عنوان مقاله [English]
Organic fertilizer tea is a treated solution of organic fertilizers that contains a variety of organic compounds, nutrients and a wide range of microorganisms and their metabolites. In recent years production and use of organic tea as a liquid biological fertilizer or biological pesticides is expanding towards sustainable agriculture. There are many benefits to using tea compost, including providing the nutrients for plant which can reduce the use of chemical fertilizers. A variety of organic compounds can be used to make tea. In the preparation of aerobic organic tea, except for the type of organic matter, preparation conditions such as particle size, temperature, aeration time and fertilizer to water ratio can affect the chemical and biological properties of the produced tea (Shaban et al., 2015). In this regard, the present study was conducted to investigate the effect of aeration time and fertilizer to water ratio on some chemical properties of cow manure and vermicompost tea.
Materials and methods
An experiment was conducted based on completely randomized design with factorial arrangement and three replications. The treatments included aeration time (0, 24, 48 and 72 hours), fertilizer to water ratio (1:10, 1:25 and 1:50) and type of organic fertilizer (vermicompost and cow manure). The part passed through a 2 mm sieve and the rest on a 0.5 mm sieve of air-dried cow manure and vermicompost were used to determination of some chemical properties of organic fertilizers and making tea. After preparing the ratios with distilled water, an air pump was used for aeration. Changes in acidity (pH), electrical conductivity, dissolved organic carbon, mineral forms of nitrogen, dissolved phosphorus and potassium in organic fertilizers tea (cow manure and vermicompost) were evaluated.
Results and discussion
The characteristics of the studied organic fertilizers showed that the total amount of nitrogen, phosphorus and potassium in vermicompost was higher than cow manure. According to the results of analysis of variance, among the main effects, the effect of organic matter type on soluble organic carbon, nitrate and the effect of ratio on nitrate were not significant. The interaction of organic matter type and time on electrical conductivity and the interaction effect of organic matter type and ratio on dissolved organic carbon was not significant. The effect of two-factor interactions on nitrate was not significant. Among the three-factor interactions, the effect of organic matter type, time and ratio on electrical conductivity, acidity (pH), organic carbon and nitrate was not significant. The results showed that aeration decreased the pH and increased the electrical conductivity in both cow manure and vermicompost tea. Despite the higher total amount of nitrogen, phosphorus and potassium in vermicompost, cow manure tea contained higher amounts of soluble ammonium, phosphorus and potassiumcompared to vermicompost tea. The chemical structure of organic matter and the distribution of element in different organic and inorganic fractions can be effective on the dissolution of the mineral part and the biological decomposition of organic part. Changes in the ratio and aeration time had no significant effect on the amount of ammonium and soluble phosphorus in vermicompost tea. In cow manure tea the highest percentage of increase in soluble phosphorus and potassium was obtained by increasing the aeration time up to 72 hours compared to the zero time (without aeration) in a ratio of 1:50. In general, organic carbon decreased as a result of aeration, and only at a ratio of 1:10, this reduction was not significant at 48 and 72 hours. The only factor affecting the amount of nitrate was the aeration time and compared to zero time the amount of nitrate decreased at 24 and 48 hours and increased at 72 hours.
The results showed that the effect of aeration time and fertilizer to water ratio on nutrient concentrations in teas made from cow manure and vermicompost was different. Despite the higher total concentration of nutrients in vermicompost, the vermicompost tea contained lower amounts of nutrients compared to cow manure tea. In other words, the total amount of nutrients in organic fertilizer cannot determine their amount in the produced tea.