Kulasekaran Ramesh

Zeolites and Their Potential Uses in Agriculture

Abstract Zeolites are natural crystalline aluminosilicates. They are among the most common minerals present in sedimentary rocks. Zeolites occur in rocks of diverse age, lithology, and geologic setting, and represent valuable indicators of the depositional and postdepositional ( diagenetic ) environments of the host rocks. It was reported that, of the 40 naturally occurring zeolites studied by research groups, the most well-known ones are clinoptilolite, erionite, chabazite, heulandite, mordenite, stilbite, and phillipsite. Structurally, zeolites are tectosilicates exhibiting an open three-dimensional structure containing cations needed to balance the electrostatic charge of the framework of silica and alumina tetrahedral units. Pores and voids are the key characteristics of zeolite materials. The pores and interconnected voids are occupied by cations and water molecules. The internal surface area of these channels are reported to reach as much as several hundred square meters per gram of zeolite, making zeolites an extremely effective ion exchangers. The Si/Al ratio is an important characteristic of zeolites. The charge imbalance due to the presence of aluminum in the zeolite framework determines the ion-exchange property of zeolites and is expected to induce potential acidic sites. The Si/Al ratio is inversely proportional to the cation content, however directly proportional to the thermal stability. Cations can be exchanged by ion exchange and water can be removed reversibly by application of heat. The unique physical and chemical properties of zeolites, coupled with their abundance in sedimentary deposits and in rocks derived from volcanic parent materials, have made them useful in many agricultural applications. Most of the initial research on the use of zeolites in agriculture took place in the 1960s in Japan. A brief review of the literature has pointed out that Japanese farmers have used zeolite rock over years to control the moisture content and to increase the pH of acidic volcanic soils. Ion-exchange properties of zeolites can be utilized in agriculture because of their large porosity and high cation-exchange capacity. They can be used as both carriers of nutrients and a medium to free nutrients. Zeolites are important materials with very broad applications in agriculture and environmental engineering. Zeolite incorporation in soil was found to increase crop yields and to promote nutrient use efficiency. Other possible uses being investigated include applications as a carrier of slow-release fertilizers, insecticides, fungicides, and herbicides, and as a trap for heavy metals in soils.

Production potential of Stevia rebaudiana (Bert.) Bertoni. under intercropping systems

Abstract Stevia (Stevia rebaudiana[Bert.] Bertoni.) is a crop of recent domestication in many countries. The cultivation of this plant in hilly and frost-prone areas provides an opportunity for intercropping of various food crops since the crop undergoes winter dormancy in India. This was studied through intercropping (additive series) at two spacings of the main crop, namely, 45×45 cm and 60×45 cm. Wheat, barley, lentil and gobhi sarson were intercropped. Intercropping reduced the production of S. rebaudiana up to 50% when compared to sole cropping. However, a row spacing of 60×45 cm resulted in less competition than the former, although, single cropping of S. rebaudiana produced the maximum stevioside. Intercropping with wheat increased the stevioside content when compared to other intercrops. The introduction of wheat resulted in higher monetary benefits at 60×45 cm spacing. Results indicated that reduction in S. rebaudiana biomass was mainly due to overlapping of the emergence period of the main crop with rapid growth and development of the intercrops. In conclusion, to lower competitive effects, the intercrop needs to be early maturity. Identifying suitable varieties for intercropping should be the priority research area to increase the productivity of the system.

Effects of shade regimes and planting geometry on growth, yield and quality of the natural sweetener plant stevia (Stevia rebaudiana Bertoni) in north-western Himalaya

During 2008 and 2009, field experiments were conducted at the research farm of CSIR-Institute of Himalayan Bioresource Technology, Palampur, India to assess the effect of shade levels (no shade, 25% shade, 50% shade, 75% shade) and plant geometry levels [30 × 15 cm (north–south, N–S), 45 × 10 cm (N–S), 30 × 15 cm (east–west, E–W) and 45 × 10 cm (E–W)] on the growth, yield and quality of stevia. Plant development was fastest in controls and slowest in stevia plants growing at minimum light (75% shade). These plants showed delayed bud formation and flowering. Significantly, higher dry leaf yield was recorded when the crop was grown under 25% shading than under 50 and 75% shade. Total steviol glycosides content decreased with increasing shade levels. All shade levels resulted in the same leaf-to-stem ratio, which was significantly higher than that obtained under ambient light. Plant geometry significantly affected the number of leaves and leaf dry weight plant–1. During both years, dry leaf weight was highest in the wider row spacing (45 × 10 cm) than in the narrow row spacing (30 × 15 cm). Stevia spaced at 30 × 15 cm in an E–W direction recorded significantly higher total steviol glycosides at 2 months after transplanting (MAT).

