Oil palm (Elaeis guineensis Jacq.) is the most significant plantation crop in Southeast Asia, occupying approximately 18.7 million hectares in Malaysia, Indonesia and Thailand (Wong and Smith, 2020). But farmers in the area have a hard time growing on sandy soils that are not very good for farming. The typic haplorthod of Thailand (like the Ban Thon series), the typic quartzipsamment of Indonesia (like the Pasir Putih series) and the typic kandiudult of Malaysia (like the Rengam series) all have low levels of organic matter and cation exchange capacity. It rains a lot (2,000-3,000 mm per year), which makes them lose nutrients quickly (Chan and Lim, 2021; Suparno et al., 2022). These problems mean that small farmers need a lot of fertiliser. They pay for 35 to 45 per cent of the costs of making things (Mohamad et al., 2023). Ghazali and Ali (2023) say that goats are used in integrated crop-livestock systems (ICLS) to cut down on the use of synthetic fertilisers, add organic matter, control weeds and make more money in the end.
       
In Malaysia (28%), Thailand (28%) and Indonesia (17%), the proportion of total oil palm plantation area managed under integrated crop-livestock systems (ICLS) has significantly increased since 2015 (Department of Veterinary Services, 2023; Indonesian Ministry of Agriculture, 2023). Despite widespread promotion, a fundamental inconsistency exists between relatively stable manure supply from fixed livestock populations and dramatically changing nutrient requirements across oil palm life cycles. During establishment (years 1-3), young palms require approximately 781 kg/ha organic matter annually to support vegetative development and root establishment (Land Development Department [LDD], 2017). On the other hand, the production phase (years 4-20+) needs about 3,906 kg/ha to keep making fruit and sending nutrients out through fresh fruit bunches (Malaysian Agricultural Research and Development Institute [MARDI], 2019). This is a five-fold rise that makes it very hard to keep integrated systems that are still economically viable as plantations get older (Hassan and Karim, 2022). The current literature (Devendra, 2004, 2020; Tohiran et al., 2019) discusses the agronomic benefits of integrating livestock. Nonetheless, there are no quantitative life-cycle analyses that compare the variations in manure supply and demand in controlled environments between the establishment and production stages. The MARDI in Malaysia (2020), the IAARD in Indonesia (2021) and the Land Development Department (LDD) in Thailand (2019) all report that bringing in livestock is good during the establishing phase. But they don’t go into much detail about how to make it last through the whole plantation cycle. As a result, smallholders are left with unclear rules and unreasonable expectations.
       
The knowledge gap exists in understanding whether age-invariant manure supply under fixed-herd management a common smallholder practice can adequately meet the sharply increasing nutrient demands associated with plantation maturation and at what point the economic viability of livestock integration fundamentally changes. This study explicitly compares the contribution of goat-derived organic matter in young (<3 years) and mature (≥3 years) oil palm plantations under rigorously controlled management conditions using a Fixed Herd, Variable Density design with identical 64-goat populations across both plantation ages to isolate the effect of changing palm nutrient demand from confounding livestock management factors. The objectives of this study were to: (1) measure system-level manure delivery (kg/ha) at different stages of plantation life under fixed-herd management, (2) look at organic matter coverage (% of requirement met) and find patterns of deficit between the establishment and production phases and (3) look at the economic viability of using manure as a fertilizer substitute at different plantation ages.

This study was conducted during 2025 at Princess of Naradhiwas University, Narathiwat, Thailand, in collaboration with Tamod District Agricultural Extension Office, Phatthalung, Thailand and Rural Development Express Nepal, Salyan, Nepal. Research took place in Narathiwat Province, southern Thailand (6°25'N, 101°49'E and 3-8 m above sea level). The area has a tropical monsoon climate, with an average annual rainfall of 2,380 mm (mostly from November to January), an average temperature of 27.8°C and a relative humidity of 78-82%. The USDA Soil Taxonomy classifies the soils at all of the experimental sites as Typic Haplorthod.  This soil type was selected as a controlled proxy site representing the broader class of marginal sandy soils constraining oil palm cultivation across Southeast Asia. Baseline soil properties (0-30 cm depth, n=15 composite samples per site) were: sand content 75.2%, silt content 16.1, clay content 8.7%, pH 5.0, organic matter 1.5%, available N 21.3 mg/kg, available P.
       
