Abstract:Abstract. Effects of oil-palm (Elaeis guineensis Jacq.) management on silicon (Si) cycling under smallholder oil-palm plantations have hardly been investigated. As oil palms are Si accumulators, we hypothesized that management practices and topsoil erosion may cause Si losses and changes in spatial Si concentration patterns in topsoils under oil-palm cultivation. To test this hypothesis, we took topsoil samples under mature oil-palm plantations in well-drained and riparian areas of Jambi Province, Indonesia. T… Show more
“…Thus, the majority of biomass-bound Si returns to soil under frond piles, where phytoliths are released upon litter decomposition Greenshields et al, 2023). Additional disturbances of Si cycling may be caused by fruit harvest and topsoil erosion, which can both lead to Si export from the system .…”
Section: Approach and Thesis Structurementioning
confidence: 99%
“…Old palm fronds are cut off and stacked in every second row, called "interrow". The remaining "empty" interrows are used as paths for oil-palm pruning, herbicide application, and fruit-bunch harvesting Greenshields et al, 2023). Herbicides (e.g., glyphosate) are commonly sprayed every six months to clear understory vegetation in the interrows and NPK fertilizers are applied within the palm circle , i.e., the immediate circulate area (~ 2 m radius) surrounding the palm stem .…”
Section: Sampling Schemementioning
confidence: 99%
“…(2022) and Greenshields et al (2023). Vander Linden and Delvaux (2019) identified soil Si pools associated to topsoils (mainly phytogenic Si) as important soil Si pools in rainforest biomes.…”
Section: Soil Sim Siad and Siorg Stocks Per Hectare And Depth Distrib...mentioning
confidence: 99%
“…Vander Linden and Delvaux (2019) identified soil Si pools associated to topsoils (mainly phytogenic Si) as important soil Si pools in rainforest biomes. In oilpalm plantations, on the other hand, von der Lühe et al ( 2022) and Greenshields et al (2023) found litter return and decomposition to be largely restricted to frond piles areas, which may make up as little as 15 % of a plantation . This is a crucial finding because the decomposition of palm fronds provides most plant-available Si to soils under oil-palm plantations.…”
Section: Soil Sim Siad and Siorg Stocks Per Hectare And Depth Distrib...mentioning
confidence: 99%
“…This is a crucial finding because the decomposition of palm fronds provides most plant-available Si to soils under oil-palm plantations. Litter return on oil-palm plantations is additionally restricted because interrows are commonly kept free of vegetation, which prevents litter production, promotes topsoil erosion and promotes Si leaching from soils Greenshields et al, 2023).…”
Section: Soil Sim Siad and Siorg Stocks Per Hectare And Depth Distrib...mentioning
Barbara von der Lühe for supervising my doctoral thesis and for trusting me as a geologist, to research in tropical soil science. I really enjoyed the practical teachings in the field and laboratory, learning about soils and interacting environmental processes. Special thanks to Dr. Barbara von der Lühe for her continuous support and open discussions about the research work. My thanks also go to my thesis referees, Prof. Dr. Daniela Sauer and Prof. em. Dr. Gerhard Gerold, as well as my thesis advisory committee, Prof. Dr. Daniela Sauer, Dr. Barbara von der Lühe and Dr. Marife Corre for providing guidance throughout the PhD. My sincere thanks to Prof.
“…Thus, the majority of biomass-bound Si returns to soil under frond piles, where phytoliths are released upon litter decomposition Greenshields et al, 2023). Additional disturbances of Si cycling may be caused by fruit harvest and topsoil erosion, which can both lead to Si export from the system .…”
Section: Approach and Thesis Structurementioning
confidence: 99%
“…Old palm fronds are cut off and stacked in every second row, called "interrow". The remaining "empty" interrows are used as paths for oil-palm pruning, herbicide application, and fruit-bunch harvesting Greenshields et al, 2023). Herbicides (e.g., glyphosate) are commonly sprayed every six months to clear understory vegetation in the interrows and NPK fertilizers are applied within the palm circle , i.e., the immediate circulate area (~ 2 m radius) surrounding the palm stem .…”
Section: Sampling Schemementioning
confidence: 99%
“…(2022) and Greenshields et al (2023). Vander Linden and Delvaux (2019) identified soil Si pools associated to topsoils (mainly phytogenic Si) as important soil Si pools in rainforest biomes.…”
Section: Soil Sim Siad and Siorg Stocks Per Hectare And Depth Distrib...mentioning
confidence: 99%
“…Vander Linden and Delvaux (2019) identified soil Si pools associated to topsoils (mainly phytogenic Si) as important soil Si pools in rainforest biomes. In oilpalm plantations, on the other hand, von der Lühe et al ( 2022) and Greenshields et al (2023) found litter return and decomposition to be largely restricted to frond piles areas, which may make up as little as 15 % of a plantation . This is a crucial finding because the decomposition of palm fronds provides most plant-available Si to soils under oil-palm plantations.…”
Section: Soil Sim Siad and Siorg Stocks Per Hectare And Depth Distrib...mentioning
confidence: 99%
“…This is a crucial finding because the decomposition of palm fronds provides most plant-available Si to soils under oil-palm plantations. Litter return on oil-palm plantations is additionally restricted because interrows are commonly kept free of vegetation, which prevents litter production, promotes topsoil erosion and promotes Si leaching from soils Greenshields et al, 2023).…”
Section: Soil Sim Siad and Siorg Stocks Per Hectare And Depth Distrib...mentioning
Barbara von der Lühe for supervising my doctoral thesis and for trusting me as a geologist, to research in tropical soil science. I really enjoyed the practical teachings in the field and laboratory, learning about soils and interacting environmental processes. Special thanks to Dr. Barbara von der Lühe for her continuous support and open discussions about the research work. My thanks also go to my thesis referees, Prof. Dr. Daniela Sauer and Prof. em. Dr. Gerhard Gerold, as well as my thesis advisory committee, Prof. Dr. Daniela Sauer, Dr. Barbara von der Lühe and Dr. Marife Corre for providing guidance throughout the PhD. My sincere thanks to Prof.
