Differences in Root Nitrogen Uptake Between Tropical Lowland Rainforests and Oil Palm Plantations

Abstract

Conversion of lowland tropical rainforests to intensely fertilized agricultural land-use systems such as oil palm (Elaeis guineensis) plantations leads to changes in nitrogen (N) cycling. Although soil microbial-driven N dynamics has been largely studied, the role of the plant as a major component in N uptake has rarely been considered. We address this gap by comparing the root N contents and uptake in lowland rainforests with that in oil palm plantations on Sumatra, Indonesia. To this aim, we applied 15 N-labeled ammonium to intact soil, measured the 15 N recovery in soil and roots, and calculated the root relative N uptake efficiency for 10 days after label application. We found that root N contents were by one third higher in the rainforest than oil palm plantations. However, 15 N uptake efficiency was similar in the two systems. This finding suggests that lower N contents in oil palm roots were likely caused by plant internal utilization of the absorbed N (e.g., N export to fruit bunches) than by lower ability to take up N from the soil. 15 N recovery in roots was primarily driven by the amount of root biomass, which was higher in oil palm plantation than rainforest. The oil palms unveiled a high capacity to acquire N, offering the possibility of enhancing sustainable plantation management by reducing N fertilizer application.

Soil physicochemical properties change by age of the oil palm crop

“…Another study revealed that when was evaluated the N application and N uptake e ciency in oil palm crop versus a tropical forest, the root N content was onethird higher in the tropical forest compared with oil palm plantations. Nevertheless, the absorption e ciency was similar in both systems (Edy et al, 2020). Both in our results and in those discussed previously suggest that the decrease in the content of the elements in the soil is due to the need for absorption or use required by the oil palm for the formation of clusters of fresh fruits (Edy et al, 2020;Manorama et al, 2021).…”

“…Nevertheless, the absorption e ciency was similar in both systems (Edy et al, 2020). Both in our results and in those discussed previously suggest that the decrease in the content of the elements in the soil is due to the need for absorption or use required by the oil palm for the formation of clusters of fresh fruits (Edy et al, 2020;Manorama et al, 2021). In this line, the present experiment showed that higher values of the elements K, Mg, Cu, S, Mn, and Zn are present in 3-year-old plots and the pastures compared to 15-year-old adult plants.…”

Legacy Effects Overshadow Tree Diversity Effects on Soil Fungal Communities in Oil Palm-Enrichment Plantations

“…Therefore, P and N availability are likely limiting factors for soil microorganisms; consequently, tight associations between soil nutrients and community composition occur frequently [27,30,97,98]. However, the shifts in fungal communities are unrelated to root N uptake, which is similar in rainforests to that in oil palm plantations [99].…”

Mulching with pruned fronds promotes the internal soil N cycling and soil fertility in a large-scale oil palm plantation

“…It is important to note that our measured soil N cycling rates represented soil conditions beyond the short-term pulse effects of N-fertilizer application, which generally caused elevated mineral N concentrations for up to six weeks following fertilization (Hassler et al 2017). Thus, the generally comparable soil N cycling rates between the fertilized palm circle and the unfertilized inter-row suggest that excess N from pulse N fertilizer application may have been taken up by the palms (Edy et al 2020), lost via gaseous emissions (Hassler et al 2017), or moved down in the soil profile and eventually leached (Formaglio et al 2020). The low gross N mineralization in the palm circle illustrated the inherently low N-supplying capacity of the soil in this intensively managed area, and illustrated its dependence on chemical fertilizer inputs to maintain palm productivity.…”