Response of Soybean to Hydrochar-Based Rhizobium Inoculation in Loamy Sandy Soil

Hydrochar is rich in nutrients and may provide a favorable habitat or shelter for bacterial proliferation and survival. Therefore, in this study, we investigate the efficiency of a hydrochar-based rhizobial inoculant (Bradyrhizobium japonicum) on the symbiotic performance of soybean under both greenhouse and field conditions. There were positive and significant effects of hydrochar-based inoculation on the root and shoot growth of soybean as compared to uninoculated plants grown under irrigated and drought conditions. The drought stress significantly inhibited the symbiotic performance of rhizobia with soybean. Soybean inoculated with hydrochar-based B. japonicum produced twofold more nodules under drought stress conditions as compared to plants inoculated with a commercial preparation/inoculant carrier B. japonicum (HISTICK). The N concentration of inoculated plants with hydrochar-based B. japonicum was by 31% higher than that of un-inoculated plants grown in pots and by 22% for HISTICK. Furthermore, the soybean treated with hydrochar-based B. japonicum showed higher grain yield of 29% under irrigated conditions and 40% higher under rainfed condition compared to un-inoculated plants. In conclusion, the obtained results proved the potential of hydrochar-based B. japonicum inoculant for soybean in terms of increased symbiotic performance and agronomic traits, especially under rainfed conditions.

Effectiveness of organic culture media combination on propagation of Gigaspora sp. indigenous to Sorowako, Indonesia

Utilization of arbuscular mycorrhizal spores carrier media which has heavyweight, not optimal utilization of organic material as arbuscular mycorrhiza inoculant carrier, and founded of arbuscular mycorrhizal spores which have wide adaptability and tolerance on land contaminated with heavy metals are the basis for implementation of this research. The aim of this research was to determine combination of organic culture media which is good for increasing the abundance and diameter of indigenous Gigaspora sp. This research was carried out at Universitas Muhammadiyah Parepare, and Balai Penelitian dan Pengembangan Lingkungan Hidup dan Kehutanan Makassar. The research was compiled using a completely randomized design. The combination treatment of organic culture media used was a combination of rice husk charcoal, sand, zeolite; rice husk charcoal, sand, sawdust; rice husk charcoal, sand, cocopeat; rice husk charcoal, sand, paddy soil; rice husk charcoal, sand, cold larva. The results showed that combination of rice husk charcoal, sand, cocopeat; and combination of rice husk charcoal, sand, paddy soil gives the best results on growth and development of Gigaspora spores. Combination of rice husk charcoal, sand, and cocopeat, can be recommended as media an effective, efficient, and inexpensive spore carrier medium, but should be used after decomposing into compost.

Survival of an Actinomycete in a Carbonized Rice Hull-Based Carrier

Carbonized rice hull (CRH) is an alternative to wood charcoal as a carrier component in making inoculants. Being a waste product in rice farming, the use of CRH is more practical and environment-friendly. This study determined the survival of an actinomycete in a CRH-based carrier. Its cell population was counted periodically up to 250 days of incubation using the spread plate method. The initial population of 2.2 x 104 cfu/g increased to 2.9 x 107 cfu/g (135, 160%) 5 days after inoculation (DAI). However, number of cells decreased to 1.5 x 107 cfu/g 170 DAI, gradually increasing to a final population of 1.8 x 107 cfu/g at 250 DAI; 8.17 x 107 percent of the initial population remained viable in the CRH-based carrier. The survival of the actinomycete demonstrates the potential of CRH as inoculant carrier. However, which carrier can sustain high populations of the actinomycete has yet to be determined. Keywords - Microbiology, actinomycete, survival, CRH-Based carrier, Nueva Ecija, Philippines

