Bacterial populations on the phyllosphere of Mediterranean plants: influence of leaf age and leaf surface

In the present study, we estimated the size of phyllosphere bacterial populations in young and mature leaves from the same plants and also assessed the population abundance on adaxial and abaxial leaf surfaces. We examined eight perennial species naturally occurring in the same area, in Halkidiki (northern Greece). They are Arbutus unedo, Quercus coccifera, Pistacia lentiscus, and Myrtus communis (evergreen sclerophyllous species), Lavandula stoechas and Cistus incanus (drought semideciduous species), and Calamintha nepeta and Melissa officinalis (nonwoody perennial species). Young and mature leaves were examined from the four sclerophyllous evergreen species for their epiphytic bacterial colonization, and it was found that mature leaves were highly populated compared to the younger ones except in M. communis. As regards the bacterial colonization of the two leaf surfaces, no differences were found in most species except for the drought semideciduous type where the two leaf surfaces behaved differently.     

Litter dynamics and soil properties under different tree species in a semi-arid region of Rajasthan,India

Litterfall and decomposition are the two main processes accounting for soil enrichment in agroforestry. The extent of enrichment in soil properties depends on the tree species, management practices and the quantity and quality of litter. A field investigation was carried out to study litterfall production, decay rates, release of nutrients and consequent changes in soil physicochemical properties under crowns of four multipurpose tree species (MPTs) in irrigated conditions in farm fields. The species were Prosopis cineraria (L.), Dalbergia sissoo (Roxb.) ex DC, Acacia nilotica (L.) Del. and Acacia leucophloea (Roxb.) Willd. Annual accretion of litter ranged from 36 to 54 kg tree⁻¹ year⁻¹ and was highest under D. sissoo and lowest under A. nilotica. Total litterfall production was in the order: P. cineraria > A. leucophloea > A. nilotica > D. sissoo. P. cineraria showed the highest NPK concentration in litter. For all MPTs, a large pulse of litterfall coincided with the winter season (November to February). Litter of P. cineraria decomposed fastest while that of A. nilotica was slowest. More than 95% of the leaf litter of P. cineraria decomposed in 6 months, of D. sissoo in 7 months and A. leucophloea and A. nilotica in 9 months. Decomposition rate of litter was highly correlated with neutral detergent fibre (NDF) (r = −0.94) and P (r = −0.91) concentration. N, P and K release were best correlated with NDF, acid detergent fibre (ADF), P, lignin, lignin/N and C/P ratios and NDF alone explained 88% to 94% of the variability in litter decomposition and nutrient release rates. There was significant build up of soil organic carbon and available NPK in the agrisilvicultural systems but also a decrease in soil pH. Build up in soil fertility was significantly correlated with litterfall and soil improvement was greatest under P. cineraria.     

Fractionation, characterization, and study of the emulsifying properties of corn fiber gum

Corn fiber gum (CFG) has been fractionated by hydrophobic interaction chromatography on Amberlite XAD-1180 resin using ionic, acidic, basic, and hydrophobic solvents of different polarities. Characterization, including determination of total carbohydrate, acidic sugar, and protein content, has been done for each fraction together with measurements of molar mass, polydispersity, radius of gyration, Mark-Houwink exponent, and intrinsic viscosity using multiangle laser light scattering and online viscosity measurements. Emulsification properties of all fractions in an oil-in-water emulsion system with 20:1 oil to gum ratio were studied by measuring turbidity over 14 days. The results indicate that CFG consists of different components differing in their molecular weights and carbohydrate and protein contents. The main fraction eluted with NaCl, although low in protein content, has the highest average molecular weight and was determined to be a better emulsifier than the other fractions. The unfractionated CFG, which contains different molecular species, is the best emulsifier.     

Improving rhizospheric environment and sugarcane ratoon yield through bioagents amended farm yard manure in udic ustochrept soil

A field experiment was conducted for two crop cycles during 2003–2005 and 2004–2006 at the Indian Institute of Sugarcane Research, Lucknow in subtropical India. Trichoderma viride and Gluconacetobacter diazotrophicus amended farm yard manure (FYM) increased organic carbon (19.44 Mg ha⁻¹) and available nitrogen (260 kg N ha⁻¹) content of soil from 14.78 Mg ha⁻¹ (OC) and 204 kg N ha⁻¹ observed under farmer's practice (sole N application). Application of bioagents amended FYM improved soil porosity and reduced compaction (bulk density—1.39 Mg m⁻³ over 1.48 Mg m⁻³ under farmer's practice). Sugarcane ratoon crop removed the highest amount of nitrogen (N—165.7 kg ha⁻¹), phosphorus (P—24.01 kg ha⁻¹) and potassium (K—200.5 kg ha⁻¹) in the plots receiving FYM with Trichoderma and Gluconacetobacter. Inoculation of FYM with bioagents improved population of ammonifying and nitrifying bacteria in the soil. Phosphorus and potassium uptake of the crop was greatest in the plots receiving FYM, Trichoderma and Gluconacetobacter. Bioagents (Trichoderma and Gluconacetobacter) amended FYM increased ratoon cane (70.2 Mg ha⁻¹) and sugar yields (7.93 Mg ha⁻¹) compared with control (62.3 and 7.06 Mg ha⁻¹ ratoon cane and sugar yields, respectively).     

