Earthworm compound and rock biofertilizer enriched in nitrogen by inoculation with free living diazotrophic bacteria

Abstract

Free living diazotrophic bacteria are known to enrich nitrogen of organic matter sources. In this paper we report of experiments using rock biofertilizers mixed with two types of organic matter (earthworm compound and ice cream waste) inoculated with free living diazotrophic bacteria. The earthworm compound and P and K biofertilizers were mixed to form substrates S 1 (earthworm compound 3 dm 3 ? PK biofertilizer 1 dm 3 and waste ice cream 1 dm 3 ); S 2 (earthworm compound 2.5 dm 3 ? PK biofertilizer 1.5 dm 3 and waste ice cream 1 dm 3 L) and S 3 earthworm compound 2.0 dm 3 ? PK biofertilizer 2.0 dm 3 and waste ice cream 1 dm 3 ), and subsequently inoculated (100 mL pot -1 ) with 3 free living diazotrophic bacteria isolated from different Brazilian soils. The control was an uninoculated earthworm compound. Samples were collected at various incubation time (0; 15; 30 and 45 days) and analyzed for total N. Total N concentrations were highest in S 1 , S 2 and S 3 substrates at 34, 27 and 29 days, respectively. The isolate NFB 1001 increased total N in all substrates and the best results were obtained at 34 days in S 1 substrate which contained the highest amount of earthworm compound. The isolates promoted a decline in N content after 30 days of growth, indicating the best time to produce the organic biofertilizer. The organic biofertilizer enriched in nitrogen by free living diazotrophic bacteria is of relevance to organic agriculture.

Plant and soil characteristics affected by biofertilizers from rocks and organic matter inoculated with diazotrophic bacteria and fungi that produce chitosan

“…The reduction in pH values was evident in the biofertilizer (NPKB) with inoculation of the free living bacteria (NFB 1001) and with the addition of C. elegans. Similar pH results were obtained by Lima et al (2010) in a study evaluating the effect of diazotrophic bacteria on the chemical parameters of biofertilizer produced from earthworm compound inoculated with different strains of free living diazotrophic bacteria. Comparing the results from the mixed biofertilizer (NPKB) and the biofertilizer with the addition of the fungi C. elegans, there was no change in pH reduction, likely due to the short incubation time (10 days).…”

“…The isolate (NFB 1001) was cultured in LG liquid media (50 mL) in 125 mL Erlenmeyer flasks, shaken (180 rpm) for 96 h at ±28 °C and applied at 100 mL per tray, according to Lima et al (2010). After inoculation, the trays were incubated for 30 days at 28 ±5 °C.…”

“…Therefore, it is necessary to use organic matter with high pH to control the acidic effects of rock biofertilizers (Lima et al, 2010). Studies carried out in tableland soil from the Brazilian Northeast reported that sulfur inoculated with Acidithiobacillus is a promising material for soil fertilization because it releases P and K from rock minerals, which reduces the nutrient deficiency of acidic soils used to grow different crops (Stamford et al, 2008, Lima et al, 2007, Moura et al, 2007.…”

“…However, in many cases, these materials contain low concentrations of N. Biological nitrogen fixation (BNF) is one of the most fundamental processes used to supply N to the soil, especially in combination with organic matter (Lima et al, 2010).…”

“…To produce a more complete biofertilizer, it is important to improve the N concentration of the organic matter. One method for achieving this is by adding free living diazotrophic bacteria to enrich the N content of the organic material (Lima et al, 2010).…”