椰纖介質搭配蝦蟹殼粉對草莓生長及炭疽病發生之影響

Abstract

草莓是臺灣的高經濟價值作物之一，主要產區在苗栗縣。在臺灣，草莓的耕作週期分為育苗期和本田期，而本田期除了傳統土壤栽培之外，有些農民會以高架栽培方式進行。高架栽培時，常使用介質進行種植，而椰纖 (coir pith) 是目前被使用較多的種類。然而，椰纖在製造過程中可能殘留鹽類和化學藥劑，加上椰纖微生物含量或豐度較低且化學緩衝能力弱等缺點，可能會影響草莓產量。此外，近年來臺灣草莓耕地逐年上升，但產量卻不升反降，病蟲害是原因之一，全球暖化更加劇此劣勢。幾丁質 (chitin) 作為良好的土壤改良劑，在過去研究發現除了能改善土壤性質之外，還能夠促進植物生長、提升土壤中有益微生物相對豐度以及作為微生物相關分子模式 (Microbe-Associated Molecular Patterns; MAMP) 誘發植物先天性免疫反應，因此含大量幾丁質的農業廢棄物—蝦蟹殼粉應用於農業的潛力與優勢極高。為了優化作為栽培草莓介質的椰纖，甚至賦予其提高草莓耐受重要病害—炭疽病的功能，本研究首先調整清洗椰纖方式來解決鹽類殘留問題，考慮到用水量及效果後發現，以清水：椰纖=15：1 (w/w) 泡發椰纖後再以等量水清洗的效果佳，可使電導度降至0.32 dS m-1。再以特定比例混合常用於草莓栽植的椰纖及培養土，發現以椰纖：培養土=3：1 (v/v) 種植的草莓，其第三葉葉面積及生物量顯著高於其他處理組，從土壤化學、土壤養分、土壤微生物以及介質再利用可能性等來考量，認為此混合比例為佳。在此基礎上，添加 0.1、0.5 及 1.0 % (w/w) 蝦蟹殼粉，結果顯示1.0 % 蝦蟹殼粉可使栽培介質中的有效無機氮顯著提升、促進草莓生長並抑制炭疽病發生嚴重度。雖然過氧化氫酶、超氧化物歧化酶和過氧化物酶等抗氧化酵素活性在接種炭疽病後，有無處理蝦蟹殼粉的植株並無顯著差異；但 3,3’-二氨基二丙胺染色後可觀察到處理蝦蟹殼粉的植株葉片中 H2O2 的累積較低。綜上所述，本研究結果不僅可提出清洗椰纖的建議步驟及用水量，也發現於椰纖中添加適量培養土能改善其化學性質、營養元素及微生物含量；在此基準上，搭配蝦蟹殼粉作為土壤改良劑，除了可更加促進草莓生長外，還可降低炭疽病發病情形。未來期望能將此栽培管理方式推薦給草莓農民，以害物整合管理的概念有效地降低化學肥料及化學農藥的使用量。

Strawberry is one of the high-value cash crops in Taiwan, with the main production area in Miaoli County. In Taiwan, strawberry cultivation goes through nursery and main production stages. In addition to growing strawberry seedlings directly in the soil, more and more farmers choose raised beds for strawberry production. Growing media are usually used for raised-bed farming, with coir pith being the primary choice for farmers. However, the residual salts and chemicals from the production process, the low microbial content or abundance, and the weak chemical buffer capacity may abate the quality of coir pith, causing a decline in strawberry production. Recently, strawberry farming areas in Taiwan have been increasing, but strawberry production is declining yearly due to pests and diseases, and global warming worsens such negative aspects. As an excellent soil amendment, chitin has been shown in previous studies to promote plant growth, enhance the relative abundance of beneficial soil microorganisms, and act as a microbe-associated molecular pattern (MAMP) to induce innate immunity in plants. As a result, shrimp and crab shell powder (SCSP), an organic waste containing abundant chitin, is of great potential and advantage for application in agriculture. In order to improve the quality of coir pith as a growing medium for strawberry production and even grant it the ability to enhance resistance to anthracnose, one of the major strawberry diseases, this study first aimed to solve the problem of residual salt in coir pith by adjusting the washing steps. Considering water usage and effectiveness, the coir pith soaked in water at a ratio of 15:1 (water: coir pith; w/w) and then washed again with the same amount of water performed well, reducing the electrical conductivity to 0.3 dS m-1. Next, two well-known materials for strawberry cultivation, potting soil, and coir pith, were mixed in designated proportions, and the results indicated that coir pith-to-soil at a ratio of 3:1 (v/v) significantly increased the third leaf area and biomass of strawberries compared with the other treatment groups. Based on the chemical, nutrient, and microbial analyses of the growing media and the potential for reuse, the growing medium composed of three parts of coir pith and one part of potting soil is more effective. Then, SCSP was supplemented in the growing media at 0.1, 0.5, and 1.0% (w/w). The results showed that the growing medium containing 1.0% SCSP significantly increased available nitrogen in the medium, promoted strawberry growth, and suppressed disease severity of strawberry anthracnose disease. Although there was no difference in the activities of antioxidant enzymes, including catalase (CAT), superoxide dismutase (SOD), and peroxidase (POD) between treatments with and without SCSP supplement, the 3,3’-diaminobenzidine (DAB) staining revealed that H2O2 accumulation was lower in the leaves from plants raised in growing media with SCSP. In conclusion, this study provides recommended steps and water usage for washing coir pith and identifies that the chemical properties, nutrient, and microbial abundance of coir pith can be improved by amending the proper proportion of potting soil. Based on this, supplementing SCSP as soil amendment could further promote strawberry growth and reduce the severity of strawberry anthracnose. In the future, the culture strategy developed in this study could benefit strawberry farmers by reducing the use of chemical fertilizers and pesticides more effectively using integrated pest management.