Revitalizing sub-optimal drylands: Exploring the role of biofertilizers

3.1 Soil characteristics

The site land has chemical characteristics that were relatively less optimal for plant growth, such as moderately acidic soil pH and low content of soil organic C and N. The potential P and available P elements were in high status, whereas the content of potential K was moderate and available K was high. This condition indicates an imbalance of nutrients in the soil, causing land productivity to be less than optimal. The potassium content in the soil was seen to decrease descriptively but did not change the status of the category, which was very high. The decline that occurred descriptively in all treatments was thought to be due to environmental factors, and very high rainfall throughout the study, because of which there was leaching of potassium elements. The average potassium after biofertilizer treatment was still higher than the control (Table 1).

3.2 Climate condition

In addition to limiting issues induced by soil characteristics, sub-optimal drylands are also confronted with environmental limits, particularly unpredictable rainfall, and temperature. The research location was dryland with a humid climate with an uneven distribution pattern of rainfall throughout the year. The average rainfall under normal conditions was around 1,400 mm/year, with a dry month range (<60 mm/month) of 6 months [23]. The climatic conditions during the research period (February–May 2021) are shown in Figure 1.

Figure 1

Climate condition. *The root zone wettability percentage value of 0 indicates that the soil was completely free of water and a value of 1 indicates the soil was completely saturated, where the root zone was the layer from the surface 0 to 100 cm below the soil. ^†RH2M is the relative humidity (%) at 2 m. **Source of data: NASA POWER Data Access Viewer-Prediction of worldwide energy resource-agro climatology location of latitude −8.0972, longitude 110.8008, 2021. https://power.larc.nasa.gov/data-access-viewer/.

The rainfall data during the research period (from day 59 to 151 in 2021) were far beyond normal conditions, reaching about 520 mm/3 months or about 170 mm/month, with an average air temperature of around 26°C at the soil surface. The soil moisture in the root zone was at a level of 0.9. Soil moisture at level 0.9 indicates that the soil was almost always saturated with water, almost 90% of the entire soil pore space (Figure 1).

3.3 Soil microbiology

Land improvement using biological fertilizers affects the soil’s microbial population before and after the study. The Azospirillum population increased significantly in the range of 45–63% compared to that before the study and increased by 0.6–13% from the control without biological fertilizers. The combination of Gliocompost + BioNutrient + Agrimeth increases the Azospirillum population. Meanwhile, the combined application of Agrimeth + BioNutrient increased the Azospirillum population, which was lower than the single application but still higher than the control. The Trichoderma population increased by 17–18% from before the study but was not significantly different from the control, with an average increase of 0.36–1.48%. The combination Gliocompost + BioNutrient + Agrimeth also intensifies the Trichoderma population (Figures 2–4, Table 2).

Figure 2

Soil microbial populations before and after biofertilizer application.

Figure 3

Percentage increase in microbial in biofertilizer application from before treatment.

Figure 4

Percentage increase in microbial in biofertilizer application compared to control.

3.4 Plant growth

Research on the effect of biofertilizers on the growth and production of peanuts was carried out during one growing season. The average value of the peanut plant growth variable in biological fertilizer treatments is presented in Table 3.

The application of biological fertilizers did not significantly affect the peanut’s growth component, due to very high rainfall during the study, which was 170 mm/month. Meanwhile, peanut plants require ideal growing conditions such as 800–1,300 mm/year rainfall or equivalent to 100–200 mm/month wet or about 3–7 mm/day; 28–30°C air temperature; humidity 65–75%; and slightly moist soil with good drainage (Table 3).

3.5 Yield

The study on land improvement using biological fertilizers was also carried out to see its effect on peanut crop yields. The use of biological fertilizers for land improvement is yet to show a significant effect on peanut yields. The resultant yields show a positive tendency to increase in one growing season, with relatively abnormal weather conditions. Data on the components and yield of peanuts in several biofertilizer treatments are presented in Table 4 and Figure 5.

Figure 5

Peanut yield components on biofertilizers application.

3.6 Benefit analysis

The MBCR calculation was derived from total production costs (seeds, fertilizer, labor) that change due to the new implementations of soil amelioration using a biofertilizer and revenue from the sales of peanuts. MBCR can be determined by the difference between profits and costs that can be achieved by implementing introduced innovations. The highest increase in benefit was achieved by applying a combination of three types of biofertilizers (Agrimeth + BioNutrient + Gliocompost), with an increase in the yield of 45.04% (Table 5).

4.1 Soil characteristics

The research was conducted in a dryland area with Inceptisols (Typic Dystrudepts) soil, which has a loamy clay texture. The limitations of this soil type resulted in conditions that were less than optimal. To determine the effect of using biofertilizers on land improvement, the chemical and biological properties of the soil before and after the treatment were studied. Some of the soil chemical characteristics included pH, organic C content, total and available N, total and available P, and total and available K. The biological characteristics of the soil observed included the populations of Azotobacter sp., Rhizobium sp., Azospirillum sp., Trichoderma sp., and solubilizing phosphate bacteria.