Potential effects of land-use/land-cover (LULC) transformation from lowland rainforest into oil-palm plantations on silicon (Si) pools in tropical soils remain poorly understood, although appropriate levels of plant-available Si in soils may contribute to maintain high crop yields and increase the vitality and drought resistance of oil palms. Therefore, the aim of our study was to identify possible effects of such LULC change on soil Si pools. For this purpose, we compared soil Si pools under lowland rainforest and ca. 20 year-old oil-palm plantations in Jambi Province, Indonesia. The investigated soils were Acrisols and Stagnosols, in which we quantified six different soil Si pools following a sequential extraction procedure to evaluate, whether 20 years of oil-palm cultivation has led to a depletion of these soil Si pools. The considered pools included mobile Si, adsorbed Si, Si bound in soil organic matter (SOM), Si included in pedogenic oxides and hydroxides, and Si in amorphous silica of biogenic and pedogenic origin. Finally, we also determined total Si. All oil-palm plantations established on sloping terrain and Acrisols only showed decreased Si stocks of mobile Si, adsorbed Si and SOM-bound Si; those established in floodplains and Stagnosols had decreased stocks of SOM-bound Si and biogenic-amorphous silica. Lower Si stocks were mostly attributed to a missing “stable” phytolith pool in the subsoil and less organic matter in topsoils under oil-palm plantations. When comparing well-drained and riparian areas, flooding seemed to increase phytolith dissolution. We conclude that 20 years of oil-palm cultivation has not yet led to a significant depletion of soil Si pools. As topsoils comprise the highest concentrations of SOM-bound Si and Si in amorphous silica of biogenic origin but are susceptible to erosion and surface runoff under managed oil-palm plantations, it would be advisable to instate specific management practices that maintain organic-rich and well-aired topsoils on oil-palm plantations.
Abstract. Most plant-available Si in strongly desilicated soils is provided through litter decomposition and subsequent phytolith dissolution. The
importance of silicon (Si) cycling in tropical soil–plant systems raised the question of whether oil-palm (Elaeis guineensis Jacq.) cultivation alters Si cycling. As oil palms are considered Si hyper-accumulators, we hypothesized that much Si is stored in the
above-ground biomass of oil palms with time. Furthermore, the system might lose considerable amounts of Si every year through fruit-bunch harvest. To
test these hypotheses, we analysed Si concentrations in fruit-bunch stalks,
fruit pulp and kernels, leaflets, rachises, and frond bases of mature oil palms on eight smallholder oil-palm plantations in Sumatra,
Indonesia. We estimated Si storage in the total above-ground biomass of oil palms, Si return to soils through decomposing pruned palm fronds, and Si
losses from the system through harvest. Leaflets of oil-palm fronds had a
mean Si concentration of > 1 wt %. All other analysed plant parts had < 0.5 wt % Si. According to our estimates, a single
palm tree stored about 4–5 kg Si in its total above-ground biomass. A smallholder oil-palm plantation stored at least 550 kg Si ha−1 in the
palm trees' above-ground biomass. Pruned palm fronds returned 111–131 kg of Si ha−1 to topsoils each year. Fruit-bunch harvest corresponded to
an annual Si export of 32–72 kg Si ha−1 in 2015 and 2018. Greater
Si losses (of at least 550 kg Si ha−1) would occur from the system if
oil-palm stems were removed from plantations prior to replanting. Therefore,
it is advisable to leave oil-palm stems on the plantations, e.g. by distributing chipped stem parts across the plantation at the end of a
plantation cycle (∼ 25 years).
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