Doongar R. Chaudhary

Paclobutrazol Arrests Vegetative Growth and Unveils Unexpressed Yield Potential of Jatropha curcas

Although the process for making EN 14214 grade Jatropha methyl ester (biodiesel) capable of running unmodified diesel engines in neat form has been demonstrated, getting higher seed yield from Jatropha shrubs in wastelands is critical to the success of Jatropha biodiesel. But, low productivity is inherent to many Jatropha curcas germplasms and raising large-scale plantations using such untested planting material can lead to wasteful expenditures. Unreliable and poor flowering and fruiting are important factors responsible for low productivity in the species. Although much is known about growth retardants applied to field and horticultural crops, their role in improving the seed productivity of Jatropha has never been explored. Here we report for the first time that paclobutrazol could be an extremely useful chemical, whose dose and time of application, if optimized, can significantly reduce unwanted vegetative growth, with concomitant improvement in yield and seed oil content of Jatropha. In the year following application of paclobutrazol, an unexpected increase in seed yield, as high as 1127% relative to controls, was obtained from one such unproductive Jatropha germplasm. We hypothesize that low seed production in this species may be a result of excess vegetative growth caused by an unfavorable endogenous hormonal configuration which competes with growth and development of flower, fruit, or seed. This undesired physiological state can be reversed by paclobutrazol application to achieve maximum oil yield from this energy shrub that holds great promise in the future.

SEAWEED SAP AS AN ALTERNATIVE LIQUID FERTILIZER FOR YIELD AND QUALITY IMPROVEMENT OF WHEAT

The experiment was conducted on a farmers field near Bhavnagar (Gujarat, India) during the Rabi season of 2008–2009 to study the effect of foliar applications of Kappaphycus alvarezii and Gracilaria edulis sap on growth and yield response of wheat var. ‘GW 496’. Three foliar sprays of both saps were applied at the rate of 2.5, 5.0, 7.5, and 10.0% (v/v) along with water as a control at different stages of the crop. It was found that yield of grain was increased significantly by 19.74% and 13.16% for plants receiving 7.5% and 5.0% concentrations of K. alvarezii and G. edulis sap, respectively, over control. The increase in yield was attributed to increases in the number of spike, spike weight, spike length and 100 seed weight. Foliar applications of K. alvarezii sap at 7.5% increased nutrient contents in grains from 7.91% (K) – 31.82% (S) whereas G. edulis sap increased nutrient content 5.72% (N) – 37.54% (Mg).

Microbial Profiles of Rhizosphere and Bulk Soil Microbial Communities of Biofuel Crops Switchgrass (Panicum virgatum L.) and Jatropha (Jatropha curcas L.)

The production of biofuels from the low-input energy crops, switchgrass (Panicum virgatum L.) and jatropha (Jatropha curcas L.), is a sustainable approach that can provide more usable energy and environmental benefits than food-based biofuels. Plant rhizosphere affects the microbial community structure due to variations in root exudation rates and residue chemistry. The objective of this investigation was to determine the profiles of microbial communities associated with rhizosphere and bulk soils of switchgrass or jatropha using phospholipid fatty acid (PLFA) analysis and length heterogeneity PCR (LH-PCR). Switchgrass soil contained a significantly (Pl0.05) higher abundance of Gram-positive (i14:0, i15:0, a15:0), Gram-negative (16:1ω5c, 16:1ω7c, 18:1ω5c), and saturated (14:0, 15:0) PLFAs compared to jatropha soil, whereas jatropha had a higher abundance of fungal (18:2ω6, 9c), 18:1ω9c, 20:1ω9c, and 18:0 PLFAs compared to switchgrass soil. Irrespective of plant type, rhizosphere soil contained a significantly (Pl0.05) higher abundance of saturated PLFAs (16:0, 18:0, 20:0), actinomycetes (10Me17:0), and fungal (18:2ω6, 9c) PLFAs compared to bulk soil; whereas bulk soil had higher abundance of saturated (14:0), Gram-negative (16:1ω9c, 16:1ω5c, 16:1ω7c), and 18:1ω9c PLFAs compared to rhizosphere soil. Multivariate principle component analysis of PLFAs and LH-PCR percent relative peak areas successfully differentiated the microbial communities of rhizosphere and bulk soils of switchgrass and jatropha.

Soil characteristics and mineral nutrient in wild jatropha population of India

Abstract Mature leaves of naturally occurring Jatropha curcas plants and soils samples were collected from four different populations to determine the soil characteristics, soil‐available nutrients, and leaf nutrient contents. This study provides a reliable account of the endogenic concentrations of nutrients present in jatropha leaves. Soil manganese [diethylenetriamine pentaacetic acid (DTPA)‐Mn] was the only soil‐available nutrient significantly correlated with its content in the plant. Relationships between soil characteristics, available nutrient in soil, and their content in plant leaves were also attempted.

