The role and significance of vegetable fertilization in soil preservation

Introduction

Industrial agriculture, which implies a high specialization of production, (e.g., two-field wheat-rapeseed or soy-corn), the mass application of mineral fertilizers and pesticides, as well as the use of powerful, excessively heavy machinery, has caused serious environmental consequences on a global level. As a result, agriculture is the main cause of the decrease in global biodiversity by 30%. The total number of insects globally has declined by 76–82% when compared with 27 years ago (Hallmann, 2017). Food production systems are responsible for 34% of the human-caused greenhouse effect, with the negative impact of mass livestock production being especially significant.

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Already, 52% of agricultural land is moderately or severely affected by land degradation. This could affect a 12% drop in the productivity of the global food production system over the next 25 years, leading to a 30% increase in food prices (Menzies, 2019). The conclusion of numerous studies is that current farming methods are simply not sustainable in the long term.

Under our conditions, Vasin et al. (2021) determined that the average decrease in the content of organic matter in the soils of Vojvodina over a period of 20 years (1991–2011), was 0.5%, i.e. that the share of soils with very low humus content (1–2%) doubled. They also concluded that this degradation process is accelerating, and that one of the main causes is the decrease in the use of organic fertilizers during the previous half century. Inadequate processing measures, the burning and removal of harvest residues and their use for energy production, as well as the introduction of irrigation on surfaces without the application of organic fertilizers, also have had a negative effect.

One of the main priorities of LoginEKO is the development of the technology of using crops for green fertilization in order to improve the quality of the soil, while simultaneously providing enough elements of mineral nutrition for plants, primarily nitrogen.

LoginEKO has been operating in the Republic of Serbia since 2017. During that time, by realizing its vision of “Healthy food for all people,” LoginEKO has invested EUR 75.4 million in the purchase of 4,400 ha of agricultural land, in the acquisition of the most up-to-date agricultural machinery, and the initiation of research and agricultural production. The establishment of LoginEKO provided the necessary natural, technical, and personnel resources for the initiation and maintenance of research and development activities in the field of organic precision agriculture, with a special emphasis on arable and vegetable production on large areas. The main areas of development that we deal with are: crop cultivation, software development, development of finished products for human consumption, and the improvement of legislation in the field of agriculture and ecology.

Figure 1. LoginEKO test fields in Mužlja (A), winter peas – nitrogen source (B)

LoginEKO develops and uses a model of sustainable organic, precise plant production based on the collection and analysis of digital data, successfully combining the latest knowledge in the field of agronomy and information technology. We are engaged in the study and production of cereals, legumes, oilseeds, and vegetable species that are exclusively used for human consumption or for green fertilization. We have developed and are constantly improving our own farm management software. Our software enables the collection of all data from the plot and their visualization on the map. The software provides automation of work tasks, generation of advanced proposals for plant production, as well as full traceability of used materials, harvested crops, and processed products.

Bearing in mind the fact that agriculture is one of the main sources of environmental pollution, LoginEKO is developing a production model that will exclude any pollution of underground and surface water, and soil degradation – while air pollution will be reduced significantly compared to conventional, industrial agriculture. Our model is based on the cultivation of legumes in order to provide green manure, and implies the complete omission of artificial fertilizers and pesticides.

LoginEKO has 150 full-time employees, including six with PhDs, five with Master’s degrees, 12 agronomists, two agro-economists, three mechanists, 24 tractor operators, six UAV (drones) operators, and three experts in organic production certification and product traceability. The employee average age is 36 years old; and each employee has his own mentor and development plan.

LoginEKO was registered as a research and development center in 2022, the first stage in the creation of a scientific institute for sustainable, organic agriculture. LoginEKO enjoys extensive scientific cooperation with domestic and international scientific and educational institutions. Research and production are carried out on our own land, which has been certified for organic production. Most of our land is located in Banat (in the surroundings of Zrenjanin and Novi Kneževac). The land at our disposal belongs to the category of heavy clay soils, rich in organic matter, of slightly acidic pH reaction, reduced water permeability, and as such is suitable for growing mainly arable crops. Vegetable production is organized on better quality land with a lighter mechanical composition in Sanad.

Over the next five years, LoginEKO plans to build three production systems, including a central silo for storing organic grain with a capacity of 18,000–24,000 tons, as well as a processing center for certified organic seeds of arable and vegetable crops.