Weeds in a changing climate: vulnerabilities, consequences, and implications for future weed management

Whilst it is agreed that climate change will impact on the long-term interactions between crops and weeds, the results of this impact are far from clear. We suggest that a thorough understanding of weed dominance and weed interactions, depending on crop and weed ecosystems and crop sequences in the ecosystem, will be the key determining factor for successful weed management. Indeed, we claim that recent changes observed throughout the world within the weed spectrum in different cropping systems which were ostensibly related to climate change, warrant a deeper examination of weed vulnerabilities before a full understanding is reached. For example, the uncontrolled establishment of weeds in crops leads to a mixed population, in terms of C3 and C4 pathways, and this poses a considerable level of complexity for weed management. There is a need to include all possible combinations of crops and weeds while studying the impact of climate change on crop-weed competitive interactions, since, from a weed management perspective, C4 weeds would flourish in the increased temperature scenario and pose serious yield penalties. This is particularly alarming as a majority of the most competitive weeds are C4 plants. Although CO2 is considered as a main contributing factor for climate change, a few Australian studies have also predicted differing responses of weed species due to shifts in rainfall patterns. Reduced water availability, due to recurrent and unforeseen droughts, would alter the competitive balance between crops and some weed species, intensifying the crop-weed competition pressure. Although it is recognized that the weed pressure associated with climate change is a significant threat to crop production, either through increased temperatures, rainfall shift, and elevated CO2 levels, the current knowledge of this effect is very sparse. A few models that have attempted to predict these interactions are discussed in this paper, since these models could play an integral role in developing future management programs for future weed threats. This review has presented a comprehensive discussion of the recent research in this area, and has identified key deficiencies which need further research in crop-weed eco-systems to formulate suitable control measures before the real impacts of climate change set in.

Diazocoupling reaction for the spectrophotometric determination of physiologically active catecholamines in bulk and pharmaceutical preparations

A simple and sensitive spectrophotometric method for the determination of four catecholamines viz., adrenaline bitartarate (ABT), methyldopa (MDP), dopamine hydrochloride (DPH), and levodopa (LDP), in both pure form and in pharmaceutical formulations is described. The method is based on the reaction of diazotized sulphanillic acid (DSA) with catecholamines in a basic medium to yield orange-red colored products having absorption maxima at 507 nm for MDP and at 475 nm for others analytes. The colored species obeyed Beer’s law in the range of 1–27, 0.5–17, 0.6–15, and 1.5–19.2 μg/mL for ABT, MDP, DPH, and LDP, respectively. The molar absorptivity values as obtained from Beer’s law data were found to be 0.812 × 104, 0.947 × 104, 0.927 × 104, and 0.709 × 104 L/(mol cm), while Sandell’s sensitivity values were observed to be 412.03, 25.15, 20.44, and 27.81 ng/cm2 for ABT, MDP, DPH, and LDP, respectively. Common excipients did not interfere with the proposed method. The results of the proposed methods compare favorably with those of official methods. The proposed method offers a simplicity, reliability, rapidity, and accuracy compared to the existing methods.

