Ecological and economical value of green manuring for Polissia organic agrocenoses

Purpose. Purpose of the article is deep research of ecological and economical as well as organisational and agronomical aspects of the use of green manure crop planting during intermediate (after harvesting main cultures) periods in crop rotations of organic farming in crop farms of Polissia. Methodology / approach. The study was conducted at the Institute of Agricultural Microbiology and Agro-industrial Manufacture of the National Academy of Agrarian Sciences of Ukraine (NAAS) during 2011–2020 within the tasks of the relevant programs of scientific studies of the NAAS. Ecological and economical as well as organisational and agronomical aspects of using planting of green manure crop during intermediate (after harvesting main cultures) periods were analysed based on the results of the original study at the example of summarization of predicted results of the developed common models of organic crops rotations for crop farms of Polissia zone. The main methods: prediction (prediction of entry of nutrition elements, organic matter, etc.); calculation and constructive (calculation of the costs for cultivation of green manure crops and calculation of the value of fertilizing ability of their biomass, etc.); abstract-logical (making conclusions by the results of conducted studies); comparative analysis (comparison of green manure crops by the complex of biological, economical and organizational aspects); statistical series adjustment (determining a share of contribution of green manure crop planting during intermediate (after harvesting main cultures) periods in forming fertilizing potential of the developed models of crop rotation over time); monographic (studying biological and agronomical aspects of the use of green manure crops based on the results of other authors). Results. It was revealed that planting of green manure crops during intermediate (after harvesting main cultures) periods, when there is no possibility to use such important source of fertilization as manure is an important factor of improving fertilization potential of crop rotation and consequently productivity of agrocenoses. The above is particularly true for Polissia with its relatively low-productive soils on one hand and favourable natural climatic conditions for the use of green manure crops during intermediate (after harvesting main cultures) periods on the other hand. Our theoretical calculations have found that the developed organic crop rotations for plant farms of Polissia, the share of planting of green manure crops during intermediate (after harvesting main cultures) periods under their contribution in the fertilizing potential may be 18.5 to 27.0 % from all sources taken into account. At the same time, contribution of green manure crops in the processes of humus formation (humus maintenance) are less meaningful (4.7–6.4 %), however, namely due to the biomass of green manure crops as the additional source of forming (maintaining) humus, positive balances of humus are achieved in the range of cases. Originality / scientific novelty. Wide use of green manure crop planting during intermediate (after harvesting main cultures) periods for organic crop rotations of plant farms in Polissia was proposed for the first time and justified by ecological and economical, as well as organisational and agronomical parameters. To the best of our knowledge, we have performed the first economic evaluation of the fertilizing potential of the most common green manure crops in the practice of domestic agrarian production and calculated the value of nutrition elements contained in their biomass under different options of their use. Practical value / implications. Practical implications of the main results of the study involve, first of all, ecological and economic justification of the feasibility of wide use of green manure crop planting during intermediate (after harvesting main cultures) periods in crop rotations of organic production in Polissia and also recommendations in terms of their selection depending on the organisational and economic conditions of the certain farm. Moreover, feasibility of green manure crop planting during intermediate (after harvesting main cultures) periods is also topical for conventional farming system.