Assessment of Land Characteristics and Recommendation for Improvements in Patchouli Plantations in Aceh Province, Indonesia

Patchouli (Pogostemon cablin Benth) is considered as prospective aromatic plant for its essential oil. Indonesia is the world’s largest producer of patchouli, 90% of global market in the world, contributing to the increase of national economy in Indonesia (Nasruddin et al., 2020). The demand of patchouli oil is increasing, as this oil has been used as fixative agent in cosmetic, perfume and soap industries. Unfortunately, the patchouli production in Indonesia still unable to meet the great demand of this commodity in global market as the production has continued to decrease in the last 4 years (Dirjenbun, 2018). Patchouli production varies between places in Indonesia. The highest was found in Sumatra Utara and Aceh Provinces. The data collected by Dirjenbun (2018) for the last 4 years (2014-2017) revealed the production in Sumatra Utara reached up 215.34 kg/ha/year, followed by Aceh (211.80 kg/ha/year) and other places (<140.00 kg/ha/year). Aceh patchouli oil demonstrated better quality compared to oil produced from patchouli in Sumatra Utara, enables Aceh patchouli to become more popular worldwide. Acehnese patchouli exhibited rendement 2-3% and patchouli alcohol 30%. These characteristics have lead Acehnese patchouli to be the main supplier of patchouli oil in Indonesia (±70%) (Ayu et al., 2016).

The oil production 211-215 kg/ha/year is considered low. It is only 60% from the potential exhibited by Tapaktuan, Lhokseumawe and Sidikalang varieties, where they usually produce 375.76, 355.89 and 315.95 kg/ha/year (Pujiharti et al., 2008). The oil production and quality are possible to be increased by evaluating its land characteristics, where these characteristics influence the patchouli growth, production and quality. Land characteristics for patchouli were released by Rosman et al., (1998) and Ministry of Agriculture (2014). However, these characteristics considered inadequate as they did not mention humidity, wet season, base saturation and nitrogen.  Ritawati et al., (2019) and Setiawan et al., (2021) also did not mention base saturation and nitrogen. Temperature, rainfall, humidity and wet season play a crucial role in the plant growth and yield (Pugnaire et al., 2019). Base saturation and nitrogen are needed to be considered in land characteristics as they greatly influenced the plant growth and yield (Wahyunto et al., 2016). Base saturation represents soil fertility and nitrogen is important for plant physiology (Havlin et al., 2013; Gojon, 2017; Meshram et al., 2019). Therefore, we conducted this research to classify land suitability class for patchouli in AU and GL districts in order to establish the best land suitability for Acehnese patchouli.

Study area, time, tool and materials
 
The research was conducted in September-November 2020 at smallholders’ farming in AU and GL Regencies, Aceh Province, Indonesia (Fig 1). Geographically, the territory of AU stretch from 96°.52'.00'' to 97°.31'00''E longitude and 04°.46'.00'' to 05°.00’.40''N at an altitude of 263-674 m asl, while GL stretch from 96°.43'.15.65'' to 7°.55'.24,29''E longitude and 03°.40'.46,13'' to 04°.16'.50.45''N at an altitude of 641-869 m asl.



The material used in this research for survey, soil analysis etc were H₂O, HCl 30%, natrium pyrophosphate (Na₄P₂O₇10H₂O), distilled water, K₂Cr₂O₇1N, concentrated H₂PO₄, H₃PO₇ 85%, FeSO₄ 1N and NH₄OAc 1N. The tools used were soil auger kit, hoe, machete, knife, bayonet knife, used magazines, compass, measuring tape, transparent plastic (size 1 kg), labeled paper, GPS (Global position system), abney level, camera, stationery, computers and maps (land use map, administrative map, slope and soil maps).
 