Irradiance stress and plant spacing effect on growth, biomass and quality of wild marigold (Tagetes minuta L.) – an industrial crop in western Himalaya

A study was carried out over 2 years (2009 and 2010) at the CSIR–Institute of Himalayan Bioresource Technology, Palampur, India, to investigate the effect of irradiance stress and plant spacing on growth, biomass yield, essential oil content and composition in wild marigold (Tagetes minuta L.). Four shade levels (0%, 25%, 50% and 75%) and three plant spacing (45 × 30, 45 × 45 and 60 × 45 cm) were tested as per split plot design. Heavy shading (50% and 75%) strongly reduced the total essential oil content in fresh leaves and flowers. The essential oil content of leaves, flowers and the total oil increased up to the 25% shade level and declined thereafter, with a decrease in irradiance level. Ocimene and dihydrotagetones concentration in leaf oil decreased with decrease in irradiance level; however, tagetone and ocimenone showed the reverse trend. In flower oil, ocimene decreased with an increase in shade levels. Fresh leaf, stem, flower, leaf + flower biomass, and total biomass was significantly higher in the 45 × 30 cm spacing level. Essential oil content in flowers of T. minuta grown in 25% shade at 45 × 45 and 45 × 30 cm spacing recorded significantly higher essential oil content than other treatments.

Effects of Growth Regulator Application on Growth, Flower, Oil Yield, and Quality of Clary Sage (Salvia sclarea L.)

ABSTRACT The effects of growth regulator applications (kinetin, IAA and Paclobutrazol) on field grown Salvia sclarea L. were studied during 2005 to 2006 at the Institute of Himalayan Bioresource Technology, Palampur, India. Growth was monitored by measuring plant height, canopy spread, leaf number, primary branches, and yield characteristics (inflorescence length and flower and oil yield). Quality was evaluated. Maximum height and leaf numbers were observed after application of kinetin 10 μL L−1 and IAA 50 μL L−1, respectively. Maximum flower and oil yield were observed after application with 40 μL L−1 paclobutrazol (PBZ) application. Application of 80 μL L−1 paclobutrazol application increased the linalool-linalyl acetate content of the plant about 12% higher than the untreated control.

Morpho-physiological and biochemical response of maize (Zea mays L.) plants fertilized with nano-iron (Fe3O4) micronutrient

ABSTRACT Nano-sized formulations of micronutrient iron (Fe) were found to substantially alter the growth and metabolism of maize plants. Plants fertilized with the optimal recommended dose of Fe in the nano-form (54 μM) registered an enhancement in morphological features, viz. plant height, biomass (shoot and root), and diminution in antioxidant enzyme activities than the plants fertilized with the sub-optimal dose of Fe in the macroform (salts). However, half of the recommended dosage of Fe (27 μM) in the nano-form positively influenced leaf area and proline content of plants too. This indicated that there is a possibility of reducing the dose of Fe supplement for plants in the nano-form to increase the nutrient use efficiency in a major cereal crop like maize. This may open a new era in plant nutrient management with a scope for improvement in nutrient use efficiency using nano-nutrient formulations.

More Efficient Use of Agricultural Inputs as Part of Adoption of Preparedness Strategies: Multiple Cropping

Desai (1988) indicated already 20 years ago that accelerated growth in agricultural production of developing countries depends on exploiting more fully the existing production potential and continuously raising that potential through technological change. He indicated that this requires sustained rapid growth in the use of inputs such as seeds of better quality, fertilizers, pesticides, farm implements, and machinery. Price policy issues at that time dominated in discussions on how to increase the use of these inputs, often without sufficient attention to certain non-price factors and policies. We now know that both price and non-price factors remain important. It must also be acknowledged that at present no achievements would have been in place, had millions of resource-poor farmers living mostly in the developing world not adopted new crops, varieties/hybrids, cropping systems and innovative production technologies. Thus, the secret of success lies in wide scale adoption of improved technologies by millions of small and marginal farmers (Paroda 2004).

Heavy Metal Toxicities in Soils and Their Remediation

Pollution of soils with heavy metals from various sources has become a common feature across the globe due to increase in anthropogenic activities and industrial development and has attracted the attention of all stakeholders. In spite of the differential tolerance of plants to heavy metal toxicities, impairment in the productivity of most of the agricultural crops is steadfast throughout the globe. Bio-transfer of these metals remains unabated from polluted sites and even through animal milk and dung. The remediation methods are broadly grouped into engineering, electrokinetics, and bioremediation. These have their own merits and demerits, but the bioremediation is quite effective and the current results are encouraging. Therefore, the sources of heavy metals to soils (including pathways), their effect on soils and plants, and few of the proven phytoremediation methods have been elaborated here.