Fertilization experiments in post-tin mining area on Bangka Island, Indonesia

Abstract:

The field experiment in a post-tin mining area on Bangka Island was established and has been managed through a collaboration between UGM, local farmer cooperatives, and BOKU since 2018. The experiment is aimed to reclaim severely degraded soil after tin mining for crop production by utilizing locally available soil amendments such as dolomite, compost, charcoal and sawdust to ensure food security. Crops were selected and cultivated in intercropping systems based on co-creation between local farmers and researchers. Crop yields were consistently recorded. Plant and soil samples were collected for laboratory analysis at UGM and BOKU. In 2023, all collaborative partners agreed on amending strategies to enhance soil fertility and crop production. This involved applying inorganic fertilizer to compost-free treatments and dolomite to compost-incorporated treatments. The project results have been disseminated through several peer-reviewed articles and presentations at academic conferences. Various video documentation and online articles about the project are currently accessible to the public and interested audiences online. Furthermore, collaboration between UGM and BOKU in the project includes lab training and knowledge exchange. This has strengthened the institutional capacity in improving soil health, particularly in degraded tropical soil, and promoted research-based learning in both institutions.

Figure 8

The students practically performing ammonium analysis. (photo credit: Orracha Sae-Tun)

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Implementation Period:

01/2024 – 10/2024

Project:

Field experiment to find rehabilitation strategies

In the context of a farmer cooperative (eight families) working on ex-mining land a field experiment has been established since 2018 aiming to identify sustainable strategies for increasing soil fertility. The experiment was established on the coarse quartz-sand remaining after mining which is a substrate barely suitable for crop production in its initial un-amended state (very low cation exchange and water holding capacity). Strategies tested there are pH-regulation by dolomite liming, addition of compost, addition of biochar and a mix of compost + biochar and sawdust + compost, all of these strategies being compared to an untreated control. The materials used in the experiment are locally available to assure their affordability and accessibility to the locals.

On-field activities – February

In December 2023, rice and mung beans were planted in the experimental field as followed intercropping system. According to the results previously observed during the experiment, inorganic nitrogen fertilizer was applied to dolomite and charcoal treatments when planting in this season to additionally supply nitrogen to the soil and expected to promote crop growth.

During a field experiment visit in January-February 2024, Orracha Sae-Tun and Murtiningrum together with the local farmers conducted manual weed control to promote crop growth (Figure 1). Fresh weight of the weeds was also recorded (Figure 2). The weeds were sampled and collected for further laboratory analysis at UGM. The inorganic nitrogen fertilizer was reapplied to the dolomite and the charcoal plots after weeding (Figure 3). It was observed that crops as well as weeds grew better in the plots amended with compost and charcoal-compost combination. However, rice and mung beans in all plots grew more slowly than expected which might be a result of unusual longer dry spell period in the study area. In addition to weed samples, soil samples were collected from nearby rice paddy fields for the training on ammonium nitrogen (NH₄⁺-N) analysis at UGM (Figure 4).

Sample preparation and laboratory work in Indonesia

After finalizing sampling on the field and on-site planning with farmers, samples were taken to the laboratory at UGM in Yogyakarta. Some preliminary evaluations were done there, and for other analysis, samples were prepared for shipping to BOKU. Soil and plant samples will be transported to Austria during the visit of two further UGM researchers in September 2024

Preliminary evaluations at UGM were intended to get first insights into the impacts of the treatments on biomass production and soil status, as well as establish some new analytical methods in the lab at UGM.

At Faculty of Agricultural Technology, UGM, the elementary analyser has been installed in the Food Technology Laboratory with support of BOKU. In July 2023, BOKU team gave an intensive training on carbon and nitrogen analysis using this elementary analyser to the participants and on maintaining the machine to the lab technicians. After the training, the participants prepared the samples and analysed with the elementary analyser. However, there was a leakage of nitrogen gas (N₂), and some signal results were missing.