Carbon and nitrogen mineralization potential of biofuel crop (Jatropha curcas L.) residues in soil

Use and management ofjatropha residue is currently an important global issue for attaining sustainability in biofuel production from Jatropha curcas on wastelands. Perhaps, knowledge about the decomposition characteristics and nutrient release pattern from jatropha residues amended soils are lacking. Thus, the objective of present research was to characterize the carbon (C) and nitrogen (N) mineralization of jatropha residues during decomposition in soil. The chemical composition of the residues, in terms of C, N, cellulose, hemicelluloses, lignin and phenolics contents were determined. Laboratory incubation studies were carried out with two soils (inside and outside-canopy soil ofjatropha shrub) and four jatropha residues (1% w/w) amendments (cake, leaf, fruit shell or control soil only). The cumulative CO2 evolution of the added residues was in the magnitude of fruit shell>leaf>cake>control soil. Net C mineralized in soils were in the range of 46-50, 66-67 and 75-77% of C added by cake, leaf and fruit shell, respectively at the end of incubation study. Soils amended with leaf immobilized N during the first 64 days but subsequently released inorganic N. The addition of cake and fruit shell resulted in net N mineralization and net N immobilization, respectively throughout the incubation period. Cumulative N released by the end of incubation was in the order of cake>leaf>control>fruit shell. Net N mineralization in soils during the study was 75-92 and 21-27% of N added by cake and leaf, respectively whereas there was net N immobilization in fruit shell amended soil. Cumulative CO2 evolution as well as N mineralization during incubation were higher in inside-canopy soil compared with that of outside-canopy soil. Jatropha cake and leaf proved to be a potential source of mineral N, however leaf will take about 60-70 days as gestation period to mineralize the nitrogen. Similarly, leaf and fruit shell also exhibited a good potential of C mineralization.

Fame Profiling and Activity of Microbial Communities During jatropha curcas L. Residue Decomposition in Semiarid Soils

There is widespread interest in the renewable biofuel potential of Jatropha curcas L., a shrub that exists under indigenous conditions in India. Following oil extraction from seeds, the remaining shell and cake residue can be used as a soil amendment. Microbial decomposition of organic residues can improve the quality of soils, but little is known about Jatropha as a soil amendment. Therefore, the objective of this study was to determine the influence of Jatropha residue on soil microbial community structure during decomposition. Soil microcosms amended with Jatropha leaves, cake, or fruit shell or an unamended control were incubated in the laboratory and destructively sampled at 3, 10, 20, 40, and 60 days. At each sampling, soil microbial communities were analyzed using fatty acid methyl ester (FAME) profiles, and enzyme assays performed for &bgr;-glucosidase, cellulase, and urease. Microbial biomass (FAMEtot) and bacterial and fungal FAME concentrations were significantly higher in cake-amended soil compared with other treatments. Averaged across all treatments, FAMEtot and fungal and bacterial FAMEs were highest on Day 3 and subsequently decreased significantly. Higher fungal-to-bacterial FAME ratios were found in residue-amended soils over control, with the highest ratio occurring in fruit shell-amended soil (except Day 3). A significantly lower ratio of the stress indicator (saturated to monounsaturated FAMEs) was found in cake-amended soil compared with other amendments. Fungal, bacterial, and actinomycetes biomarkers were significantly correlated with &bgr;-glucosidase and cellulase activities. The study shows that decomposition of Jatropha affected the soil microbial community, differently depending on residue type, but overall had positive effects in promoting the microbial diversity and activity, thus making Jatropha residue a favorable amendment for soils.

Biomass production, nutrient cycling, and carbon fixation by Salicornia brachiata Roxb.: A promising halophyte for coastal saline soil rehabilitation

ABSTRACT In order to increase our understanding of the interaction of soil-halophyte (Salicornia brachiata) relations and phytoremediation, we investigated the aboveground biomass, carbon fixation, and nutrient composition (N, P, K, Na, Ca, and Mg) of S. brachiata using six sampling sites with varying characteristics over one growing season in intertidal marshes. Simultaneously, soil characteristics and nutrient concentrations were also estimated. There was a significant variation in soil characteristics and nutrient contents spatially (except pH) as well as temporally. Nutrient contents in aboveground biomass of S. brachiata were also significantly differed spatially (except C and Cl) as well as temporally. Aboveground biomass of S. brachiata ranged from 2.51 to 6.07 t/ha at maturity and it was positively correlated with soil electrical conductivity and available Na, whereas negatively with soil pH. The K/Na ratio in plant was below one, showing tolerance to salinity. The aboveground C fixation values ranged from 0.77 to 1.93 C t/ha at all six sampling sites. This study provides new understandings into nutrient cycling—C fixation potential of highly salt-tolerant halophyte S. brachiata growing on intertidal soils of India. S. brachiata have a potential for amelioration of the salinity due to higher Na bioaccumulation factor.

