溶磷菌溶磷效率特性之評估

Abstract

磷肥常為影響作物產量的重要因子之一，作物接種溶磷菌常作為提高作物磷吸收的策略，故商品化的溶磷菌肥料已因應市場而產生。本研究計畫目的在於評估本研究主要探討培養基種類對溶磷菌溶磷活性和有機酸分泌的影響，並評估4 種市售溶磷菌肥料對促進莧菜生長和磷吸收的效應。本研究使用12 株菌株和4 種溶磷培養基，培養基包含AFS3183-1 培養基 (蔗糖或葡萄糖)、NBRIP 及Pikovskaya’s medium (PVK)，以評估培養基對溶磷活性、培養基pH、菌數落和有機酸分泌量的影響。盆栽試驗使用鹼性和酸性土壤，鹼性土壤施用之商品化溶磷菌肥料為PSB2 和PSB3，酸性土壤施用之溶磷菌肥料為PSB1 和PSB4，分別探討溶磷菌肥料對莧菜生長和磷吸收的影響。結果顯示，培養基種類顯著影響溶磷菌之溶磷活性，供試菌株中以Pseudomonas grimontii CHB 1107 之溶磷活性為最高，其培養於AFS3183-1 以葡萄糖為碳源之溶磷活性達 7946 g/mL/day。整體而言，溶磷菌培養於PVK 培養基之溶磷活性顯著高於培養於其他培養基者，其可能由於PVK 培養基所含的養分較高有關，且僅此培養基含酵母抽出物。培養基之pH 與溶磷活性呈顯著負相關 (r = -0.75, P < 0.0001)，顯示酸性環境有助於培養基中磷酸三鈣之溶解。培養基種類顯著影響溶磷菌菌株分泌有機酸的種類和濃度，供試菌株分泌之有機酸濃度以2-ketogluconic acid、gluconic acid 及pyruvic acid 為較高，且溶磷菌分泌此三種酸的濃度與溶磷活性呈顯著負相關，其中2-ketogluconic acid 有最高之相關係數達 0.66。盆栽試驗顯示，半量化學肥料+PSB3 和半量化學肥料+ 滅菌PSB3 之莧菜植株乾重顯著高於半量化學肥料者達125-140%。然而，等量PSB3 化學肥料處理之植株乾重顯著高於半量化學肥料者達83.6%，顯示該溶磷菌肥料中所含養分的效應遠大於溶磷菌本身促進植株生長之效應。相反的，半量化學肥料 +PSB2和半量化學肥料+滅菌之PSB2並未顯著促進植株生長。半量化學肥料+PSB3 處理和半量化學肥料+滅菌PSB3 處理之植株磷吸收量顯著高於半量化學肥料者達 54.8-73.9%，但等量PSB3 化學肥料處理之植株磷吸收量亦顯著高於半量化學肥料者達 41.0%，顯示該溶磷菌肥料中所含的磷肥可能為顯著增加植株磷吸收量之主要原因。然而，半量化學肥料+PSB2 處理之植株磷吸收量顯著高於半量化學肥料+ 滅菌之PSB2 達 38.0%，顯示此溶磷菌肥料可顯著增加植株磷吸收量。與半量化學肥料相較，酸性土壤施用半量化學肥料+PSB1 或半量化學肥料+PSB4 皆顯著降低莧菜植株乾重。此外，酸性土壤施用半量化學肥料+PSB1 或半量化學肥料+PSB4 皆未能顯著增加磷吸收量，顯示酸性土壤施用溶磷菌肥料促進莧菜生長和磷吸收之效益較低。培養基種類影響溶磷菌之溶磷活性分析，商品化溶磷菌功效不ㄧ，而原料中養分含量可能顯著影響其肥功效。 Phosphate fertilization is an important factor to influence crop yields. It has been suggested that inoculation of crops with phosphate-solubilizing bacteria (PSB) can enhance phosphate uptake, and thus commercialized products of PSB are increasingly available for growers. The purposes of this study were to evaluate the effects of culture media on phosphate-solubilizing activity and organic acids produced and to determine the efficiency of four commercial phosphate-solubilizing (PS) biofertilziers. Twelve PSB strains and four culture media including AFS3183-1 (glucose or sucrose as sole carbon source), NBRIP, and Pikovskaya’s medium (PVK) were used to evaluate their effects on PS activity, medium pH, PSB colonies, and organic acids secreted by PSB. In order to evaluate the effect of four commercial PS biofertilizers on the growth and P uptake of amaranth plants (Amaranthus mangostanus L.), commercial PSB2 and PSB3 were applied into an alkaline soil and the other two commercial PSB1 and PSB1 were used in an acid soil. Culture media significantly affected phosphate-solubilizing activities of PSB, and Pseudomonas grimontii CHB 1107 showed a significantly high level of PS activity up to 7946 µg/mL/day. In general, PSB cultured in PVK resulted in a higher level of PS activity partly because of this medium containing yeast extract. There was a significantly negative correlation between medium pH and PS activity (r =-0.75, P < 0.0001), suggesting acidic conditions helpful for solubilizing tricalcium phosphate. In addition, culture media significantly affected the concentration of organic acids secreted by PSB. Of these organic acids, the concentration of 2-ketogluconic acid, gluconic acid, and pyruvic acid were the highest. PS activity was significantly correlated with the concentration of these three organic acids, with the highest Pearson correlation coefficient of -0.66 for 2-ketogluconic acid. Compared with half the recommended rate of chemical fertilizers, the alkaline soil applied with half the recommended rate of chemical fertilizers with non-sterilized or sterilized PSB3 resulted in a significant increase in dry weight by 125-140%. However, the chemical fertilizer treatment equal to the nutrient content in PSB3 also significantly increased dry weight by 83.6%, suggesting that the nutrients rather than PSB in PSB3 might significantly improve amaranth growth. In contrast, half the recommended rate of chemical fertilizers with non-sterilized or sterilized PSB2 did not significantly improve amaranth growth. The alkaline soil applied with half the recommended rate of chemical fertilizers with non-sterilized or sterilized PSB3 significantly increased P uptake of amaranth by 54.8-73.9% in comparison with half the recommended rate alone. However, the chemical fertilizer treatment equal to the nutrient content in PSB3 also significantly increased P uptake of amaranth up to 41.0%, suggesting that phosphate fertilization rather than PSB in PSB3 might significantly increase P uptake of amaranth. Conversely, half the recommended rate of chemical fertilizers with non-sterilized PSB2 significantly increased P uptake of amaranth by 38.0% compared to half the recommended rate with sterilized PSB2, suggesting that PSB in PSB2 could improve P uptake by amaranth roots. Compared with half the recommended rate of chemical fertilizers alone, the acid soil applied with half the recommended rate of chemical fertilizers with non-sterilized PSB1 or PSB4 significantly reduced dry weight of amaranth and did not increase P uptake of amaranth, suggesting a low efficiency of PSB in the acid soil. In conclusion, media used for culturing PSB affect PS activity, and commercial PSB vary in improving P uptake and plant growth. Moreover, the nutrients in these commercial biofertilizers may considerably affect nutrient uptake and growth of plants.