Biofertilizer is expected to be an alternative technology that can help improve soil nutrient balance, increase land productivity, and increase plant growth in the long run [10,19,21]. Land improvement using biofertilizers did not show changes in soil chemical properties from before the study. The available nitrogen content ( NH 4 + and NO 3 − ) increased significantly while the total nitrogen content was low.

The influence of the activities of symbiotic and non-symbiotic bacteria contained in biofertilizers, such as Azotobacter, Azospirillum, Bacillus sp., Rhizobium sp., Pseudomonas fluorescent, and Bradyrhizobium, the available P₂O₅ content remained very high before and after the assessment, there was a tendency that rose descriptively in some biofertilizer treatments.

In the treatment of BioNutrient (P3) and Gliocompost (P4), there was an increase in the content of available P by 12 and 19% compared to before research, and 20 and 27% higher than the control. The increased availability of phosphate elements were thought to be one of the effects of using biological fertilizers containing Pseudomonas fluorescens and Aspergillus sp.

This increase in the availability of elemental content was the results of previous studies, that the application of biofertilizers containing N-fixing bacteria and phosphate solubilizing microbes + 50% N, P, and K increase soil phosphorus availability [9]. Applying organic and inorganic fertilizers, and biofertilizer packages significantly affect the parameters of organic C and soil available P [24].

4.2 Climate condition

Soil quality and climate conditions were indicators for evaluating increased crop production. Climate change mitigation was needed in managing agriculture based on nutrient-rich soil research. The pattern of suboptimal land management also needs to be driven by policy support [40].

Rainfall that exceeded normal during the study impacted the optimization of land improvement processes and plant productivity by applying biofertilizers. The effectiveness of commercial biofertilizers was incredibly reliant on seasonal and site-specific environmental factors [25]. Flowers would be challenging to pollinate and fall out due to excessive rains. It affects rising soil water content and air moisture, causing poor plant growth and the rotting of some roots and pods [26].

Uncertainty of rainfall intensity and distribution was a major constraint and limiting agriculture factor in dryland. Therefore, in the long run, it was necessary to identify and delineate dryland areas with several main weather factors that often occur to obtain accurate information regarding land potential and alternative technological innovations to be implemented.

An integrated approach of two methodologies, Moderate Resolution Imaging Spectroradiometer and Normalized Difference Vegetation Index data, has been used to estimate the long-term changes in agricultural development areas. Three independent variables (rainfall, temperature, and agricultural area) were used in the multiple regression analysis to understand the impact of the main drivers affecting the crop production indicating an increasing trend in crop production. Correlation analysis indicated that crop production was significantly related to annual rainfall but less sensitive to temperature [27].

4.3 Soil microbiology

The application of biofertilizers seems to increase the population of phosphate-solubilizing bacteria, especially the Agrimeth + BioNutrient combination, by 10–12% before the study. The combination of Agrimeth + BioNutrient also significantly increases the population of phosphate-solubilizing bacteria compared to the control (7–9%).

The use of Gliocompost only caused a slight increase in the population. Even when Gliocompost was combined with Agrimeth and BioNutrient, the phosphate-solubilizing bacteria population decreased slightly. This fact indicates the need for further research on mixing biofertilizers with phosphate-solubilizing bacteria populations. Adding bio-fertilizer changed the organization of the soil microbial population, backing up this theory. They found that adding biofertilizers had a more significant impact, notably in soil treated with bio sludge and bio sludge + Azotobacter [28].

The descriptive explanation confirms the prior knowledge that each biofertilizer tends to change specific microbial populations in suboptimal land. Agrimeth tends to increase the population of Azospirillum and phosphate-solubilizing bacteria positively. BioNutrient affects an increase in the populations of Azotobacter, Azospirillum, and phosphate-solubilizing bacteria. Meanwhile, Gliocompost tends to increase the population of Azotobacter and Azospirillum.

The combination of Agrimeth affected the population of Azotobacter and phosphate-solubilizing bacteria. Meanwhile, combining the three biofertilizers only increased the Azospirillum population. Continuous application of biofertilizers allows the microbial population to persist and grow in the soils, assisting in soil fertility maintenance and contributing to sustainable agriculture [29].

4.4 Plant growth

Applied biofertilizers tend to increase peanut growth by increasing plant height, plant crown diameter, and several branches. This performance was consistent with the findings of the present study, inoculation of Bacillus subtilis QST713 resulted in enhanced plant growth and total phosphorus content in cucumber plants and P total. [19,30]. Meanwhile, based on the development of peanuts, Gliocompost biofertilizer significantly influenced the rise in root nodules but was not significantly different from the biofertilizers Agrimeth + BioNutrient.

The use of Agrimeth + BioNutrient has proven to increase the number of nodules, but not statistically significantly different from the control. The combination of Agrimeth + BioNutrient produced the highest increase in root nodules. The number of nodules increased in the Agrimeth + BioNutrient + Gliocompost combinations. This increase supports the findings of other studies [31,32], which concur that the presence of Bradyrhizobium in the soil promotes the formation of root nodules in peanuts and nitrogen fixation.