Fate of Carbon in Water-Stable Aggregates during Decomposition of 13C-Labeled Corn Straw

Fundamental knowledge about decomposition, fate of crop residue, and allocation of residue-derived carbon (C) in soil aggregates is essential to understand the C dynamics in soil. The incorporation of C derived from corn residue in water-stable aggregate fractions, particulate organic C (POC), and mineral-associated C (MAC) in soil were examined using the 13C tracer technique. Soil was treated with corn straw at the rate of 1% dry mass of soil brought to 66% of field capacity and incubated for 70 days at 25 °C. Samples were taken at 20, 35, and 70 days and analyzed for water-stable aggregates. Values for POC and MAC were analyzed for total C and 13C enrichment. The addition of corn straw caused a shift in the distribution of recoverable particles with significant decreases in <53-μm silts and clays, microaggregrates (53–250 μm), and smaller macroaggegates (250–2000 μm); however, the large macroaggegates (>2000 μm) increased significantly. Macroaggregates contained greater amount of C than microaggregates. The proportion of 13C recovered in the fractions <53 μm (silt and clay), 53–250 μm, and 250–2000 μm increased during decomposition of corn straw, whereas there was no significant change in >2000-μm fraction. Most (70–76%) of the soil organic C was affiliated with MAC (<53 μm). Carbon (13C) derived from corn straw decreased in POC but increased in MAC as decomposition proceeded. In the long term, microaggregate fraction appears to be involved in storage and stabilization of the C derived from corn straw and is important for soil quality and soil C sequestration point of view.

Value-Addition of Jatropha Cake and Its Utilization as Manure in Jatropha and Other Crops

For every metric ton of biodiesel produced, roughly thrice the amount of solid Jatropha cake is produced as one of the main byproducts. Presence of toxins and anti-nutrients make it unfit for use as animal feed although it has high protein content, making its disposal a concern. Different environmentally sustainable ways to effectively utilize Jatropha cake are discussed in this chapter. Jatropha cake is a rich source of plant macro- and micronutrients and was found to effectively substitute for inorganic mineral fertilizers. Jatropha plant itself significantly responded well to Jatropha cake and was demonstrated to have better fertilizer effect as compared to other cakes (neem, mahua, karanja) on selected vegetable crops. It has also shown to possess good nematicidal and insecticidal properties. Soil amended with Jatropha residues showed that microbial biomass (FAMEtot) and bacterial and fungal FAME concentrations were significantly higher in cake-amended soil compared to other treatments. The degradation of toxic phorbol esters present in cake was studied in soil and it was found that they are biodegradable and that its degraded products also appear to be innocuous. Thus, Jatropha cake based organic fertilizer application enables sustainable agriculture with yield enhancements and is a viable alternative to synthetic inorganic fertilizers. Utilization of Jatropha cake for biogas has also been discussed along with other avenues like production of low cost industrial enzymes by solid-state fermentation of Jatropha seed cake, and its utilization as a substrate for growth of biocontrol agents. Scientific advances made towards detoxification of cake to make it suitable for animal feed purpose has also been explained.

Spatial and halophyte-associated microbial communities in intertidal coastal region of India

ABSTRACT Microbial communities in intertidal coastal soils respond to a variety of environmental factors related to resources availability, habitat characteristics, and vegetation. These intertidal soils of India are dominated with Salicornia brachiata, Aeluropus lagopoides, and Suaeda maritima halophytes, which play a significant role in carbon sequestration, nutrient cycling, and improving microenvironment. However, the relative contribution of edaphic factors, halophytes, rhizosphere, and bulk sediments on microbial community composition is poorly understood in the intertidal sediments. Here, we sampled rhizosphere and bulk sediments of three dominant halophytes (Salicornia, Aeluropus, and Suaeda) from five geographical locations of intertidal region of Gujarat, India. Sediment microbial community structure was characterized using phospholipid fatty acid (PLFA) profiling. Microbial biomass was significantly influenced by the pH, electrical conductivity, organic carbon, nitrogen, and sodium and potassium concentrations. Multivariate analysis of PLFA profiles had significantly separated the sediment microbial community composition of regional sampling sites, halophytes, rhizosphere, and bulk sediments. Sediments from Suaeda plants were characterized by higher abundance of PLFA biomarkers of Gram-negative, total bacteria, and actinomycetes than other halophytes. Significantly highest abundance of Gram-positive and fungal PLFAs was observed in sediments of Aeluropus and Salicornia, respectively than in those of Suaeda. The rhizospheric sediment had significantly higher abundance of Gram-negative and fungal PLFAs biomarkers compared to bulk sediment. The results of the present study contribute to our understanding of the relative importance of different edaphic and spatial factors and halophyte vegetation on sediment microbial community of intertidal sediments of coastal ecosystem.