A field experiment design was employed to compare two groups of plantations. Two plantation sites representing the two life-cycle stages were selected and matched on soil type, climate and management to isolate the effect of plantation age on livestock nutrient contribution. The two groups had the same number of goats, management methods and environmental conditions. At the start of the trial, the plantations in Treatment 1 (Young Oil Palm <3 years) were between 18 and 30 months old. They planted 1,098 palms on 7.68 hectares (48 rai) of land with an open canopy closure that covered 30-45% of the ground. The palms were spaced 9 m x 9 m x 9 m apart. Treatment 2 (Mature Oil Palm ≥3 years) comprised plantations aged 4-7 years at the commencement of the study, encompassing 33.28 hectares (208 rai) with a uniform planting density of 143 palms per hectare, resulting in a total of 4,759 palms exhibiting closed canopy closure (75-90% ground coverage). This design allows for a direct comparison of livestock contributions while keeping the herd size and management the same and controlling for soil type, climate and agronomic practices. This way, the effect of changing palm nutrient demand can be seen on its own. The study comprised two experimental units (Treatment 1: young plantation, 7.68 ha; Treatment 2: mature plantation, 33.28 ha), each representing one replicate of its plantation age class, with n=24 goats per treatment group assigned from the 64-goat fixed herd for individual-level measurements over a 12-month period in 2025.  A fixed herd of 64 crossbred goats (50% Boer x 50% local Thai Native) was maintained throughout the study period under semi-intensive management. Goats grazed rotationally across both plantation types for 6 hours daily (06.00-09.00 AM. and 3.00-6.00 PM), with controlled access reflecting biophysical limitations: young plantations had 8.3 goats/ha nominal stocking density (open canopy supporting dense understory vegetation) while mature plantations had 1.9 goats/ha nominal stocking density (closed canopy limiting forage availability). This resulted in a 4.4-fold difference in stocking density, a key controlled variable reflecting spatial constraints on manure deposition as plantation area expands.
       
Individual-level manure measurements were conducted monthly (n=64 goats) including fresh manure output via 72-hour collection in metabolism crates per goat, dry matter content via oven-drying at 65°C to constant weight and annual production calculated as monthly average x 12 months. Fresh manure samples (n=36 composite samples per year, pooled monthly from each treatment) were analyzed using AOAC (2019) methods: total nitrogen (N) by Kjeldahl digestion, total phosphorus (P₂O₅) by spectrophotometry after wet digestion, total potassium (K₂O) by flame photometry, organic matter by loss on ignition (550°C, 4 hours) and moisture content by oven-drying (105°C, 24 hours). Mean nutrient composition (dry weight basis) was N 2.1±0.3%, P₂O₅ 1.3±0.2%, K₂O 2.8±0.4% and organic matter 6.84±5.2% (Singh et al., 2024). Age-specific organic matter standards were derived from converging regional recommendations: young palms (<3 years) require 125 kg/rai/year (781 kg/ha/year) while mature palms (≥3 years) require 625 kg/rai/year (3,906 kg/ha/year), reflecting establishment-phase vegetative development needs versus production-phase continuous nutrient export via harvested fresh fruit bunches [LDD, 2017, 2019; MARDI, 2019; Indonesian Agency for Agricultural Research and Development (IAARD), 2021]. Local agricultural residues such as oil palm empty fruit bunches have also been identified as viable compost inputs for supplementing organic matter in Narathiwat Province soils (Wongkrachang and Anurut, 2025).
       
