E. V. S. Prakasa Rao

Effect of concentration, temperature, moisture, liming and organic matter on the efficacy of the nitrification inhibitors benzotriazole, o-nitrophenol, m-nitroaniline and dicyandiamide

Laboratory experiments were carried out to study the effect of various factors that affect the efficacy of the nitrification inhibitors, benzotriazole, o-nitrophenol, m-nitroaniline and dicyandiamide. In a Paleustalf, increasing concentrations of the inhibitors from 0 to 15 mg/kg soil prolonged the nitrification up to 60 days. Increase in temperature from 10 to 30°C decreased the efficacy of all four nitrification inhibitors (by 6–62% at 30 days). Benzotriazole was equally effective in soil moisture conditions ranging from 40 to 80% of the maximum water holding capacity of the soil (WHC). o-Nitrophenol and m-nitroaniline were more effective at 60% WHC, while the efficacy of DCD was more at 40% WHC. Addition of 1000 mg/kg soil of fresh organic matter reduced the efficacies of o-nitrophenol, m-nitroaniline and benzotriazole by 55, 65 and 22%, respectively while the reduction in the efficacy of dicyandiamide was non-significant. Liming an acidic soil (Kandiustalf) to change the pH from 5.4 to 8.3 decreased the efficacies of the nitrification inhibitors and decreased the ammonium content in the soil at 30 days from 55 to 9 mg/kg in case of o-nitrophenol and m-nitroaniline and from 53 to 35 mg/kg in case of benzotriazole and dicyandiamide.

Effect of arbuscular mycorrhizal fungi and Pseudomonas fluorescens on root-rot and wilt, growth and yield of Coleus forskohlii

Abstract Root-rot and wilt caused by Fusarium chlamydosporum affects the cultivation of Coleus forskohlii, a medicinal plant grown for its roots, which contain a pharmaceutically important compound called forskolin. In this study, management of this disease under low and high inoculum levels was assessed with four arbuscular mycorrhizal (AM) fungi and a strain of Pseudomonas fluorescens. The AM fungus Glomus fasciculatum and P. fluorescens were the most effective treatments that reduced the severity of root-rot and wilt of C. forskohlii by 56–65% and 61–66%, respectively, under lower and higher levels of pathogen F. chlamydosporum. G. fasciculatum increased the dry shoot and root weight by 108–241% and 92–204%, respectively, while in plants treated with P. fluorescens, an increase of 97–223% and 97–172% in dry shoot and root weight, respectively, was observed. Although P. fluorescens was effective, it gave higher root yields only under lower inoculum level of the pathogen. G. fasciculatum performed equally well under both lower and higher inoculum levels. Increase in yields with both the biocontrol agents was accompanied by increase in P uptake (230–303%) and in K uptake (270–335%). The forskolin content of the roots was significantly increased (14–21%) by G. fasciculatum, P. fluorescens or G. mosseae under lower inoculum level of pathogen.

Agronomical and Chemical Studies on Tagetes minuta Grown in a Red Soil of a Semiarid Tropical Region in India

Abstract The agronomic performance and chemical composition of Tagetes minuta L. was evaluated in a new agro-climatic region of semiarid tropical India. T minuta performed well under these conditions and responded to application of 50 kg N/ha. Analysis of the leaf and flower oils by GC revealed that the leaf oil contained dihydrotagetone (6l.0%) and (Z)-tagetone (16.1%), while the flower oil was rich in (Z)-β-ocimene (47.9%) and (Z)-tagetenone (19–6%).

Influence of Nitrogen and Potassium Fertilization on Yield and Quality of Rosemary in Relation to Harvest Number

Rosemary is an important aromatic and spice plant. Its cultivation for production of its essential oil has gained importance in recent years. An experiment was conducted in a red sandy loam (Kandiustalf) soil to study the impact of cultivation of this multiharvest crop at different nitrogen (N) and potassium (K) application regimes on soil fertility and crop yield at the farm of the Central Institute of Medicinal and Aromatic Plants, Resource Center, Bangalore, during 2003–2005. The treatments consisted of all combinations of N levels (0, 150, and 300 kg per hectare per year) and K levels (0, 50, and 100 kg per hectare per year). Five harvests were taken at about 5‐month intervals. The results showed that initially the soil alone was able to meet the crop requirements for K, but with the progress of time, addition of K to the soil in the form of fertilizer became necessary for obtaining optimum yields. At the end of five harvests, exchangeable K in soil was significantly lower as application of K decreased from 100 to 50 and 0 kg per hectare per year. Soil fertility could be maintained and oil yields of rosemary from four harvests could be increased from 146.6 L to 344.7 L per hectare by application of 150 kg N and 100 kg K.

