1.75 m meanwhile collection drain is made with a size of 2 x 1.5 m and a depth of 1.75 m (Figure 3).The function of the collection drain is to directly collect water from the surface of the field, especially the lower parts, then drain it into the primary/main drain.The sizes of main and collection drains are very dependent on the amount of water that needs to be accommodated.A field drain or so-called subsidiary drain is a drain that collects water from the area or from the lowlands and channels it directly to the collection drains.The field drain is made with a size of 1 x 0.45 m and a depth of 0.8 -1 m.Field drain is built parallel to the row of plants to drain water into the collection drain (Figure 3).A typical illustration of embankment or heightening of both banks of the river is given in Figure 4.The width of 3 meters is maintained throughout the areas designed for embankment.Soils to top up the bank were also taken from the riverside, approximately 3 meters away from the base of the banks.This 3-meter distance from the base of the riverbank is necessary to ensure the stability of the bank.On the other side (i.e.field side), a bund drain is constructed so that this drain can channel out any excess water from a river due to leaking through the bund or rainwater.

Figure 4: Illustration of embankment areas along the proposed riverbanks
When making a drain, lay out the drain that has been determined in the drawing on the work map and marked with stakes or pegs, or rope in the field.Drain work starts from the large ditch, then followed by the smaller one, and drain digging starts from the outlet (downstream) to adjust the depth of the drain.

Monitoring Progress of Embankment Project
The embankment project was carried out phase by phase in both Seret Ayon and Lembah Bawang estates in 2017 and 2019 respectively.A total of 38.39 km along the rivers of Sebangkau, Setangau, and Sepang in Seret Ayon Estate while for Lembah Bawang Estate, a total of 8.9 km along the Sepang and Karangan rivers (Figure 5).Efforts should be taken to ensure the stability of riverbanks together with embankments.After a heavy pour, a patrol should carry out monitoring and checking of any weakness in the embankment area such as the sudden collapse of the riverbank (due to a more sandy type of soil texture) and /or overflow of the river after an extended period of rainfall.Estate personnel must continue monitoring the riverbanks throughout the year, wet or dry seasons.

Basic Maintenance Works
In all situations, for an embankment system to be effective, constant supervision and good maintenance of the water-control structures such as monitoring water gates, flap-gates, weeds in the drains, and smooth removal of excess water after rain should be carried out (Figure 6).
Outlet drains are desilted and thus, improved the water flow for smooth removal of excess water during the high pour and flooding seasons.It is necessary to pay attention to the maintenance/desilting/washing of the drains.Normally the drains are desilted at least once every two years and this desilting program is depending on the condition of the drains.Desilting of drains can be done mechanically by deepening the drains that are heavily silted up over the period.While the manual method can be done to small drains by cleaning/removing mud, wood, and other rubbish.Maintenance/desilting of drains is very important because it will greatly affect the volume and smoothness of the outgoing water to the main outlets.Repairing of main drains, collection drains, field drains, or outlet drains, must be attended immediately to prevent any breakdown of embanked riverbanks.Immediate attention should be given to any water gates or flap gates that require repairs or fixings (Figure 7 (a & b)).Vetiver grasses were also established on riverbanks (Figure 7 (c)).Planting of such Vetiver grass would help to reduce soil erosion and thus it is envisaged that the lifespan of embankment be extended.