With the support from BOKU (Orracha Sae-Tun), a valve controlling gas pressure of the elementary analyser was successfully replaced with a new one in February 2024. There was still a problem with systematic signal missing which could be a result of delay time during signal conversion. The lab technicians were involved in every step during this maintenance process, so they were familiar with maintaining and operating the elementary analyser. During the visit of Orracha Sae-Tun (in January-February 2024), she gave a training on carbon and nitrogen analysis for under- and postgraduate students. The training was divided into two sessions: i) refreshing of total carbon and total nitrogen analysis with elementary analyser and ii) ammonium nitrogen analysis (NH₄⁺-N).

Due to an on-going maintenance process at UGM (Figure 5), the training for total carbon and total nitrogen analysis focused on an overview on the analysis background, data calculation, and sample preparation (Figure 6, Figure 7). The participants could thus prepare the soil samples appropriately and could process with the results obtained from the elementary analyser for their future works.

Besides total nitrogen determination, measurement of available nitrogen was necessary to assess soil fertility which is related to crop productivity and soil health. Thus, this training included ammonium nitrogen (NH₄⁺-N) analysis using microplate as it is less laborious, easy to handle and requires small amounts of chemicals and samples. During the training, the participants experienced preparing fresh soil samples (Figure 7), which were collected during the experimental field visit, and conducted the laboratory analysis (Figure 8) as well as result calculation and discussion (Figure 9). Furthermore, colorimetry was introduced to the participants as it is a principle of both ammonium nitrogen (NH₄⁺-N) and ammonium-cation exchange capacity (NH₄⁺-CEC) measurements. Thus, if the participants wish, they can easily conduct ammonium-cation exchange capacity (NH₄⁺-CEC) measurement to determine cation exchange capacity (CEC) for their future works.

On-field activities – July

In July 2024 local farmers together with researchers from UGM (Rizki Maftukhah and Ngadisih) and BOKU (Katharina Keiblinger, Franziska Weinrich, Niklas Bruhn and Rebecca Hood-Nowotny), checked the mung bean performance prior to the harvesting (Figure 10). In the next step mung bean plants were harvested, and shoot and root biomass was weight, and sub-samples put into plastic bags for further analyses (Figure 11). Next, disturbed (Figure 12) and undisturbed (Figure 13) soil samples were taken from the field trial. All the samples were collected in plastic bags to be analysed for further parameters in the lab. Together with the farmers, a discussion on the continuation of the field trial and their motivation was conducted (Figure  14, Figure  15). As the situation has changed since the set-up of the experiment, limited support of external inputs has caused some nearby land to be abandoned. We jointly agreed to continue the activities in an adopted fertilization treatment as designed (Figure 16), together with the growing of chili as a cash crop of high relevance to the farmers. The chili seedlings were prepared by the local community and the researchers on site in small polybags (Figure  17), and covered with banana leaves for germination (Figure 18).

Prior to chili transplanting, compost, lime and fertilizer need to be recovered from the local research station or suppliers, and was weight for each planting hole of the experimental plots.

The activities on Bangka Island also involved meeting with the dean and the vice dean of the Faculty of Agricultural Technology of UGM and the local government, to share our ongoing work and ask for support also for future activities. The support from the local authorities resulted in a continued meeting with the national planning agency just the week after, to work on a joint concept for an excellence of tropical soil health to be implemented on Bangka Island.

Publications from this project

Publication and manuscripts:

• Maftukhah, R; Mentler, A; Ngadisih, N; Murtiningrum, M; Hood-Nowotny, R; Gartner, M; Kral, RM; Ploszczanski, L; Mayer, H; Keiblinger KM (in preparation). In-situ application of local soil amendments to post-tin mining soils – effects on heavy metal concentrations in crops and soils..
• Sae-Tun, O.; Maftukhah, R.; Susanto, S.; Ngadisih, N.; Murtiningrum, M.; Hood-Nowotny, R.; Mentler, A.; Bodner, G.; Keiblinger, K.M. Organic carbon-based amendments effectively reclaim post-tin mining site via modified soil organic carbon characteristics. Plant and Soil 2024. https://doi.org/10.1007/s11104-024-06833-1
• Maftukhah, R. Local amendments to restore soil health and agricultural production in degraded post-mining soils. Doctoral dissertation, 2023, University of Natural Resources and Life Sciences, Vienna.