The application of biofertilizers significantly increases the growth of shoots and roots in green beans, cowpeas, and soybeans compared to controls. Biofertilizers were very effective on plant growth, nodulation, nitrogen fixation, nitrogen uptake, phosphorus, potassium, and yield of green bean and soybean seeds from N application [33].

Furthermore, biofertilizers Bradyrhizobium japonicum, Bradyrhizobium elkanii, and Streptomyces griseoflavus significantly increased plant growth, nodulation, nitrogen fixation, nutrient uptake, and soybean yields. Overall, the effectiveness of biofertilizers and the efficiency of soybean varieties have an important role in plant growth, nodule formation, nitrogen fixation, and higher yields [34].

4.5 Yield

The combination of biofertilizer Agrimeth + BioNutrient produced the highest dry weight compared to other treatments, with an increase of 85% than the control. Furthermore, the Agrimeth + BioNutrient + Gliocompost increased dry weight by 68%. The combinations of Agrimeth + BioNutrient (P5) and Agrimeth + BioNutrient + Gliocompost (P6) also significantly affect the quantitative parameters of dry unpeeled peanuts. Both treatments increased by 59 and 56% compared to the control, respectively.

The treatment of Agrimeth + BioNutrient + Gliocompost resulted in the highest dry seed weight but produced a dry seed weight 56% heavier than the control. Furthermore, the high dry seed weight was obtained in the combination of Agrimeth + BioNutrient, with an increase of approximately 47% over the control.

Demonstrated that biofertilizer inoculation increased peanut development and yield components [32]. The use of biofertilizer 500 g Agrimeth/ha plus fertilizers (50 kg Urea + 150 kg Phonska)/ha also increases plant growth and yield by 0.25–0.70 t/ha or 15.15–33.33% compared to planting without biofertilizer [41].

The biofertilizer application has not significantly affected peanuts’ growth and yield components. The same was also seen in the average achievement of peanut yields, as presented in Table 4. The biofertilizers, independently or in combination, did not show statistically significant differences between controls and treatments. However, the yield of peanuts achieved by all treatments using biological fertilizers was relatively higher than when not using them. The 41.3% increase in yield was achieved in the combination treatment of Agrimeth + BioNutrient + Gliocompost (P6). Then, successive increases were shown in the treatment of P5 (28.7%), P4 (22.0%), P2 (4.5%), and P3 (2.2%).

Gliocompost biofertilizer contains a Pseudomonas microbe, which positively increases peanut yield. Pseudomonas-based biofertilizers could be an appropriate alternative to increase sweet potato yields, saving 50% of the currently recommended mineral fertilizers, and making them more environmentally friendly to support efficient and productive sustainable agriculture [35]. Furthermore, the application of biofertilizers such as Gliocompost, Probio, and Starmix were combined with 50% NPK recommended giving the increased yield, which means biofertilizers can make fertilizers efficient [42].

This phenomenon indicated that biofertilizers in a synergistic and integrated conditions have a better yield than the independent and partial applications. This study also gives hope that, in the long term, biofertilizers have positive prospects for field improvement and increased crop productivity.

The results indicated the application of biofertilizers proved to be able to increase the available P content, population of soil microbes (Azospirillum, Trichoderma, Phosphate-solubilizing bacteria), and peanut yield, although still at small level. This points that land improvement and crop productivity using biofertilizers needs to be carried out continuously but still must prioritize the ease and cheapness of the application. Therefore, the application of this innovation needs to be combined with more efficient technology.

Automation systems through the Internet of Things and cloud computing was one of the alternatives offered by two technologies that contribute to the development of smart technology by replacing traditional agricultural practices [36]. These smart devices monitor the needs of the plant health through sensors that can monitor temperature, soil moisture, sunlight intensity, soil air quality values, vibration, and humidity in the environment surrounding the plants. The network of sensors ensures that the plants will continue to be healthy and function in the right way. Follow-up research on dryland crop yields can be conducted to determine carbohydrates, protein, moisture, ash, fat, and fiber contents [43].

4.6 Benefit analysis

Benefit and MBCR analysis were presented in the use of innovative soil improvement technologies using a combination of three types of biofertilizers (Agrimeth-BioNutrient-Gliocompost) proved effective in increasing the yields and profits compared to the existing ones. The highest increase in profit was achieved by applying a combination of three types of biofertilizers together, with an increase in yield of 45.04%.

The second increase in profit occurred in Agrimeth and BioNutrient biofertilizers simultaneously. Meanwhile, Gliocompost biofertilizer proved to be the most effective in increasing yields and profits in biofertilizers independently, with a profit increase of 25.72% compared to the existing ones.

Application of technology using single or combinations of biological fertilizers in treatments P4, P5, and P6 was economically feasible and can be recommended to farmers [22]. Increasing benefits and reducing costs occurring in the application of this technology not only plays an important role in sustainably improving land but is also a solution for small farmers on marginal lands who want cheap inputs [37,38].