Data collection   
 
The data collected in this research was divided into primary and secondary data. Primary data described soil characteristics, patchouli growth (plant height, number of primary and secondary branches), oil production and quality (level of patchoulol). Secondary data showed us patchouli production of a soft production that lacks of leathery woods, collected by local farmers and staff from the Department of Agriculture and Plantation in those regencies, along with climatic data obtained from climate stations located in Malikussaleh, North Aceh and Indrapuri, Aceh Besar.  Braak formula (1928) in Ritung et al. (2007): T = t°C-(0.61°C × h × 0.01) was employed to estimate air temperature of selected research places.tis average temperature per year (26.63°C), obtained from climate station Malikussaleh, North Aceh. This average temperature was used to forecast the temperature on the research sites. The identification of soil characteristics and its environment such as the elevation, soil depth, drainage, the slopes, the erosion hazard, stoniness and rocks outcrop were carried out at 22 patchouli plantations, 11 plantations in AU (AU1-AU11) and 11 plantations in GL (GL1-GL11). Peat thickness, salinity, alkalinity and sulfidic depth were not assessed due to the land did not show those characteristics. Purposive sampling method was used in the selection of research site. The soil samples were taken from each plantation at a depth 0-30 cm using soil auger kit. All samples (22 samples) were air dried and then sieved using sieve 2 mm (10 mesh) to determine the physical properties of the soil such as soil texture 3 fraction (hydrometer) and the chemical properties such as soil pH (w/s:2.5:1) using pH meter (model WTW 330i/Germany), organic-C (Walkley  and Black), total-N (Kjedahl), level of P₂O₅ (Extract HCl 25%), level of K₂O (Extract HCl 25%), cation exchange capacity-CEC (NH₄OAc pH 7.0) and BS (NH₄OAc pH 7.0) at Assessment Institute for Agricultural Technology (AIAT) Sumatra Utara.
 
Determination of land suitability class
 
The land suitability class was determined by matching the land characteristics of each plantation with the criteria of land suitability which has been modified and required by Rosman et al. (1998) and Ministry of Agriculture (2014). Nutrient retention of BS and total-N are considered as land characteristics influencing the growth and yield of patchouli specifically. Furthermore, the determination of the best land suitability for patchouli refers to land characteristics with the highest growth and yield. The developed criteria of land characteristics for patchouli have considered nutrient retention of BS and total-N as important aspects to be assessed. 

Land characteristics
 
The results showed the differences on elevation, temperature, rainfall and wet season between AU and GL. The plantations are located in lowland and highland (263-869 m asl), where average annual temperature is 25.03°C. AU demonstrated higher temperature (26.46°C) compared to GL (21.33°C), rainfall rate in AU is lower (1490.3 mm) compared to GL (1809.3 mm). Also, the wet season in AU is lower (8 months) compared to GL (11 months). However, both plantations have well to moderate drainage, dominated by sandy loam. Its soil depths are varied (40-90 cm). The shallowest (40 cm) was found in plantation AU9, AU10 and GL7, where this condition was found to be a constraint. Chemical, physical and biological properties in soil are important for plant growth, oxygen and nutrients availability (Fadlalla and Elsheikh, 2016; Meena et al., 2016).

CEC value varied between 4.55-30.99 cmol (+)/kg, where the lowest found in AU 3 and the highest in AU1. Base saturation was between 23.55-332.75%, which the lowest found in GL8 and the highest in AU3. pH valued between 4.70-8.13, the lowest in GL8 and the highest in AU3. Organic-C was between 0.94-5.47%, where the lowest in AU3 and the highest in AU1. N, P, K elements also varied.  N element was 0.06-0.50%, where the lowest found in AU2 and the highest in AU1. P element was 4.02-33.86 ppm, where the lowest found in GL9 and the highest in GL3. K element was 0.25-1.86 me/100g, the lowest found in AU3 and the highest in AU6.  The variety of characteristics found in the study site was influenced by parent material, low organic matter and intensive cultivation (Soares et al., 2005; Parikh and James, 2012). The slopes were between 5.24-16.73%, the minimum in AU1, AU5, GL1 and GL2 and the maximum in GL10. Stoniness <7% in AU2 and outcrop rocks 3% in AU9, AU10 and GL6.
 