Conferences (presentation and poster):

• Sae-Tun, O.; Maftukhah, R.; Ngadisih, N.; Murtiningrum, M.; Bodner, G.; Hood-Nowotny, R.; Mentler, A.; Keiblinger, K.M. Local organic soil amendments enhance temporal changes in soil basic properties and crop yield in post-tin mining soils [Tropentag 2024: Explore opportunities… for managing natural resources and a better life for all, September 11 – 13, 2024]. (presentation)
• Keiblinger K, Maftukhah R, Ngadisih, Hood R, Kral R, Murtiningrum, Weinrich F, Rosinger C, Huber S, Sae-Tun O, Bieber M, Bernardini L, Schneider M, Wieser S, Mentler A, Bodner G. Regenerative Agriculture for Soil Health and Environmental Conservation 6th Summer Course Adaptive Technology for Sustainable Agroindustrial Sector in a Reponse to Climate Change, August 7, 2024 (presentation)
• Keiblinger K, Weinrich F, Maftukhah R, Ngadisih, Hood R, Kral R, Murtiningrum, Rosinger C, Huber S, Sae-Tun O, Bieber M, Bernardini L, Schneider M, Wiese S, Mentler A, Bodner G. Modern Agricultural Technology for Soil Management and Environmental Conservation Guest lecture at the Universitas Muhamadiyah Kalimantan Timur July 1, 2024 (presentation)
• Keiblinger K, Maftukhah R, Mentler A, Ngadisih, Hood R, Kral R, Murtiningrum, Bodner G. Local soil amendments for improving soil health and crop yield in degraded post-mining soils; BRA-Award Ceremony during the ASEA Uninet Plenary Meeting 2024, Penang February 2024 (presentation)

Video documentation:

• Post Doctoral Program DTPB UGM 2023 (2023): https://www.youtube.com/watch?v=4N4iT6JdjLA
• Training on Elementary Analyse of Carbon and Nitrogen (2023): https://www.youtube.com/watch?v=S1zBbiJt11w

Others:

• Penelitian Lanjutan Pemanfaatan Lahan Pasca Tambang Timah untuk Pertanian Berkelanjutan di Provinsi Bangka Belitung oleh UGM dan BOKU University (2024): https://tpb.tp.ugm.ac.id/id/2024/08/13/penelitian-lanjutan-pemanfaatan-lahan-pasca-tambang-timah-untuk-pertanian-berkelanjutan-di-provinsi-bangka-belitung-oleh-ugm-dan-boku-university.xhtml (In Indonesian)
• Center of excellence for tropical soil health meeting on the 17^th July 2024 with BAPPENAS (National Planning Agency), BAPPEDA Bangka, UGM, and BOKU.
• Small-scale Circular Agriculture Enterprises for Food Security: Transition with Eco-Innovations in Post Tin Mining Area of Bangka Island – Indonesia Proposal For RIIM International Collaboration on Southeast Asia – Europe Joint Funding Scheme for Research and Innovation in The Thematic Areas of Circular Economy and Clean, Accessible and Secure Energy Supply, by Lilik Sutiarso, Katharina Keiblinger, Rosnah Shsmudin, Sigit Andy Cahyono and Team members from UGM, UPM and BOKU
• Students and technicians from the Department of Agricultural and Biosystem Engineering attend the Maintenance Training for CN Analyzer & Available N Analysis in Soil (2024): https://tpb.tp.ugm.ac.id/en/2024/02/15/students-and-technicians-from-the-department-of-agricultural-and-biosystem-engineering-attend-the-maintenance-training-for-cn-analyzer-available-n-analysis-in-soil.xhtml