Regional fertiliser prices were used to calculate the NPK value of manure. In 2024, the average price for urea (46-0-0) was THB 12.19/kg N, triple superphosphate (0-46-0) was THB 23.81/kg P₂O₅  and muriate of potash (0-0-60) was THB 11.00/kg K₂O. Deficit-bridging costs are the costs of synthetic fertilisers that are needed to make up for the organic matter that is still needed after taking into account the manure contribution. All statistical analyses were performed using SPSS Statistics version 26.0 (IBM Corp., Armonk, NY, USA) at a significance level of α=0.05. Descriptive statistics (means, standard deviations and 95% confidence intervals) were calculated for all continuous variables. Data normality was assessed using the Shapiro-Wilk test and homogeneity of variance was verified using the Levene test. Independent samples t-tests were used to compare individual goat manure production between young and mature plantation treatments where data met parametric assumptions. For data not meeting parametric assumptions, the Mann-Whitney U test was employed to compare system-level manure delivery per hectare between treatments. Sample size was justified based on preliminary data (effect size d=1.2 for system-level delivery differences), with n=24 goats per treatment providing >90% statistical power (G*Power 3.1).

Productivity of livestock compared to system-level nutrient delivery
 
Individual goat productivity remained remarkably stable across plantation life cycles, with no significant difference in total annual manure output between treatments (Table 1). Young plantation goats produced 4,322±412 kg/year (67.5±6.4 kg/goat/year) compared to mature plantation goats at 4,503±458 kg/year (70.4±7.1 kg/goat/year; t=-1.01, p=0.32). This 4.2% difference falls within normal biological variation and demonstrates that canopy closure does not inherently suppress individual animal productivity when feeding strategies are adjusted. However, this stability at the animal level masks a critical system-level constraint. When the same 64-goat herd operates across mature plantations, manure delivery per hectare collapses to only 135 kg/ha compared to 563 kg/ha in young plantations (p<0.001). Adding animals to oil palm systems that are already in place is mostly a problem because it cuts the system’s nutrient delivery by 4.2 times. The difference is because the plantation area has grown 4.3 times (from 7.68 ha to 33.28 ha) to give the palms more room between rows as they get older and their canopies need more room to grow. To keep the goats from eating the palms, the nominal stocking density needs to be cut by 4.4 times, from 8.3 to 1.9 goats per hectare. This way, the same amount of manure can cover a much larger area.


 
Substantial reduction in organic matter coverage
 
The fixed goat herd produced stable manure output (4,322 vs. 4,503 kg/year), but this consistency collided with dramatically divergent organic matter demands (Table 2; Fig 1). In young plantations (less than 3 years old), the 64 goats provided 72.0% of the total organic matter needed (6,000 kg per year). But in mature plantations (≥3 years), the same herd only met 3.5% of the demand (130,000 kg per year). This shows how much less organic matter there is when plantations move from the establishment phase to the production phase. The difference in coverage is 20.6 times. The collapse is caused by two changes happening at the same time: the plantation area has grown 4.3 times as palms mature and canopies expand and the age-specific requirements have risen sharply (5.0 times) as production-phase palms need a lot more nutrients to keep harvesting fresh fruit bunches. Together, these factors drive total annual demand up 21.7-fold while manure supply remains essentially constant.




       
This quantitative pattern confirms life-cycle-based fertilizer management standards issued by Thailand’s Land Development Department (LDD, 2019), Malaysia’s MARDI (2020) and Indonesia’s IAARD (2021), which document modest establishment-phase needs followed by multi-fold increases once palms enter full production. The breakdown of livestock-oil palm integration in mature systems is fundamentally demand-driven rather than supply-driven. No reasonable change to herd management can make up for a 125-ton annual shortfall without also increasing the number of livestock by the same amount. Closed canopies further limit grazing access and understory forage availability (Tohiran et al., 2019; Azhar et al., 2021), making supplementary organic inputs compost, empty fruit bunch mulch, or biochar essential for mature systems (Hassall et al., 2022; Wongkrachang and Anurut, 2025; Wongkrachang and Chimniam, 2026; Begum et al., 2025). The integrated use of organic manures and inorganic fertilizers has been shown to improve soil physico-chemical properties and crop yield in tropical soils, supporting a complementary rather than substitutive approach to nutrient management (Singh et al., 2024).
 