We have launched our own breeding program for the creation of new varieties of agricultural and vegetable plant species for organic production conditions. All newly created varieties will be made public, i.e. freely available for reproduction and cultivation to all producers in Serbia and beyond. LoginEKO will establish a cooperative relationship with smaller organic producers in Serbia, providing them with advanced cultivation technology and monitoring of organic production free-of-charge. It will provide sufficient quantities of affordable organic seeds, certified storage capacities for storing field crop grains, as well as certified cold storage for storing organic vegetables. We will build processing capacities for protein and carbohydrate products, as well as a plant for packing vegetables. For the realization of all our projects, we plan to hire between 400–500 employees. In this way, LoginEKO will create the perfect conditions for a significant increase in areas under certified organic production in the Republic of Serbia; that is, it will create an environment of interest for current conventional producers to switch to an organic production system. All of this will have a great economic and ecological impact, and at the same time will contribute to increasing self-sufficiency in food production in Serbia.

The knowledge gained by LoginEKO will be shared through scientific and professional publications, and seminars and workshops directly with all interested partners, farmers, and organizations. Successful solutions in the form of improved production technology, improved research methods, innovations, patents, and newly created varieties are immediately introduced into our own production on a large scale. After verification of our surfaces, the new solutions will be offered free-of-charge to the domestic and international scientific and professional public.

Year after year, the influence of the LoginEKO model of sustainable organic production of field and vegetable crops increases, as does the perception of the Republic of Serbia as a center of healthy food production for all people.

Discussion

The drastic increase in the price of energy sources and mineral fertilizers during 2022 once again reinforces the importance of alternative sources of nitrogen for agricultural production. Crops for green fertilization (GF), whose primary purpose is to provide nutrients for the next crop, can be that alternative source. By growing winter peas as a fertilizer, it is possible to provide 150–300 kg/ha of pure nitrogen, which corresponds to the amount of 550–1100 kg KAN.

The number of operations that include some types of soil cultivation in organic agriculture is usually higher than in conventional production. Therefore, the biggest environmental challenge in organic production is the potential reduction of humus content in the soil. The consequences of low humus content are serious damage to the structure and water-air regime of the soil, i.e. an irreversible decrease in the natural fertility of the soil. The most effective solution for preserving and gradually improving soil quality is to introduce all crop residues into the soil, as well as additional amounts of organic fertilizer. Whenever organic fertilizer is mentioned, most producers think of manure. However, like other Eastern European countries, Serbia does not have nearly enough manure to prevent soil degradation due to its modest livestock reserves, so it is necessary to find new solutions. What is very interesting is that in the Netherlands, which has a problem with an excessive amount of manure, there is a growing movement of producers who use organic fertilisers exclusively of plant origin, due to the growing awareness of the harmful effects of intensive livestock production on the environment in general.

LoginEKO, due to both the aforementioned reasons, bases its production model on the intensive use of crops for green fertilization, and the total share of land for improving soil quality on our land is 33%. For these purposes, we most often use plants from the leguminous, cabbage, and grass families, but also from others as well (Polygonaceae, Boraginaceae). Plants from these families differ among themselves in their ability to provide basic nutrients for other plants in the structure and depth of the root system, and in their influence on the water and air properties of the soil. What they have in common is the characteristic of fast growth, a short vegetation period, the ability to quickly occupy vacant land, and provides good competition against weeds. At LoginEKO, winter peas and alfalfa for green fertilization are the most represented, while fodder sorghum, Sudan grass, buckwheat, and cow cabbage occupy a slightly smaller area.

There are several scenarios for using GF which are defined by the primary goal of production. The goal of production may be to provide nitrogen for the next crop, then to prevent the leaching of nutrients into the deeper layers of the soil, to repair the structure and reduce soil compaction, to increase the efficiency of sequestration (removing carbon from atmospheric CO2 and incorporating it into plant tissues through the process of photosynthesis), to reduce the emission of greenhouse gases from the soil, to prevent soil erosion, increase biodiversity and landscaping, and to prevent crop contamination.

Depending on the chosen scenario, a specific plant species is selected for the GF and the method of production is determined, which primarily refers to the time of sowing. The timing of sowing is of particular importance in the semi-arid conditions of the Banat, when there is a significant risk for ensuring emergence and achieving the optimal crop density for GF. The crop usage scenarios for GF in LoginEKO are as follows:

