Effects of different phosphatase-producing fungi on growth and nutrition of mung beans [Vigna radiata (L.) Wilczek] in an arid soil

Summary The efficiency of different phosphatase-producing fungi in arid soils was studied in pot experiments in order to evaluate the effect of these organisms on the enhancement of rhizosphere enzyme activities, the uptake of different nutrients, dry matter production, and grain yields of the mung bean. A significant increase in phosphatase (acid and alkaline), nitrogenase, and dehydrogenase activities was observed upon inoculation. Inoculation with phosphatase-producing fungi significantly increased dry matter production and grain yields compared with uninoculated controls. In general, there was a significant improvement in the uptake of N, P, K, Ca, Mg, Fe, and Zn while no effect on Na, Mn, and Cu was recorded. A significant positive correlation was observed between the activities of various enzymes in the rhizosphere on the one hand and N and P uptake, dry matter production, and grain yields of the mung bean on the other. Aspergillus rugulosus was the best of the phosphatase-producing fungi that were tested, followed by A. terreus. The experiment confirmed that phosphatase-producing fungi have a significant effect on growth and nutrient uptake in the mung bean and indicated that these fungi are particularly important in arid soils.     

2,3,5-Triphenyltetrazolium chloride (TTC) as electron acceptor of culturable soil bacteria,fungi and actinomycetes

Dehydrogenase assays based on the reduction of 2,3,5- triphenyltetrazolium chloride (TTC) to the creaming red-coloured formazan (TPF), have been used to determine microbial activity in soil. By spraying TTC on culturable microbial colonies, whose growth was induced by applying glucose, we observed that from 72 to 100% of the bacterial and actinomycetes colonies in different soils were capable of using TTC as an electron acceptor. This percentage decreased to only 5% in the case of fungal colonies.     

Influence of crops, crop residues and manure on amino acid and amino sugar fractions of organic nitrogen in soil

A field experiment was carried out to study the effect of: (1) the cultivation of a cereal (pearl millet) and two legumes (mung bean and clusterbean), and (2) incorporation of crop residues and manure in soil, on depletion or enrichment of pools of amino acid-N and amino sugar-N in soil. Both legumes enriched amino acid and amino sugar fractions but pearl millet cultivation depleted them. Enrichment of these fractions was partly attributed to the conversion of N biologically fixed during legume cultivation to these fractions and partly to the conversion of unknown and non-hydrolysable N fractions to amino acid-N and amino sugar-N. Mineralization of amino acid-N and amino sugar-N fractions along with their conversion to unknown and non-hydrolysable fractions were the plausible reasons for the decline in their concentrations after pearl millet cultivation. Application of residues or manure reversed this effect of pearl millet.