Economic implications: from viable to marginal
 
The economic value of goat manure as a substitute for NPK fertiliser follows a similar pattern of stage-specific effectiveness (Table 3). The 64-goat herd produced the same amount of NPK value in all treatments (4,293 THB/year in young plantations vs. 4,472 THB/year in mature; 1.04x ratio), which means that each goat’s productivity stayed the same. However, when distributed across the plantation area, the value per hectare dropped from 559 THB/ha to 134 THB/ha-a 4.2-fold decrease mirroring the system-level delivery pattern. Consequently, manure offset 15-20% of typical fertilizer budgets in young plantations but only 2-3% in mature ones. When it figures out how much it will cost to make up for the lack of organic matter with synthetic NPK fertilisers, you can see how bad it is for the economy when there isn’t enough manure coverage. Young plantations needed only 200 THB/ha to add to the manure inputs, which was 8-12% of their yearly fertiliser budgets. Mature plantations, on the other hand, had to pay 3,452 THB/ha to make up for the shortfall. This was 17.3 times more and used 82-92% of the normal fertiliser budgets. Adding animals to the mix didn’t help the economy at all. When deficit-bridging costs exceed 80% of fertilizer budgets, manure-based nutrient substitution becomes economically insignificant. This threshold is crossed definitively by year 4. Local farming groups said that the results confirm their expectations for the economy. MARDI (2020) states that animal waste can lower the cost of fertilizer when palms are first planted, but not by much thereafter. The Land Development Department of Thailand (LDD, 2019) report that sandy soils don’t hold nutrients well and lose a lot of them through leaching. This means that you shouldn’t rely on just one organic nutrient source. The Indonesian IAARD (2021) also reports that adding livestock to mature plantations should be seen as a way to improve soil health, not as a way to get more nutrients. This is why many small farmers in Thailand, Malaysia and Indonesia use livestock integration during the first three years of their farming operations. When the canopy closes, it doesn’t matter anymore (Syahbudin, 2020; Hassan and Karim, 2022). Farmers who have this attitude do not lack knowledge or the use of technology. Instead, it shows that they are acting logically within the clear structural, biophysical and economic limits set by national institutional policies. To put the results in context for Southeast Asia, the 1,720 kg of nutrients in the annual production of goat manure (555 kg N, 298 kg P₂O₅, 867 kg K₂O) is worth 23,404 baht (2,909 MYR; 672,300 IDR; 653 USD). This means that smallholders can save 15-25% on fertiliser costs during the establishment phase (Table 4). Potassium makes up the biggest part (40.8% of total value; 9,540 baht), which is very important for sandy soils in Southeast Asia that are likely to lose potassium.

This study provides quantitative evidence that fixed-herd goat integration in oil palm plantations on Southeast Asian sandy soils exhibits distinct stage-specific viability patterns across the plantation life cycle. Individual goat productivity remained stable regardless of plantation age, yet the system-level contribution collapsed dramatically due to expanding plantation area requirements as palms matured. Young plantations during the establishment phase (years 1-3) achieved 72.0% organic matter coverage from a 64-goat herd, providing substantial fertilizer cost offsets of 15-20% and demonstrating economic viability as a primary nutrient source. In contrast, mature production-phase plantations (years 4+) received only 3.5% coverage from the identical herd, resulting in an acute deficit of 3,771 kg/ha and deficit-bridging costs that consumed 82-92% of fertilizer budgets, effectively rendering livestock integration economically marginal. It is important to emphasize that these findings apply specifically to fixed-herd management systems, which are common among smallholders in Southeast Asia who maintain a constant number of animals. Systems with proportionally scaled herds may sustain higher organic matter coverage in mature plantations, though this would require substantially greater land, feed and capital resources. Based on these findings, smallholder extension programs are recommended to guide farmers to transition from a goat-as-primary-fertilizer strategy to a goat-as-soil-conditioner strategy upon reaching plantation Year 3, complemented by cost-effective organic matter supplements such as empty fruit bunch compost, biochar derived from oil palm bunches, cover crops, or targeted synthetic NPK fertilization to bridge the structural nutrient deficit in mature oil palm systems on sandy soils.

The present study was supported by Princess of Naradhiwas University for providing research facilities and financial support under the Fundamental Fund and the cooperating farmers in Narathiwat Province for their participation.
 
Disclaimers
 
The views and conclusions expressed in this article are solely those of the authors and do not necessarily represent the views of their affiliated institutions. The authors are responsible for the accuracy and completeness of the information provided, but do not accept any liability for any direct or indirect losses resulting from the use of this content.

The authors declare that there are no conflicts of interest.