• Leguminous post-harvest sowing – After the early harvest of vegetables or the harvest of winter stubbles, the harvest residues are mulched, the soil is shallowly cultivated, and leguminous seeds (usually peas) are sown. The goal is to maintain a green cover on the plot until autumn, which will provide a sufficient amount of nitrogen for the next crop. This method is considered a “real” green fertilization in Serbia. Challenge: sowing and sprouting in post-harvest sowing takes place in the driest and hottest months of July–August, which is why the moisture content of the soil is often insufficient for timely sprouting. Potential solutions: Identifying legumes that better tolerate the Banat drought, adjusting cultivation technology – move the sowing date to the end of August, when night temperatures are lower. Introducing an agile approach to sowing – sowing will be done only in case of a favorable weather forecast.
• Cultivation of winter peas for GF in crop rotation – this way it is possible to provide extremely high amounts of N. Peas, that are sown as a pure crop or in a mixture with stubble at the beginning of October. In mid-May they are mulched and incorporated into the soil. In our example from 2021, the dry matter yield was 9.3 t/ha with a nitrogen content of 3.92%, i.e. the amount of organic nitrogen produced was 364 kg/ha solely in the above-ground mass. Subsequent sowing of non-leguminous crops (forage sorghum, buckwheat, millet) prevents possible leaching of mineralised N into deeper layers, provides additional organic matter, as well as additional ecological services. The total mass of sorghum is mulched and returned to the soil so that losses of nitrogen produced by peas are minimal. Challenge: this scenario is acceptable to producers who are at the beginning of the soil conversion period, producers who have an irrigation system, as well as gardeners engaged in the production of late vegetables. We are conducting intensive research with the aim of testing the hypothesis in this way, so that sufficient nitrogen can be provided for the next 2–3 crops.
• Introduction of legumes for grain production into the cropping structure – Nitrogen provided by symbiotic fixation becomes available to other plants after mineralization of pea crop residues. The dry matter yield of pea plant residues is 3.5-5.5 t/ha x 1.5-2% N = 50-110 kgN/ha. Challenge: there are no pea processing capacities in the wider region, so the areas where peas are grown for grain in Serbia are relatively small.
• Intercropping of legumes with main crops – by intensive research in field conditions, LoginEKO has developed the so-called ‘relay intercropping.’ Peas or small seed legumes are sown in established crops of crush grains or sunflowers. For this method of providing nitrogen, we use alfalfa, red clover, and bird’s-foot trefoil. The main challenge is to ensure timely sprouting of multi-cut legumes. This production system has the greatest potential on quality, structural soils. The goal of production is to regenerate the leguminous crop after harvesting the main crop, and to reach a height of about 50 cm by mid-November. In this way, it is possible to provide a sufficient amount of practically free nitrogen for the next crop, as well as numerous additional ecological services (biological control of weeds, repair of the structure, and the reduction of soil compaction, increase in biodiversity, increase in the number of pollinators, and prevention of erosion).
• Cut and Carry – Intensive vegetable production under irrigation conditions requires extremely large amounts of readily available nitrogen in the soil in precisely defined periods of vegetation. For such purposes, we are developing a technology for the production and use of multi-cut cultures, of which the yield of above-ground mass, after fermentation and a certain period of storage, is transported and applied on plots of interest. Challenge: this technology involves significantly higher costs of logistics and transport, intended exclusively for the most intensive crops.

Conclusion

If green fertilization is such an effective solution, why is it rarely applied in Serbia? The most common reason is the insufficient amount of precipitation after harvesting winter stubble, i.e. insufficient soil moisture for timely sprouting. Another reason is the simplicity of application, and, until recently, the relatively acceptable price of mineral fertilizers, as well as the very low awareness of producers about the negative consequences of omitting fertilization with organic matter. In addition, the wider research community has already changed focus of their research after the first failures with mineral fertilisers and challenges with securing funds for research. LoginEKO conducts intensive research in order to find an economically and ecologically sustainable model for providing the necessary nitrogen in the soil. After verifying the results of this research on our large areas, with a clearly defined production technology, LoginEKO will distribute the model free-of-charge to all interested producers.

Đura Karagić*, Niko Gamulin**, Sreten Terzić*, Bojan Mitrović*, Miroslav Zorić*

* LoginEKO Research and development center , Bulevar Zorana Đinđića 125, 11070, Novi Beograd, Serbia
** Login5 Foundation, Kirchstrasse 1, 9490 Vaduz, Lichentstein
Contact author: djura.karagic@logineko.com

***

Sources:

• Hallmann CA, Sorg M, Jongejans E, Siepel H, Hofland N, et al. (2017) More than 75 Percent Decline over 27 Years in Total Flying Insect Biomass in Protected Areas. PLOS ONE 12(10): e0185809. https://doi.org/10.1371/journal.pone.0185809
• Menzies, Neal & Wang, Peng & McKenna, Brigid & Lombi, Enzo. (2019). Soil and the Intensification of Agriculture for Global Food Security. Environment International. 132. 105078. 10.1016/j.envint.2019.105078.
• Vasin J., Ninkov J., Zeremski T., Milić S., Jakšić S., Živanov M. (2021): Zemlјišta Vojvodine – kvalitet i organska materija. Zbornik „Racionalno korišćenje zemljišta i voda u Srbiji“ Izdavač: Srpska akademija nauka i umetnosti, Odeljenje hemijskih i bioloških nauka, Knjiga 19, str. 133–138.