Giving Bacteria Can Increases Availability of Nitrogen in Soil
Nitrogen (N) element in the soil is one of the limiting factors to support the growth and productivity of rice crops. Nitrogen-fixing bacteria have the ability to bind nitrogen in the air to make it available in the soil. The use of nitrogen inhibiting bacteria has the potential to reduce the application of nitrogen fertilizer.
Four researchers from the Faculty of Agriculture, Bogor Agricultural University (IPB), Sugiyanta, Ida Widiyawati, Ahmad Junaedi and Rahayu Widyastuti, conducted a research on rice nitrogen-fixing bacteria in the fields. The aim was to know the role of N-fixing bacteria in reducing the use of inorganic N fertilizer in wetland rice.
The N element in the soil is important to support the growth and development of rice. Air contains about 78 percent of the N element, but plants cannot use it directly because the form is N2 gas, so N fertilizer should always be added. There are both symbiotic and free-living soil bacteria that have the ability to fix N from the air. "The provision of nitrogen is biologically done by utilizing free nitrogen-fixing bacteria such as Azotobacter and Azospirillum that live freely in root and plant tissue," said Sugiyanta.
N-fixing bacteria, often called diazotrof bacteria, are capable of using N air as a source of N for its growth. The use of these bacteria has the potential to reduce the need for synthetic N, increase production and farm income with cheaper inputs. The research was conducted in plastic house of Experimental Garden at Babakan Sawah Baru, IPB. Two factors studied were the dose of nitrogen fertilization and the type of bacteria. The N (urea) fertilizer dose factor consisted of four levels, namely 0, 50, 75, and 100 kilograms of Nitrogen per hectare. Bacteria type factor consisted of four levels, namely without bacteria, Azotobacter-like, Azospirillum-like, and consortium.
This experimental unit used a tarpaulin plot with a ground depth of 0.3 meters. Rice seedlings aged 17 days after seeding (HSS) were planted on a plot with jajar legowo planting distance. Urea fertilizer as a treatment was given twice, namely a half dose at seven days after planting (HST) and a half dose at 30 HST. Inoculation of bacteria was administered three times by sprinkling the bacterial solution around the root of the plant per plot at planting session, two weeks after planting (MST), and four MST.
From the results, it was found that the dose of N fertilization had significant effect on all variables, except on the percentage of empty grain per panicle, the weight of thousand grains, and the N content in plants. This research explained that the type of bacteria had a significant effect on root dry weight, the number of filled grain per panicle, the greenness of the leaves, the N uptake and content (canopy and grain), and weight of grain per plot. The bacterial consortium was able to reduce 25 percent of the inorganic N-fertilizer from recommended doses (100 kilograms nitrogen per hectare) based on relative agronomic effectiveness.
"Giving bacteria on growing media increases the possibility of N availability. Bacteria help the supply of nutrients by acting as N-fixing. The leaves greenness, content, and uptake of N were higher in the soil with provision of bacterial consortium than without bacteria. This showed that the consortium of bacteria potentially increased the variables," he said. (TK)