Long‐term effects of vehicular passages on soil carbon sequestration and carbon dioxide emission in a no‐till corn‐soybean rotation on a Crosby silt loam in Central Ohio,USA

Research information from a systematic planned study on the effects of vehicular passages and axle load on soil carbon dioxide (CO₂) fluxes and soil carbon (C) sequestration under long‐term NT farming is scanty. Therefore, the present study was conducted on an on‐going 20‐year experiment to assess the impacts of variable vehicular passages of a low axle load on soil CO₂ emission and soil C sequestration from a no‐till (NT) managed corn (Zea mays L.)–soybean (Glycine max Linneo) rotation in comparison with that a soil under woodlots (soils under natural wooded plantation). The experimental treatment consisted of an empty wagon [0 Mg load for compaction (C‐0; control)] compared with 2 (C‐2) and 4 (C‐4) passages of 2.5 Mg water wagon axle load, applied to the entire plot every year during April/May for 20 consecutive years. Soil samples were obtained in November 2016 to determine the effects of various vehicular passages on C and nitrogen (N) contents and CO₂ emissions. Soil CO₂ fluxes were measured from November 16, 2016, to May 30, 2017, on the bi‐weekly (November to December and April to May) and monthly (January to March) basis by using high‐density polyvinyl chloride static gas chambers. The soil CO₂ fluxes ranged from –1.05 to 9.03 g CO₂ m^?2 d^?1. The lowest soil CO₂ fluxes were observed in December coinciding with the minimum soil temperature. In general, daily soil CO₂ fluxes were higher under C‐0 than those under other treatments. Vehicular traffic and axle load reduced the cumulative emission of CO₂ by 22.6 and 29.8% under C‐2 and C‐4, respectively, compared with that under C‐0 (6.09 Mg ha^?1). Soil and air temperatures had a significant positive correlation with the diurnal fluxes of soil CO₂ in all the treatments except that under C‐4. Electrical conductivity, soil C and N contents and pools did not differ significantly among the treatments. Further, 2 to 4 passages of vehicles with 2.5 Mg of axle load decreased the soil CO₂ emission on Crosby silt loam under NT as compared to that under the control. Therefore, continuous cultivation of row crops with moderate trafficking under NT and residue retention is recommended, and it also reduces the potential of soil CO₂ emission while improving the soil organic C pools of well‐drained soils of Central Ohio.     

Cellulase production by Aspergillus unguis in solid state fermentation

Lignocellulosic substrates are a good carbon source and provide rich growth media for a variety of microorganisms which prodLuce industrially important enzymes. Cellulases are a group of hydrolytic enzymes such as filter paperase (FPase), carboxymethyl cellulase(CMCase) andβ-glucosidase-responsible for release of sugars in the bioconversion of the lignocellulosic biomass into a variety of value-added products. This study examined cellulase production by a newly isolated Aspergillus unguis on individual lignocellulosic substrates in solid state fermentation (SSF). The maximum peak production of enzymes varied from one substrate to another, however,based on the next best solid support and local availability of groundnut fodder supported maximum enzyme yields compared with other solid supports used in this study.Groundnut fodder supported significant production of FPase (5.9 FPU/g of substrate), CMCase (1.1 U/g of substrate) andβ-glucosidase activity (6.5 U/g of substrate) in SSF. Considerable secretion of protein (27.0 mg/g of substrate) on groundnut fodder was recorded. Constant increment of protein content in groundnut fodder due to cultivation of A. unguis is an interesting observation and it has implications for the improvement of nutritive value of groundnut fodder for cattle.     

