In current mainstream agricultural practice, more than half of the applied chemical N fertiliser in cropping systems can be lost to the environment, and this problem has been classified as a pressing global issue. In addition, chemical fertilisers that are currently the primary source of fertilisers rely on limited natural resources such as petroleum, phosphate rock, and potassium salts. The unavoidable depletion of these products will lead to problems for farmers, including interrupted availability and increasing costs. Organic nutrients have gained much interest in the recent decade for their positive roles in plant nutrition and in generating healthy soils. With the recognition of the importance of organic nutrients and the detrimental effect of chemical fertilisers when applied in excess, modern agriculture is progressing to reduce the use of chemical fertilisers, compensating it with organic fertilisers. Several studies have shown the beneficial effects that this practice has on soil chemical-biological properties and crop yields. To maximise the efficiency of this system, plant growth promoting rhizobacteria  have great potential. For example, the addition of PGPR to soils amended with a mixture of 50% organic and 50% chemical N fertiliser increases the growth of Kikuyu grass , leading to yield similar to 100% chemical N fertiliser. Importantly, the presence of PGPR also reduced N loss by 95% relative to full chemical fertiliser treatment. To further demonstrate the benefit of using PGPR to support organic and chemical fertilisers mixture in agriculture, we tested this combination on another plant, sugarcane , in glasshouse and field trials. Sugarcane is a global industrial-scale crop, grown in over 110 countries worldwide, and is one of the most important plants for sugar, biomaterials, and renewable energy production.

Sugarcane seedlings were grown in the glasshouse  on soils containing two different kinds of fertiliser. The first is “Soil Mate” from MitrPhol Sugar Corporation consisting of a combination  of chemical fertiliser and organic fertiliser . The second is EcoNPK, an organic-chemical fertiliser from Sustainable Organic Solutions Pty Ltd. All treatments received the same N application rate  in the absence  or presence of PGPR  coated on a mineral carrier in an application of 10 g  per pot . Each pot contained one sugarcane seedling,tall pot stand and each treatment consisted of 12 replicates. Plants were grown for 8.5 months. We observed that the application of SOS3 PGPR enhances plant growth, sett number, and sugar yield in both fertilisers treatments . In the Soil Mate treatment, PGPR increased the weight by 22%, the sett’s number by 13%, and the sucrose yield by 22% . In the EcoNPK treatment, PGPR increased the weight by 33%, the sett’s number by 36%, and the sucrose yield by 32% . To validate the glasshouse results, we tested sugarcane in the field following commercial standard practices . Sugarcane was grown using two types of fertiliser combination, the first corresponding to Soil Mate , and the second consisting of a mixture of Soil Mate and EcoNPK . In the latter, the addition of 50% of Soil Mate was necessary to compensate for the low NPK levels in EcoNPK . Compared to most other crops, sugarcane requires high amounts of NPK which could not be practically sustained by EcoNPK alone in large-scale fields. All treatments received the same N application rate , in the absence  or presence of 15 kg ofmineral carrier coated with SOS3 . Sugarcane was grown for nine months. The plot size was 6400 m2 . The field trial showed similar results to the glasshouse experiment. The addition of PGPR to the Soil Mate treatment led to an increase of sugarcane  and sucrose yield , and its addition to the 1/2Soil Mate + EcoNPK treatment increased sugarcane and sucrose yields by 13%  and 17% , respectively . Our present study on sugarcane, in accordance with the previous research made on Kikuyu grass, strongly suggests that the use of PGPR along with a combination of organic and chemical fertilisers can offer a viable avenue in agriculture. The nutrient use efficiency is the main target of nutrient management to control fertiliser losses, which otherwise causes significant economic damage and severely pollutes the environment via leaching, runoff and volatilisation etc.. PGPR appears to be complementary to the use of organic fertilisers, through the enhancement of organic nutrient acquisition and assimilation by the plant . Notably, this combination has also the potential to increase soil health due to the application of organic matter content, which plays a vital role for soil physical, chemical and biological properties. The use of PGPR in sustainable agriculture has received much interest in the past decade due to their beneficial effects such as productions of phytohormones, nitrogen fixation, iron sequestration, phosphorus solubilisation, and alleviation of plant biotic and abiotic stress conditions .

However, it’s known that the efficacy of PGPR differs widely, with reported benefits ranging from none to considerable. This variability is caused by environmental factors and specific host interactions, limiting its application for agriculture. In conclusion, the addition of PGPR to the combined use of inorganic and organic has potential implications for agricultural sectors seeking innovative ways to achieve improved nutrient value without harming the environment. The future research needs to verify this system in field measurements at different spatial and temporal scales with different crops. In addition, research should focus on optimising the application techniques to maximise the efficiency of inoculation with PGPR. Soil as a complex system is an important part of environment. It acts as a reactor where many different processes between organic and inorganic phases occur. Soil biodiversity, representing the variety of living organisms belowground, is an important soil health indicator. In general, soil biodiversity is directly influencing the main soil property, which is soil fertility. In 1989, the World Wide Fund for Nature defined biodiversity as “the wealth of life on Earth, millions of plants, animals and microorganisms, including the genes they contain, and as complex ecosystems that create the environment”. Biodiversity is affected by altitude, climate, relief, water availability, bedrock, soil but also human intervention. Biodiversity is represented at three basic levels as genetic , generic  and ecosystem . It is a very sensitive system highly dependent on its individual components, and disruption of one of them can lead to the extinction of a number of other components. This negative tendency can be observed also in soil. Biodiversity in agricultural land in Europe is threatened. Amount and the diversity of animal species is declining significantly. It is the result of the number of causes. Among the most striking are the intensification of agricultural production, the use of pesticides, the ploughing of field boundaries and the cultivation of monocultures in large areas. Since 1990, populations of birds and meadow butterflies—which are a good indicator of changes—have fallen by more than 30% . Biodiversity contributes to enhanced ecosystems, such as ecosystem stability and productivity, and improved nutrition and human health.