Classification of land suitability
 
In this study, we classified land suitability through examining the data collected and modifying the established land suitability by Rosman et al., (1998) and Ministry of Agriculture (2014). The results were presented in Table 1, showing the land classes were marginally suitable (S3) and not suitable (N). S3 class demonstrated several limiting factors such as altitude, erosion hazard, temperature, water availability, root media and nutrient retention, while N class possessed erosion hazard, root media and nutrient retention as its limiting factors. In AU, patchouli planted at S3 class experienced slope, rainfall, organic-C, pH and CEC, while at N class, the plants experienced slope, soil depth and pH. 



In GL, S3 class exhibited several limiting factors such as altitude, temperature, slope and organic-C, while N class demonstrated similar condition shown in AU. Altitude, temperature and soil depth are un-improvable. Soil slopes in AU and GL have been improved through applying soil conservation by building silt pits and mounds and planting avocado. Therefore, the N classes in GL possessed with slope did not affect the patchouli growth and yield. Similar phenomenon also occurs in S3 classes in AU and GL where at slope <25% there is possibility to cultivate crops as the conservation applied properly to support the plant growth (Chen et al., 2020).

CEC and organic-C in S3 class in study sites observed were improved by applying organic matter. However, it needs to be increased and continued to optimize the organic matter in the soil. Organic matter significantly improves the soil’s capacity to store and supply essential nutrients and carbon and also it enhances CEC and water infiltration (Havlin et al., 2013).
 
Value of land characteristics for patchouli plantation
 
The growth, production and the quality of patchouli oil were determined by the value of land characteristics for patchouli (Table 2), where the best and highest growth, production and quality of patchouli oil were often found in lands with distinctive characteristics. The land characteristics and values were presented in Table 3.





Data in Table 4 presented the best land characteristics required for patchouli in AU and GL. Each characteristic was classified into S1, S2 and S3 classes. The land in S3 class was characterized by its rainfall 1490.3 mm which found AU plantations, where it is possible to be improved by irrigation, silt pits forming, bio-pores and retention basin to maximize water availability in the soil. The water is essential for nutrient absorption, biota activities and plant physiology (Razaq et al., 2017; Weih et al., 2018). The organic-C 1.58% found in GL1 also has been fixed by the provision of organic matter in the soil, resulting in an increased yield from 316 kg/ha/year to 375 kg/ha/year. Organic-C is also crucial for enhancing soil properties, attributed to soil fertility and productivity (Jacoby et al., 2017; Johns, 2017; Elayaraja and Sathiyamurthi, 2020).
 
Recommendation of criteria of land characteristics requirement for patchouli plantation
 
We were trying to enhance the land characteristics required for patchouli plantation, where these indicators were a modification from land suitability requirement released by Rosman et al., (1998) and Ministry of Agriculture (2014) with adjusting several suitable characteristics such as altitude, temperature, wet season, drainage, soil texture and formation, soil depth, CEC, pH and organic-C. We also considered BS, total-N, the erosion hazard, stoniness and rock outcrops to be assessed.

The modified and improved land characteristic requirements for patchouli was revealed in Table 4, where the requirements have been appointed based on this  research in the sites, the correlation between land characteristics and patchouli growth and yield (Table 5) and also the evaluation of soil fertility at the plantation. The land characteristics we assessed from each land suitability class attributed to the growth and yield of patchouli.

The elevation and climate varied with plantations and showed differences between the plantations AU and GL, where patchouli has been grown in highlands (>700 m asl) in GL. That contributed to differences in land characteristics and AU and GL.

Land suitability in AU and GL was classified into S3 (marginally suitable) and N (not suitable).  N class was found at AU6, AU9 and AU10, while in GL was found at GL3, GL7, GL8, GL9 dan GL10. The plantations with maximum slope (GL8, GL9 and GL10) have been upgraded using conservation technology, while in AU (AU9 and AU10), its soil depth was unfixable. The pH value in GL3 has been lowered through application of organic matter. 

The best criteria and land indicators in Aceh were laid between S1-S3 classes with implementation of land improvements. However, this study offers scope for further improvements by adding base saturation, total-N, the erosion hazard, stoniness and rockoutcrops as essential land characteristics to ensure higher production of patchouli oil.