Four Materials as Carriers for Phosphate Dissolving Rhizobium Sp. Inoculants

As the most commonly used carrier for commercial inoculants, the development of peat has been limited because peat is a material of nonrenewable resource. Many other materials have been evaluated as alternatives to peat as carriers of rhizobia, yet seldom have been included in inoculants of phosphate dissolving rhizobia. As accessible and inexpensive carriers for rhizobial inoculants, corn stalk powder, loessal soil and vermiculite powder were used in the study to compare with peat carrier on the capacities of rhizobial solution absorption, pH value maintaining of microenvironment, viable rhizobial cells maintaining and the control of contamination. Completely randomized design and 4 replicates were used in the experiment. Twelve different compositions of selected inoculant carrier with different absorption volumes of rhizobial suspension, and were evaluated the ability of maintaining viable rhizobial cells and undesired microbes during the period of 120 days at room temperature. Thereafter, pH value, viable rhizobial cell number and undesired microbes of inoculants with selected absorption volume of rhizobial suspension that stored at 4 and room temperature respectively, after 1a storage, were evaluated. Viable rhizobial cells in inoculants were examined after 120d and 1a storage by plate counting method, and ratio of undesirable microbes was examined by antibiotic-carrying and normal plates counting method. The result indicated that: for a period of 120days at room temperature, maximum viable rhizobial cells were found in peat, vermiculite powder, corn stalk powder and loessal soil based inoculants when the absorption volume of rhizobial suspension of inoculants were 450, 500, 1000 and 200ml/kg, respectively; viable rhizobial cell numbers were better maintained in corn stalk powder than in peat, loessal soil and vermiculite, but undesired microbes contamination was a severe problem. In the study, viable rhizobial cell numbers in loessal soil was found the highest, followed by peat, while the most serious contamination was found in peat inoculants; corn stalk powder and vermiculite could not be used as inoculant carrier because fewer viable rhizobial cells existed in these inoculants. The greatest pH change was found in peat and loessal soil based inoculants during 1a storage because of enhanced acidification caused by metabolism of phosphate dissolving rhizobia; more viable rhizobial cells were found in the 4 carriers that stored at 4 than at room temperature after 1a storage. As carriers of phosphate dissolving Rhizobium inoculants, viable rhizobial cells of corn stalk powder after short time storage (120d) and of loessal soil after long time storage (1a) were found better than that of peat, and was also found more cost effective compared with peat, commercially. Both of the two carriers could be used as inoculant carriers at room temperature, but corn stalk powder could only be used as carrier with short shelf life.

Polymers as carriers for rhizobial inoculant formulations

The aim of this work was to evaluate the efficiency of carboxymethyl cellulose (CMC) and starch blends as carrier materials of rhizobial inoculants regarding their capacity to maintain viable cells and promote cowpea (Vigna unguiculata) nodulation. The experimental design adopted was completely randomized, with three replicates. Forty different compositions of carboxymethyl cellulose (CMC) with starch, compatibilized or not with different proportions of MgO or ZnO, were evaluated regarding their ability of maintaining rhizobial viable cells during the storage period of one month at room temperature, in an initial screening. Thereafter, selected inoculant carrier blends were evaluated regarding their ability to maintain viable rhizobial cells for a period of 165 days, and their performance as inoculant carriers was compared to a peat-based inoculant carrier under greenhouse conditions. Rhizobial cells were better maintained in blends containing 50-60% CMC. Compatibilizing agents did not increase survival of rhizobial cells for 30 days of storage. The cowpea nodulation of polymer blends was statistically the same of peat-based inoculants. CMC/starch polymer blends are efficient carriers to rhizobial inoculants for up to 165 days of storage, when compatibilized with MgO (1%).

Relationship between nitrogen sources, germination and vigor of soybean seeds

This research was conducted in two experimental areas; the first had been under cultivation with Bradyrhizobium japonicum anually inoculated for several years and the second was cultivated with sugarcane for many years receiving only mineral fertilization. Mineral nitrogen (urea and ammonium) effect was compared with the effects of inoculant treatments (liquid and peat carriers) on plant development, yield and seed quality. After harvesting, seeds were stored under normal environmental conditions and tested periodically. Germination, accelerated aging, electrical conductivity and seedling emergence tests showed that seeds coming from the area where inoculation was practiced have better quality. Best plant performance regarding plant height at different growth stages and yield was also found in this area. Among the nitrogen sources studied, best results were obtained when peat was the inoculant carrier.