Regulation of Nitrification by Benzotriazole, o-Nitrophenol, m-Nitroaniline and Dicyandiamide and Pattern of NH3 Emissions from Citronella Field Fertilized with Urea

Nitrification inhibitors areuseful for reducing fertilizer related environmentalpollution. Use of such nitrification inhibitors as,benzotriazole, o-nitrophenol, m-nitroaniline anddicyandiamide has effectively regulated nitrification in acitronella (Cymbopogon winterianus Jowitt.) fieldfertilized with urea. At 450 kg N ha-1 yr-1, there wassubstantially higher accumulation of NH+4-N in thesoil. Proper placement (5 cm below soil surface) offertilizers have minimized NH3 emissions even fromnitrification inhibitor treated urea plots. Thus, thenitrification inhibitors can potentially reduceenvironmental pollution connected to NO-3 in soilwhile maintaining low NH3 gas emissions, if thefertilizer is properly placed.

Evaluation of nitrification inhibitors for use under tropical conditions

Abstract Six simple chemical compounds were evaluated for inhibition of nitrification. The compounds of o‐nitroaniline, m‐nitroaniline, o‐nitrophenol, benzotriazole, and 2,4,6‐trinitrophenol were compared with dicyandiamide by adding 10 μg inhibitor/g of a sandy loam soil, incubating for 30 days at 30°C and analyzing for NH+ 4, NO‐ 2, and NO‐ 3 formation. The results indicated that benzotriazole, o‐nitrophenol, and m‐nitroaniline were very effective nitrification inhibitors.

Determination of nitrate in soil by second derivative ultraviolet spectrometry

Abstract A second derivative UV‐spectrometry method is described for the determination of nitrate in soils. Ammonium, nitrite, and urea may be determined in the same extract. The method generally requires no pretreatment of soil extracts, and hence is very rapid. It is largely free from interferences. Recoveries of added nitrate in four soils by the proposed method compared favourably with the phenoldisulphonic acid method.

Effect of Irrigation and Levels of Nitrogen on Herb and Oil Yield of Geranium (Pelargonium sp.) under Semiarid Tropical India

ABSTRACT The effect of irrigation given at various cumulative pan-evaporation levels (CPE) (50, 75 and 100 mm) and three depths of irrigation water (IW) (20, 30 and 40 mm per irrigation) in Bangalore was studied. The irrigation at four IW/CPE ratios (1.0, 0.50, 0.30 and 0.25 mm, with 30 mm depth of irrigation water) and three nitrogen levels (0, 100 and 200 kg N/ha/year) was also studied. Results revealed that irrigation at 50 mm CPE with 30 mm depth of irrigation gave the optimum herb and oil yield and the other experiment showed that geranium has to be irrigated at 0.50 IW/CPE ratio and supplied with 100 kg N/ha/year for achieving high yields. Content and quality of oil were not affected by irrigation and levels of nitrogen.

Elimination of chloride interference in the phenoldisulphonic acid method of nitrate determination in soils

Abstract A technique was developed to eliminate chloride interference using antimony (III) in the determination of nitrates in soils by phenoldisulphonic acid method. This method was found effective upto nearly 300 ppm Cl‐ in soils ranging in pH from 5.6 to 8.3. By avoiding repeated filtrations of chloride precipitates, this method allowas quick analysis of soils for nitrates in single soil extracts containing other mineral nitrogen fractions.

Assessment of Organic and Inorganic Fertilizers for Growth, Yield and Essential Oil Quality of Industrially Important Plant Patchouli (Pogostemon cablin) (Blanco) Benth.

Abstract The present study was conducted to evaluate the right proportion of organic and inorganic fertilizers for growth, oil yield and nutrient uptake pattern of patchouli. The results indicated that significantly higher oil yield was recorded in 75 % VC+25 % NPK (256 %) followed by100 % NPK (249 %) as compared to control. An increase of 6 % in essential oil content was achieved in treatment with 75 % VC+25 % NPK and 25 % VC+75 % NPK but the effect was non-significant. Also, the quality of essential oil, which is basically measured by patchouli alcohol, was not affected by any treatments. Enhancement in vermicompost doses significantly improved the bulk density (0.61- 13.94 %), total organic carbon (3.3-34.4 %) and soil microbial biomass (3-149 %). Availability of N, P and K was significantly higher in 75 % VC+25 % NPK (20 %, 103 % and 64 %, respectively) over control. Maximum nutrient (N, P and K) uptake was found in treatment with 100 % NPK (78 %, 67 % and 54 %, respectively) followed by 75 % VC+25 % NPK (76 %, 63 % and 51 %, respectively). The present study clearly indicated that 75 % chemical fertilizer could be saved by integrating 75 % vermicompost with 25 % chemical fertilizer resulted similar oil yield and improved soil health.