Yield Improvement after Embankment Project
As a result of the embankment project, the total areas improved by 2022 are 413.48ha and 152.97 ha in Seret Ayon and Lembah Bawang estates respectively.In Seret Ayon Estate, with the construction and elevation of the embankment, FFB yield production has increased from 10.48 tons/ha in 2019 to 33.05 tons/ha in 2022 (Figure 8).This represents an increment of 22.57 tons/ha or 315%.Although increasing palm age could be a contributing factor for better yield, palm growth, and field condition in this floodprone region was improved purely due to the implementation of 'embankment'.If converted to the current price of palm oil in the West Kalimantan region of IDR 2,370/Kg, the profit due to the embankment project is IDR 53,490,900/Ha (22,570 Kg/Ha x IDR 2,370/Kg).As approximately 413.48 ha of land was improved from the adverse impacts of frequent floodings, a total of IDR 22,117,417,332 was realized in 2022 (IDR 53,490,900/Ha x 413.48 Ha).
Similarly, there was an increment in FFB production in Lembah Bawang Estate from 11.66 tons/ha in 2017 to 25.94 tons/ha in 2022, representing an increase of 14.28 Tons/ha or 223%.With the palm oil price of IDR 2,370/Kg in the West Kalimantan region, the profit from the increased FFB production is IDR 33,843,600/Ha (14,280 Kg/Ha x IDR 2,370/Kg).As such, for an improved area from frequent flooding incidences of 152.97 ha in Lembah Bawang Estate, IDR 5,177,055,492 worth of FFB production is realized in 2022 (IDR 33,843,600/Ha x 152.97 Ha).Assuming the conversion rate of 1 USD = IDR 15,000, an additional income due to the embankment project for Seret Ayon and Lembah Bawang estate is equivalent to USD 1,474,494 and USD 345,137 respectively.
. The improvement in field conditions, drains, and roads resulted in the betterment of FFB evacuation and transportation of FFB to mills.As a result, there was a major FFB yield improvement realized in 2022 in both estates.As shown in Figure 8, throughout the years 2016-2021, yields in Lembah Bawang Estate were higher than those from Seret Ayon Estate for the same period.However, in 2022, there was a significantly higher FFB yield production in Seret Ayon Estate (33.05 tons/ha/yr) as compared to those from Lembah Bawang Estate (25.94 tons/ha/year).This might have been attributed due to an earlier embankment project in 2017 for Seret Ayon Estate as compared to Lembah Bawang Estate, where an embankment project was initiated only in 2019.Furthermore, the total areas improved due to the embankment project in Seret Ayon Estate was approximately 413.48 ha as compared to the 152.97 ha of improvement areas in Lembah Bawang Estate.As such, the FFB yield increment in Seret Ayon Estate was better than Lembah Bawang Estate.Figure 9 shows the improvement on the ground before and after the embarkment of the embankment project in Seret Ayon and Lembah Bawang estates in STAR.

Conclusions
FFB yields were satisfactorily increased from mere production of 6.61 tons/ha/yr in 2017 to 33.05 tons/ha/yr in 2022 in Seret Ayon Estate.Meanwhile, for the same period in Lembah Bawang Estate, FFthe B yield increased from 11.66 tons/ha/yr to 25.94 tons/ha/yr.This FFB yield increment was attributed mainly to the implementation of the embankment of riverbanks within the project areas.FFB yield production of more than 35 tons/ha/yr is highly possible, even in areas with annual rainfall reaching above 4000 mm per year.There were also other agronomic practices implemented throughout the same period to ensure maximum FFB production in these frequently-flooding areas, such as continuous application of fertilizer at optimal rates and field maintenance.Although other agronomic practices played equally significant roles, the embankment project remained a single major factor in ensuring maximum FFB yields in the flooding areas.
Besides improving FFB yields, palm growth was also satisfactorily improved in frequently flooding areas, especially after three years of water management by embankment.Maintenance and cleaning works on embankment areas also should be carried out to ensure that embankments are not damaged, for example, (i) monitoring vetiver grass planted on the edges of the embankments and (ii) monitoring riverbanks before heavy rainy days.As such, the decision to carry out an embankment project, especially in heavy rainfall areas really could bring fruitful returns, at four to six years of embankment project.

Figure 1 :
Figure 1: Location of study areas with four main rivers and directions of water flow in respective river

Figure 2 :
Figure 2: Conditions of rivers as well as surroundings of fields during heavy rainfall season within the study area

Figure 3 :
Figure 3: Dimension of drains in the surroundings of embankment areas (a) main drains, (b) collection drains, and (c) field drains (in-field drains)

Figure 5 :
Figure 5: Heightening of banks along the rivers (a) works by excavators, (b) embankment in progress, and (c) completed embankment with 3-meter width on the top surface

Figure 6 :
Figure 6: Monitoring fields during the embankment project

Figure 7 :
Figure 7: Maintenance and repair works (a) fixing culvert, (b) flap-gate maintenance, and (c) planting of Vetiver grass on recently embankment area, so not easily eroded if the water rises.

Figure 9 :
Figure 9: Field condition and appearance of palm health before and after the embankment project in the same areas in Seret Ayon and Lembah Bawang estates, near Sambas, Indonesia