The higher the soil biodiversity, the better the soil fertility. Conservation and/or increasing soil fertility is extremely important because soil is a key element of the agroecosystem. Its biological activity, which is related to the processes occurring therein, can be greatly affected by anthropogenic interventions. In plenty of works it is also stated that in agricultural areas, conventional intensive farming practices have led to a significant decline in the biological diversity of soils. It is caused by the use of fertilisers as well as pesticides. Excess of especially N fertilisers induces decrease of plant’s metabolites, which contribute to the stability of soil structure, thus the stability of soil aggregates is decreased together with elimination of soil metabolites. Pesticides have negative effect on soil micro and macrofauna, e.g. earthworms. Many biochemical reactions in this environment are dependent or influenced by the presence of soil enzymes. The soil enzymatic activity reflects the activity of microorganisms, controls the release of plant nutrients and the growth of microorganisms. Enzymes can be used as indicators of soil quality. Soil sustainability can be evaluated using enzyme activities and can give also direct information concerning soil biodiversity. Higher organisms like earthworms represent also soil biodiversity indicators. Earthworms constitute a significant share of soil organisms and, owing to their activity in soil, 25 liter pot are referred to as “ecosystem engineers” . The activities of earthworms have significant effects on various ecosystem functions such as soil structure, nutrient cycling processes, decomposition of organic matter. Lumbricidae contribute to the development of specific soil properties by improving its structure and increasing the field capacity. Earthworms influence soil structure by creating burrows, by bringing litter into the soil, fragmenting it and mixing it with humus and mineral soil, by homogenizing the soil. Christensen and Mather showed that earthworm number and biomass reflect both; natural soil parameters, e.g. sand content on one side and agricultural practices on the other side. They react very sensitively to soil degradation or sanation. Cultivation technologies, which lead to the increase of soil microbial activity and occurrence of earthworms, can be considered as good agricultural practices. As stated in the research of The Can Caesar-TonThat, the proportion of soil aggregating Gram-negative bacteria, represented predominantly by pseudomonads and Stenotrophomonas maltophilia, was higher under irrigated no-till type of soil cultivation for barley in comparison to the other soil cultivation managements.

Amount of soil aggregating bacteria was the lowest in conventional soil cultivation practices under irrigation, lower than in soils without irrigation. From these results, it is clear that the type of soil cultivation has higher effect on the amount of bacteria contributing to the stability of soil structure than application or omitting of irrigation. Main reasons for cultivation technologies development can be divided into the economical, ecological and technological. Economical reasons evaluate mainly savings of work and energy, reducing workload, lowering staffing and increased machine performance. Ecological reasons are complex and they are focused on climate change mitigation, soil structure restoration and soil degradation prevention and/or sanation. They contribute directly to soil biodiversity conservation and/or improvement. Humankind at present time came to the progressive conclusions concerning preservation of nature. It is not possible to exploit natural resources in a non-safety and sustainable way anymore, otherwise we will destroy ourselves. Several environmental movements at political and/or societal level started, e.g. Agenda 2030 at global level. One of the newest at European level is the new Biodiversity Strategy to 2030 with the title “Bringing nature back into our lives” . Concerning soil, the new biodiversity initiative opened the public discussion about new Soil strategy, which is its part. This initiative will update the current strategy  to address soil degradation and preserve land resources aiming to achieve land degradation neutrality—LDN. Our research has ambition to contribute to the efforts to improve the focus on soil from purely economic views also to the environmental and sustainable ones. Good agricultural practises and organic farming provides practical conditions for farmers to use their soils in sustainable way and in a way, which cannot only preserve soil properties but also improve them from economical as well as environmental point of view.The soil cultivation is provided in spirals and individual fields have circle shape. This cultivation is based on low soil surface disintegration without turning the soil layers and without heavy machinery and artificial fertilizers. It is realized by a rotating arm fixed in the middle of the field.It is possible to fix interchangeable tools that can serve as a spade, rotary tiller, and seeder or for drip irrigation. The circular fields are located side by side and one working arm can be easily moved to an adjacent field. On this farm, vegetables are cultivated. According to World Reference Base for Soil Resources, WRB, 2014 , studied soil belongs to soils with little or no profile differentiation. Soil type is calcaric Fluvisol. According to the texture, soil is medium heavy. Coefficient of soil structure is higher in the soil from Agrokruh in the whole profile in comparison with soil with traditional cultivation. In varies according to the depth; from 1.8 for Agrokruh in the depth 0 – 20 cm, 2.3 in 20 – 40 cm to 5 in the depth 40 – 60 cm. For conventional cultivation it is: 1.6 in the depth 0 – 20 cm, 0.9 in 20 – 40 cm to the 1.7 in the depth of 40 – 60 cm.