Biomass and Carbon Sequestration Potential of Poplar-Wheat Inter-cropping System in Irrigated Agro-ecosystem in India

An attempt has been made to assess the productivity as well as the carbon sequestration potential of this mixture. The grain as well as straw yields were significantly lower in poplar block plantations than in the open （14 to 64% and 13 to 66% grain and straw yield, respectively under one to six year plantation）. The annual productivity of poplars was recorded maximum after fourth year and later the annual wood increment decreased （42.4, 39.8 and 35.6 m^3/ha/yr after 4^th, 5^th and 6^th year, respectively）. The enrichment of soil through litter and roots enhanced the organic carbon in the surface layer of soil （0-15 cm） under poplar blocks as compared to open fields with wheat crop only. The carbon storage potential in agroforestry system was recorded very high in comparison to sole crop. The carbon storage in agroforestry system increased with the age of the plantation and the major contribution came from the timber, roots and litter （37.30 mg/ha after six years）. However, wheat crop yield decreased under poplar but this may be compensated by the poplar trees in terms of biomass, economic returns and the carbon sequestration potential.     

Wheat quality and productivity as affected by varieties and sowing time in Haryana, India

Of the wheat grown in North-West India the majority is consumed as traditional Indian flat bread (chapatti). Chapatti quality is important to consumers and people are willing to pay more for better quality wheat flour, but farmers do not specifically target quality outcomes as the majority of their wheat is sold with no segregation. For farmers the main objective is to harvest maximum yields, but in the last decade productivity growth for wheat yields has slowed in the areas where the wheat is grown in a double cropping pattern. Nutrient depletion and temperature-related stress are possible causes for this decline in productivity growth. Farmers meanwhile are looking to opportunities to maintain profitability and, with consumers willing to pay a higher price for better chapatti wheat, an opportunity exists for farmers to manage their wheat to improve both the yield as well as quality of wheat. In this paper we evaluate management practices that best achieve high yield and better chapatti quality, and assess the temperature environment for the winter wheat growing season. A step-wise analysis of the long-term temperature trend for sites in NW India showed that mean annual temperature has increased by 0.7-1.0 °C during the last decade. Field experiments with wheat varieties (C-306, WH-283, DBW-17, PBW-343, PBW-502, PBW-550, Raj-3765 and WH-1025) were conducted at farmers’ fields under 4 different sequential cropping rotations for the 2007-08 and 2008-09 winter seasons in Haryana (India). C-306 and WH-283 are varieties with excellent chapatti quality but are lower yielding by 15-26% than the more widely grown varieties such as PBW-343 and PBW-502. The replicated experiments involved three sowing times, these being an early sowing (late October to early November, timely sowing (mid November) and a late sowing (early December). A differential response of varieties was observed to sowing time with the yield of C-306 better whereas that of WH-283 and Raj-3765 was poor in early sown conditions. The varieties DBW-17, PBW-343 and PBW-502 were the highest yielding wheat with similar performance under early as well as timely sowing. All the varieties had lowest yield in December sowing. In general, late sowing had lower thousand grain weight but higher protein content. Of the quality measure grain hardness was the only attribute with a consistent positive correlation with chapatti quality. The chapatti score was higher for varieties C-306 and WH-283 compared to the other varieties but grain hardness and chapatti score was not much affected by sowing time. With all varieties included in the analysis there was no correlation between protein and chapatti score, but within an individual variety usually higher protein resulted in a higher chapatti score. There was no association of grain test weight or sedimentation value with chapatti score. From the results shown here it is evident that farmers will be able to manage with variety choice and timely sowing to obtain chapatti quality without losing grain yield benefits.     

Drought response of pearl millet landrace-based populations and their crosses with elite composites

Drought is the primary constraint in pearl millet (Pennisetum glaucum) production in the drier semi-arid and arid regions of south Asia and Africa. The traditional landraces from drier regions are good sources of drought adaptation but often lack high yield under near-optimum growing environments. The objective of this paper was to assess whether crosses between landrace populations and elite germplasm can produce hybrids with better grain yield under favourable conditions than landraces, without compromising grain yield under drought. The research evaluated 20 crosses and their nine parents (consisting of landrace-based populations and elite composites) under drought and non-drought conditions. Drought response index (DRI), based on flowering and grain yield measured in drought and non-drought environments, was used to assess drought tolerance. Landrace populations yielded significantly more grain under drought stress than elite composites and crosses and had the highest mean DRI (3.99). In contrast, composites showed maximum sensitivity to drought with significantly negative DRI (−3.64). Adaptation to either drought or high productivity conditions appeared to be associated with different plant types: higher panicle number, lower grain number per panicle, and smaller seed size were associated with drought adaptation; low tillering and greater number of large-sized seeds per panicle were favoured for optimum growing conditions. Crosses yielded significantly better than composites under drought, better than landrace populations under non-drought and had a wide range in drought sensitivity. Around 40% of crosses produced on average 23% higher grain yield than the best landrace under favourable conditions, without compromising grain yield under drought. The results illustrate that hybridization of landrace populations with elite composites can produce germplasm that combines drought tolerance of traditional material with high production potential of elite genetic material.