Cultivation of catch crop as asustainable way of reducing CO2 content in the atmosphere

INTRODUCTION

The average global temperature is still growing (IPCC 2013), which is correlated with increasing concentration of green-house gases (GHG), mainly CO2 in the atmosphere. Various actions are taken for mitigation of GHG emission. But, taking into account the current trends in socio-economic development, reduction of ССЬ emission will not be easy (Xu & Li 2018). Development of our civilization is inseparably connected with growing demand of energy while the energy production is still basing on fossil fuels (Hui-Ming ct al. 2012, Johansson & Pirouzfar 2019). Combustion of these fuels is the main anthropogenic source of the emission of CO2 (IPCC 2013). Therefore, the gradual insertion of renewable sources to the energy production systems should be implemented (Lata-Garcia ct al. 2018). At the same time, it is necessary to seek more efficient ССЬ sinks.

The control of C02 exchange between the atmosphere and terrestrial and marine ecosystems is promising way for removing C02 from the atmosphere. It was observed that the net amount of the C02 absorbed in ocean water increased from 3.7 Gt C02/yr in 1960-1969 to 9.5 Gt ССЬ/уг in 2016 (Trujillo & Thurman 2017). However, this sink will decrease with time, as a result of ocean water acidification. Within the period from 1700 to 1994. the pH of ocean water dropped from 8.25 to 8.14 (Jacobson, 2005). A decrease in the pH of ocean water negatively influences the ocean ecosystem, among others it cause the damage of the coral reefs. Attempts are made to mitigate this phenomena by enhancing the absorption of C02 by algae in the photosynthesis process. Fertilization of ocean water with Fc ions are carried out in order to achieved this purpose. Intensification of algae growth enhances the absorption of CO2 by ocean water and has a beneficial effect on fishing (Cai 2018).

The studies carried out by Lc Quere et al. (2018) shows that starting from the 1960s, the share of another important sink, i.e. net absorption of CO2 by plants is growing from 5.1 Gt C02/yr in 1960-69 to 11.0 Gt C02/yr in 2007-2016, reaching 8.9 Gt C02/yr in 1970-1979, 9.2 Gt ССЬ/уг in 1990-1999 and 10.6 GtCCb/yr in 2000-2009. In 2016, its value reached at 9.9 GtCCb/yr, which was lower than the average from the previous decade.

There are further possibilities of reducing atmospheric CO2 concentration with using terrestrial ecosystems, such as the decrease of ССЬ emission from soils, by slowing down the oxidation of soil organic compounds, e.g. by applying the crop rotation, cover cropping, catch cropping, intercropping, mulching, and no tillage practice (Wang ct al, 2010) or the increase of CO2 absorption by plants in the photosynthesis process.

Characteristics of catch crops

Enhancement of carbon sequestration is one of the main tasks of a sustainable agriculture. This agricultural system bases on the soil conservation practices, such as: limiting the soil disturbance (no-till farming) or permanent soil covering by plant biomass combined with the crops rotations (Hobbs et al. 2007).

The catch crops and intercrops arc used to prevent the wind and water erosion (Hobbs ct al. 2007), thus the name “cover crops” is also suitable for them.

Catch crops are the fast-growing plant species that arc grown between the successive main crops (Lockhart & Wiseman 2014), and intercrops arc the two or more crops cultivated in the same space at the same time (Lithourgidis et al. 2011). The name “catch crops” refers to the possibility of the plants to take up and retain the nutrients from the soil, that prevents leaching out these substances from the surface to deeper layers.

Catch crops can be cultivated in pure or mixed sowing. There are mainly the plants with a short vegetation period. The legumes (e.g. clover, pea and vetch), grasses (e.g. rye, ryegrass, wheats, barley), and mustards are usually cultivated as the catch crops in the temperate region (Wang ct al. 2010).

The appropriate selection of plant species used as the catch crops is necessary to achieve the sufficient yield under the specified soil properties and environmental conditions. The species used in the mixture should have different types of root system, which arc characterized by different depth. This causes that the soil is enriched with organic substances on several levels. Additionally, such a differentiation allows the nutrients from different depths to move up the soil profile, along the roots, to the above-ground parts, where they become again available for the main crop plants (Thorup-Kristensen 2006). An important function of catch crops is improve the soil physical properties, such as aggregation, porosity, water and air conditions, due to increase of humus content. Impact of cover crops on soil water content is explicit. During the vegetation season the cover crops decrease soil water content, because of transpiration, but after ploughed or using as mulch they increase the soil water retention (Qi & Helm- ers 2010).

Depending on the sowing time, three types of catch crops can be distinguished:

  • - stubble crops - seeds arc sown in summer, while the crops arc harvested in autumn for green forage, mowed and filched or plowed without mowing. After mowing, plants may be also left for winter in the form of mulch. The plants which are most commonly cultivated as this type of intercrops arc: brassicas (white mustard, black mustard, rapesced, oilseed radish, stubble turnip, Brassica oleracea var. meduUosa), legumes (horse bean, yellow lupin, narrowleaf lupin, sugarsnap peas, field peas, spring vetch, serradella), and other species (blue tansy, sunflower, oat)
  • - undersown crops - spring cereals sown in spring or, rarely sown with winter cereals
  • - winter catch crops - sown at the autumn and harvested in spring of the next year. According to their harvest period the plants arc divided on: early (winter agrimony, winter rape- seed), intermediate (winter rye), and late (Lolium westerwoldicum, crimson clover) (Finch et al. 2014).

The appropriate selection of the plant species allows for achieving a high yield of plant biomass under certain field conditions. The yields of shoot and root biomass of the selected catch crops arc presented in Table 1. The results showed a significant differentiation of the yields, both between the plant species, and also between the same species under different locations.

 
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