Agroecological Efficiency of Traditional and New Organic Fertilizers

Abstract

Municipal waste in the form of sewage sludge and the use of unconventional sources of organic raw materials, in particular, is of great importance as a result of the critical shortage of organic fertilizers, the use of which has not exceeded 15–18% of the demand in Russia in recent years. Research in this direction is relevant due to the poor knowledge of the effects of sewage sludge and products based on them on the soil-plant system. The goal of the study is to establish the comparative agroecological effectiveness of the effect and long–term aftereffect of compost from sewage sludge and dung manure at different application rates when cultivating perennial grasses. The research was carried out in the conditions of the long-term micro-field experiment arranged by the Pryanishnikov Institute of Agrochemistry in Moscow oblast (Barybino village). In the experiment, orchard grass was sown under a cover of spring barley. The design of the experiment considered the following options: (1) control without fertilizers, (2) compost one at a rate of 10 t/ ha, (3) compost one at a rate of 35 t/ha, (4) compost two at a rate of 10 t/ha, (5) compost two at a rate of 35 t/ha, (6) manure at a rate of 10 t/ha, and (7) manure at a rate of 35 t/ha on a dry weight basis. Compost is prepared from sewage sludge from the Kur’yanovskaya aeration station; specifically, compost one from sludge from filter presses and compost two from sludge from the drain beds. Compost two was characterized by a higher content of heavy metals, the total amount of which was two times higher than in compost one and ten times higher than in dung manure. All fertilizers were introduced before sowing crops in 2000 and then their aftereffect was tested for 22 years. The rates of all organic fertilizers are given on a dry weight basis. According to the results of the long-term studies, comparison between two types of compost contaminated with heavy metals to different degrees shows that the greatest effect was achieved from compost with a lower pollution level, that is, produced from fresh (nontreated) sludge from filter presses at an increased rate of 35 t/ha on a dry weigh basis, from which gain in the yield was 41% relative to the control. This improvement due to the use of dung manure varied from 28 to 73% depending on the application rate. As for the accumulation of heavy metals in the soil and in the dry matter of perennial grasses, there were no clear dependencies on the types and rates of fertilizers applied. At the same time, levels of cadmium, nickel, and lead in the plant and soil samples did not exceed the permissible values.