Linear Macropore Installation to Reduce Red-Soil Erosion in Sugarcane Fields

Journal of Soil Science and Plant Nutrition (2023) 23:4572–4582 https://doi.org/10.1007/s42729-023-01373-6 ORIGINAL PAPER Linear Macropore Installation to Reduce Red‑Soil Erosion in Sugarcane Fields Eisei Morioka1 · Thanh Long Bui1 · Yasushi Mori1 · Kazutoshi Osawa2 · Akira Hoshikawa3 Received: 30 August 2022 / Accepted: 23 June 2023 / Published online: 5 July 2023 © The Author(s) 2023 Abstract This study determines the cause of soil erosion in red soils in sugarcane fields, especially even with the use of subsoiling fissures, and to compare the effectiveness of a novel artificial linear-macropore with the insertion of fibrous material into the fractures. Four column treatments (tillage, subsoiling, linear-macropore with plant residue fillings, and no-tillage-withmulching) were established. A subsoiler was used to break up hard soil layers to enhance infiltration, whereas mulching reduced the impact of raindrops on the soil. Sugarcane residue was inserted in the empty fissure to reinforce the structure, making linear macropore. Simulated rainfall with 20 m mh−1 was applied to the soil surface for 6 h per day for two days. Surface runoff, soil erosion, and drainage were measured during each run. Erosion was minimal (1/7 reduction), and bottom drainage was observed in the linear-macropore and no-tillage-with-mulching plots. Conversely, due to the formation of an impermeable layer or surface crust, high erosion (0.282 t-C ha−1 yr−1) and decreased drainage levels were detected in the subsoiling and tillage plots. Moreover, the aboveground protrusion of fibrous material at the linear-macropore maintained infiltration, even following crust formation. Field application of these four management strategies revealed the effectiveness of linear-macropore and mulching in reducing surface flow. Linear-macropore application maintains appropriate levels of infiltration, and insertion of plant residue fillings reinforces the macropore structure while also avoiding clogging. Hence, the linear-macropore scheme may represent an effective strategy for reducing surface runoff and red soil erosion. Keywords Soil erosion · Surface runoff · Macropore · No-tillage · Sugarcane 1 Introduction In the Okinawa region of Japan, which is located in the subtropical zone, red soil runoff causes loss of nutrient-rich topsoil, leading to reduced agricultural productivity. Agricultural surface soils contain a large amount of organic matter, while soil erosion, which occurs with surface flow, also significantly disrupts the terrestrial carbon budget (Wang et al. 2017). In addition, tropical soils are inherently vulnerable to organic matter loss due to rapid weathering and * Yasushi Mori 1 Graduate School of Environmental and Life Science, Okayama University, 3‑1‑1 Tsushimanaka, Okayama 700‑8530, Japan 2 School of Agriculture, Utsunomiya University, 350 Minemachi, Utsunomiya 321‑8505, Japan 3 Sekiseishouko Coral Reef Fund, 221 Ishigaki, Ishigaki 907‑0023, Japan 13 Vol:.(1234567890) thin organic matter layers caused by intense solar radiation and poor land management (Guillaume et al. 2015). Under these conditions, the impact of soil erosion due to heavy rainfall is likely significant (Lal 2001). The eroded topsoil is then transported into the ocean, adversely affecting coral reef ecosystems, which require clear, nutrient-poor waters to grow (Ikeda and Kan 2014). Agricultural land is responsible for most of the erosion of red soil (Nakasone et al. 1998). During the early stages of cropping, a significant proportion of agricultural land is bare, thus highlighting the need for improved measures to reduce surface runoff and soil erosion. There are several measures that can be taken to prevent soil erosion as part of agricultural practices. For instance, mulching with sugarcane residue and no-till farming effectively reduce red soil erosion (Noda et al. 2009; Osawa et al. 2005; Tebrügge and Düring 1999). In no-till farming, sugarcane residue acts as a mulch to mitigate the effects of raindrops, thereby preventing red soil erosion. In fact, no-till cultivation techniques are becoming increasingly popular globally, as means to reduce soil movement toward Journal of Soil Science and Plant Nutrition (2023) 23:4572–4582 lower elevation (Komissarov and Klik 2020), reduce soil compaction by heavy machinery (Richard et al. 2001), reduce global warming (Yagioka et al. 2015), and increase biological diversity (Miura et al. 2016). In contrast, tilling destroys soil aggregates, increases contact with oxygen, and tends to accelerate organic matter decomposition (Six et al. 2000). Although the application of no-tillage has gradually increased within the Okinawa region, yields have continued to decrease in semi-humid and humid areas (Kanazawa 1995). Moreover, the aversion of farmers to landscapes with plant residues and weeds has limited the application of notill farming. To avoid soil erosion while mitigating the current reduction in revenue and landscape degradation, the primary research focus has shifted toward investigating subsoil crushing management, which can be accomplished with machinery and does not negatively impact the landscape. More specifically, this strategy improves permeability by crushing hard soil layers to create fissure-like gaps and is a management technique described in the sugarcane cultivation guidelines (Okinawa Prefecture 2014). However, it is unclear how long this technique, developed in the temperate zones, will remain effective when exposed to the heavy rainfall unique to subtropical regions. In particular, within the subtropical climate of the Okinawa region, subsoiler treatments that create vertical fissures may initially prove effective; however, the intense rainfall and the typhoons passing through the subtropical zone may ultimately cause erosion, resulting in small particles clogging subsoil cracks. Accordingly, we have adopted an artificial macropore system to address red soil erosion. Artificial macropores are constructed to mimic the structural characteristics of root pores in natural soils (Mori et al. 1999a, b) while also promoting vertical infiltration and horizontal diffusion (Mori and Higashi 2009; Mori et al. 2013). Solute transport through artificial macropores has been investigated numerically (Lamy et al. 2009) and experimentally (Gjettermann et al. 2004), and this preferential flow enhanced salt leaching in the arid area (Zhang et al. 2021). In previous studies, artificial macropores—cylindrical pores filled with fibrous material—were introduced to the soil (Mori and Hirai 2014; Mori et al. 2014). As empty macropores are prone to collapse and clogging, fibrous materials are inserted to reinforce the structure and induce water flow through capillary forces (Mori and Hirai 2014). Application of this process has successfully enhanced infiltration, increased the soil organic matter content, and nearly doubled plant biomass production at a faster rate than expected (...truncated)