Ascorbic Acid, Sugars, Phenols, and Nitrates Concentrations in Tomato Grown in Animal Manure Amended Soil

Abstract

We studied the impact of animal manure that was mixed with biochar (a product of wood pyrolysis) on the nitrates (NO−3), vitamin C, total phenols, and soluble sugars concentrations in tomato fruits (Solanum lycopersicum var. Marglobe) of plants that were grown in raised plastic-mulch of freshly tilled soils. Sewage sludge (SS), horse manure (HM), chicken manure (CM), vermicompost (worm castings), commercial inorganic fertilizer, commercial organic fertilizer, and bare soil used for comparison purposes were the soil amendments. Each of the seven treatments was mixed with 10% (w/w) biochar to make a total of 42 treatments. Chemical analysis of mature tomato fruits revealed that the fruits of plants grown in SS amended soil contained the greatest concentration of NO−3 (17.2 µg g−1 fresh fruits), whereas those that were grown in SS biochar amended soils contained the lowest concentrations of nitrate (5.6 µg g−1 fresh fruits) compared to other soil treatments. SS that was amended with biochar increased vitamin C and total phenols in tomato (22 and 27 µg g−1 fresh fruits, respectively) when compared to SS alone (11µg g−1 fresh fruits). Growers and scientists are seeking strategies to increase antioxidants and reduce anti-nutritional compounds, like nitrates in food, while recycling animal waste. The results of this investigation revealed the role of biochar in reducing nitrates and optimizing the nutritional composition of tomato.