Effect of the Combination of Liquid Biofertilizers and N, P, K Fertilizer on Soil N-Total, N Uptake, N-Fixing Bacteria and Sweet Corn (Zea mays L. Saccharata) Results in Fluventic Eutrudepts

The availability of nutrients in the soil is the main factor to determine the success of plant cultivation. Nutrients have an important role in increasing the yield and quality of plants. The availability of nutrients in the soil is able to maintain a balance of nutrients so that plant productivity is optimal with fertilization (Wulansari et al., 2022).

The main problem in agriculture is the decline in the quality of agricultural soil which causes low agricultural productivity due to degradation of soil fertility. This is due to excessive and uncontrolled use of inorganic fertilizers by farmers. According to Iwuagwu et al. (2016) the continuous use of inorganic fertilizers can result in damage to the physical, chemical and biological properties of the soil so that the level of soil fertility decreases. This is supported by the research of Pangaribuan et al. (2019) that excessive application of inorganic fertilizers to the soil can affect environmental factors, soil quality and cause reactions in the soil such asP fixation, NO3 and N2O volatilization. Inorganic fertilizers can also reduce soil organic matter levels to <2.00% and damage the soil structure.

Solutions to increase the value of agricultural production can be done by preserving agricultural resources, strategies and appropriate efforts such as utilizing biofertilizers. Bio-fertilizers contain symbiotic bacteria (Rhizobium) and non-symbiotic bacteria (Azotobacter and Azospirillum) which correlate with each other in improving soil fertility and increasing crop yields (Fadiluddin, 2019). This is inline with the statement of Setiawati et al. (2020) that the bacterial content in biofertilizers is able to provide nutrients and increase crop yields. Bacteria Azospirillum sp. is one of the bacteria that can fix nitrogen and can produce the hormone Indole Acetid Acid (IAA) as a soil aggregate stabilizer and stimulate plant growth (Eckert et al., 2001). The agricultural sector utilizes Azospirillum sp. optimally formulated as a special carrier material for biofertilizers in increasing nutrient availability and increasing plant productivity. Basically, biofertilizers cannot fully optimize the availability of nutrients in the soil, because they are accompanied by the provision of inorganic fertilizers N, P and Kin balanced doses so that they have an effect on plant growth and yields. According to Rop et al. (2019) N and P nutrients are needed by plants in the growth process to be precise in the vegetative phase while K nutrients are needed in the generative phase.

This study also used sweetcorn (Zea mays L. saccharata) as an indicator in supporting the successful use of a combination of liquid biofertilizers with N, P and K fertilizers. Sweetcorn of the Talenta variety is a plant that has a high sugar content of 13-15 obrix while in Ordinary corn has a sugar content of 2-3% (Sukur & Rifianto, 2014). The productivity of sweetcorn in Indonesia in 2018 averaged 8.31 t.ha-1 while the yield potential of sweetcorn was able to reach 14-18 t.ha-1 (Rinanti et al., 2021). Based on these results indicate that the low productivity of sweetcorn is caused by several things, namely the limitations of sweetcorn cultivation due to soil fertility problems and pest and disease attacks.

The aim of the study was to determine the effect of a combination of liquid biofertilizers and N, P, K fertilizers on soil N-total, N uptake, N fixing bacteria and sweetcorn (Zea mays L. saccharata) yields in Fluventic Eutrudepts.