Research on biodiversity of N-fix bacteria was performed on rhizosphere of Tithonia diversifolia grown at acid soil Ultisol. This study aimed to determine the biodiversity and populations of N-fix bacteria along with the growth rate of Tithonia and characterized the bacterial isolates obtained from the rhizosphere of this plant. Soil rhizosphere samples were taken from rhizospheres of Tithonia with different criteria of stem diameter i.e Ø <3 cm, and 3 to 6 cm that grown at Faculty of Agriculture Andalas University experimental station.From these results it can be concluded that the diverse and larger population were found in Tithonia with 3 to 6 cm stem diameter an average of 19.7 x 103 cfu per g of soil. N-fix bacterial isolates obtained have a round, slimy, slippery and convex colonies and gram variable. Based on the color of their colonies, N-fix bacterial isolates obtained were classified into 3 groups with the following characteristics: (1) white milk isolates (A1ps, a2ps, B3ps), flourescent white and yellow, have flagella and produce auxin, (2) yellow isolate (B2K and B3K), with yellow flourescent, have flagella and produce auxin, and (3) the clear isolates that could separated into two groups i.e the flourescent group and produce auxin and has flagella isolates (A2b, A3b, and B2b) and non flourescent group, no flagella and does not produce auxin isolates (B1b, B3B). The optimum growth conditions for the all isolates were pH media nearly 7 with 35 o C incubation temperature. The translucent isolates (A3b and B3B) have a optimum range pH from 4.36 to 6.17, while isolates with a yellow colonies (B2K) has a range of incubation temperature 25 o C to 35 o C. However, from the characterization performed could not permit to specify the isolates obtained into species.

Abstr actRhizobacteria from various research results have shown an important role in producing organic compounds (phytohormone) which can affect plant physiological processes even in low concentrations. This research aimed to study the production of Indole Acetic Acid (IAA) in several plants rhizosphere, to calculate the rhizobacteria population that able to produce and synthesize IAA and to isolate these rhizobacteria from several rhizospheres of cultivated plants (maize and peanut) and bush plant i.e. karamunting (Rhodomyrtus tomentosa) and titonia (Tithonia diversifolia). All plants and crops were obtained from experimental station Faculty of Agriculture Andalas University. Further research is conducted in Soil Biology Laboratory Faculty of Agriculture. Experimental design in this study was not used but the data obtained from 3 replications tested by T test at 5% level and if it was significantly different it would be followed by further HSD tests at 5% level. Highest content of IAA was found in the peanut crop (67.30 ppm), followed by maize (53.61 ppm) and 28.53 ppm for titonia. Whereas the lowest content of IAA was found in karamunting rhizosphere, it was 22.29 ppm. The highest amount of rhizobacteria was obtained from peanut rhizosphere followed by maize and titonia i.e 18.28, 12.08 and 7.87% of the total population, respectively. There was no IAA producing rhizobacteria population was found in karamunting rhizosphere. Based on the results of the ability of the test to produce IAA in the King's B liquid medium at low pH (pH 4.0), the leading isolates were obtained in each rhizosphere, namely: J.2b and J.3b isolates from maize rhizosphere; Kc.1b, Kc.2b and Kc.3b from peanut isolates, and Ti.3c isolates from titonia rhizosphere.

Polluted irrigation can degrade soil chemical properties and then decrease land productivity. This research aimed to compare the effectiveness of biochar against manure in reducing the concentration of some heavy metals(HM) in the polluted rice field. This pot trial was conducted at Glasshouse using two types of amelioration (biochar and manure). Biochar and manure were incubated with paddy soil under field capacity at the glasshouse for one month. The results showed that increasing the dosage of either biochar or manure applied decreased the availability of HM, especially Fe (r=-0.87, r=-0.89) and Mn (r=-0.82, r=-0.91), respectively. However, there was no effect of biochar (r=0.25) but increased by manure (r=0.95) application on Zn concentration. Furthermore, some other heavy metals concentration also decreased, such as Ag (r=-0.89), Pb (r=-0.54), Cu (r=-0.51), Cr (=- 0.50), and Ni (r=-0.64) by applying biochar but tended to increase by applying manure. Both biochar and manure could increase some plant nutrients, especially K (r=0.74, r=0.82), P (r=0.85, r=-0.44), Mg (r=0.98, r=0.91) and Ca (r=0.98, r=0.84), respectively.

In the first stage of arbuscular-mycorrhiza (AMF) fungi development on plant roots showed that root exudates, is a substance that determines the success of the establishment of mycorrhizal symbiosis. This secondary metabolites produced is intended to keep mold growth during the phase preinfection. Therefore, it is interesting to know whether to add the root extract of the plant could enhance CMA fungal infection in its host plant. The purpose of this study was to determine the type of root extract can stimulate CMA infection at the root and its influence on the growth of Tithonia diversifolia. This experiment used Completely Randomized Design (CRD) with 4 treatments and 3 replications, and continued with advanced test DNMRT at level 5%. The treatments assayed were: control, Tris-HCl buffer pH 7 (A), root extract of weed Imperata cylindrica (B); root extract of taro (C), and root extract of cassava (D). Base on the results obtained we concluded that the extract of the roots of weeds, taro and cassava does not give effect to the increased growth of Tithonia. However, the roots extract stimulated and had influenced on the percentage and intensity of AMF infection at the root of Tithonia and the number of spores obtained in the rhizosphere of Tithonia. In this case the root extract of taro showed the best stimulatory effect of infection with the percentage and intensity of infection are 99.3% and 30.59% consecutively with the number of spores found reach 113 spores/ 100 g soil.Key words: Stimulation, arbuscular-mycorrhiza, root extract, Tithonia diversifolia

Regosol, a suboptimal land, is rarely cultivated due to its low water retention and nutrient content. It is needed organic matter to improve the soil physical, chemical, and biological properties. A research conducted in glasshouse and soil laboratory was aimed to find out the best dosses of compost derived from rice straw and tithonia to improve soil chemical properties of Regosol as well as onion production. There were 9 levels of compost dosses (0; 2.5; 5.0; 7.5; 10.0; 12.5; 15.0; 17.5; and 20.0 tonha-1) applied to soil with three replications. The experimental units were allocated based on Completely Randomized Design (CRD). Crop data resulted were statistically analyzed using F-test and then continued using Least Significance Difference (LSD) at 5% level of significance if F-calculated > F-table. The result showed that compost application up to 20 ton ha-1 did not significantly affect chemical properties of Regosol as well as onion production. The highest weight of onion bulb was found at application of 7.5 t compost ha-1, however the highest N, P, and K uptake was found at dosses 20 t compost/ha-1. Therefore, it was needed further study to determine the appropriate compost dosses for optimal onion production in Regosol.